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...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.展开更多
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 r...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.展开更多
Triglycine sulfate crystal and potassium bromide doped triglycine sulfate crystals were grown from aqueous solution by slow evaporation method. Energy dispersive X-ray analysis identifies the elements present in the c...Triglycine sulfate crystal and potassium bromide doped triglycine sulfate crystals were grown from aqueous solution by slow evaporation method. Energy dispersive X-ray analysis identifies the elements present in the crystal. The Fourier Transform Infrared spectroscopy has been recorded in the range 400 to 4000 cm-1 and the functional groups of the grown crystals have been identified. The structural studies on the grown crystals were carried out by X-ray diffraction analysis technique and found that the grown crystal crystallizes in monoclinic structure. The lattice cell parameters of pure Triglycine sulfate are a = 9.6010 ?, b = 12.5600 ?, c = 5.4500 ?. Ultraviolet-Visible spectra show that the grown crystals have wide optical transparency in the entire visible region.展开更多
Kinetics of the decomposition of racemic ibuprofen crystals were studied by non-isothermal analysis. Thermogravimetric analysis revealed that ibuprofen is thermally stable up to 152.6°C and the initial loss of ma...Kinetics of the decomposition of racemic ibuprofen crystals were studied by non-isothermal analysis. Thermogravimetric analysis revealed that ibuprofen is thermally stable up to 152.6°C and the initial loss of mass was due to evaporation only. Activation energy, pre-exponential factor, activation entropy and Gibbs free energy for the decomposition of ibuprofen were determined using the integral method of Coats-Redfern (CR). Geometrical contraction models were found to be the best fits. The Arrheinus equation for the thermal decomposition of ibuprofen is k = (1.1 × 107) e–79125/RT sec–1.展开更多
The phosphate mineral struvite is basically formed in urinary tracks and kidney. One of the analogous compounds of struvite is potassium magnesium phosphate hexahydrate (KMgPO4·6H2O), known as struvite-k crys...The phosphate mineral struvite is basically formed in urinary tracks and kidney. One of the analogous compounds of struvite is potassium magnesium phosphate hexahydrate (KMgPO4·6H2O), known as struvite-k crystal and found in animal urinary calculi. In the present investigation, struvite-k crystals were grown by single diffusion and double diffusion techniques in agar gelmedium. The grown crystals were analyzed by optical microscopy, scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDXA) and thermogravimetric analysis (TGA). Optical microscopy and SEM exhibited the different morphologies. The FTIR spectra revealed the presence of water molecules, stretching and bending vibrations of phosphate (PO4) ions. However the powder XRD results from the crystalline nature. Elemental composition in the crystal was obtained by EDXA, while 36.89% weight loss of water molecules is observed in TGA study.展开更多
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 diss...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.展开更多
Nano-composite, perovskite Ba(1- x - y)Sr(x)TiFe(y)O3, denoted as (BSTFe) in powder form was derived via sol-gel (SG) method followed by sintering at fixed temperature 750℃ for one hour. The chemical composition, mor...Nano-composite, perovskite Ba(1- x - y)Sr(x)TiFe(y)O3, denoted as (BSTFe) in powder form was derived via sol-gel (SG) method followed by sintering at fixed temperature 750℃ for one hour. The chemical composition, morphology and structure of the powder samples were investigated by using X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The XRD characterization indicates formation of a cubic crystalline phase in the pure BST. A well defined perovskite phase with nano-crystallite sizes equal to about 34 nm was achieved from XRD for B10ST3F sample, while TEM study confirmed the obtained XRD results giving the following crystallite size value about 33.75 nm for the same sample. The dielectric A.C. conductivity was evaluated as a function of temperature and frequency ranging from 42 Hz up to 1 MHz.展开更多
A series of five chalcone derivatives with different substituents in para and meta posions have been synthesized, and single crystals were successfully grown in aceton solution by slow evaporation solution growth tech...A series of five chalcone derivatives with different substituents in para and meta posions have been synthesized, and single crystals were successfully grown in aceton solution by slow evaporation solution growth technique (SESGT). Single crystal X-ray studies revealed that all the crystals crystallized in noncentrosymmetric space group with their molecular dipoles perfectly aligned in a direction-favorable for large nonlinear optical effects. Kurtz powder tests revealed that all five materials have second-harmonic-generating properties with maximum efficiencies of approximately 14 times that of urea standard. UV-vis-NIR spectroscopy and thermogravimetric analyses are also presented for all of the reported materials. Among the five chalcones, high quality single crystals of 4-Methoxy-4'-chlorochalcone were grown by SESGT, and its crystalline perection were studied by using a high resolution X-ray diffractometry (HRXRD).展开更多
Single crystals of L-Valinium picrate were grown from aqueous solution by slow evaporation technique. Single crystal X-ray diffraction analysis reveals that the crystal belongs to monoclinic system. The optical transm...Single crystals of L-Valinium picrate were grown from aqueous solution by slow evaporation technique. Single crystal X-ray diffraction analysis reveals that the crystal belongs to monoclinic system. The optical transmission study reveals the transparency of the crystal in the entire visible region and the cut off wave length has been found to be 470 nm. The optical band gap is found to be 2.55 eV. The transmittance of L-Valinium picrate crystal has been used to calculate the refractive index (n), the extinction coefficient (K) and both the real (εr) and imaginary (εi) components of the dielectric constant as functions of wavelength. Low dielectric loss at high frequency region is indicative of enhanced optical quality with lesser defects. Photoconductivity measurements carried out on the grown crystal reveal the negative photoconducting nature.展开更多
Here we show the results of experimental observation of decomposition of the solution components into the neighboring cells. The liquid solution under crystallization first gets into the unstable state and then decomp...Here we show the results of experimental observation of decomposition of the solution components into the neighboring cells. The liquid solution under crystallization first gets into the unstable state and then decomposes. The decomposition result is fixed in the solid phase as inhomogeneous component distribution. Our experimental results enable to argue that the eutectic pattern forms due to interface instability and spinodal decomposition of non-equilibrium solution forming in front of the interface.展开更多
A new semiorganic nonlinear optical crystal of bisthiourea nickel bromide (BTNB) was grown successfully by slow evaporation technique using water as solvent. The lattice parameters of the grown crystal have been deter...A new semiorganic nonlinear optical crystal of bisthiourea nickel bromide (BTNB) was grown successfully by slow evaporation technique using water as solvent. The lattice parameters of the grown crystal have been determined by X-ray diffraction studies. Vibrational spectrum is recorded to determine symmetries of molecular vibrations. Optical absorbance spectrum recorded revealed that this crystal has good transparency in the visible region. The second harmonic generation test of BTNB confirmed the nonlinear nature of the crystal. The BTNB crystal was analyzed by a differential thermal analysis and thermogravimetric analysis (DTA-TGA) to obtain its thermal stability. Vickers microhardness test done on the crystal shows that the crystal has greater physical strength.展开更多
Single crystals of holmium oxalate heptahydrate are grown by gel diffusion method using organic agar gel as a medium of growth. The crystals grow in the agar gel with hexagonal morphology having well defined habit fac...Single crystals of holmium oxalate heptahydrate are grown by gel diffusion method using organic agar gel as a medium of growth. The crystals grow in the agar gel with hexagonal morphology having well defined habit faces Powder X-ray diffraction results show that the crystals belong to monoclinic system bearing the space group P21/c with cell parameters;a = 12.197? , b = 11.714 , c = 6.479 , α = 90°, β = 120.12°, γ = 90°, V = 799.6? 3. Fourier transform Infrared spectrum of the crystals shows the presence of water and other associated functional groups. Thermogravimetric analysis support the presence of 7 H2O molecules associated with holmium oxalate crystal lattice. The thermal decomposition in the nitrogen atmosphere leads to the formation of holmium oxide as the final product.展开更多
Biopolymer electrolyte based on carboxymethyl cellulose has been prepared by doping with different concentration of oleic acid via solution casting technique. Fourier Transform Infrared spectroscopy was used to study ...Biopolymer electrolyte based on carboxymethyl cellulose has been prepared by doping with different concentration of oleic acid via solution casting technique. Fourier Transform Infrared spectroscopy was used to study the complexation between the salt and polymer. New peak was observed at 1710, 2850, 2920 cm-1. X-ray diffraction study reveals the amorphous nature of the biopolymer electrolyte. Impedance study shows the highest ionic conductivity, σ, was found to be 2.11 × 10-5 S·cm-1 at room temperature (303 K) for sample containing 20 wt.% of oleic acid and the biopolymer electrolyte obeys Arrhenius behaviour.展开更多
The recrystallization behavior of cold-drawn 0.12 wt% C steel during annealing at temperatures 600°C and 650°C was investigated. Hardness tests were used to characterize the recrystallization kinetics. The m...The recrystallization behavior of cold-drawn 0.12 wt% C steel during annealing at temperatures 600°C and 650°C was investigated. Hardness tests were used to characterize the recrystallization kinetics. The micrographs of the steel were obtained using optical microscopy (OM) to characterize the grain microstructure of the non-treated and the annealed steel samples. Annihilation of dislocation defects occur within the soaking time of 5 - 10 minutes for all the deformed steel after annealing at 650°C. Specifically at 5 minutes soaking time the grains elongation is still observed indicating that reformation of grains is not taking place but recovery of the deformed grains. At the 10 minutes annealing time, new grains are observed to begin and full recrystallization is achieved at 15 minutes annealing time. At annealing time between 20 - 25 minutes, grains coarsening are observed indicating the onset of grain growth. The hardness of the material reduces with increasing annealing temperature for all the degree of cold drawn deformation. On the basis of the experimentally obtained hardness values, recrystallization increases with increasing degree of cold drawn deformation for the annealed steel. Recovery process was found to prolong in the 20% cold drawn steel as compared to the 55% cold drawn steel. The prolong recovery process is due to reduction in the driving force. Full recrystallization of the annealed steel is achieved at different soaking time depending on the degree of the cold drawn steel.展开更多
A continuous melt suspension crystallization process has been presented for the purification of the phosphoric acid in this study, which is performed in the cascade of a mixed suspension mixed product removal (MSMPR) ...A continuous melt suspension crystallization process has been presented for the purification of the phosphoric acid in this study, which is performed in the cascade of a mixed suspension mixed product removal (MSMPR) crystallizer and a gravity wash column for the subsequent solid-liquid separation. Dynamic behavior in the crystallizer and role of reflux ration on the purification efficiency of column are studied in detail. A reasonable steady state with respect to the liquid phase is achieved after 2 to 3 hrs, which is followed by a solid-phase steady state in terms of the slurry density after 4 hrs. Reflux ratio is the effective parameter for separation and purification by the crystallization equipment from the influences of reflux ratio on the purity of product, the number of theoretical plates and the stability of the operations.展开更多
Ferro nematic suspensions are the prominent materials to enhance the electro optical performance of liquid crystal displays. Electro optical properties of polymer dispersed liquid crystal (PDLC) display with the intro...Ferro nematic suspensions are the prominent materials to enhance the electro optical performance of liquid crystal displays. Electro optical properties of polymer dispersed liquid crystal (PDLC) display with the introduction of Barium Titanate nanoparticles have been investigated in this article and it is shown that there is a considerable enhancement in electro-optical response of the displays. The nanoparticles lower the switch-on electric field and thereby increase the optical transmission at certain voltages of the displays. The electro-optical characteristics of the PDLC cells were investigated with a He-Ne laser followed by MatLab calculations.展开更多
A pair of new anticancer nucleosides based on 1,2,4-triazole nucleosides and 1-((2-hydroxyethoxy) methyl)-5-(phenylthio)-1H-1,2,4-triazole-3-carboxamide have been synthesized, and have given the corresponding products...A pair of new anticancer nucleosides based on 1,2,4-triazole nucleosides and 1-((2-hydroxyethoxy) methyl)-5-(phenylthio)-1H-1,2,4-triazole-3-carboxamide have been synthesized, and have given the corresponding products in excellent yields. Its structures and conformations were confirmed by single crystal X-ray diffraction.展开更多
We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Mic...We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Microwave irradiation induced periodic patterns of precipitation because polar molecules vibrate and rotate in an electromagnetic field. For example, the number of patterns increased with the irradiation power. Accordingly, microwave irradiation nonlinearly accelerated the diffusion of ionic molecules.展开更多
The crystal growth and nucleation in glasses in the lithium silicate system have been investigated. Phase separation in ultimately homogenized glasses of the lithium silicate system xLi<sub>2</sub>O·(...The crystal growth and nucleation in glasses in the lithium silicate system have been investigated. Phase separation in ultimately homogenized glasses of the lithium silicate system xLi<sub>2</sub>O·(100 ﹣ x)SiO<sub>2</sub> (where x = 23.4, 26.0, 29.1, and 33.5 mol% Li<sub>2</sub>O) has been studied. The glasses of these compositions have been homogenized using the previously established special temperature-time conditions, which make it possible to provide a maximum dehydration and removal of bubbles from the glass melt. The parameters of nucleation and growth of phase separated in homogeneities and homogeneous crystal nucleation have been determined. The absolute values of the stationary nucleation rates I<sub>st</sub> of lithium disilicate crystals in the 23.4Li<sub>2</sub>O·76.6SiO<sub>2</sub>, 26Li<sub>2</sub>O·74SiO<sub>2</sub> and 29.1Li<sub>2</sub>O·70.9SiO<sub>2</sub> glasses with the compositions lying in the metastable phase separation region have been compared with the corresponding rates I<sub>st</sub> for the glass of the stoichiometric lithium disilicate composition 33.51Li<sub>2</sub>O·66.5SiO<sub>2</sub>. It has been found that the crystal growth rate has a tendency toward a monotonic increase with an increase in the temperature, whereas the dependences of the crystal growth rate on the time of low temperature heat treatment exhibit an oscillatory behavior with a monotonic decrease in the absolute value of oscillations. The character of crystallization in glasses with the compositions lying in the phase separation region of the Li<sub>2</sub>O-SiO<sub>2</sub> system is compared with that in the glass of the stoichiometric lithium disilicate composition. The conclusion has been made that the phase separation weakly affects the nucleation parameters of the lithium disilicate and has a strong effect on the crystal growth.展开更多
Using differential thermal analysis, X-ray phase analysis, electron microscopy, and optical microscopy, the nucleation of crystals in glass obtained by blending metallurgical slag with silicon dioxide has been studied...Using differential thermal analysis, X-ray phase analysis, electron microscopy, and optical microscopy, 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·TiO2);in this phase a nucleation of the main phase occurs: melilite (solid solution of gehlenite 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 Ist, time of unsteady state nucleation τ, crystal growth rate U, and activation energy of frictional flow. The temperature dependences of Ist, τ, and U are obtained. The kinetics of the crystallization of glass is studied and the rates of the surface crystal growth are determined in the glass of nine compositions. The influence of grinding the particles of the original glass on the sequence of deposition of the crystalline phases was studied. Practical recommendations are presented for the use of blast-furnace slag as a raw material for the synthesis of glass and their further utilization.展开更多
文摘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.
文摘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.
文摘Triglycine sulfate crystal and potassium bromide doped triglycine sulfate crystals were grown from aqueous solution by slow evaporation method. Energy dispersive X-ray analysis identifies the elements present in the crystal. The Fourier Transform Infrared spectroscopy has been recorded in the range 400 to 4000 cm-1 and the functional groups of the grown crystals have been identified. The structural studies on the grown crystals were carried out by X-ray diffraction analysis technique and found that the grown crystal crystallizes in monoclinic structure. The lattice cell parameters of pure Triglycine sulfate are a = 9.6010 ?, b = 12.5600 ?, c = 5.4500 ?. Ultraviolet-Visible spectra show that the grown crystals have wide optical transparency in the entire visible region.
文摘Kinetics of the decomposition of racemic ibuprofen crystals were studied by non-isothermal analysis. Thermogravimetric analysis revealed that ibuprofen is thermally stable up to 152.6°C and the initial loss of mass was due to evaporation only. Activation energy, pre-exponential factor, activation entropy and Gibbs free energy for the decomposition of ibuprofen were determined using the integral method of Coats-Redfern (CR). Geometrical contraction models were found to be the best fits. The Arrheinus equation for the thermal decomposition of ibuprofen is k = (1.1 × 107) e–79125/RT sec–1.
文摘The phosphate mineral struvite is basically formed in urinary tracks and kidney. One of the analogous compounds of struvite is potassium magnesium phosphate hexahydrate (KMgPO4·6H2O), known as struvite-k crystal and found in animal urinary calculi. In the present investigation, struvite-k crystals were grown by single diffusion and double diffusion techniques in agar gelmedium. The grown crystals were analyzed by optical microscopy, scanning electron microscopy (SEM), fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), energy dispersive X-ray analysis (EDXA) and thermogravimetric analysis (TGA). Optical microscopy and SEM exhibited the different morphologies. The FTIR spectra revealed the presence of water molecules, stretching and bending vibrations of phosphate (PO4) ions. However the powder XRD results from the crystalline nature. Elemental composition in the crystal was obtained by EDXA, while 36.89% weight loss of water molecules is observed in TGA study.
文摘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.
文摘Nano-composite, perovskite Ba(1- x - y)Sr(x)TiFe(y)O3, denoted as (BSTFe) in powder form was derived via sol-gel (SG) method followed by sintering at fixed temperature 750℃ for one hour. The chemical composition, morphology and structure of the powder samples were investigated by using X-ray diffraction (XRD), transmission electron microscope (TEM) and scanning electron microscope (SEM). The XRD characterization indicates formation of a cubic crystalline phase in the pure BST. A well defined perovskite phase with nano-crystallite sizes equal to about 34 nm was achieved from XRD for B10ST3F sample, while TEM study confirmed the obtained XRD results giving the following crystallite size value about 33.75 nm for the same sample. The dielectric A.C. conductivity was evaluated as a function of temperature and frequency ranging from 42 Hz up to 1 MHz.
文摘A series of five chalcone derivatives with different substituents in para and meta posions have been synthesized, and single crystals were successfully grown in aceton solution by slow evaporation solution growth technique (SESGT). Single crystal X-ray studies revealed that all the crystals crystallized in noncentrosymmetric space group with their molecular dipoles perfectly aligned in a direction-favorable for large nonlinear optical effects. Kurtz powder tests revealed that all five materials have second-harmonic-generating properties with maximum efficiencies of approximately 14 times that of urea standard. UV-vis-NIR spectroscopy and thermogravimetric analyses are also presented for all of the reported materials. Among the five chalcones, high quality single crystals of 4-Methoxy-4'-chlorochalcone were grown by SESGT, and its crystalline perection were studied by using a high resolution X-ray diffractometry (HRXRD).
文摘Single crystals of L-Valinium picrate were grown from aqueous solution by slow evaporation technique. Single crystal X-ray diffraction analysis reveals that the crystal belongs to monoclinic system. The optical transmission study reveals the transparency of the crystal in the entire visible region and the cut off wave length has been found to be 470 nm. The optical band gap is found to be 2.55 eV. The transmittance of L-Valinium picrate crystal has been used to calculate the refractive index (n), the extinction coefficient (K) and both the real (εr) and imaginary (εi) components of the dielectric constant as functions of wavelength. Low dielectric loss at high frequency region is indicative of enhanced optical quality with lesser defects. Photoconductivity measurements carried out on the grown crystal reveal the negative photoconducting nature.
文摘Here we show the results of experimental observation of decomposition of the solution components into the neighboring cells. The liquid solution under crystallization first gets into the unstable state and then decomposes. The decomposition result is fixed in the solid phase as inhomogeneous component distribution. Our experimental results enable to argue that the eutectic pattern forms due to interface instability and spinodal decomposition of non-equilibrium solution forming in front of the interface.
文摘A new semiorganic nonlinear optical crystal of bisthiourea nickel bromide (BTNB) was grown successfully by slow evaporation technique using water as solvent. The lattice parameters of the grown crystal have been determined by X-ray diffraction studies. Vibrational spectrum is recorded to determine symmetries of molecular vibrations. Optical absorbance spectrum recorded revealed that this crystal has good transparency in the visible region. The second harmonic generation test of BTNB confirmed the nonlinear nature of the crystal. The BTNB crystal was analyzed by a differential thermal analysis and thermogravimetric analysis (DTA-TGA) to obtain its thermal stability. Vickers microhardness test done on the crystal shows that the crystal has greater physical strength.
文摘Single crystals of holmium oxalate heptahydrate are grown by gel diffusion method using organic agar gel as a medium of growth. The crystals grow in the agar gel with hexagonal morphology having well defined habit faces Powder X-ray diffraction results show that the crystals belong to monoclinic system bearing the space group P21/c with cell parameters;a = 12.197? , b = 11.714 , c = 6.479 , α = 90°, β = 120.12°, γ = 90°, V = 799.6? 3. Fourier transform Infrared spectrum of the crystals shows the presence of water and other associated functional groups. Thermogravimetric analysis support the presence of 7 H2O molecules associated with holmium oxalate crystal lattice. The thermal decomposition in the nitrogen atmosphere leads to the formation of holmium oxide as the final product.
文摘Biopolymer electrolyte based on carboxymethyl cellulose has been prepared by doping with different concentration of oleic acid via solution casting technique. Fourier Transform Infrared spectroscopy was used to study the complexation between the salt and polymer. New peak was observed at 1710, 2850, 2920 cm-1. X-ray diffraction study reveals the amorphous nature of the biopolymer electrolyte. Impedance study shows the highest ionic conductivity, σ, was found to be 2.11 × 10-5 S·cm-1 at room temperature (303 K) for sample containing 20 wt.% of oleic acid and the biopolymer electrolyte obeys Arrhenius behaviour.
文摘The recrystallization behavior of cold-drawn 0.12 wt% C steel during annealing at temperatures 600°C and 650°C was investigated. Hardness tests were used to characterize the recrystallization kinetics. The micrographs of the steel were obtained using optical microscopy (OM) to characterize the grain microstructure of the non-treated and the annealed steel samples. Annihilation of dislocation defects occur within the soaking time of 5 - 10 minutes for all the deformed steel after annealing at 650°C. Specifically at 5 minutes soaking time the grains elongation is still observed indicating that reformation of grains is not taking place but recovery of the deformed grains. At the 10 minutes annealing time, new grains are observed to begin and full recrystallization is achieved at 15 minutes annealing time. At annealing time between 20 - 25 minutes, grains coarsening are observed indicating the onset of grain growth. The hardness of the material reduces with increasing annealing temperature for all the degree of cold drawn deformation. On the basis of the experimentally obtained hardness values, recrystallization increases with increasing degree of cold drawn deformation for the annealed steel. Recovery process was found to prolong in the 20% cold drawn steel as compared to the 55% cold drawn steel. The prolong recovery process is due to reduction in the driving force. Full recrystallization of the annealed steel is achieved at different soaking time depending on the degree of the cold drawn steel.
文摘A continuous melt suspension crystallization process has been presented for the purification of the phosphoric acid in this study, which is performed in the cascade of a mixed suspension mixed product removal (MSMPR) crystallizer and a gravity wash column for the subsequent solid-liquid separation. Dynamic behavior in the crystallizer and role of reflux ration on the purification efficiency of column are studied in detail. A reasonable steady state with respect to the liquid phase is achieved after 2 to 3 hrs, which is followed by a solid-phase steady state in terms of the slurry density after 4 hrs. Reflux ratio is the effective parameter for separation and purification by the crystallization equipment from the influences of reflux ratio on the purity of product, the number of theoretical plates and the stability of the operations.
文摘Ferro nematic suspensions are the prominent materials to enhance the electro optical performance of liquid crystal displays. Electro optical properties of polymer dispersed liquid crystal (PDLC) display with the introduction of Barium Titanate nanoparticles have been investigated in this article and it is shown that there is a considerable enhancement in electro-optical response of the displays. The nanoparticles lower the switch-on electric field and thereby increase the optical transmission at certain voltages of the displays. The electro-optical characteristics of the PDLC cells were investigated with a He-Ne laser followed by MatLab calculations.
文摘A pair of new anticancer nucleosides based on 1,2,4-triazole nucleosides and 1-((2-hydroxyethoxy) methyl)-5-(phenylthio)-1H-1,2,4-triazole-3-carboxamide have been synthesized, and have given the corresponding products in excellent yields. Its structures and conformations were confirmed by single crystal X-ray diffraction.
文摘We studied precipitation patterns in a Liesegang system under microwave irradiation in order to investigate metal salt diffusion in an electrolyte gel. The salt species and microwave irradiation power were varied. Microwave irradiation induced periodic patterns of precipitation because polar molecules vibrate and rotate in an electromagnetic field. For example, the number of patterns increased with the irradiation power. Accordingly, microwave irradiation nonlinearly accelerated the diffusion of ionic molecules.
文摘The crystal growth and nucleation in glasses in the lithium silicate system have been investigated. Phase separation in ultimately homogenized glasses of the lithium silicate system xLi<sub>2</sub>O·(100 ﹣ x)SiO<sub>2</sub> (where x = 23.4, 26.0, 29.1, and 33.5 mol% Li<sub>2</sub>O) has been studied. The glasses of these compositions have been homogenized using the previously established special temperature-time conditions, which make it possible to provide a maximum dehydration and removal of bubbles from the glass melt. The parameters of nucleation and growth of phase separated in homogeneities and homogeneous crystal nucleation have been determined. The absolute values of the stationary nucleation rates I<sub>st</sub> of lithium disilicate crystals in the 23.4Li<sub>2</sub>O·76.6SiO<sub>2</sub>, 26Li<sub>2</sub>O·74SiO<sub>2</sub> and 29.1Li<sub>2</sub>O·70.9SiO<sub>2</sub> glasses with the compositions lying in the metastable phase separation region have been compared with the corresponding rates I<sub>st</sub> for the glass of the stoichiometric lithium disilicate composition 33.51Li<sub>2</sub>O·66.5SiO<sub>2</sub>. It has been found that the crystal growth rate has a tendency toward a monotonic increase with an increase in the temperature, whereas the dependences of the crystal growth rate on the time of low temperature heat treatment exhibit an oscillatory behavior with a monotonic decrease in the absolute value of oscillations. The character of crystallization in glasses with the compositions lying in the phase separation region of the Li<sub>2</sub>O-SiO<sub>2</sub> system is compared with that in the glass of the stoichiometric lithium disilicate composition. The conclusion has been made that the phase separation weakly affects the nucleation parameters of the lithium disilicate and has a strong effect on the crystal growth.
文摘Using differential thermal analysis, X-ray phase analysis, electron microscopy, and optical microscopy, 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·TiO2);in this phase a nucleation of the main phase occurs: melilite (solid solution of gehlenite 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 Ist, time of unsteady state nucleation τ, crystal growth rate U, and activation energy of frictional flow. The temperature dependences of Ist, τ, and U are obtained. The kinetics of the crystallization of glass is studied and the rates of the surface crystal growth are determined in the glass of nine compositions. The influence of grinding the particles of the original glass on the sequence of deposition of the crystalline phases was studied. Practical recommendations are presented for the use of blast-furnace slag as a raw material for the synthesis of glass and their further utilization.
