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1.
This study aimed to evaluate the combined effects of eggshell extract and ultrasonic irradiation on the polymorphic transformation of calcium carbonate (CaCO 3). In this context, XRD, Raman spectroscopy, SEM, AFM, TGA-FTIR, BET, and zeta potential analysis were used to identify and characterize the different polymorphs of CaCO 3 obtained in the absence and presence of eggshell extract in the media with and without ultrasonic irradiation. The morphology and polymorphic nature of the CaCO 3 crystals were observed to change, which indicated that the eggshell extract and ultrasonication influenced the structure and crystallization of CaCO 3. The structural analysis results indicated that the addition of eggshell extract to the media resulted in the full transformation of calcite to the vaterite polymorph. The results also showed that ultrasonic irradiation had a more significant influence on the BET specific surface area of the crystals compared to the eggshell extract media. Furthermore, a Box–Behnken design with response surface methodology was employed to determine the optimal operating conditions for CaCO 3 crystallization. The effects of stirring rate, extract concentration, and ultrasonic power on the BET surface area were investigated. The results show that the data sufficiently fit the second-order polynomial model. Understanding the eggshell extract-mediated polymorphic transformation with ultrasonic irradiation obtained in this study makes it possible to control the polymorphic formation and modify the product characteristics. 相似文献
2.
Calcium carbonate (CaCO 3)/iron oxide composites were synthesized through a simple one‐step impregnation procedure by mixing iron oxide nanoparticles (γ‐Fe 2O 3 and Fe 3O 4) of about 6 nm in size and CaCO 3 microparticles (Φ = 2 µm–8 µm, vaterite phase). The morphology and structural properties of CaCO 3, iron oxide nanoparticles and CaCO 3/iron oxide composites were characterized as a function of low iron content (0 %w to 3.2 %w) by scanning electron microscopy and transmission electron microscopy, X‐ray diffraction and 57Fe Mössbauer spectrometry. The phase transformations induced by thermal treatment and laser irradiation were investigated in situ by X‐ray thermodiffraction (XRTD) and Raman spectroscopy. We have shown that the phase transformations observed by XRTD are also observed under laser irradiation as a consequence of the absorption of the laser irradiation by iron oxide nanoparticles. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
3.
The purposes of this article were to investigate the influences of synthesis strategy on the CaCO 3 crystals on the cellulose substrate. In this study, CaCO 3 crystals were synthesized using cellulose as matrix by the microwave-assisted method and ultrasound agitation method, respectively. The CaCO 3 crystals on the cellulose substrate were characterized by means of X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy (SEM). Experimental results demonstrated that the synthesis strategy had a dramatically influences on the phase, microstructure, morphology, thermal stability, and biological activity of the CaCO 3 crystals. The pure phase of vaterite spheres with the diameter of about 320–600 nm were obtained by ultrasound agitation method, meanwhile, the mixed phases of calcite and vaterite with the diameter of about 0.82–1.24 μm were observed by microwave-assisted method. In view of experimental results, one can conclude that the ultrasound agitation method do more favors to the synthesis of CaCO 3 crystals with uniform morphology and size, compared with microwave-assisted method. Furthermore, cytotoxicity experiments indicated that the CaCO 3 crystals on the cellulose substrate had good biocompatibility and could be a candidate for the biomedical applications. 相似文献
4.
Isotactic polypropylene (IPP) and calcium carbonate (CaCO 3) nanocomposites were prepared by melt extrusion in a twinscrew extruder. The effect of CaCO 3 nanoparticles on the crystallization and thermal conductivity (TC) of PP was studied by thermal analysis (DSC) and thermal conductivity analysis (TCA). The introduction of CaCO 3 nanoparticles resulted in an increase in crystallinity. The incorporation of this nanoparticle (up to 15 phr) caused a significant increase of TC of PP, especially for larger filler content. Several models were used for prediction of TC of the nanocomposites. The experimental results had a good correlation with the Ce Wen Nan Model. 相似文献
5.
In the present work, nano-calcium carbonate powder was prepared by micropore dispersion method with assistance of oleic acid as surfactant. CO 2 gas was dispersed into the Ca(OH) 2/H 2O slurry via a glass micropore-plate with the diameter of micropore about 20 μm. To investigate the effect of oleic acid on the size of CaCO 3 particles, different amount of oleic acid was added in Ca(OH) 2/H 2O slurry at 5 °C and 25 °C, respectively. XRD patterns show that cubic calcite is the only crystalline phase in all cases. ZPA data and TEM photo indicate that the average particle size synthesized at 5 °C without oleic acid is of about 40 nm, slightly smaller than that of prepared at 25 °C, and that the dispersity of sample prepared at 5 °C is better than that of 25 °C. When oleic acid is added in both temperatures, the average particle size decreases a little. FT-IR spectra demonstrate that oleic acid interacts with Ca 2+ and carbon-carbon double bond existed on the surface of particle. Consequently, two opposite roles of oleic acid during the process of preparation of nano-CaCO 3 were proposed, namely preventing nanoparticles from growing during reaction and making nanoparticles reunite to a certain extent after reaction. 相似文献
6.
Abstract The Raman spectrum of polycrystalline vaterite is presented and compared to spectra of calcite and aragonite, the other two common CaCO 3 polymorphs; Raman spectroscopy easily distinguishes between these three polymorphs. An important feature of the Raman spectrum of vaterite is splitting of both the ν 1 and ν 4 peaks. The splitting of the ν1 peak implies two distinct site symmetries for the CO 3 ?2 groups. A definitive crystal structure determination of vaterite is not yet available, but none of the three proposed structures for vaterite show such a feature. 相似文献
7.
The hydration, precarbonation, and postcarbonation microstructural and compositional attributes of 2 variants of concrete were studied using scanning electron microscope, energy dispersive spectroscopy, and X‐ray diffraction techniques. Results obtained showed presence of large number of diffraction peaks indicative of SiO 2 as major phase. Higher pH, alkalinity, and absence of effects of carbonation were suggested from the presence of portlandite peaks. Evidence of effect of carbonation was studied through the analysis of the experimental diffraction peaks obtained postexposure to accelerated carbonation in a controlled environment. Presence of all the 3 polymorphs of calcium carbonate (CaCO 3) such as aragonite, vaterite, and calcite depending upon the moisture content and the material constituting the concrete sample were envisaged signifying carbonation. Precipitation of these CaCO 3 crystals was responsible for depletion of CH as well as calcium–silicate–hydrate, ettringite with the progress of carbonation as suggested by their absence in the X‐ray diffraction diffractograms of the carbonated samples. The crystal structure of the newly formed minerals in both the variants of concrete sample was highly controlled by the stages of carbonation, with development of amorphous CaCO 3 (amalgamated with that of calcium hydrates) in early stages of carbonation as well as fully developed rhombohedral CaCO 3 crystals in later stages. 相似文献
8.
In this study γ-Fe 2O 3 nanoparticle, surface-coated with increasing amount of oleic acid, have been prepared while the stability against particle degradation under laser excitation intensity was investigated. Maghemite nanoparticle was obtained via oxidation of magnetite nanoparticle, the latter synthesized by co-precipitation of Fe (II) and Fe (III) ions in alkaline medium. By varying the experimental conditions of surface-coating maghemite nanoparticles with oleic acid, samples with different grafting coefficient were obtained and investigated using X-ray diffraction and different spectroscopic techniques, namely Raman, Mössbauer, and infrared. The amount of oleic acid adsorbed on the maghemite surface was estimated via the carbon content obtained from elemental analysis. 相似文献
9.
A new route to prepare CaCO 3 nanoparticles/polyvinylpyrrolidone (PVP) nanofibers is reported. An aqueous solution of K 2CO 3 was added to a solution of CaCl 2/PVP, resulting in in-situ preparation of CaCO 3 nanoparticles. Then composite nanofibers containing CaCO 3 nanoparticles were successfully prepared by electrospinning. The morphology of the resulting composite nanofibers was characterized by field-emission scanning electron microscopy. In addition, the products were characterized by thermogravimetry analysis and Fourier transform infrared spectra. 相似文献
10.
Pimelic acid (PA) was used as a new surface modifier for CaCO 3. The effects of PA treatment on the crystallization, morphology, and mechanical properties of PP/CaCO 3 composites were investigated. Fourier transform infrared (FTIR) spectroscopy analysis revealed that PA bonded to CaCO 3 and formed a calcium pimelate surface layer after reacting with CaCO 3. The results of wide angle X-ray diffraction (WAXD), differential scanning calorimetry (DSC), and polarized light microscopy (PLM) proved that the PA treated CaCO 3 induced a large amount of β -iPP and decreased the spherulitic size of PP. The results of scanning electron microscopy (SEM) showed that the PA treatment enhanced the interfacial adhesion between the filler and the matrix, indicating the improvement of the compatibility between PP and CaCO 3. The toughness of the composites was improved by the more ductile β -form spherulites. When 1% of PA treated CaCO 3 was added, the notched impact strength reached its maximum, a value of 19.79 kJ/m 2, which was 3.64 times greater than that of the pure PP. 相似文献
11.
Lecithin-adsorbed magnetic nanoparticles were prepared by three-step process that the thermal decomposition was combined with ultrasonication. Experimental parameters were three items—molar ratio between Fe(CO) 5 and oleic acid, keeping time at decomposition temperature and lecithin concentration. As the molar ratio between Fe(CO) 5 and oleic acid, and keeping time at decomposition temperature increased, the particle size increased. However, the change of lecithin concentration did not show the remarkable particle size variation. 相似文献
12.
In this study, the influence of surface coating on the magnetic and heat dissipation properties of Fe 3O 4 nanoparticles was investigated. Fe 3O 4 nanoparticles that ranged in size between (particle sizes of 20 and 30 nm) were coated with polyethylenimine (PEI), oleic acid, and Pluronic F-127. Surface coatings that were composed of thick layers of oleic acid and Pluronic F-127 reduced dipole interactions between the particles, and resulted in reduced coercivity and decreased Néel relaxation times. The ac magnetization measurements revealed that the heat dissipation of the PEI-coated Fe 3O 4 nanoparticles was induced by hysteresis loss and Brownian relaxation loss and that of the oleic-acid-coated Fe 3O 4 nanoparticles was mainly induced by hysteresis loss and Néel relaxation loss. 相似文献
13.
The influence of high-density polyethylene (HDPE) and nano-CaCO 3 of various content ratios on the crystallization of polypropylene (PP) was investigated by differential scanning calorimetry, dynamic rheology, wide angle X-ray diffraction (WAXD), and Izod impact strength measurements. The results showed that HDPE and PP were phase separated in their blends and the additive CaCO 3 filler mainly dispersed in the PP phase, acting as a nucleation agent to promote the crystallization of PP. For the samples HDPE/ nano-CaCO 3 30/0 and 25/5, the β crystals content was much higher than the other samples. The reason is that the viscosity difference between HDPE and PP led to a velocity difference, which could induce shear stress at the interfaces of HDPE and PP during injection molding. The intensive shear stress at their phase interfaces is advantageous for orientation of the chains, inducing the formation of β crystals. However, with the increment of CaCO 3 content, there were dual effects of CaCO 3 on the crystallization of PP: at low CaCO 3 content, it would hamper the orientation of PP chains, thus leading to a decrease of β crystals; at high CaCO 3 content, it would induce β crystals by itself. 相似文献
14.
An aqueous magnetic suspension was prepared by dispersing amphiphilic co-polymer-coated monodispersed magnetite nanoparticles synthesized through thermal decomposition of iron acetylacetonate (Fe(acac) 3) in a mixture of oleic acid and oleylamine. The average diameter of narrow-size-distributed magnetite nanoparticles varied between 5 and 12 nm depending on the experimental parameters such as reaction temperature, metal salt concentration and oleic acid/oleylamine ratio. Though the as-synthesized particles were coated with oleate and were dispersible in organic solvent, their surfaces were modified using amphiphilic co-polymers composed of poly(maleic anhydride-alt-1-octadecene) and polyethylene glycol-methyl ether and made dispersible in water. Infrared spectra of the sample indicated the existence of −COOH groups on the surface for further conjugation with biomolecules for targeted cancer therapy. 相似文献
15.
Bilayer oleic acid-coated Fe 3O 4 nanoparticles can be applied in more areas than single layer oleic acid-coated ones because they can be well dispersed not only in nonpolar carrier liquids but also in polar carrier liquids, while the single layer oleic acid-coated ones can be dispersed only in nonpolar carrier liquids. Therefore, it is of significance to characterize the surface structure of bilayer and single layer oleic acid-coated Fe 3O 4 nanoparticles. However, there existed a discrepancy in the characteristic FTIR spectrum of the secondary layer in bilayer oleic acid-coated Fe 3O 4 nanoparticles. The goal of this paper was to resolve the discrepancy through using FTIR and TGA together with dispersibility to characterize the surface structure of bilayer and single layer oleic acid-coated Fe 3O 4 nanoparticles. The results showed that the band at 1710 cm −1 was the characteristic band of the secondary layer in bilayer oleic acid-coated Fe 3O 4 nanoparticles. It can be used to distinguish whether the oleic acid-coated Fe 3O 4 nanoparticles are bilayer or not. 相似文献
16.
The synthesis of calcite (CaCO 3) nanoparticles by mechanochemical reaction and subsequent heat treatment was investigated. A solid-state displacement reaction CaCl 2 + Na 2CO 3 CaCO 3+2NaCl was induced during mechanical milling of a CaCl 2+ Na 2CO 3 powder mixture. Heat treatment of the as-milled powder at 350°C completed the reaction, forming crystalline CaCO 3 nanoparticles separated from each other in a dry-salt matrix. A simple washing process to remove the matrix yielded calcite single phase ultrafine powder. The mean particle size was controlled by changing the volume fraction of CaCO 3 in the matrix. 20% volume fraction yielded nanoparticles of ~ 140 nm in size, whereas 10% volume fraction led to ~ 80 nm size nanoparticles. 相似文献
17.
Detailed X-ray analysis of variations in the structure of yttrium orthoborate in the process of successive high-temperature isothermal anneals of an originally amorphous precursor state is performed. It is established that the diffraction reflex intensity distribution of YBO3 measured at room temperature, obtained in the initial stages of crystallization, corresponds to the known low-temperature vaterite phase with the space group (sp. gr.) P63/m and, after a series of high-temperature anneals, it transforms into a distribution known for the vaterite modification with the sp. gr. P63/mmc and the same lattice parameters. This result is explained on the basis of the sphericity of X-ray waves and is connected with the transformation of the crystallites from a spherical shape upon low-temperature anneals to a dumbbell shape upon high-temperature anneals. As a result of in situ experiments conducted at 1250°C, it was established that the initial low-temperature hexagonal vaterite cell transforms above 1000°C into a monoclinic cell. 相似文献
18.
Zinc blende (ZB) CdSe hollow nanospheres were solvothermally synthesized from the reaction of Cd(NO 3) 2·4H 2O with a homogeneously secondary Se source, which was first prepared by dissolving Se powder in the mixture of ethanol and oleic acid at 205 °C. As Se power directly reacted with Cd(NO 3) 2·4H 2O in the above mixed solvents, wurtzite (W) CdSe solid nanoparticles were produced. Time-dependent experiments suggested that the formation of CdSe hollow nanospheres was attributed to an inside-out Ostwald ripening process. The influences of reaction time, temperature and ethanol/oleic acid volume ratio on the morphology, phase and size of the hollow nanospheres were also studied. Infrared (IR) spectroscopy investigations revealed that oleic acid with long alkene chains behaved as a reducing agent to reduce Se powder to Se 2− in the synthesis. Photoluminescence (PL) measurements showed that the ZB CdSe hollow nanospheres presented an obvious blue-shifted emission by 42 nm, and the W CdSe solid nanoparticles exhibited a band gap emission of bulk counterpart. 相似文献
19.
The influence of the oleic acid surface coating on Fe 3O 4 and NiFe 2O 4 nanoparticles on their magnetic and calorimetric characterization was investigated. Fe 3O 4 nanoparticles (particle sizes of 15-20 and 20-30 nm) and NiFe 2O 4 nanoparticles (particle sizes of 20-30 nm) were dispersed in oleic acid. The surface coating resulted in a decrease in the dipole-dipole interaction between the particles, which in turn affected the coercivity and heat dissipation of the nanoparticles. The coercivity of the oleic-acid-coated nanoparticles was found to be lower than that of the uncoated nanoparticles. The temperature rise in the oleic-acid-coated nanoparticles was greater than that of the uncoated nanoparticles; this temperature rise was associated with the relaxation losses. The viscosity dependence on the self-heating temperature of Fe 3O 4 nanoparticles (15-20 and 20-30 nm) under an ac magnetic field was measured. The temperature rise for both the Fe 3O 4 nanoparticles (15-20 and 20-30 nm) exhibited a strong dependence on viscosity at each magnetic field frequency, and the contribution of Brownian relaxation loss to the temperature rise was revealed. Moreover, an in vitro cytotoxicity test of Fe 3O 4 and NiFe 2O 4 was performed using human cervical carcinoma cells (HeLa), and the cytotoxicity of NiFe 2O 4 nanoparticles was compared to that of Fe 3O 4 nanoparticles. 相似文献
20.
Calcium carbonate (CaCO 3) nanoparticles (9, 15, and 21 nm) were synthesized by solution spray of CaCl 2 and NH 4HCO 3 with sodium lauryl sulfate (SLS) as a stabilizing agent, and their effect was studied on polybutadiene rubber (PBR) with variations in wt% loading (4, 8, and 12%). The results of PBR nanocomposites were compared with commercial CaCO 3 (40 μm) and fly ash (75 μm) filled PBR microcomposites. Properties such as tensile strength, young modulus, elongation at break, glass transition temperature, decomposition temperature, and abrasion resistances were determined. Profound effect in properties was observed, because nanometric size of CaCO 3 particles synthesized using solution spray technique. Maximum improvement in mechanical and flame retarding properties was observed at 8 wt% of filler loading. This increment in properties was more pronounced in 9-nm size CaCO 3. The results were not appreciable above 8 wt% of nanofillers because of agglomeration of nanoparticles. In addition, an attempt was made to consider modeling Young’s modulus of PBR–nano CaCO 3 which was predicted by modified Halpin–Tsai equation. It was observed that the predication by the Guth equation and modified Halpin–Tsai equation agreed very well with experimental, whereas the Halpin–Tsai equation can only applied to predict the modulus of rubber nanocomposites in the range of low addition of nanofiller, which agrees the Nielsen equation. 相似文献
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