KNO3 Crystals Research Articles

Switchable phase transition of crystalline to amorphous state of potassium nitrate single crystal

High-pressure materials science always has a special benchmark in the current research areas wherein dynamic shock waves have also made striking inroads on a par with high-pressure experiments in solids and have marked a tremendous impact in expanding the materials science research both in academics as well as applications point of view. In this context, we report and demonstrate the switchable phase transition of crystalline to the amorphous state of potassium nitrate (KNO3) single crystal at shocked conditions such that the observed results of phase transition have been evaluated by X-ray diffraction (XRD), Raman and optical spectroscopic as well as Field –emission scanning electron microscopic (FE-SEM) techniques. The observed phase transition sequence is crystal-crystal-crystal-amorphous-crystal-glassy crystalline nature that is exhibited by KNO3 crystals with respect to 0, 1, 2, 3, 4, and 5 shock pulses. The formation of amorphous KNO3 is because of the rotational disorder of the oxy-anions of the NO3 units and the positional disorder of potassium ions. Strikingly, to date, it could be the first report of amorphization on KNO3 considering both the static pressure and temperature experiments. Due to the ability of potential switching between crystalline and amorphous states, the title material is a good fit for the applications of optical data storage and molecular switching.

Characterization of Pure and L-Proline Doped Potassium Nitrate and Sodium Nitrate Crystals

The crystals of pure and L-Proline doped Potassium nitrate and Sodium nitrate were grown in solution by slow evaporation technique using supersaturated solution of the salts. Characterization studies of the crystals have been done to find the impact of the L-Proline on the regular lattice arrangement of the pure crystal. The Powder XRD spectrum reveals that the pure and doped KNO3 crystals belong to orthorhombic structure; and pure and doped NaNO3 are rhombohedral in nature. This is a unit cell with parameters a = b = c; α = β = γ ≠ 90°. There are small changes in the unit cell dimensions but the structure of the pure and doped crystals remain to be orthorhombic in nature. The FTIR spectrum shows the functional group analysis of the samples. The various decomposition process of the crystals with respect to temperature have been carried out in thermal analysis. The dielectric properties exhibit the variation of dielectric constant, and capacitance with frequency at various temperatures for pure and doped crystals. The doped crystals found to have considerable effect on the optical, thermal and dielectric properties.
 HIGHLIGHTS
 
 Effect of dopant L-Proline on the growth of Potassium nitrate and Sodium nitrate crystals by solution growth was carried out for the first time
 The studies based on dielectric properties and thermal analysis gives a broad understanding about the influence of the dopant on the pure crystals
 Variation of dielectric constant, resistance, and capacitance with respect to frequency at various temperatures reveals that the dopant L-Proline has a significant effect
 
 GRAPHICAL ABSTRACT

Nonpolarized light absorption in pure, doped with the nitrite ions, and photolyzed KNO3 crystals

Absorption of nonpolarized light by pure, doped with the nitrite ions, and photolyzed KNO3 crystals has been studied. It is shown that the absorbance registered in nonpolarized light, directed perpendicular to the crystallographic с axis of both pure doped with the nitrite ions crystals, linearly depends on the thickness of crystal in the region of high (A>0.5) and low (A<0.3) absorbance. With the photolysis time increase one can observe the shift of maximum absorption band due to peroxynitrite formed under photolysis of KNO3 crystal. The shape of peroxynitrite absorption band calculated as the difference between a total spectrum and host matrix spectrum depends on the absorbance in the maximum of the former.

Protein Composite Materials by Crystallization: Product and Process Design

AbstractThe product and process design of protein composite materials continuously produced by reactive extrusion are studied in detail. A suitable process design and operating window are presented. Potassium nitrate (KNO3) was used as a model additive and as a tool for modifying the physiochemical properties of the extruded protein films. The crystalline structures were identified and correlated to the tensile properties of the films. Uniformly distributed trigonal phase‐III KNO3 crystals were observed within the film, which led to significantly higher elongation values of the films. Appropriate downstream operations are able to prevent the undesired polymorph transition to the orthorhombic phase II of KNO3 which would strongly reduce the mechanical performance.

Study of the behavior of chromium(III) in potassium nitrate solutions at 25°C

Solubility in the KNO3-Cr(NO3)3-H2O system at 25°C was studied by an isothermal method. The existence of solid phases of potassium nitrate and chromium(III) nitrate nonahydrate was confirmed by constructing a phase diagram, chemical analysis, and IR spectroscopy. Crystallization of potassium nitrate from aqueous solutions was studied. Potassium nitrate does not interact with chromium(III) nitrate within the range of micro and macro concentrations. The capture of chromium(III) by KNO3 crystals is due to adsorption and occlusion of a mother solution.

Wavelength Modulation Absorption Spectroscopy Using a Frequency-Quadruped Current-Modulated System

A wavelength modulation absorption spectrometry (WMAS) with a frequency-quadruped system is demonstrated. The frequency-quadruped system consists of a two-frequency doubled external enhancement cavity with KNO3 and BBO crystals, and a current-modulated 906-nm single mode external cavity diode laser (ECDL), which generates the tunable wavelength modulated radiation at 226.7 nm used to detect the NO absorption line that belongs to the combined Q22(10.5) and QR12(10.5) lines of 7(0, 0) band within the A2Σ+ – X2II electronic transition system. The 1st, 2nd and 3rd harmonic spectra are accomplished to show that it is possible to detect samples using the frequency quadruped system combined with the WMAS technique that can find practical applicability in the future.

Ferroelectric phase transitions in KNO3 embedded into porous glasses

This paper presents the results of dielectric and dilatometric measurements of porous glasses filled with KNO3 from water solution and from the melt. It was shown that ferroelectric phase transition is observed during the cooling process only in KNO3 nanocrystals introduced into the porous matrix. The phase diagram of transition temperatures versus average values of pore dimensions was obtained. The phenomenological model describing the phase transition and size effects in KNO3 crystals is proposed.

Eutectic Freeze Crystallization with an Aqueous KNO3−HNO3 Solution in a 100-L Cooled-Disk Column Crystallizer

Eutectic freeze crystallization is a novel technique for processing waste and process streams of aqueous electrolyte solutions, separating them into pure water and pure solid salt. A dedicated apparatus, a 100-L cooled-disk column crystallizer, has been developed and tested, combining crystallization and solid/solid separation of ice and salt. Experiments have been performed with a ternary system of aqueous KNO3−HNO3. Heat-transfer rates were achieved in the range of 1300−4600 W·m-2·K-1, which are related to the square root of the scraping rate. The ice product slurry contained 0.15 wt % salt. The ice impurity content after three washing cycles was as low as 15 ppm K+. Well-faceted KNO3 crystals are produced with high purity.

Growth of Crystal Phases in Porous Media

The purpose of this paper is to investigate the growth of KNO3 crystals in porous stones of artistic interest such as Carrara marble, Pietra di Firenzuola (Firenzuola stone), Pietraforte (Forte stone), and Travertine. Salt crystallization within the pores produces a general decrease of the porosity and a shift of the pore size distribution toward coarser pores. These effects were also observed in very compact materials such as Carrara marble, that mostly present submicroporosity. The incomplete wetting of the porous substrates was studied by contact angle measurements, which demonstrated that the liquid infiltration into the porous matrix, that is, the depletion, was the driving factor. Optical microscopy and scanning electron microscopy indicated that the morphology of the KNO3 crystals grown on the porous matrix strictly depended on the physicochemical nature of the substrate, suggesting that the crystal habitus was mainly governed by the interactions with the crystallization support. The importance of these results for the conservation of humanity's cultural heritage is stressed.

Scaling properties of the ν1 Raman active nitrate mode in doped ammonium and potassium nitrate crystals

The Raman intensity behavior of the nitrate modes during phase transitions is analyzed via the power law |T−Tc|β for (F−, Cl−, Br−)-doped NH4NO3 and (Na+, Rb+, Cs+, Ag+)-doped KNO3 crystals. The exponent β is shown to be highly dependent on the degree of doping. This observation is based on the resonance behavior of the resident dopant. The spatial extent of the resonance mode is shown to be the characteristic dimension for the crystal domains during phase transition. This extent is demonstrated to be proportional to dc, the characteristic average distance between dopant ions at which β values of the nitrate ν1 and ν4 modes are the same. The scaling property as evidenced by β of the ν1 mode is analyzed via the (mass of the dopant)−1/2 scaled average distance between dopant ions which is an important parameter for characterizing the doping effect. Previous results for the (Na+, K+, Ag+, Pb2+)-doped NH4NO3 crystals are also employed to complete the analysis [S. Ma, G. Wu, and H. Wang, J. Chem. Phys. 108, 7758 (1998)].

The dispersion of growth rate as a result of different crystal perfection

The aim of the cooperative work of the above mentioned institutes was to find out the reason for growth rate dispersion (GRD). Measurements of growth rate (overall or face-specific), microhardness (HV), etch pit density (EPD) and crystal perfection (X-ray topography and Laue X-ray method) were carried out using KAl(SO4)2 · 12H2O (PA) and KNO3 (PN) crystals. The investigated crystals were grown under different conditions and treated in different ways.It is possible to influence the growth rate by well-directed alternations of supersaturation (σ1, σ2, σ1), strain, mechanical stress, annealing and surface roughening. Depending on observation time, the constant crystal growth model (CCG model) (a few hours) as well as the random fluctuation model (RF model; a few days up to a month) describe the growth behaviour of PA. The growth of PN can only be described by the RF model.At constant supersaturation, the average growth rate of small particles in the subsieve size range (up to 60 μm) is considerably smaller than the average rate of larger crystals of the product size range (500 μm) in an MSMPR (mixed suspension mixed product removal) crystallizer.

Etude par Microscopie Raman de la Couche Liquide Située au Contact d'un Cristal en Cours de Dissolution dans sa Solution Mère: Systèmes LiNO3H2O et KNO3H2O

AbstractThe composition of the dissolution layer of LiNO3 and KNO3 crystals in their respective unsaturated mother liquors was studied by Raman microscopy coupled with a multi‐channel acquisition of data. Preliminary examination of homogenous solutions at various concentrations of LiNO3 and KNO3 revealed the existence of individual Raman bands assigned to different solvated species, namely free aquated ions, solvent‐separated ion pairs and/or contact ion pairs. Weak bands due to a small amount of aggregates (LiNO3)n or (KNO3)n were also identified. Spectral parameters of each individual band were calculated. Raman spectra of dissolution layers recorded at different steps of the crystal dissolution revealed considerable reinforcement of aggregates and contact ion pair concentrations compared with that existing in the bulk of the unsaturated mother liquors. The aggregate concentration in the dissolution layer was found to be even higher than that calculated for the corresponding saturated solution. The behaviours of LiNO3 and KNO3 were shown to differ considerably.

Ultra‐micro‐hardness measurements of non‐metallic crystals and an attempt for their calculation

AbstractThe ultra‐micro‐hardness of non metallic crystals has been measured for 16 substances. These are products usually produced in mass‐crystallization; inorganic, organic, with hydrates and unhydrates. The hardness‐force‐dependency was examined and data are compared to literature. KNO3 crystals showed a strong direction dependency (a factor of 2). In the end there has been made a first attempt to introduce a correlation of the measured micro‐hardness and physical properties of the crystals, but so far this was only possible for face centred cubic lattices.

Vibrations of Isotopic Impurities in Crystals Built up by Complex Ions

AbstractThe IR reflection and Raman spectra of NaNO3, Ba(NO3)2, KNO3, and NH4Cl crystals containing isotopic impurities of 15N and 18O are studied. The experimental data on local vibration modes are compared with those calculated by the method of Green's functions, the density of vibration states being determined from two‐phonon spectra, as well as those following from the model of additive refraction (AR). The latter is found to yield satisfying results provided the isotopic shift exceeds the vibrational bandwidth. A nomograph is provided by means of which the deviation of frequency and intensity of a local mode calculated in AR approximation can be estimated. The absence of isotopic structure in vibration spectra of some crystals studied by other authors is also explained.

Electron Paramagnetic Resonance Studies of VO2+ in KNO3 and CsNO3 Single Crystals

The electron paramagnetic resonance spectra of the VO2+ ion doped in KNO3 and CsNO3 single crystals have been investigated over a wide temperature range. Room-temperature studies reveal that there is a very fast readjustment of VO2+ ion, in both crystals, which is manifested in the presence of a single isotropic octet, thereby exhibiting a low viscous “liquidlike” nature. At low temperatures an anisotropic spectrum is obtained due to the hindered rotation of the VO2+ ion. The effect of CsNO3 in hindering the rotation of a vanadyl ion is found to be greater than that of KNO3. The linewidths at room temperature are found to depend upon the mI quantum number, and an attempt is made to fit the linewidth data of the present study in the theoretical expressions of Kivelson. It is found that Kivelson's theory can qualitatively explain the observed variation of linewidth with nuclear quantum number mI, but the experimental data could not be fit quantitatively into the theory. All the spectra are analyzed using the usual spin-Hamiltonian method.