Microwave assisted synthesis of hydroxyapatite nano strips

Synthesis of hydroxyapatite (HAP) nano strips was carried out by chemical precipitation method followed by microwave irradiation. The microwave assisted reactions proceed at fast rates. It is found that the presence of the complex reagent EDTA plays an important role in the morphological changes of nanostructure hydroxyapatite. EDTA acts as a hexadentate unit by wrapping itself around the Ca²⁺ metal ion with, four oxygen and two nitrogen atoms and forms several five member chelate rings. The relative specific surface energies associated with the facets of the crystal determines the shape of the crystal. Scanning electron microscopy revealed the presence of hydroxyapatite nano strips with the range 50‐100 nm in EDTA influenced HAP powders. Fourier transform‐infrared spectroscopy (FT‐IR) result combined with the X‐ray diffraction (XRD) indicates the presence of amorphous hydroxyapatite (HAP) in the as‐prepared material. X‐ray patterns collected on the powder after heat‐treatment at 1100 °C for 2 h in air exhibits single phase of HAP. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

X‐Ray Powder Diffraction,DTA and Vibrational Studies of CdNH4PO4.6H2O Crystals

Cadmium Ammonium Phosphate Hexahydrate (CAPH) is analogous to naturally occurring struvite. CAPH crystals are grown by slow evaporation technique. These crystals are characterised by X‐ray, TG‐DTA and Infra‐red studies. Powder X‐ray pattern indicates the orthorhombic crystal structure analogous to struvite. TG‐DTA analysis suggests loss of water of hydration (6H₂O) between 113 and 391°C. Later the substance melts and only Cd remains around 780 °C. Infra Red spectrum is characteristic of H₂O, PO₄^3‐ and NH₄⁺ radicals.     

Electron microscopy of biomaterials based on hydroxyapatite

Three types of biomaterials based on hydroxyapatite are synthesized and investigated. Hydroxyapatite nanocrystals or microcrystals precipitated from low-temperature aqueous solutions serve as the initial material used for preparing spherical porous granules approximately 300–500 μm in diameter. Sintering of hydroxyapatite crystals at a temperature of 870°C for 2 h or at 1000°C (for 3 h) + 1200°C (for 2 h) brings about the formation of solid ceramics with different internal structures. According to the electron microscopic data, the ceramic material prepared at 870°C is formed by agglomerated hydroxyapatite nanocrystals, whereas the ceramics sintered at 1200°C (with a bending strength of the order of 100 MPa) are composed of crystal blocks as large as 2 μm. It is established that all the biomaterials have a single-phase composition and consist of the hydroxyapatite with a structure retained up to a temperature of 1200°C.     

Optical,mechanical and thermal properties of p‐bromoacetanilide

Solubility and metastable zonewidth were estimated for p‐Bromoacetanilide. Employing slow evaporation method crystals of size 22x17x6 mm³ and 38x25x10 mm³ were grown at a constant temperature of 40°C and room temperature respectively from methanol solution. The cell dimensions were obtained by single crystal X‐ray diffraction study. The placement of protons was identified from NMR spectral analysis. UV‐Visible and fluorescence spectral analyses were carried out for the grown crystals. Vickers microhardness test was performed on the prominent (110) of the as grown crystal. Thermogravimetric and differential scanning calorimetric studies were carried out to determine the thermal properties of the grown crystal. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Synthesis,spectral and thermal properties of non‐linear optical crystal ZnMg(SCN)4

Single crystals of zinc magnesium tetra thiocyanate [ZnMg(SCN)₄], a bimetallic thiocyanate complex, were grown by slow evaporation solution growth technique at room temperature. The bright, transparent and colourless crystals have well defined faces. The grown crystals were characterized through elemental analysis, powder X‐ray diffraction (XRD), thermogravimetric (TG) and differential thermal analysis (DTA), differential scanning calorimetric analysis (DSC), Fourier Transform Infra red (FTIR) and Optical studies. The elemental analysis confirms the stoichiometry of the synthesized crystals. The compound crystallizes under monoclinic structure with lattice parameters a = 10.055 Å, b = 7.44 Å, c = 6.00 Å and β = 90.113°. The TGA indicates 25 % weight loss at 205°C from which the decomposition pattern is formulated. The DSC study indicates that the crystal undergoes only first order phase transitions. The FTIR spectrum indicates among others the presence of metal‐nitrogen and metal‐sulphur bonds thus confirming the formation of the complex. The second harmonic‐generation (SHG) was confirmed by the emission of green radiation using Nd: YAG laser. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth of barium oxalate crystals in agar–agar gel and their characterization

Single crystals of barium oxalate have been grown by gel method using agar‐agar gel as media of growth at ambient temperature. The optimum conditions were established by varying various parameters such as concentration of gel, concentration of reactant, gel setting time etc. Prismatic platy shaped transparent crystals were obtained. The grown crystals were characterized through powder X‐ray diffraction (XRD), Fourier transform infrared (FT‐IR) studies, Thermogravimetric (TGA) and Differential thermal analysis (DTA). The compound crystallizes under monoclinic structure with lattice parameters a = 6.6562 Å, b = 8.0464 Å, c = 2.8090 Å, β= 96.832°, and V = 149.38 ų. The FT‐IR spectrum indicates OH and carbonyl group along with the presence of metal‐oxygen bond. The TGA indicates 17.75% weight loss at 550°C from which the decomposition pattern is formulated. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A novel thermolysis method of colloidal protein precursors to prepare hydroxyapatite nanocrystals

A novel thermolysis method of colloidal protein precursors is introduced to prepare hydroxyapatite (HAP) nanocrystals. The colloidal protein precursors are sonochemically synthesized from saturated Ca(OH)₂ aqueous solution, Ca(H₂PO₄)₂ aqueous solution and bovine serum albumin (BSA) molecules. The colloidal protein precursors are amorphous and composed of 15‐90 nm near spherical calcium phosphate nanoparticles and BSA molecules. The particle size analysis shows the volume particle size distribution is from 9.0 nm to 222.6 nm and the volume‐averaged particle size is 45.8 nm. During the calcination procedure BSA molecules are burningly removed and the HAP nanocrystals can be obtained at 500 °C. The effects of BSA concentration on the properties of samples are discussed. Results show that BSA combustion can promote the transformation of crystalline HAP from amorphous material. Moreover, the increase of BSA concentration reduces the crystalline sizes of HAP crystals and the crystallinity of product. With BSA concentration of 5 g/L, the obtained HAP nanocrystals are mainly 25∼100 nm similar spherical nanoparticles besides some 40∼70 nm×75∼150 nm short rod‐like crystals. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Studies on multiphased mixed crystals of NaCl,KCl and KI

Multiphased mixed crystals of NaCl, KCl and KI were grown by the melt method, for the first time. Densities and refractive indices of all the grown crystals were determined and used for the estimation of the composition in the crystal. Atomic absorption spectroscopic measurements were done to estimate the metal atom contents in the crystal. Lattice parameters and thermal parameters (Debye‐Waller factor, mean square amplitude of vibration, Debye temperature and Debye frequency) were determined from the X‐ray powder diffraction data. DC and AC electrical measurements were done at various temperatures ranging from 40 to 150°C. Activation energies were also estimated. The observed lattice parameters showed that the system exhibits three phases each nearly corresponds to NaCl, KCl and KI. The thermal and electrical parameters show a highly nonlinear bulk composition dependence. Results are reported. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Thermal behavior of biogenic apatite crystals in bone: An X‐ray diffraction study

The thermal behavior of the bovine bone mineral and synthetic stoichiometric hydroxyapatite was investigated by X‐ray diffraction. The bone samples in solid (planar oriented pieces) and in powder form were examined to elucidate how the microstructural and textural properties of bone mineral are modified under heating. As could be expected, the thermal behavior of the bone mineral depends not only on the structural distortions, but also on the crystal habit, texture and ordering of biocrystals in tissue. The temperature growth of biogenic apatite crystals, unlike synthetic hydroxyapatite, is seen to be nonmonotonic and multi‐staged. At 600 to 700°C the biomineral crystallites grow rapidly due to disappearance of the mosaic structure as the lattice imperfections are annealed. After heating between 700°C and 900°C the bone mineral appears to be composed of roughly equidimensional ≥200 nm crystals. The further growth of the crystals in the range from 900 to 1300°C occurs by the mass transport mechanism, supporting the idea that the bone mineral is not a discrete aggregation of crystals, but rather a continuous mineral phase with direct crystal‐crystal bonding. Estimates are presented to show the important role of the surface mass transport mechanism in the growth of apatite crystals. The material obtained by heating a cortical bone fragment between 900°C and 1300°C turns out to be composed of two crystal types: crystals oriented along the bone axis (major morphology) and those of differing shape and orientation (minor morphology). The heating‐induced variations in the longitudinal and transverse dimensions of differing‐morphology crystals are found to be coherent. Small amounts of CaO, MgO and other crystalline phases are seen to be formed in the bone mineral under heating. © 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim     

Nucleation kinetics and growth aspects of organic nonlinear optical L‐arginine trifluoroacetate single crystals

Experimental determination of solubility, metastable zonewidth and induction period for an organic nonlinear optical (NLO) L‐arginine trifluoroacetate (LATF) crystal is reported. The interfacial tension for different supersaturation conditions has been estimated for the LATF solution at 45°C. Bulk crystal of dimensions 57x5x3 mm³ has been grown by temperature lowering technique using optimized growth parameters. Powder X‐ray diffraction and FTIR studies confirm the crystalline nature and the functional groups of the grown crystals respectively. Linear optical property of the grown crystal has been studied by UV‐Vis spectrum. Thermal analyses have revealed that the compound is thermally stable upto 212°C. Kurtz powder SHG test confirm the nonlinear optical properties of the as‐grown LATF crystal. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Crystal structure,spectroscopic studies and non‐linear optical properties of 2‐amino‐3‐nitropyridinium trichloroacetate

A new quadratic nonlinear optical crystal, 2‐amino‐3‐nitropyridinium trichloroacetate (2A3NPTCA), was synthesized and the single crystals were grown by slow evaporation method at room temperature. Single crystal X‐ray diffraction and powder X‐ray diffraction experiments were carried out in order to confirm the structure and crystalline nature of 2A3NPTCA crystal. The chemical bonding and various functional groups present in the 2A3NPTCA were identified from FT‐IR spectrum. The UV–visible–NIR transmission spectrum shows that it is suitable for frequency‐converting in the wavelength region of 431–1200 nm. Thermogravimetric (TG) and differential thermal analysis (DTA) were carried out to characterize the thermal behaviors of the grown crystals. Kurtz and Perry powder method for second harmonic generation (SHG) measurements demonstrate that 2A3NPTCA is a phase matching material and its nonlinear optical efficiency is two times that of KDP. All the above results suggest that 2A3NPTCA is a potential candidate of NLO material.     

Microstructural characterization of CPPD and hydroxyapatite crystal depositions on human menisci

Meniscus is a fibrocartilaginous tissue composed mainly of water and a dense elaborate collagen network with a predominantly circumferential alignment. Crystal formation and accumulation on meniscal tissue is frequently observed especially in elderly. In this study, we used X‐ray diffraction (XRD), FTIR and FT‐Raman for the structural identification of the depositions and Optical microscopy, Scanning Electron microscopy (SEM/EDX) and Atomic Force microscopy (AFM), in order to investigate the structural relationship between the crystal deposits and the collagen fibers of human meniscal tissues. We are reporting on the formation of intercalary “colonies” of Calcium Pyrophosphate Dihydrate (CPPD) crystals with two distinct morphologies corresponding to the monoclinic and the triclinic phase, as well as the formation of micro‐aggregations composed of nano‐crystalline HAP aggregations which are developed along the longitudinal axis of collagen fibers without extensively disturbing the collagens arrangement.     

Growth and Characterization of a New Nonlinear Optical Crystal: Bis Thiourea Zinc Chloride

Bis Thiourea Zinc Chloride (BTZC) a new semiorganic nonlinear optical material has been synthesized. The solubility studies have been carried out in the temperature range 30°‐ 55°C. Single crystals of BTZC have been grown by slow evaporation of saturated aqueous solution at room temperature. The lattice parameters of the grown crystals have been determined by single crystal X‐ray diffraction technique. The UV‐Vis‐NIR transmittance spectrum has been recorded in the range 200‐2000 nm. The FT‐IR spectrum has been recorded in the range 400‐4000 cm^‐1 and the spectral bands have been compared with similar thiourea complexes.     

Structural and optical investigations on Mn doped Li2B4O7 crystals

Lithium tetraborate crystals have great demand due to its non‐critical phase matching at 90°. Transparent and good optical quality single crystals of undoped and Mn doped Li₂B₄O₇ were grown by Czochralski technique in air atmosphere. The crystalline phase was determined by X‐ray diffraction. Doping of Mn in the grown crystals was confirmed by energy dispersive analysis of X‐rays (EDAX) technique. Transmission spectra show that the crystal is transparent in the visible region. Birefringence interferograms were recorded to qualitatively analyse the optical homogeneity of the grown crystals and to quantify the birefringence of the samples in desired crystal direction. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth,spectral and thermal studies of ibuprofen crystals

RS ‐Ibuprofen was crystallized for the first time in silica gel under suitable pH conditions by reduction of solubility method. The grown crystals were characterized by single crystal X‐ray diffraction and density measurement. The functional groups present in the crystal were identified using Fourier transform infrared spectroscopy. Optical bandgap energy of ibuprofen was estimated as 3.19(3) eV from UV‐Vis spectrum. Thermogravimetric analysis revealed that ibuprofen is thermally stable upto 102.9 °C and the initial loss of mass was due to evaporation only. Morphological study showed that the growth is prominent along b‐axis and the prominent face is {100}. (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of semi organic nonlinear optical LHPCL crystals

The growth of single crystals of L‐histidinium perchlorate (LHPCL), a semi organic nonlinear optical material with dimension upto 5 × 6 × 2.5 mm³ is reported. Good optical quality single crystals were grown from aqueous solution by slow solvent evaporation technique. The grown crystals were characterized by single crystal X‐ray diffraction (XRD), FT‐IR and optical transmission studies. Thermal studies confirm that LHPCL has a fairly high thermal stability (272°C) when compared with other members of histidine family. The scanning electron microscopy (SEM) provides information on the quality of the samples and grain distribution over the surface of the sample. The dielectric constant and dielectric loss of the compound were measured at different frequencies, and also at varying temperatures and the results of these experiments are discussed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Terrestrial and space-grown HAP and OCP crystals: effect of growth conditions on perfection and morphology

This paper reports comparative characterizations of calcium phosphate crystals grown on earth and in space. At the CaCl2 and KH2PO4 + K2HPO4 solution concentrations and the pH used, only hydroxyapatite (HAP) crystals grow under terrestrial condition while both HAP and octacalcium phosphate (OCP) crystals grew during the space experiment. The space-grown OCP crystals reach 3 mm in size, the space-grown HAP crystals reach sizes up to 100 times larger than the earth-grown crystallites. It was found also that the space-grown crystallites are more perfect than the terrestrial ones, being more stable under electron beam during HRTEM examination. Spherolites of hydroxyapatite consist of small and thin HAP crystals with different orientations. Space-grown OCP crystals containing almost pure OCP phase show strong striations along the c direction due to thickness variations. Terrestrial OCP crystals grown at lowest supersaturation on earth may be almost as large as the space-grown ones, possess a regular habit and are homogeneous in thickness. However, they always contain substantial regions of HAP structure. Also, in these crystals electron irradiation induces phase transformation from crystalline to amorphous (disordered) state during transmission electron microscopy observations. In the space-grown crystals, such transformation needs longer radiation time. We believe that the differences described above come from much lower supersaturation and different pH for crystals nucleating and growing in space compared to those formed on earth.     

Growth and characterization of cadmium magnesium tetra thiocyanate crystals

Cadmium Magnesium Tetra Thiocyanate, CdMg(SCN)₄, [CMTC] belongs to bimetallic thiocyanate complexes. CMTC crystals has been grown by solution growth technique at room temperature. The morphologies of the grown crystals are identified by single crystal analysis. Also the Powder X‐ray Diffractogram of the crystal has been recorded and the various planes of reflection are identified. The title compound crystallizes under triclinic structure with lattice parameters a = 10.0976 Å, b = 7.5015 Å, c = 5.7720 Å and β = 90.2135°. The presence of magnesium and cadmium in the grown crystals were confirmed through Atomic Absorption Spectroscopy. The grown crystals are analysed qualitatively by Fourier Transform Infrared (FTIR) and Fourier Transform Raman spectral measurements. The transmittance spectrum of the crystal in the UV‐Visible region has been recorded and analysed. The dielectric measurements for the crystals were carried out in the microwave region. The thermal stabilities of the crystals were studied by using different thermal analyses like Thermo Gravimetric Analysis (TGA), Differential Thermal Analysis (DTA) and Differential Scanning Calorimetry (DSC). (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth,optical and thermal studies of nonlinear optical L‐arginine perchlorate single crystals

A potentially useful semiorganic nonlinear optical (NLO) material, L‐arginine perchlorate, has been synthesized and bulk crystals have been grown by slow cooling technique. The grown crystals were characterized by single crystal X‐ray diffraction, UV‐Vis‐NIR spectroscopy, FT‐IR, thermal analysis and SHG measurements. The grown crystals were thermally stable upto 153°C and exhibit SHG efficiency of about 0.17 with respect of Urea. The etching studies have been carried out on the grown crystal. LAPC has good optical transmission not only in the visible range, however, also in the near UV part of the spectra and hence it is a potential material for nonlinear frequency conversion. The refractive index was measured by the Brewster's angle method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Growth and characterization of a new semi organic NLO material: L‐tyrosine hydrochloride

Single crystals of L‐Tyrosine hydrochloride were grown by using the submerged seed solution method. The grown crystals were characterized by using single crystal X‐ray diffraction. Functional groups and the modes of vibrations were identified by FTIR spectroscopy. The TGA/DTA studies showed that the crystal is stable up to 232°C. Microhardness study revealed that the crystal is a hard material. It is transparent in the entire visible region. The SHG efficiency was determined by the Kurtz and Perry method. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)