Growth and study of barium oxalate single crystals in agar gel

Barium oxalate was grown in agar gel at ambient temperature. The effect of various parameters like gel concentration, gel setting time and concentration of the reactants on the growth of these crystals was studied. Prismatic platy shaped spherulites and dendrites were obtained. The grown crystals were characterized by X-ray powder diffractometry, infrared spectroscopy, thermogravimetric and differential thermal analysis. An attempt is made to explain the spherulitic growth mechanism.     

Growth and study of some gel grown group II single crystals of iodate

Single crystals of calcium iodate and barium iodate were grown by simple gel technique by single diffusion method. The optimum conditions were established by varying various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of the reactants etc. Crystals having different morphologies and habits were obtained. Prismatic, dendritic crystals of barium iodate and prismatic, needle shaped, hopper crystals of calcium iodate were obtained. Some of them were transparent, some transluscent, and few others were opaque. Both the crystals were studied using XRD, FT-IR, and thermal analysis. The crystals were doped by iron impurity. The effect of doping was studied using IR spectroscopy and thermal analysis.     

Growth of single crystals of bismuth sulpho chloride in gel

Single crystals of the sparingly soluble compound, BiSCl have been grown in sodium silicate gel using straight tube and U-tube methods. Thiourea and bismuth trioxide dissolved in 10 N HCl are used as the reactants. The optimum conditions for growth of this crystal have been determined by studying the effect of the concentrations of the inner and outer reactants and that of the gel density. Single crystals of BiSCl upto 10 mm in size have been grown in a period of 20 to 25 days. The crystals grown have been identified as BiSCl by X-ray diffraction analysis.     

Synthesis,characterization and properties of ferroelectric rubidium hydrogen tartrate single crystals

Rubidium hydrogen tartrate single crystals were grown in silica hydrogel. Controlled reaction was employed between tartaric acid and rubidium chloride solutions by slow diffusion process in the gel medium. Colourless transparent crystals were grown at room temperature. The average density of crystals measured pyknometrically was 2·263 g cm⁻³. Thermal stability of the materials was studied. Chemical etching was employed to determine the perfection of these crystals.     

On the growth of calcium tartrate tetrahydrate single crystals

Calcium tartrate single crystals were grown using silica gel as the growth medium. Calcium formate mixed with formic acid was taken as the supernatant solution. It was observed that the nucleation density was reduced and the size of the crystals was improved to a large extent compared to the conventional way of growing calcium tartrate crystals with calcium chloride. The role played by formate-formic acid on the growth of crystals is discussed. The grown crystals were characterized by atomic absorption spectroscopy (AAS), X-ray diffraction analysis (XRD), microhardness measurement, Fourier transform infrared spectroscopy (FTIR), thermogravimetry (TG) and differential thermal analysis (DTA). The results obtained are compared with the previous work.     

Growth features of ammonium hydrogen<Emphasis Type="Italic">d</Emphasis>-tartrate single crystals

Ammonium hydrogend-tartrate (d-AHT) single crystals were grown in silica gel. The growth features of these crystals with variation of parameters like specific gravity of the gel, gel pH, acid concentrations, concentration of the feed solution and gel age were studied in detail.     

Nucleation and growth of potassium dihydrogen phosphate crystals in silica gels

Kinetic studies on nucleation and growth of potassium dihydrogen phosphate crystals in silica gels show that the rate-determining process for the growth of these crystals in silica gels is diffusion. Morphology, microhardness and perfection of gel grown crystals are also reported.     

Growth and characterization of calcium pyrophosphate dihydrate grown in silica gel

Calcium pyrophosphate dihydrate crystals, which are responsible for various arthritic diseases, were grown in sodium metasilicate gel. Variations in gel density, pH value and concentration of the reactants were found to have profound effect on the growth of the crystals. The grown crystals were characterized using IR, XRD, TGA and optical microscopy.     

Thermal behaviour of strontium tartrate single crystals grown in gel

Thermal behaviour of strontium tartrate crystals grown with the aid of sodium metasilicate gel is investigated using thermogravimetry (TG) and differential thermal analysis (DTA). Effect of magnetic field and dopant (Pb)²⁺ on the crystal stability is also studied using thermal analysis. This study reveals that water molecules are locked up in the lattice with different strengths in the grown crystals.     

Dielectric and magnetic studies of gel-grown copper malonate trihydrate crystals

Single crystals of copper malonate trihydrate were grown in silica gel by slow diffusion of copper nitrate by sodium metasilicate gel impregnated with malonic acid. The grown crystal was subjected to dielectric studies and magnetic studies. The dielectric properties of the crystal were analyzed as a function of frequency and temperature. A vibrating sample magnetometer was used to determine the hysteresis properties of the crystals by measuring the magnetic moment for different applied fields. The crystal is found to be weakly ferromagnetic.     

Growth mechanism of Herring-Bone and Hour-glass synthetic gypsum

Synthetic gypsum crystals are grown from sodium meta silicate gel when 1M calcium chloride solution diffuses into the gel imbedded with 1M amonium sulphate solution. Acicular-shaped crystals of Herring-Bone structure are observed. When methanol was added to the gel medium, tabular crystals revealing Hour-glass structure are rarely observed. In the presence of methanol the silicate particles are inhibited from being incorporated into the crystals as a result of pushing and incorporating mechanisms. Inclusion of silicate particles in traces gives rise to Hour-glass pattern. The implications are discussed. Contribution No. 602     

Growth and study of mixed crystals of Ca-Cd iodate

Mixed crystals of calcium-cadmium iodate were grown by a simple gel technique using diffusion method. The optimum conditions were established by varying various parameters such as pH of gel solution, gel concentration, gel setting time, concentration of reactants etc. Crystals having different morphologies and habits were obtained. Prismatic, dendritic crystals of calcium-cadmium iodate and prismatic needle shaped, hopper crystals of mixed iodate were obtained. Some of them were transparent, some transluscent and a few others were opaque. The crystals were characterized using FT-IR, EDAX, XRD, TGA and DTA.     

Praseodymium barium molybdate—its growth and structural characterization

Praseodymium barium molybdate (PBM) single crystals grown by gel method, reveal multiple and isolated octahedral bipyramidal crystals as well as spherulites of PBM at different depths from the surface inside the gel. Oscillation X-ray diffraction pattern of the sample reveals that PBM is single crystalline in nature. Infrared absorption spectrum confirms the presence of molybdate (MoO₄)²⁻ ions in PBM, while the thermogravimetric analysis shows that PBM loses molybdenum oxide component around 420°C. Energy dispersive X-ray analysis establishes the presence of Pr, Ba and Mo in the sample. X-ray photoelectron spectroscopic studies of PBM establish the presence of Pr, Ba and Mo in their respective oxide states. An empirical structure has been proposed on the basis of these findings. The implications are discussed.     

Lanthanum samarium oxalate — its growth and structural characterization

Lanthanum samarium oxalate (LSO) single crystals are grown in silica gels by the diffusion of a mixture of aqueous solutions of lanthanum nitrate and samarium nitrate into the test tube having the set gel impregnated with oxalic acid. Tabular crystals of LSO having well defined hexagonal basal planes are observed at different depths inside the gel. LSO crystals grown by this method are colourless and transparent. Laue transmission X-ray diffraction pattern of LSO reveals well defined spots with two-fold symmetry along the horizontal axis. Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) support that LSO loses water around 120°C, and CO and CO₂ around 350–450°C. The infrared (IR) absorption spectrum of LSO establishes the presence of oxalate (C₂ O₄)²⁻ ions. Energy dispersive X-ray analysis (EDAX) confirms the presence of La and Sm in the sample. X-ray photoelectron spectroscopic (XPS) studies of LSO confirm the presence of La and Sm in their respective oxide states. An empirical structure for LSO has been proposed on the basis of these findings.     

Thermal characteristics of pure and substituted gel grown Gd-molybdate crystals

Polycrystalline spherulitic crystals of pure Gd-heptamolybdate and single and twinned crystals of substituted Gd-Ba-molybdate were grown by using gel encapsulation technique. The thermal behaviour of these crystals was studied using the thermoanalytical techniques, which included TG, DTA and DSC. Thermal analysis suggests decomposition of the materials in one or more than one stages. Results obtained on application of TG based models viz. Horowitz-Metzger, Coats-Redfern and Piloyan-Novikova, are reported. According to the results of the kinetics of thermal decomposition, the random nucleation model is shown to be the one that is relevant to the decomposition of single rare earth (Gd) containing material and contracting sphere to the decomposition of the substituted (Gd-Ba) one. The kinetic parameters viz. the order of reaction, frequency factor and energy of activation using above-mentioned models, are computed and shown to bear reasonably good agreement.     

凝胶体系中混合羧酸钾对草酸钙结晶的调控作用

酒石酸钾(K₂tart)、柠檬酸钾(K₃cit)和乙二胺四乙酸钾(K₂edta)均可用于防治草酸钙(CaOxa) 结石, 但它们各有其优缺点. 本文采用双扩散法比较研究了这3种羧酸钾以不同比例两两混合时对CaOxa结晶的影响, 结果表明, 混合剂或者能够诱导更多的二水草酸钙(COD)和三水草酸钙(COT)晶体, 或者减小一水草酸钙(COM)的尺寸, K₂edta-K₃cit混合剂还能诱导(100)晶面减小、螺旋式生长的COD晶体, 该COD与肾小管细胞膜的粘附力较弱. 这些均有利于抑制草酸钙结石形成, 表明混合剂的防石效果优于单一钾盐.     

Growth of single crystals of some complex salts in silica gels

Single crystals of ammonium nickel sulphate, potassium nickel sulphate, ammonium alum and potassium alum are grown in sodium-metasilicate gels. The method of gel preparation and growth procedure are described. Both single diffusion and double diffusion methods are used. Studies on nucleation and characterisation of crystals are also reported. Crystals grown are illustrated.     

In-vitro crystallization of spherulites of monosodium urate monohydrate

Sherulitic and an aggregate of bow shaped crystals of monosodium urate monohydrate which had a close resemblance to that of those crystals found in gouty synovial fluids and articular cartilage have been grown using tetramethoxysilane and silica gel.Thermogravimetric analysis (TGA), and infrared (IR) and X-ray diffraction were used to analyse the grown samples. Crystals were obtained for a wide range of pH (3–10), without using any biological component at room temperature and were found to be monohydrate form of monosodium urate.     

Growth of anthraquinone crystals by gel aided solution technique and their characterization

Anthraquinone, an oxidation product of anthracene, has been grown by gel aided solution technique employing sodium metasilicate. Needle shaped crystals were obtained in 0–5% (w/v) solution of anthraquinone for pH 5-5. The grown crystals were characterized by optical microscopy, SEM, IR, UV and XRD.