Ambalal Ranchhodhbhai Patel

Crystal growth in gel media

An attempt has been made in this review to cover the existing information on the growth of single crystals in gels. Preparation of various types of gels, in which crystals can be grown, has been briefly described. The growth of single crystals from gels is reviewed using the following classifications: (i) Crystal growth by reaction. (ii) Crystallization by complex dilution method. (iii) Crystal growth by reduction of solubility. A compact list of some important crystals grown in gels is given. Growth mechanism and nucleation problems are discussed. Morphologies of various gel-grown crystals are described. Researches on gel-grown single crystals are also briefly described.

Growth of single crystals of BaSO4 and SrSO4 from gels

Abstract Single crystals of BaSO 4 and SrSO 4 up to 2 mm in length have been grown in silica gels and identified. The progressive deterioration in crystal quality with the increasing size observed in the present work has been studied and is attributed to the incorporation of gel during growth. The amount of gel inclusion is found to increase with the increasing size of the crystal producing opaque and poorly faceted crystals. The effect of temperature on the crystal morphology has been studied. It is observed that at a temperature of 35°C, crystals with {011} and {120} habit faces grow, while at about 20°C additional {001} faces appear. Also, interpenetrating twinning of these crystals occur at this temperature.

Gel growth of single crystals of barium and strontium tungstates

Abstract An account of the growth of single crystals of the tungstates of barium and strontium in gels has been presented. While “impure” gel has been found to produce three-dimensional spherulites, good quality single crystals have been obtained by using “pure” gel. Some aspects, such as (i) crystallization apparatus, (ii) effect of pH value, temperature, and concentration changes in reactants, have been studied and described. A simple procedure to contrl nucleation sites in gels has been adopted, which has resulted into a dramatic increase in the size of the crystals.

Nucleation and growth of KClO4 single crystals in silica gels

Abstract As part of a continuing effort on the growth of KClO 4 single crystals in gels, this paper describes the variation of nucleation density and growth of these crystals as a function of concentration of feed solution, gel ageing, gel density, gel pH and intermediate neutral gel column. While high density and high pH gels have been found to produce opaque crystals, good quality transparent single crystals have been obtained at low density and low pH gels. It is observed that the intermediate neutral gel column and gel ageing considerably reduce the number of nucleation sites. A simple procedure to control nucleation sites in gels has been adopted, which has resulted in a dramatic increase in the size of the crystals.

Growth of single crystals of KClO4 in silica gels

Single crystals of KClO4 up to 20 × 10 × 6 mm size have been grown in silica gels at ambient temperature and identified by X-ray diffraction and suitable chemical analysis. The crystals are grown with different crystallization apparatus, different reactants and the effect of reaction waste products on crystal quality and size has been studied. The effect of concentration of reactants on habit modification has also been studied. It is observed the at lower concentration of reactants, crystals with large {101}, {210} and smaller {001} habit faces grow, while at higher concentrations, {001} faces disappear and the crystal grow in the form of needles. Cups have been observed during the growth of these crystals.

Growth of strontium tartrate tetrahydrate single crystals in silica gels

Growth of single crystals of strontium tartrate tetrahydrate by controlled diffusion in silica gels has been narrated. In the field of material science, there is always a keen and competitive race to grow perfect single crystals with sufficient purity and perfection. Successful attempts to larger as well as more perfect crystals of SrTr are described in this paper and thus probably the largest (about 2 in. across) ever grown size of gel-grown products is reported here. The effect of several parameters, e.g. crystallization apparatus, environmental temperature, reactant concentration, gel density, gel-ageing and gel pH, on the size, quality and morphology of the crystals has also been studied.

Growth features of PbS crystals grown in silica gels

Growth patterns on cube and octahedral faces of PbS crystals grown in silica gels at room temperature, and the etch pattern of growth strata on a crystal cleavage are described. The observations are discussed in relation to the mechanism and conditions of crystal growth.

Gel growth and perfection of orthorhombic potassium perchlorate single crystals

Abstract The present paper describes detailed studies made on the growth and perfection of potassium perchlorate (KClO 4 ) single crystals. Studies of various reactants on the growth of these crystals have been discussed. The advantages and disadvantages of different acid set gels to grow these crystals have also been discussed. It has been shown that in test tube experiments, percholic acid set gels are better, whereas in a beaker-single tube system, organic acid set gels yield better results than the mineral acid set gels. The effect of temperature on nucleation, growth and morphology of these crystals has been studied. It has been found that the nucleation density decreases as the temperature increases. A mixture of 36N H 2 SO 4 and 0.25M Na 2 SO 3 in the volume ratio 1 : 1 has been found to reveal as grown as well as freshly introduced dislocations in these crystals.

Growth of mixed Sr1−xCaxC4H4O6 crystals in gel

Abstract Mixed crystals of strontium-calcium tartrates of different configurations have been grown for the first time in silica gels. Growth in a more convenient and simple apparatus has been accomplished and described here. Suitable chemical and X-ray diffraction methods have been employed for the characterization of grown crystals.

Growth of barium sulphate single crystals by chemically reacted flux method

A mixture of analytical grade Na2SO4 (melting point 884 °C) and BaCl2 (melting point 925 °C) is heated in a platinum crucible in a muffle furnace to a temperature of 1000 °C for 1 hour and then gradually allowed to cool down to room temperature. It is observed that the following reaction in the molten state has taken place: Na2SO4+BaCl2→2NaCl+BaSO4 During cooling BaSO4 crystals have been formed. Examination by X-rays and also by cleaving and etching have shown them to be perfect single crystals. Thus a new method of growing BaSO4 single crystals has been reported. The implications are discussed.