Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was...Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was added into the CaCl2 solution by slow titration or in multiple stages over 2-8 h followed by 2 h equilibration.In order to regenerate KCl solution as concentrated as possible,K2SO4 solid was added into the given CaCl2 solution instead of K2SO4 solution,obtaining gypsum crystals with almost the same quality by multistage addition with[SO4 2-]/[Ca 2+]molar ratio no larger than 0.8.However,impurity of K2SO4·CaSO4·H2O was detected by XRD and was further confirmed by SEM-EDS in the produced crystals when the[SO4 2-]/[Ca 2+] ratio increased to 1.1.It is proved that appearance of the double sulfate is attributed to the relatively high concentration of K2SO4.So,it is essential to properly control the[SO4 2-]/[Ca 2+]ratio and make sure[Ca 2+ ]in excess to suppress the solubility of CaSO4 even at the expense of low calcium removal rate.展开更多
The mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes were researched by comparing the blank extraction with the extraction with calcium fluoride as aid-leaching reagent. The lea...The mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes were researched by comparing the blank extraction with the extraction with calcium fluoride as aid-leaching reagent. The leaching experiments were carried out under the conditions of 95 ℃, 6h, 1.5 mlg-1 , 15 vol % H2SO4 , and 5 % calcium fluoride (mass ratio of CaF2 to stone coal). The concentrations of hydrogen ion were adjusted from initial 1.82 and 4.79 mol L -1 to the pH of 1.80 ± 0.05 by 200 g L-1 lime milk, respectively. The solvent extraction experiments were carried out under the organic phase using 15 vol% D2EHPA, 5 vol% TBP, and 80 vol% sulfonated kerosene and O/A phase ratio of 1/4. The leaching rate of vanadium and six-stage countercurrent solvent extraction rate of vanadium can be remarkably improved from 66.71 to 92.97 % and 81.15 to 98.81 %, respectively, when calcium fluoride was added as aid-leaching reagent. In the leaching process, fluorine can enhance the breakage of the structure of vanadium-bearing minerals. Meanwhile, fluoride ion can combine with iron ion to generate acid-insoluble iron fluoride hydrate (Fe2F57H2O) and consume all ferric ions and a portion of ferrous ions. In adjusting pH value process, the massive impurities are decreased to form KAlSO4 and FeAlF5 . In solvent extraction process, fluorine can prevent the formation of ferric hydroxide colloids and eliminate the formed unstable ferric hydroxide colloids and the silicon-containing colloids to promote the sufficient contact between the aqueous phase and the organic phase and the sufficient reaction.展开更多
To elucidate the behavior of slag films in an electroslag remelting process, the fluoride evaporation and crystallization of CaF_2–CaO–Al_2O_3–(TiO_2) slags were studied using the single hot thermocouple technique....To elucidate the behavior of slag films in an electroslag remelting process, the fluoride evaporation and crystallization of CaF_2–CaO–Al_2O_3–(TiO_2) slags were studied using the single hot thermocouple technique. The crystallization mechanism of TiO_2-bearing slag was identified based on kinetic analysis. The fluoride evaporation and incubation time of crystallization in TiO_2-free slag are found to considerably decrease with decreasing isothermal temperature down to 1503 K. Fish-bone and flower-like CaO crystals precipitate in TiO_2-free slag melt, which is accompanied by CaF_2 evaporation from slag melt above 1503 K. Below 1503 K, only near-spherical CaF_2 crystals form with an incubation time of less than 1 s, and the crystallization is completed within 1 s. The addition of 8.1wt% TiO_2 largely prevents the fluoride evaporation from slag melt and promotes the slag crystallization. TiO_2 addition leads to the precipitation of needle-like perovskite(CaTiO_3) crystals instead of CaO crystals in the slag. The crystallization of perovskite(CaTiO_3) occurs by bulk nucleation and diffusion-controlled one-dimensional growth.展开更多
A copper-zinc alloy doped with rare earth elements was prepared and the mechanism was demonstrated in a simulating boiler and circulating cooling water with rigidity 1 mmol·L-1. The polar curve and scale inhibiti...A copper-zinc alloy doped with rare earth elements was prepared and the mechanism was demonstrated in a simulating boiler and circulating cooling water with rigidity 1 mmol·L-1. The polar curve and scale inhibiting ability of the alloy was tested by a corrosion measurement system and a scale inhibition evaluation system, respectively. Scale samples were characterized with SEM and XRD. It is found that the transfer of cations could be promoted by doping with proper rare earth elements, and the corrosion potentials descend by 25～126 mV. The results indicated that the copper-zinc alloy doped with rare earth elements has higher scale inhibiting ability of CaCO3. The growth of calcite was affected by zinc ions dissolved because of primary battery reaction, and the transition of calcium carbonate from aragonite to calcite was hampered resulting in the proportion of aragonite to calcite is changed from 1.7∶1 to 2.7∶1.展开更多
Simulate the production of phosphoric acid by wet process is conducted in batch experiments facilities by adopting phosphorus concentrate as raw material from Wengfu, Dazhou city, with a view to study sulfuric acid co...Simulate the production of phosphoric acid by wet process is conducted in batch experiments facilities by adopting phosphorus concentrate as raw material from Wengfu, Dazhou city, with a view to study sulfuric acid concentration, reaction time, crystallization temperature of calcium sulfate, active additive, the influence of seed crystal on the size and shape of calcium sulfate crystal under conditions of Wet process phosphoric acid productive process. The research results show that under the conditions of the liquid-solid ratio of 4:1, the sulfate acid stoichiometric ratio of 1.1, phosphoric acid mass fraction of 21%, the crystallization temperature of 75°C, crystallization time of 120 min, when (NH4)2SO4 taken as active additives, Mg-doped calcium sulphate crystal as crystal seed can obtain rodlike crystallization of stability, thickness, uniformity.展开更多
To investigate the hydrogen permeability of calcium fluoride used for electroslag remelting(ESR) process,"Gas-slag-metal" osmosis process under argon atmosphere saturated with water vapor at 318 K was used t...To investigate the hydrogen permeability of calcium fluoride used for electroslag remelting(ESR) process,"Gas-slag-metal" osmosis process under argon atmosphere saturated with water vapor at 318 K was used to study the hydrogen permeability of slag containing calcium fluoride.The results indicate that the conventional slag,consisting of 70% CaF2 and 30% Al2O3,has the lowest hydrogen permeability.A parameter EH was proposed for evaluation of the hydrogen permeability of slags containing calcium fluoride.The hydrogen permeability decreases with increasing EH to a certain extent.An appropriate choice of slag for the ESR process can be obtained.These results also suggest that the hydrogen pick-up in steel after remelting might be reduced when a slag with low hydrogen permeability is used.展开更多
BACKGROUND Calcium pyrophosphate dihydrate deposition disease(CPPD),or pseudogout,is an inflammatory arthritis common among elderly patients,but rarely seen in patients under the age of 40.In the rare cases presented ...BACKGROUND Calcium pyrophosphate dihydrate deposition disease(CPPD),or pseudogout,is an inflammatory arthritis common among elderly patients,but rarely seen in patients under the age of 40.In the rare cases presented of young patients with CPPD,genetic predisposition or related metabolic conditions were almost always identified.CASE SUMMARY The authors report the case of a 9-year-old boy with no past medical history who presented with acute knee pain and swelling after a cat scratch injury 5 d prior.Synovial fluid analysis identified calcium pyrophosphate dihydrate crystals.Further MRI analysis identified osteomyelitis and a small soft tissue abscess.CONCLUSION This case presents the extremely rare diagnostic finding of calcium pyrophosphate dihydrate crystals in a previously healthy pediatric patient.The presence of osteomyelitis presents a unique insight into the pathogenesis of these crystals in pediatric patients.More research needs to be done on the role of CPPD in pediatric arthritis and joint infection.展开更多
The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater discharged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirrin...The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater discharged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from platelet-like and needle-like shape to rod-like shape when the temperature was increased from 25 to 70 °C. An increase in the agglomeration of calcium sulfate was found with increasing lime concentration. Metal ions markedly retard the rate of crystallization of calcium sulfate dihydrate. The crystallization of gypsum was slowed with the existence of Mg2+in the solution, and the morphology of gypsum was transformed from platelet-like shape to rod-like shape when Mg2+ concentration reached 0.08 mol·L 1. The amorphous ferric hydroxide was coated on the calcium sulfate after the co-precipitation process while Zn2+and Al3+ions in the solution enhanced the agglomeration of the calcium sulfate by absorbing on the surface of the crystals. Comprehensive acidic wastewater containing heavy metals was efficiently purified by the two stage lime neutralization technology, and highly agglomerated gypsum precipitates with needle-like shape were obtained. The precipitates could be purified by sulfuric acid washing, and the metal ions were effectively separated from the calcium sulfate by-products.展开更多
Hydroxyapatite (Ca10(PO4)6(OH)2) is widely used as bio-ceramic materials and as adsorbents for separation of bio-molecules. These materials have also been used as adsorbents for heavy metals, supports and as catalysts...Hydroxyapatite (Ca10(PO4)6(OH)2) is widely used as bio-ceramic materials and as adsorbents for separation of bio-molecules. These materials have also been used as adsorbents for heavy metals, supports and as catalysts in oxidation and dehydrogenation reactions. The catalytic performance of these materials depend on the lattice substitution of Ca sites in Hydroxyapatite structure by varied cations as Na, Mg, Sr and Mn, which result in changes in various structural pro perties as crystallinity and morphology. Pure calcium hydroxyapatite (S1) and Cr loaded hydroxyl apatite (S2, S3, S4 and S5) of different chromium concentrations have been prepared by wet precipitated method. An in-vitro examination is essential to investigate the mechanism of the deficient HA and tissue interface reaction by preparing SBF (Simulated Body Fluid) through the elemental and chemical analysis of Ca, P and Cr. FTIR used to analyze the samples after incubation in SBF for 24 day. PH of the samples also was measured at the first period of immersion time. At high loading of chromium ions, the formation of carbonate apatite decrease. The concentrations of the chromium in the Cr_HA crystal during the soaking in SBF are very safe dose for human.展开更多
The reaction studied in this work is the synthesis of nanometric size calcium carbonate by carbonation of a suspension of lime, which represents the most common industrial route. The carbonation was proceeded in a pil...The reaction studied in this work is the synthesis of nanometric size calcium carbonate by carbonation of a suspension of lime, which represents the most common industrial route. The carbonation was proceeded in a pilot batch reactor. This article presents a method for the determination of nucleation and crystal growth rates of calcium carbonate by following two macroscopic parameters: the mass production rate by precipitation and the specific surface area. The results give a constant nucleation rate around 4 × 1015m-3 ·s-1 and a decreasing crystal growth rate between 0.2 and 2 × 10-10 m·s-1. It also provides the main characteristics of the monoparticle size distributions (i.e. the mean particle sizes and in situ coefficient of variation) in the agglomerates, which cannot be obtained by other known methods. For the carbonation carried out in this work, the mean mass particle size at the end of the reaction is about 300 nm and the coefficient of variation of 0.28 indicates a narrow particle size distribution of the monoparticles.展开更多
In Na_2O–CaO–SiO_2–H_2O system,systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumin...In Na_2O–CaO–SiO_2–H_2O system,systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumina fly ash(HAFA).The results show that crystal composition and phase may be affected by relatively low concentration of NaOH,and sodium ions are rearranged into the structure to form NaCaHSiO_4 and Na_2Ca_3H_8Si_2O_(12) with different C/S ratio at high concentration of Na OH.In addition,phases in wollastonite group possess the morphology of nano fiber.Formation of nano fiber is attributed to the difference of surface energies between axial and radial direction,and higher temperatures lead to easier growth along radial direction.The preparation of C–S–H with different phases and morphologies can guide for the application of silicate solution with high alkalinity with different purposes.展开更多
The crystallization kinetics of 38.0CaO-38.0Al2O3-10.5BaO-6.5MgO-6.0Y2O3-1.0(Na2O+K2O)(wt%) glass was studied by differential scanning calorimeter(DSC) and X-ray diffraction(XRD) techniques.The results showed that DSC...The crystallization kinetics of 38.0CaO-38.0Al2O3-10.5BaO-6.5MgO-6.0Y2O3-1.0(Na2O+K2O)(wt%) glass was studied by differential scanning calorimeter(DSC) and X-ray diffraction(XRD) techniques.The results showed that DSC curves of calcium aluminate glass have a single glass transition temperature followed by one crystallization peak for the heating rates β=5 K/min and two crystallization temperatures Tp1 and Tp2 for β≥10 K/min.The activation energies of crystallization obtained from the Gao-Wang model of the first exothermal peak and the second exothermal peak of calcium aluminate glass are 340 and 662 kJ/mol,respectively.The Avrami exponents of the both crystallization peaks are approximately 2,indicating the twodimensional crystalline growth during its transformation from amorphous to crystalline.Ca12Al14O33,Ca3Al2O6 and unknown crystalline phases firstly appear when calcium aluminate glass is heat-treated.With the extending of heat-treatment duration,BaAl2O4 phase comes out.展开更多
Nephrolithiasis seems to be the result of crystal formation,aggregation and retention in the kidney during crystalluria.These processes have to occur within the short urinary transit time through the kidney being in t...Nephrolithiasis seems to be the result of crystal formation,aggregation and retention in the kidney during crystalluria.These processes have to occur within the short urinary transit time through the kidney being in the order of few minutes.Recently much work was done on rather qualitative aspects of nephrolithiasis like genetics,metabolism and morphology.In this review we try to provide some quantitative information on urinary supersaturation with respect to stone minerals,especially Ca oxalate(CaO x),on the formation and aggregation of Ca Ox crystals and on crystal retention in the kidney.The paper is centered on idiopathic Ca nephrolithiasis being the most frequent stone disease with only partially known pathogenesis.New aspects of the role of urinary macromolecules in stone formation and of the mechanism of crystal aggregation are provided.展开更多
1 Introduction Calcium sulfate deposition is one of the most important and serious problems faced by heat transfer equipment during operation(Pavlos et al.,1999;Liu et al.,1996).The crystallization of calcium sulfate ...1 Introduction Calcium sulfate deposition is one of the most important and serious problems faced by heat transfer equipment during operation(Pavlos et al.,1999;Liu et al.,1996).The crystallization of calcium sulfate is known as a展开更多
1 Introduction There exist calcium and sulfate ions outside sodium chloride in solution mining for calcium sulfate brine.The calcium and sulfate ions not only affect the purity of the vacuum salt products,but also inc...1 Introduction There exist calcium and sulfate ions outside sodium chloride in solution mining for calcium sulfate brine.The calcium and sulfate ions not only affect the purity of the vacuum salt products,but also increase the scaling of vacuum evaporation tanks and brine reusing pipes.Additives have certain impacts on the crystallization dynamics(Randolph et al.,1971).The展开更多
Calcium phosphate film was prepared by electrochemical deposition technology. Subsequently, the alkaline treatment process of calcium phosphate film in 0.1 mol/L NaOH solution was monitored on real time by the piezoel...Calcium phosphate film was prepared by electrochemical deposition technology. Subsequently, the alkaline treatment process of calcium phosphate film in 0.1 mol/L NaOH solution was monitored on real time by the piezoelectric quartz crystal impedance (PQCI) technique. The variations of morphology and composition for the alkaline treatment products were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray diffraction (XRD), respectively. The dynamic variations of calcium phosphate can be characterized by the change of equivalent circuit parameters. The results show that the forming process of hydroxyapatite (HA) is composed of three stages: (1) acidic calcium phosphate dissolution; (2) phase transformation; and (3) HA formation. Furthermore, the correlative kinetic equations and parameters are obtained by fitting the static capacitance (Cs)—time curves.展开更多
Leaves of twenty-two (22) species of Combretum in Nigeria were examined for occurrence and distribution of different types and sizes of ergastic substances (calcium oxalate crystals). Fresh and herbarium specimens wer...Leaves of twenty-two (22) species of Combretum in Nigeria were examined for occurrence and distribution of different types and sizes of ergastic substances (calcium oxalate crystals). Fresh and herbarium specimens were used for the study. These specimens were wax embedded, sectioned, mounted and micro-photographed using Leica WILD MPS 52 microscope camera on Leitz Diaplan microscope. Results revealed two types of calcium oxalate crystals—crystal sand and druses. Based on the observed differences in the size of the crystals, three groups of calcium oxalate crystals are reported [large crystals: 180.0 - 360.0 μm (241 ± 44.57 μm), moderate crystals: 90.0 - 144.0 μm (117.0 ± 20.60 μm), and small crystals: 18.0 - 72.0 μm (50.21 ± 20.42 μm)]. Crystal sand was found only in Combretum sp. 1 but druses of varying sizes predominated amongst species of the genus. Crystals were distributed within the spongy mesophyll, palisade mesophyll, sub-epidermis adaxial, sub-epidermis abaxial and between the palisade and spongy mesophyll. The findings of this work provide information on the occurrence and distribution of the crystals in the leaf epidermis of these taxa in Nigeria. The formation, occurrence and distribution of the crystal type in the Combretum species constitute dependable taxonomic character especially when combined with other characters.展开更多
Preparation and optical characterisation of Erbium doped KY3F10 single crystals are reported. The crystals were grown using the Czochralski pulling technique. The single phase was controlled by X-ray diffraction analy...Preparation and optical characterisation of Erbium doped KY3F10 single crystals are reported. The crystals were grown using the Czochralski pulling technique. The single phase was controlled by X-ray diffraction analysis. Room temperature optical spectra were recorded between 200 and 1600 nm. They were used to fit the three phenomenological Judd-Ofelt (JO) parameters Ωt (t = 2, 4, 6). The emission transition probabilities, branching ratios and radiative lifetimes are then deduced. The possibility to use such material for laser emissions is discussed.展开更多
基金Project(50974018)supported by the National Natural Science Foundation of ChinaProject(108007)supported by Key Project of the Ministry of Education of China
文摘Gypsum crystallization along with the simultaneous regeneration of KCl was investigated by the reaction of CaCl2 solution with K2SO4.Well developed sheet structure gypsum crystals were produced when K2SO4 solution was added into the CaCl2 solution by slow titration or in multiple stages over 2-8 h followed by 2 h equilibration.In order to regenerate KCl solution as concentrated as possible,K2SO4 solid was added into the given CaCl2 solution instead of K2SO4 solution,obtaining gypsum crystals with almost the same quality by multistage addition with[SO4 2-]/[Ca 2+]molar ratio no larger than 0.8.However,impurity of K2SO4·CaSO4·H2O was detected by XRD and was further confirmed by SEM-EDS in the produced crystals when the[SO4 2-]/[Ca 2+] ratio increased to 1.1.It is proved that appearance of the double sulfate is attributed to the relatively high concentration of K2SO4.So,it is essential to properly control the[SO4 2-]/[Ca 2+]ratio and make sure[Ca 2+ ]in excess to suppress the solubility of CaSO4 even at the expense of low calcium removal rate.
基金financially supported by the Key Science and Technology Support Program (No. 2011BAB05B01) from the Ministry of ScienceTechnology of China and the Special Science and Technology Program (No. 201009013) from the Ministry of Environmental Protection of China
文摘The mechanisms of aid-leaching reagent calcium fluoride in the extracting vanadium processes were researched by comparing the blank extraction with the extraction with calcium fluoride as aid-leaching reagent. The leaching experiments were carried out under the conditions of 95 ℃, 6h, 1.5 mlg-1 , 15 vol % H2SO4 , and 5 % calcium fluoride (mass ratio of CaF2 to stone coal). The concentrations of hydrogen ion were adjusted from initial 1.82 and 4.79 mol L -1 to the pH of 1.80 ± 0.05 by 200 g L-1 lime milk, respectively. The solvent extraction experiments were carried out under the organic phase using 15 vol% D2EHPA, 5 vol% TBP, and 80 vol% sulfonated kerosene and O/A phase ratio of 1/4. The leaching rate of vanadium and six-stage countercurrent solvent extraction rate of vanadium can be remarkably improved from 66.71 to 92.97 % and 81.15 to 98.81 %, respectively, when calcium fluoride was added as aid-leaching reagent. In the leaching process, fluorine can enhance the breakage of the structure of vanadium-bearing minerals. Meanwhile, fluoride ion can combine with iron ion to generate acid-insoluble iron fluoride hydrate (Fe2F57H2O) and consume all ferric ions and a portion of ferrous ions. In adjusting pH value process, the massive impurities are decreased to form KAlSO4 and FeAlF5 . In solvent extraction process, fluorine can prevent the formation of ferric hydroxide colloids and eliminate the formed unstable ferric hydroxide colloids and the silicon-containing colloids to promote the sufficient contact between the aqueous phase and the organic phase and the sufficient reaction.
基金financially supported by the Fundamental Research Funds for the Central Universities (No. FRF-TP-14-009A1)the National Natural Science Foundation of China (No. 51444004)
文摘To elucidate the behavior of slag films in an electroslag remelting process, the fluoride evaporation and crystallization of CaF_2–CaO–Al_2O_3–(TiO_2) slags were studied using the single hot thermocouple technique. The crystallization mechanism of TiO_2-bearing slag was identified based on kinetic analysis. The fluoride evaporation and incubation time of crystallization in TiO_2-free slag are found to considerably decrease with decreasing isothermal temperature down to 1503 K. Fish-bone and flower-like CaO crystals precipitate in TiO_2-free slag melt, which is accompanied by CaF_2 evaporation from slag melt above 1503 K. Below 1503 K, only near-spherical CaF_2 crystals form with an incubation time of less than 1 s, and the crystallization is completed within 1 s. The addition of 8.1wt% TiO_2 largely prevents the fluoride evaporation from slag melt and promotes the slag crystallization. TiO_2 addition leads to the precipitation of needle-like perovskite(CaTiO_3) crystals instead of CaO crystals in the slag. The crystallization of perovskite(CaTiO_3) occurs by bulk nucleation and diffusion-controlled one-dimensional growth.
基金Key Technologies R&D Program of Tianjin (06YFGZGX02400)
文摘A copper-zinc alloy doped with rare earth elements was prepared and the mechanism was demonstrated in a simulating boiler and circulating cooling water with rigidity 1 mmol·L-1. The polar curve and scale inhibiting ability of the alloy was tested by a corrosion measurement system and a scale inhibition evaluation system, respectively. Scale samples were characterized with SEM and XRD. It is found that the transfer of cations could be promoted by doping with proper rare earth elements, and the corrosion potentials descend by 25～126 mV. The results indicated that the copper-zinc alloy doped with rare earth elements has higher scale inhibiting ability of CaCO3. The growth of calcite was affected by zinc ions dissolved because of primary battery reaction, and the transition of calcium carbonate from aragonite to calcite was hampered resulting in the proportion of aragonite to calcite is changed from 1.7∶1 to 2.7∶1.
文摘Simulate the production of phosphoric acid by wet process is conducted in batch experiments facilities by adopting phosphorus concentrate as raw material from Wengfu, Dazhou city, with a view to study sulfuric acid concentration, reaction time, crystallization temperature of calcium sulfate, active additive, the influence of seed crystal on the size and shape of calcium sulfate crystal under conditions of Wet process phosphoric acid productive process. The research results show that under the conditions of the liquid-solid ratio of 4:1, the sulfate acid stoichiometric ratio of 1.1, phosphoric acid mass fraction of 21%, the crystallization temperature of 75°C, crystallization time of 120 min, when (NH4)2SO4 taken as active additives, Mg-doped calcium sulphate crystal as crystal seed can obtain rodlike crystallization of stability, thickness, uniformity.
基金Project(50904015) supported by the National Natural Science Foundation of ChinaProject(N090402012) supported by the Fundamental Research Funds for Central Universities of China
文摘To investigate the hydrogen permeability of calcium fluoride used for electroslag remelting(ESR) process,"Gas-slag-metal" osmosis process under argon atmosphere saturated with water vapor at 318 K was used to study the hydrogen permeability of slag containing calcium fluoride.The results indicate that the conventional slag,consisting of 70% CaF2 and 30% Al2O3,has the lowest hydrogen permeability.A parameter EH was proposed for evaluation of the hydrogen permeability of slags containing calcium fluoride.The hydrogen permeability decreases with increasing EH to a certain extent.An appropriate choice of slag for the ESR process can be obtained.These results also suggest that the hydrogen pick-up in steel after remelting might be reduced when a slag with low hydrogen permeability is used.
文摘BACKGROUND Calcium pyrophosphate dihydrate deposition disease(CPPD),or pseudogout,is an inflammatory arthritis common among elderly patients,but rarely seen in patients under the age of 40.In the rare cases presented of young patients with CPPD,genetic predisposition or related metabolic conditions were almost always identified.CASE SUMMARY The authors report the case of a 9-year-old boy with no past medical history who presented with acute knee pain and swelling after a cat scratch injury 5 d prior.Synovial fluid analysis identified calcium pyrophosphate dihydrate crystals.Further MRI analysis identified osteomyelitis and a small soft tissue abscess.CONCLUSION This case presents the extremely rare diagnostic finding of calcium pyrophosphate dihydrate crystals in a previously healthy pediatric patient.The presence of osteomyelitis presents a unique insight into the pathogenesis of these crystals in pediatric patients.More research needs to be done on the role of CPPD in pediatric arthritis and joint infection.
基金Supported by the National High Technology Research and Development Program of China(2011AA060701)the National Water Pollution Control and Management Science Program of China(2009ZX07529-005)
文摘The present work focused on the recycle of the sulfate and the metal ions from acidic wastewater discharged by nonferrous metallurgical industry. The effects of the temperature, the reactant concentration, the stirring speed and the metal ions on the reactive crystallization process of calcium sulfate between sulfuric acid and lime were systematically investigated. The morphology of the precipitated crystals evolved from platelet-like and needle-like shape to rod-like shape when the temperature was increased from 25 to 70 °C. An increase in the agglomeration of calcium sulfate was found with increasing lime concentration. Metal ions markedly retard the rate of crystallization of calcium sulfate dihydrate. The crystallization of gypsum was slowed with the existence of Mg2+in the solution, and the morphology of gypsum was transformed from platelet-like shape to rod-like shape when Mg2+ concentration reached 0.08 mol·L 1. The amorphous ferric hydroxide was coated on the calcium sulfate after the co-precipitation process while Zn2+and Al3+ions in the solution enhanced the agglomeration of the calcium sulfate by absorbing on the surface of the crystals. Comprehensive acidic wastewater containing heavy metals was efficiently purified by the two stage lime neutralization technology, and highly agglomerated gypsum precipitates with needle-like shape were obtained. The precipitates could be purified by sulfuric acid washing, and the metal ions were effectively separated from the calcium sulfate by-products.
文摘Hydroxyapatite (Ca10(PO4)6(OH)2) is widely used as bio-ceramic materials and as adsorbents for separation of bio-molecules. These materials have also been used as adsorbents for heavy metals, supports and as catalysts in oxidation and dehydrogenation reactions. The catalytic performance of these materials depend on the lattice substitution of Ca sites in Hydroxyapatite structure by varied cations as Na, Mg, Sr and Mn, which result in changes in various structural pro perties as crystallinity and morphology. Pure calcium hydroxyapatite (S1) and Cr loaded hydroxyl apatite (S2, S3, S4 and S5) of different chromium concentrations have been prepared by wet precipitated method. An in-vitro examination is essential to investigate the mechanism of the deficient HA and tissue interface reaction by preparing SBF (Simulated Body Fluid) through the elemental and chemical analysis of Ca, P and Cr. FTIR used to analyze the samples after incubation in SBF for 24 day. PH of the samples also was measured at the first period of immersion time. At high loading of chromium ions, the formation of carbonate apatite decrease. The concentrations of the chromium in the Cr_HA crystal during the soaking in SBF are very safe dose for human.
文摘The reaction studied in this work is the synthesis of nanometric size calcium carbonate by carbonation of a suspension of lime, which represents the most common industrial route. The carbonation was proceeded in a pilot batch reactor. This article presents a method for the determination of nucleation and crystal growth rates of calcium carbonate by following two macroscopic parameters: the mass production rate by precipitation and the specific surface area. The results give a constant nucleation rate around 4 × 1015m-3 ·s-1 and a decreasing crystal growth rate between 0.2 and 2 × 10-10 m·s-1. It also provides the main characteristics of the monoparticle size distributions (i.e. the mean particle sizes and in situ coefficient of variation) in the agglomerates, which cannot be obtained by other known methods. For the carbonation carried out in this work, the mean mass particle size at the end of the reaction is about 300 nm and the coefficient of variation of 0.28 indicates a narrow particle size distribution of the monoparticles.
基金Supported by the National Natural Science Foundation of China(51304184)the Coal Based Key Scientific and Technological Project of Shanxi Province(MC2014-06)
文摘In Na_2O–CaO–SiO_2–H_2O system,systematic investigations of phase and morphology of calcium silicate in hydrothermal conditions were concisely conducted for high-value utilization of silicon resource in high-alumina fly ash(HAFA).The results show that crystal composition and phase may be affected by relatively low concentration of NaOH,and sodium ions are rearranged into the structure to form NaCaHSiO_4 and Na_2Ca_3H_8Si_2O_(12) with different C/S ratio at high concentration of Na OH.In addition,phases in wollastonite group possess the morphology of nano fiber.Formation of nano fiber is attributed to the difference of surface energies between axial and radial direction,and higher temperatures lead to easier growth along radial direction.The preparation of C–S–H with different phases and morphologies can guide for the application of silicate solution with high alkalinity with different purposes.
基金Funded by the National Natural Science Foundation of China(No.60808024)
文摘The crystallization kinetics of 38.0CaO-38.0Al2O3-10.5BaO-6.5MgO-6.0Y2O3-1.0(Na2O+K2O)(wt%) glass was studied by differential scanning calorimeter(DSC) and X-ray diffraction(XRD) techniques.The results showed that DSC curves of calcium aluminate glass have a single glass transition temperature followed by one crystallization peak for the heating rates β=5 K/min and two crystallization temperatures Tp1 and Tp2 for β≥10 K/min.The activation energies of crystallization obtained from the Gao-Wang model of the first exothermal peak and the second exothermal peak of calcium aluminate glass are 340 and 662 kJ/mol,respectively.The Avrami exponents of the both crystallization peaks are approximately 2,indicating the twodimensional crystalline growth during its transformation from amorphous to crystalline.Ca12Al14O33,Ca3Al2O6 and unknown crystalline phases firstly appear when calcium aluminate glass is heat-treated.With the extending of heat-treatment duration,BaAl2O4 phase comes out.
文摘Nephrolithiasis seems to be the result of crystal formation,aggregation and retention in the kidney during crystalluria.These processes have to occur within the short urinary transit time through the kidney being in the order of few minutes.Recently much work was done on rather qualitative aspects of nephrolithiasis like genetics,metabolism and morphology.In this review we try to provide some quantitative information on urinary supersaturation with respect to stone minerals,especially Ca oxalate(CaO x),on the formation and aggregation of Ca Ox crystals and on crystal retention in the kidney.The paper is centered on idiopathic Ca nephrolithiasis being the most frequent stone disease with only partially known pathogenesis.New aspects of the role of urinary macromolecules in stone formation and of the mechanism of crystal aggregation are provided.
基金financial support of National Nature Science Foundation (21376178)TIDA giant growth plan (2011-XJR13020)+3 种基金Tianjin Science and technology support program (12ZCDZSF06900)Tianjin University of Science and Technology fund for scientific research (20120119)Tianjin education commission program (20130509)Research fund for the doctoral program of higher education of China(20131208120001)
文摘1 Introduction Calcium sulfate deposition is one of the most important and serious problems faced by heat transfer equipment during operation(Pavlos et al.,1999;Liu et al.,1996).The crystallization of calcium sulfate is known as a
基金financial support of National Nature Science Foundation (21376178)TIDA giant growth plan (2011-XJR13020)+3 种基金Tianjin Science and technology support program (12ZCDZSF06900)Tianjin University of Science and Technology fund for scientific research (20120119)Tianjin education commission program (20130509)Research fund for the doctoral program of higher education of China (20131208120001)
文摘1 Introduction There exist calcium and sulfate ions outside sodium chloride in solution mining for calcium sulfate brine.The calcium and sulfate ions not only affect the purity of the vacuum salt products,but also increase the scaling of vacuum evaporation tanks and brine reusing pipes.Additives have certain impacts on the crystallization dynamics(Randolph et al.,1971).The
基金Project(2005CB623901) supported by the Major State Basic Research and Development Program of China
文摘Calcium phosphate film was prepared by electrochemical deposition technology. Subsequently, the alkaline treatment process of calcium phosphate film in 0.1 mol/L NaOH solution was monitored on real time by the piezoelectric quartz crystal impedance (PQCI) technique. The variations of morphology and composition for the alkaline treatment products were characterized by scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) and X-ray diffraction (XRD), respectively. The dynamic variations of calcium phosphate can be characterized by the change of equivalent circuit parameters. The results show that the forming process of hydroxyapatite (HA) is composed of three stages: (1) acidic calcium phosphate dissolution; (2) phase transformation; and (3) HA formation. Furthermore, the correlative kinetic equations and parameters are obtained by fitting the static capacitance (Cs)—time curves.
文摘Leaves of twenty-two (22) species of Combretum in Nigeria were examined for occurrence and distribution of different types and sizes of ergastic substances (calcium oxalate crystals). Fresh and herbarium specimens were used for the study. These specimens were wax embedded, sectioned, mounted and micro-photographed using Leica WILD MPS 52 microscope camera on Leitz Diaplan microscope. Results revealed two types of calcium oxalate crystals—crystal sand and druses. Based on the observed differences in the size of the crystals, three groups of calcium oxalate crystals are reported [large crystals: 180.0 - 360.0 μm (241 ± 44.57 μm), moderate crystals: 90.0 - 144.0 μm (117.0 ± 20.60 μm), and small crystals: 18.0 - 72.0 μm (50.21 ± 20.42 μm)]. Crystal sand was found only in Combretum sp. 1 but druses of varying sizes predominated amongst species of the genus. Crystals were distributed within the spongy mesophyll, palisade mesophyll, sub-epidermis adaxial, sub-epidermis abaxial and between the palisade and spongy mesophyll. The findings of this work provide information on the occurrence and distribution of the crystals in the leaf epidermis of these taxa in Nigeria. The formation, occurrence and distribution of the crystal type in the Combretum species constitute dependable taxonomic character especially when combined with other characters.
文摘Preparation and optical characterisation of Erbium doped KY3F10 single crystals are reported. The crystals were grown using the Czochralski pulling technique. The single phase was controlled by X-ray diffraction analysis. Room temperature optical spectra were recorded between 200 and 1600 nm. They were used to fit the three phenomenological Judd-Ofelt (JO) parameters Ωt (t = 2, 4, 6). The emission transition probabilities, branching ratios and radiative lifetimes are then deduced. The possibility to use such material for laser emissions is discussed.
