Layered metal-organic polymer [Co(L) 6 ](NO 3 ) 2 was obtained (where, L = C 3 H 4 N 2 ) and structurally characterized by X-Ray diffraction (XRD) analysis.Crystals have trigonal structure: a = b = 12.3555(10) Ǻ, c = 14.4833(3)Ǻ; α = β = 90˚; γ = 120˚; V = 1914.78(5)Ǻ; R3, Z = 3.The structure of the complex consists of discrete [Co(L) 6 ] 2+ cations and 3 NO -anions.The Co 2+ ion has a centrosymmetric octahedron configuration with a coordination site-CoN 6 .The ligand is coordinated monodentate through the pyridine nitrogen atom (N3) to the Co 2+ ion with an average Co-N bond distance of 2.1590 Ǻ. Molecules in the coordination polymer are additionally linked by intermolecular hydrogen bonds through the pyrrole nitrogen atom (-N-H) and oxygen of the nitrate group with the formation of a polymer chain of the type: N-H…O.The chains are linked in layers along the (001) plane.
The synthesis and structures of two novel zwitterionic ruthenium triazolato complexes are reported. The treatment of the ruthenium azido complex [Ru]-N3 (1, [Ru] = (η5-C5H5)(dppe)Ru, dppe = Ph2PCH2CH2PPh2) with an excess of ethyl propiolate in CHCl3 or CH2Cl2 under ambient conditions for 15 days results in the formation of a mixture of the Z- and E-forms of N(1)-bound ruthenium 3-ethylacryl-4-carboxylate-3H-1,2,3-triazolato complexes [Ru]N3(CH=CHCO2Et)C2H(CO2) (Z-3) and (E-3) in a ratio of ca. 5:2. The structures of E-3 and Z-3 were confirmed by single-crystal X-ray diffraction analysis and fully characterized by 1H, 31P, 13C NMR and IR spectroscopy, mass spectrometry, and elemental analysis. The negatively charged carboxylate moieties of the zwitterionic ruthenium triazolato complexes Z-3 and Z-3 are highly nucleophilic and reactive toward a variety of electrophiles, making Z-3 and Z-3 potential starting materials for the development of biologically active 1,2,3-triazole derivatives.
Crystal shape distribution, i.e. the multidimensional size distribution of crystals, is of great importance to their down-stream processing such as in filtration as well as to the end-use properties including the dissolution rate and bioavailability for crystalline pharmaceuticals.Engineering crystal shape and shape distribution requires knowledge about the growth behavior of different crystal facets under varied operational conditions e.g.supersaturations.Measurement of the facet growth rates and growth kinetics of static crystals in a crystallizer without stirring has been reported previously.Here attention is given to study on real-time characterization of the 3D facet growth behavior of crystals in a stirred tank where crystals are constantly moving and rotating.The measurement technique is stereo imaging and the crystal shape reconstruction is based on a stereo imaging camera model.By reference to a case study on potash alum crystallization, it is demonstrated that the crystal size and shape distributions (CSSD) of moving and rotating potash alum crystals in the solution can be reconstructed.The moving window approach was used to correlate 3D face growth kinetics with supersaturation (in the range 0.04 -0.12) given by an ATR FTIR probe.It revealed that {100} is the fastest growing face, leading to a rapid reduction of its area, while the {111} face has the slowest growth rate, reflected in its area continuously getting larger.
Unconventional ways to improve the efficiency of purification of two different semiconductor materials of current interest, ZnO and Ge, are described. It is shown that, by using chemically assisted vapour transport of ZnO with carbon as a transporting agent, the degree of chemical purity of ZnO can be increased by more than an order of magnitude. It is also found that heating of the molten Ge in the experimentally determined narrow (about 20?C wide) temperature range in which an intense evaporation of certain substances is observed, leads to a significant reduction of germanium contamination. As a result, a subsequent deep purification of pre-heat treated germanium by zone refining can be achieved at twice reduced (as compared with “non-treated” Ge) number of passes of a boat with germanium through the melting zones. Thus, the Ge purification process becomes faster, cheaper and more efficient.
A single scan has been performed in Differential Scanning Calorimetry (DSC) at a heating rate of 15oC/min under non-isothermal conditions to investigate the crystallization kinetics of glassy Se90Sb10-xAgx alloys (where x = 2, 4, 6, 8). For this purpose, Handerson’s theory based on non-isothermal method for thermal analysis of single-scan DSC data has been used. The activation energy of crystallization and order parameter has been determined and composition dependence of these parameters has been discussed.
Crystal nucleation is important to control the product properties in industrial crystallization processes. To investigate crystallization phenomena, methods which rely on microscopic volumes have gained relevance over the last decade. Microfluidic devices are suitable for carrying out crystallization experiments based on a large set of individual droplets in the nanoliter range. In this work, we propose a simple method to manufacture such devices from polycarbonate as an alternative to conventional chips made of poly (dimethylsiloxane). The microfluidic device consists of two main functional parts: A T-junction for droplet generation and a section for storage and observation of up to 400 individual droplets. Using these manufactured devices, it is easy to produce and store highly monodisperse droplets of substances that require either a hydrophilic or hydrophobic surface of the microchannel. Since crystal nucleation is a stochastic process which depends on the sample volume, a reproducible droplet volume is of great importance for crystallization experiments. The versatile applicability of the manufactured devices is demonstrated for substances which are used in different crystallization applications, for example, solution crystallization (aqueous potassium nitrate solution) and melt crystallization (ethylene glycol distearate). Finally, we demonstrate that the manufactured microfluidic devices in our experimental setup can be used to conduct crystal nucleation measurements. Based on these measurements we discuss our results with respect to state-of-the-art nucleation models.
In the present work, undoped (SnO2) and fluorine-doped tin oxide (FTO) thin films were prepared by sol-gel process using a solution composed of (SnCl2, H2O), (NH4F), and ethanol mixture. The fluorine concentration effect on structural, optical and electrical properties of SnO2 films is investigated. The electrical properties of FTO films prepared by sol gel remain relatively lower than the ones deposited by other techniques. In present paper, we try to elucidate this difference. Films composition and the FTIR analysis, of films and formed precipitate during film growth, indicate that few amounts of fluorine are incorporated in SnO2 network, most of fluorine atoms remain in the solution. The films resistivity is reduced from 1.1 Ω·cm for undoped films to 3 × 10-2 Ω·cm for 50 wt.% doped FTO, but remains higher than the reported ones in the literature. This high resistivity is explained in terms of fluorine bonding affinity in the solution.
An analytical investigation is conducted to study the effect of magnetic field on convection heat transfer through packed porous beds which consists of a horizontal fluid layer (river bed) and a porous zone with anisotropic permeability and underlined by a surface heated by a constant temperature T1. The free surface of the fluid layer overlying the horizontal porous layer receives solar rays to length of day and is then considered heated isothermally at temperature T2 such as T1 < T2. Flow in porous medium is assumed to be governed by the generalized Brinkman-extended Darcy law and in the fluid layer by the Navier-Stokes model. The Beavers-Joseph condition is applied at the interface between the two layers. The influence of Hartmann number and hydrodynamic anisotropy on the convective phenomenon is investigated analytically. It is found that the magnetic field, the anisotropic permeability and the thickness of the porous lining, e, have a strong influence of the geothermal convective flow and the heat transfer rate.
Batch crystallization studies of curcumin from hydrotropic solutions of sodium cumenesulphonate (NaCS) and of cinnamic acid from a photosensitive hydrotropic medium of sodium cinnamate (Na-CIN) were carried out, in an agitated reactor for the effect of alternate heating and cooling cycles on crystal morphology. The crystal characterization by Scanning electron microscopy (SEM) and crystal size distribution (CSD) showed formation of spheroidal curcumin crystals while cinnamic acid formed porous aggregates when subjected to thermal cycles. The UV irradiation of cinnamic acid however showed no formation of the aggregates. The type of hydrotrope used and the initial crystal morphologies of curcumin and cinnamic acid are shown to be important factors to result in a different behaviour of the crystal morphology upon thermal cycles. The CSD data were effectively used for estimation of nucleation and growth rate parameters.
Purification is a primary application of zone melting, in which the improvement of efficiency, production yield and minimum achievable impurity level are always the research focus due to the increasing demand for high purity metals. This paper has systematically outlined the whole development of related research on zone refining of metals including basic theories, variants of zone refining, parametric optimization, numerical models, and high purity analytical methods. The collection of this information could be of good value to improve the refining efficiency and the production of high purity metals by zone refining.
This paper presented the first part of the studies about the development of a tool for groundwater contamination prediction, conducted by the Laboratory of Sciences and Technology of Water (UAC/Benin). The investigation made consisted in estimating the combined effect of retardation factor and biodegradation on migration processes of leachate, in the underlying soils of household waste dumpsites, without active safety barrier. Leachate infiltration tests for different initial conditions were made on soil columns and the breakthrough curves were traced for electrical conductivity, the 5 day biochemical oxygen demand (BOD5) and total kjeldahl nitrogen TKN. A mathematical migration model was developed and solved numerically by finite difference method and implemented with Matlab R2013a. Thus, the calibration of the model was made with electric conductivity data by determining the dispersion coefficient of the studied soils (D = 0.96 cm2/min). Simulations for model verification showed that the established model can perfectly predict the migration of biodegradable organic pollution (BOD5) but did not give conclusive results for the monitoring of nitrogenous organic matter (TKN). The influence of the retardation factor on the migration of biodegradable organic pollutants in soils was linear, while the biodegradation rate of the organic material on migration showed an exponential pattern.
It is known that the dense part of any liquid metal consists of ramified clusters of almost regular tetrahedrons (triangular pyramids with atoms in their vertexes) that are connected into chains by faces. Any metal additive as a second component of liquid alloy can be both beyond these clusters as separated atoms and into them as inherent clusters. The liquid-metal alloy transfers into the second state, at the first eutectic of the solvent. This polymorphic transition of liquid matrix is discovered in the systems, Pb-K and Na-Pb, by molecular-dynamic simulating their microstructure and in experiments on scattering slow neutrons by these alloys of different compositions. In the first system, the obtained results identify both the homogeneous alloy at low concentrations of potassium in liquid lead and the alloy clustering, (Pb4K)n, at potassium concentrations following the eutectic, Pb0.91K0.09. In the second one at the concentrations of lead more than 2%, just the second state is discovered with the clusters, (Na4Pb)n. One can expect the same polymorphic transition in the eutectic, Na0.93Tl0.07, with the micro-inhomogeneity, (Na6Tl)n, and with the melting point of 64 C. This eutectic maintained by the oxygen-free technology and enriched by the isotope, 205Tl, can become the best coolant for fast nuclear reactors due to the depressed chemical activity of sodium and composition stability.
Since the early 1950’s the use of Germanium has been continuously growing as new applications are being developed. Its first commercial usage as the main material, from which the semiconductors were made, was later replaced by Silicon. The applications were then shifted to a key component in fiber optics, infrared night vision devices and space solar cells, as well as a polymerization catalyst for polyethylene terephthalate (PET). With the advance development in new technologies, the attentions have been brought back to Germanium due to its excellent semiconductor properties. New applications on the field of high efficiency solar cells, SiGe based chips, LED technologies, etc., are being developed and show a great potential. According to DERA (Deutsche Rohstoffagentur/German Mineral Resources Agency), the demand for Ge will grow considerably by 2030, pushed mostly by the increase in the fiber optics market and advanced materials sector [1]. Therefore, this paper focuses on an overview of the production chain of Germanium, especially from its concentrate up to the single crystal growth of its valuable ultra-pure metallic form to be used in high technological applications.
The crystallization of ursodeoxycholic acid drug crystals in gel by reduction of solubility method is the first of its kind to be reported in literature. Monoclinic crystalline form of the structure was confirmed using single crystal X-ray diffraction analysis. This report deals with the kinetic analysis made from the thermogravimetric analysis/differential thermal analysis (TGA/DTA) data using Coats-Redfern (CR) relation. Thermodynamic parameters were also determined. Arrhenius equation for ursodeoxycholic acid was derived as k = 3.10 × 1010 e−172581/RT mol−1•s−1.
Since the early 1950’s the use of Germanium has been continuously growing as new applications are being developed. Its first commercial usage as the main material, from which the semiconductors were made, was later replaced by Silicon. The applications were then shifted to a key component in fiber optics, infrared night vision devices and space solar cells, as well as a polymerization catalyst for polyethylene terephthalate (PET). With the advance development in new technologies, the attentions have been brought back to Germanium due to its excellent semiconductor properties. New applications on the field of high efficiency solar cells, SiGe based chips, LED technologies, etc., are being developed and show a great potential. According to DERA (Deutsche Rohstoffagentur/German Mineral Resources Agency), the demand for Ge will grow considerably by 2030, pushed mostly by the increase in the fiber optics market and advanced materials sector [1]. Therefore, this paper focuses on an overview of the production chain of Germanium, especially from its concentrate up to the single crystal growth of its valuable ultra-pure metallic form to be used in high technological applications.
Freestanding membrane (FSM) of hydroxyapatite (HA) is a thin sheet of pure HA without any supporting substrates. Our original preparation process of FSM of HA had three steps: The first was the deposition of HA layer on sacrificial layer of solvent-soluble materials, the second was separation of FSM of HA by means of dissolution of sacrificial layer, and the third was post-annealing to crystallize FSM of HA. To date, the post-annealing process was a serious bottleneck of productivity owing to its too long time. In this short report, we proposed a novel sacrificial layer, heatproof and water-soluble Ba-compound, which makes the direct deposition of crystallized HA possible due to its heatproof property because the problem on the original process was that the previous sacrificial layers have no heatproof property and HA layer should be deposited as amorphous. We can deposit the Ba-compound sacrificial layer only in 1 hour followed with the direct deposition of crystallized HA layer, substituting the 20 hours of post-annealing. The FSM of HA was separated successfully from the substrate by means of dissolution of Ba-compound with water. Our novel process can shrink the process time by 19 hours.
To increase the biocompatibility of hydroxyapatite (HA), Ca 10 (PO 4 ) 6 (OH) 2 , the Sr substitution of Ca into the HA structure was effected to yield Ca 10-x Sr x (PO 4 ) 6 (OH) 2 (Sr-HA).For medical and dental applications, it is important that Sr-HA is prepared as a thin film so that the Sr fully substitutes the Ca sites in the HA structure and does not form segregated impurities consisting of Sr compounds.If the segregated Sr forms different amounts of different impurities, the dissolution of the Sr into the living body will not be reproducible across different samples.To confirm the Sr substitution into the Ca site in the HA structure, the systematic variation in the lattice constants of the Sr-HA with Sr content was evaluated as the first step.The aand c-axis lengths were found to exhibit a linear relationship with the Sr content for six samples with different Sr contents, indicating that the prepared Sr-HA thin films likely possessed partial Sr substitution into the Ca sites of the HA structure.This result is an important first step in the accurate evaluation of the biological effects of Sr-HA thin films.
The nucleation of crystals in glass obtained by blending metallurgical slag with silicon dioxide has been studied. The type of crystallization (homogeneous or heterogeneous, volume or surface) is revealed for each of nine compositions of synthesized glass. It is shown that the first crystalline phase in a volume-crystallizing glass is perovskite (CaO · SiO2); in this phase a nucleation of the main phase occurs: melilite (solid solution of gehlinite 2CaO · Al2O3 · SiO2 in akermanite 2CaO · MgO · 2SiO2). The fundamental characteristics of homogeneous (for a catalizing phase, perovskite) and heterogeneous (for a catalyzed phase, melilite) of crystallization are determined: the steady-state nucleation rate I st, time of unsteady-state nucleation τ, crystal growth rate U, and activation energy of frictional flow. The temperature dependences of I st, τ, and U are obtained. Practical recommendations are presented for the use of blast-furnace slag as a raw material for the synthesis of glass and their further utilization.
The newly synthesized CdNa2?2C2O4?2H2O crystals having a size of 0.30 × 0.25 × 0.20 mm3 were grown by the single-diffusion reaction method in the silica gel medium at 28?C temperature. The crystalline nature of crystals was determined in 20 days by 1) varying the concentrations of the feed solutions and the gel pH level, 2) changing the specific gravity of the feed solution, and 3) changing the gel aging period. The crystals were characterized by using the methods such as powder X-ray diffraction, FTIR, UV, SEM-EDAX, TGA/DTA, and micro-hardness test. The structure of as-grown crystals was determined by the powder crystal XRD patterns. FTIR & SEM-EDAX spectral analyses were used to confirm the presence of the required functional groups of as grown crystals. UV absorption spectrum, the absorption peaks at 224.64 nanometer, determined the energy gap. TGA/DTA thermo gram was used to detect the thermal stability of sodium mixed cadmium oxalate dihydrate crystals. The present grown crystals were brittle and also plastic in nature was identified by Vickers micro-hardness test.
Titania microspheres were synthesized using hydrothermal methods to exploit a new liquid chromatography stationary phase. The prepared titania microspheres were approximately 7 μm in diameter, and the particle size distribution was relatively narrow and uniform. Furthermore, the average specific surface area was 276.0 m2·g·1, the average pore volume was approximately 0.25 mL·g·1, and the pore diameter was approximately 35.9 nm for sintering titania microspheres. These parameters indicate that the titania microspheres prepared for this study have excellent surface properties for chromatography. Additionally, columns filled with the titania microspheres were able to separate basic compounds, including benzene, nitrobenzene and o-nitroanisole. It could be proposed that the titania microspheres prepared for this study would be a promising stationary phase for liquid chromatography.
