Effect of halide ions on the dissolution of copper single crystal planes in dilute sulphuric acid

The rates of dissolution of copper single crystal planes in dilute sulphuric acid containing various concentrations (10⁻⁸ to 10⁻²M) of Cl⁻, Br⁻ and I⁻ are determined at 30°C. The dissolution rates, which are controlled by transport process in solution, are a function of the temperature, stirring rate, oxygen solubility, crystallographic orientation and the concentration of halide ions. Halide ions acted as anodic inhibitor at low concentrations and cathodic inhibitor at high concentrations. The changes in the dissolution rates have been attributed to specific adsorption of halide ions or precipitation of cuprous halides on the surface of the crystal planes.     

The anodic behaviour of copper in static and flowing hydrochloric acid solutions

The dissolution of copper in 0·36 to 3·6 HCl was studied both in static and in flowing solutions using flow rates between 0·098 and 1·14 ms⁻¹, all in the region of laminar flow.Steady state anode potential current curves, potentiodynamic sweep and potentiostatic pulse techniques and impedance measurements, in the range of 0·02–7 kHz, were used. In both static and flowing solutions dissolution of copper occurs to a monovalent state, as chloro-complexes CuCl⁻₂ and CuCl²⁻ with exchange currents for the two reactions of 1·9 × 10⁻⁵ A mm⁻² and 8 × 10⁻⁷ Amm⁻² respectively in 1·44 MHCl. The cuprous chloride layer first forms a monolayer and subsequently grows to considerable thicknesses. The double layer capacity is constant at 0·17 ± 0·03 μFmm⁻² at potentials below multilayer formation and this is interpreted as implying that there is no specific adsorption of chloride ions prior to formation of the cuprous chloride layer. As the flow rate increases the film becomes thinner so delaying the formation of the film of critical thickness required for passivation.     

Thermodynamic studies on LaFeO3(s)

The enthalpy increments and the standard molar Gibbs energies in the formation of LaFeO₃(s) have been measured using a high-temperature Calvet micro-calorimeter and a solid oxide galvanic cell, respectively. The corresponding expression for enthalpy increments is given as:

H°(T)−H°(298.15 K)(J mol⁻¹)(±1.2%)=−36887.27+103.53 T(K)+25.997×10⁻³T²(K)+11.055×10⁵/T(K).

The heat capacity, the first differential of H°(T)−H°(298.15 K) with respect to temperature, is given as:

C_p,m°(T)(JK⁻¹mol⁻¹)=103.53+51.994×10⁻³T(K)−11.055×10⁵/T²(K).

From the measured e.m.f. of the cell, (−)Pt/(LaFeO₃(s)+La₂O₃(s)+Fe(s))//CSZ//(Ni(s)+NiO(s))/Pt(+), and the relevant Δ_fG_m°(T) values from the literature, the Δ_fG_m°(LaFeO₃, s, T) was calculated, and is given as:

Δ_fG_m°(LaFeO₃, s, T)(kJmol⁻¹)(±0.72)=−1319.2+0.2317T(K).

The calculated Δ_fH_m°(LaFeO₃, s, 298.15 K) and S°(298.15 K) values obtained using the second law method are −1334.7 kJ mol⁻¹ and 128.9 J K⁻¹ mol⁻¹, respectively.     

Hydro-chemical conversion of galena in FeCl3-KCl solution

The behaviours of complexation and dissolution of PbCl₂ on the surface of galena were investigated to explore the process of hydro-chemical conversion of galena (PbS) in chloride media. By means of solution chemistry calculation, the production and dissolution of the products PbCl₂ were studied. And the passivation of the galena was studied by Tafel curve. The results show that PbCl₄²⁻ is the main form of PbCl₂ presented in the saturated potassium chloride (KCl) solution. The PbCl₂ crystal is easy to precipitate when the total concentration of chloride ion ([Cl⁻]_T) is equal to 0.92 mol/L, and it is inclined to dissolve when [Cl⁻]_T is more than 0.92 mol/L. The chloride complexing reaction rate strongly depends on the Fe³⁺ion concentration when it is less than 6×10⁻⁴mol/L, while passivation occurs on the surface of the electrode when Fe³⁺ concentration is larger than 6×10⁻⁴mol/L. The reaction rate increases obviously when KCl is added, since the activity of Cl⁻ increases; thus accelerates the dissolution of PbCl₂.     

Galvanic cells encountered in the corrosion of steel reinforcement —I. Differential pH cells

Corrosion cells resulting from differential pH values have been investigated in the absence and presence of Cl⁻ ions. Measurements of potential, galvanic current for separate and coupled electrodes, as well as experimental determination of Evans diagrams, were carried out. The results of coupling rvealed that the steel at lower pH (7 and 8) suffered from corrosion while that at the. higher pH (12 and 12·5) was completely protected even in presence of high chloride concentrations The increase in the pH range caused a relative enhancement of the anodic process. The presence of 10⁻³ or 10⁻¹M Cl⁻ ions increased the rate of the anodic reaction by 8- or 12-fold. The rate of the cathodic reaction was of the same order of magnitude both in presence or absence of Cl⁻ ions. The % anodic and cathodic control were found to be 6·4 and 93.6, respectively, in the presence of Cl⁻ ions as compared with 34·3 and 65·7 in the absence of Cl⁻ ions.     

Sorption behavior of iminodiacetic acid resin for indium

In（Ⅲ） was quantitatively adsorbed by iminodiacetic acid resin （IDAAR） in the medium of pH = 4.52. The statically saturated sorption capacity of IDAAR is 235.5 mg·g^-1. 1.0 mol·L^-1 HCl can be used as an eluant. The elution efficiency is 97.9%. The resin can be regenerated and reused without apparent decrease of sorption capacity. The sorption rate constant is k298 = 1.94 × 10-5 s^-1. The apparent sorption activation energy of IDAAR for In（Ⅲ） is 20.1 kJ·mol^-1. The sorption behavior of IDAAR for In（HI） obeys the Freundlich isotherm. The enthalpy change is AH= 17.2 kJ·mol^-1.     

Crystal structure of single phase and low sintering temperature of α-cordierite synthesized from talc and kaolin

Cordierite body with the formulation of 2.8MgO·1.5Al₂O₃·5SiO₂ was prepared from talc and kaolin as the basic raw materials. Following glass crystallization technique the glass powder was successfully heat treated at 900 °C for 2 h to form a single-phase α-cordierite. The crystal structure of α-cordierite was analysed using X-ray diffraction technique and the Rietveld structural refinement method. Differential thermal analysis (DTA), Fourier-transform infrared (FTIR), field emission scanning electron microscopy (FESEM), coefficient of thermal expansion (CTE) and dielectric properties were also performed. Results show that the materials crystallized as a hexagonal structure with space group of P6/mcc and the room temperature lattice parameters are a = 9.743742 (Å) and c = 9.389365 (Å). FTIR analysis on the glass revealed that only silicate species is the only unit that exists in the glass network. DTA also confirmed that α-cordierite completely formed after 13.5 min of isothermal heating at 900 °C. Coefficient of thermal expansion of synthesized α-cordierite is 2.5 × 10⁻⁶ °C⁻¹. The dielectric constant is between 5.0 and 5.5 for 1 MHz and 1.8 GHz, respectively, and the dielectric loss is in the range 10⁻². FESEM micrographs revealed that the material is fully densified.     

Interfacial interaction of solid nickel with liquid Pb-free Sn–Bi–In–Zn–Sb soldering alloys

The dissolution process of nickel in liquid Pb-free 87.5% Sn–7.5% Bi–3% In–1% Zn–1% Sb and 80% Sn–15% Bi–3% In–1% Zn–1% Sb soldering alloys has been investigated by the rotating disc technique at 250–450 °C. The temperature dependence of the nickel solubility in soldering alloys obeys a relation of the Arrhenius type c_s = 4.94 × 10² exp(−39500/RT)% for the former alloy and c_s = 4.19 × 10² exp(−40200/RT)% for the latter, where R is in J mol⁻¹ K⁻¹ (8.314 J mol⁻¹ K⁻¹) and T is in K. Whereas the solubility values differ considerably, the dissolution rate constants are rather close for these alloys and fall in the range (1–9) × 10⁻⁵ m s⁻¹ at disc rotational speeds of 6.45–82.4 rad s⁻¹. Appropriate diffusion coefficients vary from 0.16 × 10⁻⁹ to 2.02 × 10⁻⁹ m² s⁻¹. With both alloys, the Ni₃Sn₄ intermetallic layer is formed at the interface of nickel and the saturated or undersaturated melt at dipping times of 300–2400 s. The other Ni–Sn intermetallic compounds are found to be missing. A simple mathematical equation is proposed to evaluate the Ni₃Sn₄ layer thickness in the case of undersaturated melts. The tensile strength of the nickel-to-alloy joints is 94–102 MPa, with the relative elongation being 2.0–2.5%.     

A thermometric study of the reaction between Fe and HNO3

The reaction between Fe and HNO₃ is studied under a wide variety of conditions by the thermometric technique. Up to 4N HNO₃ ΔT varies linearly with the normality of HNO₃, while in solutions from 6 to 10N HNO₃ it is independent of the concentration. Passivity sets in solutions ≥ 10·8N HNO₃. Calculations of the reaction number (R.N.) reveal that the maximum rate of metal dissolution occurs in 7·3N HNO₃. Fe dissolution in dilute HNO₃ is promoted by additions of NO₃⁻ and NO₂⁻. That the rate-determining step of the autocatalytic process involves HNO₂ is supported by the results of addition of urea to the solution. This additive lowers the maximum measured temperature, without affecting the corresponding time necessary to reach it.Additions of HCI, NaCl, H₂SO₄ and Na₂SO₄ to dilute HNO₃ reduce the dissolution rate of Fe. The effect produced by the salts exceeds that of the acids.In contrast to its action in dilute solutions, the Cl⁻ion induces pitting corrosion in concentrated HNO₃. The attack starts after an induction period which decreases in length as the concentration of HCI is increased. Concentrated HNO₃ can tolerate a certain amount of the aggressive agent before attack starts. The concentration “N_HCl” which can be tolerated depends on that of the passivator according to logN_HCl=a+blog(N−N°)_HNO3 where a and b are constants, and N^o is the least concentration of HNO₃ necessary to cause passivity. Pitting corrosion in concentrated HNO₃ can be initiated also through NaCl. In one and the same acid solution more of NaCl is needed to cause the attack than of HCI.     

Study on the boundary structures in a series of lanthanide hexacyanoferrate(III) n-hydrates

The properties of a series of lanthanide hexacyanoferrate(III) n-hydrates were studied by means of thermal analysis, IR spectroscopy, Raman spectroscopy and X-ray crystallography. Thermal analyses showed that there were two kinds of complexes in this series, Ln[Fe(CN)₆]·5H₂O (Ln=La–Nd) and Ln′[Fe(CN)₆]·4H₂O (Ln′=Sm–Lu). The boundary complex between them was Nd[Fe(CN)₆]·5H₂O. The IR spectra of the two kinds of complexes were obviously different. For the pentahydrates, there were two sharp CN stretching bands at 2050 and 2140 cm⁻¹, and one band at 1600 cm⁻¹ assigned to the HOH bending. On the other hand, for the tetrahydrates besides the two CN stretching bands at 2050 and 2140 cm⁻¹, a new band was observed at 1940 cm⁻¹, and the HOH bending band split into three bands around 1600 cm⁻¹. From the X-ray crystal analysis, the structure of the boundary complex Nd[Fe(CN)₆]·5H₂O was determined. It belonged to hexagonal, P6₃/m, with a=7.467(2) Å, c=13.793(3) Å and Z=2 (R=0.082, R_w=0.126). Neodymium was nine-coordinated in the form of the NdN₆(H₂O)₃ group. The three coordinated water molecules of the 5H₂O complex with Nd have a large value for the equivalent isotropic thermal parameter. One of the three water molecules was dissociated easily and the 5H₂O complex changed into the stable 4H₂O complex with Nd. The crystal of the 4H₂O complex is orthorhombic, and belongs to the space group Cmcm as well as the other Ln[Fe(CN)₆]·4H₂O (Ln=Sm–Lu). Therefore, the structure of Nd[Fe(CN)₆]·5H₂O is regarded as the boundary structure.     

Magnetite stability in aqueous solutions as a function of temperature

Magnetite solubility, as a function of temperature and partial hydrogen pressure, with reference to the typical conditions of the operating fluid of a steam generator of a thermal power plant, has been studied by rigorously solving the problem of equilibria and adopting the scheme proposed by Sweeton and Baes [J. Chem. Thermodynamics2, 479 (1970)]. Stoichiometric calculations have proved that magnetite solubility attains its maximum value, which depends on the characteristics of the electrolytic solution, when the temperature is about 100°C, independently of the type of environment. A rigorous pH calculation was carried out using the method of the characteristic function, which can be applied also to complex systems, and assuming that the effect of the ionic strength may be neglected. The main aim of this study, besides helping power plant chemists to select a proper feedwater conditioning, was to calculate the pH, on a molal basis, of a solution through the best-fit of its exact values, as a function of ammonia concentration inside the inverval 1.0 × 10⁻⁸ to 9.0 × 10⁻³ m with a third-degree logarithmic polynomial. The results, which were obtained in the case of a solution containing NH₄OH and H₂CO₃, demonstrate the validity of this technique which allows the pH of a fairly complex system to be computed accurately. It also allows the correct amount of magnetite dissolution products to be evaluated without considering in detail its chemical equilibria when the solution temperature is above 200°C. This remark was derived from the pH calculations of an ammonia containing solution, which showed its independence of partial hydrogen pressure in the high temperature region, at least as far as the interval 0–1 atm was concerned. The determination of the pH, on a molar basis, of a solution at temperatures of 200, 250, 300 and 350°C, contaminated with sea water so that its acid conductivity was 300μΩ⁻¹cm⁻¹, has been performed. These results have shown that the buffering effectiveness of ammonia is negligible when its concentration falls within the interval 1.0 × 10⁻⁶ to 2.0 × 10⁻⁵ M, whereas in the range 6.0 × 10⁻⁵ to 3.0 × 10⁻⁴ M, its effect is quite pronounced.     

The preparation and thermodynamic properties of Fe(II)---Fe(III) hydroxide-carbonate (green rust 1); Pourbaix diagram of iron in carbonate-containing aqueous media

Carbonate-containing green rust 1, GR1(CO₃²⁻), is prepared by oxidation of Fe(OH)₂ in aqueous solution. Ferrous hydroxide is precipitated from NaOH and FeSO₄·7H₂O solutions and carbonate ions are added as a Na₂CO₃ solution. For sufficiently large concentrations of sodium carbonate, SO₄²⁻ ions do not play any role during the oxidation process and, at the end of the first stage of reaction, Fe(OH)₂ oxidizes into GR1(CO₃²⁻). In the second stage of reaction, GR1(CO₃²⁻) oxidizes into α-FeOOH goethite except when the transformation of ferrous hydroxide is partial, which leads to the formation of magnetite. From the X-ray diffraction analysis of GR1(CO₃²⁻), lattice parameters of its hexagonal cell are found to be a = 3.160 ± 0.005 Å and C = 22.45 ± 0.05 Å. From the Mössbauer analysis of the stoichiometric GR1(CO₃²⁻), which leads to a Fe²⁺:Fe³⁺ ratio of 2:1, the chemical formula is established to be: [Fe₄^(II)Fe₂^(III)(OH)₁₂][CO₃·2H₂O]. The 78 K Mössbauer spectrum of the compound can be fitted with three quadrupole doublets, two Fe²⁺ doublets d₁ and D₂ corresponding to isomer shifts (IS) of 1.27 and 1.28 mm s⁻¹ and quadrupole splittings (QS) of 2.93 and 2.67 mm s⁻¹, respectively, and one Fe³⁺ doublet D₃ with an IS of 0.47 mm s⁻¹ and QS of 0.43 mm s⁻¹. These three doublets were already used to fit the Mössbauer spectrum of chloride-containing GR1(Cl⁻) [see J.M.R. Génin et al., Mat. Sci. Forum8, 477 (1986) and J.M.R. Génin et al., Hyp. Int. 29, 1355 (1986)]and therefore are characteristic of GR1 compounds. From the recording of electrode potential E and the pH of the suspension versus time during the oxidation, the standard free enthalpy of formation of stoichiometric GR1(CO₃²⁻) is estimated to be ΔG °_f = − 966.250 cal mol⁻¹. Knowing the chemical formula and ΔG °_f of GR1(CO₃²⁻) the Pourbaix diagram of iron in carbonate-containing aqueous solutions is drawn.     

Influence of the prior oxide film on the growth and structure of oxides formed on Fe---26Cr alloys at 600°C

A Fe---26 Cr alloy has been oxidized at 600°C in 5 × 10⁻³, 5 × 10⁻² and 5 × 10⁻¹ torr oxygen to examine the influence of the prior oxide film on the growth and structure of oxides formed at high temperature. Different prior oxides were produced either by electropolishing or by annealing the electropolished specimen in vacuum at 600°C. Auger electron spectroscopy (AES) showed the Cr content of the prior oxide film to be increased from 50 to 95% during annealing, and electron diffraction indicated a change in oxide structure from amorphous to crystalline. At 5 × 10⁻³ torr, electropolished Fe---26 Cr oxidizes faster than the vacuum annealed specimens because the amorphous prior oxide gives rise to a finer-grained cubic oxide with more grain boundary easy diffusion paths for cation transport. From AES and electron back-scattering Fe⁵⁷ Mössbauer spectroscopy it is concluded that this cubic oxide is a duplex layer of inner γ-Cr₂O₃ and outer Fe₃O₄. The oxidation rate slows markedly when nucleated α-Fe₂O₃ covers the cubic oxide. With increased oxidation time Fe₃O₄ converts to α-Fe₂O₃ and the γ-Cr₂O₂ to α-Cr₂O₃. Annealed Fe---26 Cr oxidizes slower primarily because of a lower cation transport through a coarser-grained cubic oxide rather than because of a higher Cr content in the prior oxide. α-Fe₂O₃ nucleates at an earlier stage in the oxidation and essentially stifles the reaction. The extent of Cr incorporation into any of the Fe oxides produced in 5 × 10⁻³ torr oxygen is small ( 5%). Increasing the oxygen pressure from 5 × 10⁻³ to 5 × 10⁻² and 5 × 10⁻¹ torr has little effect on the mechanism of oxidation of vacuum annealed Fe---26 Cr, except that the overall extent of oxidation is less because of earlier α-Fe₂O₃ formation and, after a few hours of oxidation, up to 20% Cr is incorporated into the α-Fe₂O₃ lattice. On electropolished Fe---26 Cr at 5 × 10⁻² and 5 × 10⁻¹ torr oxygen nodules of α-Cr₂O₃ form and continue to grow both at grain boundaries and within the grains. Possible mechanisms for this nodule formation, which is exclusive to electropolished specimens oxidized at the higher pressures, are considered.     

High temperature oxidation of Nb-10 at. % W alloy

By means of the “interruption kinetic technique”, as applied to oxidation of tungsten under 0.048 bar O₂, the oxygen diffusion coefficient in growing WO_8−x has been determined for the temperature range of 568–908°C and may be expressed as: D = 6.83 × 10⁻² exp (−29,890/RT), with the activation energy given in cal/mole. Calculations are made to show the influence of temperature on the concentration of oxygen vacancies in WO_3−x, on their free energy of formation and on the ionic conductivity in WO_3−x. From the kinetic data of W oxidation at 800°C, prior to interruption-annealing, values of oxygen diffusion coefficients due to oxygen transport via lattice and short-circuit paths have been calculated as functions of time for growing WO_3−x. A simplified oxidation model is used for evaluation of the oxidation rate constant of W at 800°C.     

Theoretical evaluation for thermodynamic stability of constituents of Mm-based hydrogen storage alloy in 6 M KOH solution at relatively high temperatures

Potential-pOH diagrams of some components constituting AB₅-type Mm-based (Mm: misch metal) hydrogen storage alloy were drawn at various temperatures to predict the deterioration behaviors of the alloy in an alkaline solution at relatively high temperatures. Based on these diagrams, the thermodynamic stability of each constituent of the alloy in 6 M KOH solution at various temperatures was evaluated. As A components, in the charge–discharge potential range, Nd(OH)₃ was extremely stable at temperatures lower than 70°C, while Ce(OH)₃ was oxidized to CeO₂ at the end of discharge above −0.496 V versus NHE at 70°C. On the other hand, as B components, Mn, Al and Co dissolved easily as HMnO₂⁻, AlO₂⁻ and HCoO₂⁻ ions in 6 M KOH solution and their solubility increased with increasing temperature. However, HCoO₂⁻ ion was reduced to metallic Co at the charge process. All oxidation reactions, particularly the dissolution of Mn and Al, proceeded at relatively high temperatures.     

Thermo-physical and thermal cycling properties of plasma-sprayed BaLa2Ti3O10 coating as potential thermal barrier materials

Increased turbine inlet temperature in advanced turbines has promoted the development of thermal barrier coating (TBC) materials with high-temperature capability. In this paper, BaLa₂Ti₃O₁₀ (BLT) was produced by solid-state reaction of BaCO₃, TiO₂ and La₂O₃ at 1500 °C for 48 h. BLT showed phase stability between room temperature and 1400 °C. BLT revealed a linearly increasing thermal expansion coefficient with increasing temperature up to 1200 °C and the coefficients of thermal expansion (CTEs) are in the range of 1 × 10^− 5–12.5 × 10^− 6 K^− 1, which are comparable to those of 7YSZ. BLT coatings with stoichiometric composition were produced by atmospheric plasma spraying. The coating contained segmentation cracks and had a porosity of around 13%. The microhardness for the BLT coating is 3.9–4.5 GPa. The thermo-physical properties of the sprayed coating were investigated. The thermal conductivity at 1200 °C is about 0.7 W/mK, exhibiting a very promising potential in improving the thermal insulation property of TBC. Thermal cycling result showed that the BLT TBC had a lifetime of more than 1100 cycles of about 200 h at 1100 °C. The failure of the coating occurred by cracking at the thermally grown oxide (TGO) layer due to severe oxidation of bond coat. Based on the above merits, BLT could be considered as a promising material for TBC applications.     

Studies on accumulation of chloride ions in pits growing during anodic polarization

The concentration of Cl⁻ ions within pits grown on 18Cr---12Ni---2Mo---Ti austenitic stainless steel specimens immersed in vertical position in 0·5N NaCl + 0·1N H₂SO₄ and polarized to 860 mV_NHE was studied at 20°C. The Cl⁻ concentration within pits increases with time to a maximum and then decreases (for example, after 6 h 2N Cl⁻ is observed). The higher accumulation of Cl⁻ within pits, the slower their development. For slowly growing pits a maximum value of about 12N Cl⁻ was observed. The low pH values of the solution within pits are the consequence of high Cl⁻ contents occurring there.     

Conductivity of a new pyrophosphate Sn0.9Sc0.1(P2O7)1−δ prepared by an aqueous solution method

New pyrophosphate Sn_0.9Sc_0.1(P₂O₇)_1−δ was prepared by an aqueous solution method. The structure and conductivity of Sn_0.9Sc_0.1(P₂O₇)_1−δ have been investigated. XRD analysis indicates that Sn_0.9Sc_0.1(P₂O₇)_1−δ exhibits a 3 × 3 × 3 super structure. It was found that Sn_0.9Sc_0.1(P₂O₇)_1−δ prepared by an aqueous method is not conductive. The total conductivity of Sn_0.9Sc_0.1(P₂O₇)_1−δ in open air is 2.35 × 10⁻⁶ and 2.82 × 10⁻⁹ S/cm at 900 and 400 °C respectively. In wet air, the total conductivity is about two orders of magnitude higher (8.1 × 10⁻⁷ S/cm at 400 °C) than in open air indicating some proton conduction. SnP₂O₇ and Sn_0.92In_0.08(P₂O₇)_1−δ prepared by an acidic method were reported fairly conductive but prepared by similar solution methods are not conductive. Therefore, the conductivity of SnP₂O₇-based materials might be related to the synthetic history. The possible conduction mechanism of SnP₂O₇-based materials has been discussed in detail.     

Growth and microstructural stability of epitaxial Al films on (0001) α-Al2O3 substrates

Al films were grown epitaxially on single-crystal α-Al₂O₃ substrates by magnetron sputtering and molecular beam epitaxy, respectively. The microstructure and thermal stability of these films were analysed in detail using X-ray diffraction methods and electron microscopy techniques. The films consist of two twin-related growth variants, related by a 180° rotation around the <111> film normal resulting in a {111} Al || (0001) α-Al₂O₃, and ± < > Al || < > α-Al₂O₃ orientation relationship. The Al variants are separated by Σ3 { } Al twin boundaries possessing a rigid body translation of the {111} Al planes across the boundary plane in order to reduce their energy. Motion of the twin boundaries was observed by annealing plan-view samples in situ in a transmission electron microscope. The twin boundaries advance in jerky motion at velocities of several μm/s at temperatures of ˜400 °C, resulting in grain coarsening. In all cases, heat treatments resulted in increased area fraction of one twin variant, which finally will result in single-crystal films upon further annealing.     

Raman and infrared study of 100 MeV swift Ag heavy ion irradiation effects in CaSO4·2H2O single crystals

The modifications of calcium sulphate (CaSO₄·2H₂O) single crystals are investigated by means of Raman and Fourier transform infrared spectroscopy (FT-IR) using 100 MeV Ag⁸⁺ ions in the fluence range 1 × 10¹¹ to 5 × 10¹³ ions/cm². It is observed that the intensities of the Raman modes decrease with increase in ion fluence. We determined damage cross-section (σ) for all the Raman active modes and found to be different for different Raman modes. Further, FT-IR studies have been carried out to confirm surface amorphisation for a fluence of 1 × 10¹³ ions/cm². It is observed that the absorption peaks at 1132–1156 cm⁻¹ corresponds to ν₃(SO₄²⁻) mode. The decrease in Raman peaks intensity with ion fluence is attributed to degradation of ν₃(SO₄²⁻) modes present on the surface of the sample.