Crystal Structure Of Product Research Articles

Effects of ultrasound and process parameters on the precipitation of CaCO3 polymorphs from synthetic soda ash industry liquid waste

In this study, calcium carbonate has been produced continuously using synthetic soda ash industry liquid waste with different process variables. The effect of process variables such as gas flow rate (1000 to 4000 ml/min), waste liquid flow rate (80 to 280 ml/min), CO2 concentration (20% to 40%), ultrasonic probe area (2.83 to 4.90 cm2), ultrasonic probe immersion depth (2/3 h to 1/2 h), ultrasonic power (0% to 70%), and reaction temperature (30°C to 50°C) on product quality was investigated by using D-optimal design. According to the experimental results, precipitated calcium carbonate (PCC) having different particle sizes (D (4:3)) ranging from 2.9 µm to 8.7 µm was obtained. It was observed that crystal structure of product is highly dependent on the pH of reaction medium. While vaterite and aragonite crystal structure were formed at low pH values, calcite crystal structure was formed at higher pH values. Particle size decreases when ultrasound power applied at 35% when compared to silent reactions. Overall, precipitated CaCO3 with desired particle size and crystal type can be produced by controlling the process variables. The CaCO3 was produced in amounts ranging from 3.4 g to 11 g depending on the experimental conditions.

Synthesis of Zeolite X from Bentonite via Hydrothermal Method

Zeolite X were successfully synthesized from bentonite from Lopburi province, in Thailand using the two-step of hydrothermal method under optimum condition without calcination. The first step of hydrothermal were obtained at 200 °C for 3 h to remove unreacted impurity minerals such as quartz and muscovite. The secondary step of hydrothermal were obtained at 90 °C for 120 h for synthesis of zeolite X. The characterization of zeolite X were examined by x-ray diffraction (XRD), scanning electron microscopy (SEM), and infrared spectroscopy (FT-IR), respectively. The crystal structure of product was determined as zeolite X by XRD. The morphology of SEM images for zeolite X is octahedral shape. FTIR spectra are in accordance with the other characterization results.

Novel One-Pot Synthesis of Methyl 4-Hydroxy-2-thioxo-1,2-dihydroquinoline-3-carboxylate: Synthetic and Crystallographic Studies

A new suitable method of synthesis of methyl 4-hydroxy-2-thioxo-1,2-dihydroquinoline-3-carboxylate by condensation of methyl 2-isothiocyanatobenzoate and methyl malonate is described. The structure of the compound both and by-product methyl 2-(methoxycarbonothioylamino)benzoate was confirmed by means of elemental analysis, 1H NMR, 13C NMR, LC/MS and single crystal X-ray diffraction. UV/Vis and IR spectra of compounds are described. The presence of a strong intramolecular hydrogen bond between the hydroxy group and the carbonyl oxygen atom of the ester group in methyl 4-hydroxy-2-thioxo-1,2-dihydroquinoline-3-carboxylate is shown. The crystal structure of product was stabilized through intermolecular hydrogen bonds.

Insertion of 1-t-butylpropyne into singly tucked-in permethyltitanocene. Synthesis, crystal structure of product and transition-state geometry

The singly tucked-in titanocene [(η5-C5Me5)TiIII{η5:η1-C5Me4(CH2)}] (1) reacted with one equivalent of 1-tert-butylpropyne to yield the propenyl-tethered regioisomer [(η5-C5Me5)Ti(η5:η1-C5Me4CH2C(t-Bu) = κCMe)] (3). The exclusive formation of paramagnetic 3 was proved experimentally and steric reasons were clarified by DFT calculation of transition state which involves both π-systems on the alkyne for bonding interaction with the metal and with sp2 carbon atom of exomethylene group of 1. The obtained compound 3 is by 40 kJ/mol lower in energy than its hypothetical isomer having t-Bu group on Cα of the tether.

Effect of Reaction Temperature on Structure, Appearance and Bonding Type of Functionalized Graphene Oxide Modified P-Phenylene Diamine.

In this study, graphene oxides with different functionalization degrees were prepared by a facile one-step hydrothermal reflux method at various reaction temperatures using graphene oxide (GO) as starting material and p-phenylenediamine (PPD) as the modifier. The effects of reaction temperature on structure, appearance and bonding type of the obtained materials were investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). The results showed that when the reaction temperature was 10–70 °C, the GO reacted with PPD through non-covalent ionic bonds (–COO−H3+N–R) and hydrogen bonds (C–OH…H2N–X). When the reaction temperature reached 90 °C, the GO was functionalized with PPD through covalent bonds of C–N. The crystal structure of products became more ordered and regular, and the interlayer spacing (d value) and surface roughness increased as the temperature increased. Furthermore, the results suggested that PPD was grafted on the surface of GO through covalent bonding by first attacking the carboxyl groups and then the epoxy groups of GO.

CuO hollow microspheres self-assembled with nanobars: Synthesis and their sensing properties to formaldehyde

CuO hollow microspheres were synthesized via a facile hydrothermal process. Copper nitrate trihydrate (Cu(NO3)2·3H2O) was used as copper source and cetyltrimethylammonium bromide (CTAB) was used as soft template. The morphology and crystal structure of products were systematically investigated by XRD, FESEM, TEM, FT-IR and BET. CuO hollow microspheres were identified as monoclinic structure. The hollow microspheres were assembled by a number of nanobars which were composed of smaller nanograins. The formaldehyde gas sensing properties of CuO products with different morphologies were investigated. The results indicated that the sensor based on CuO hollow microspheres exhibited high gas response, fast reversible and response, good selectivity and stability to formaldehyde gas. This is attributed to hollow structures with the largest specific surface area and an effective gas diffusion path in favor of mass transportation and gas diffusion.

Large-Scale Preparation, Chemical Exfoliation, and Structural Modification of Layered Zinc Hydroxide Nanocones: Transformation into Zinc Oxide Nanocones for Enhanced Photocatalytic Properties

A convenient and effective water-bath method is developed for the preparation of layered zinc hydroxide nanocones (NCs) intercalated with dodecyl sulfate (C12H25OSO3–, DS–) anions in large quantities. Furthermore, the morphology, size, and crystal structure of products could also be readily tuned by adjusting the experimental parameters. In particular, unilamellar zinc hydroxide nanosheets with a thickness of approximately 0.9 nm could be achieved by exfoliating the layered zinc hydroxide NCs in the formamide–water mixed solution. It is worth mentioning that layered zinc hydroxide NCs could be topologically converted to basic zinc sulfates (Zn4SO4(OH)6·5H2O, Osaka mine) and zinc oxide (ZnO) NCs through a calcination process at different temperatures. Benefitting from a special structure, narrow bandgap, and higher surface area, the photodegradation behavior of ZnO NCs for methylene blue (MB) solution is better than that of ZnO nanorods.

An Efficient Synthesis of Tetracyclic Pyrano[2,3‐d]pyrimidines

A series of pyrano[2,3‐d]pyrimidine derivatives have been synthesized by the reaction of 2‐amino‐3‐cyano‐4H‐pyrans and acetic anhydride with acid catalyst . This method is very efficient because of short reaction times and easy work‐up, and it provides an efficient and promising synthetic strategy for the construction of the tetracyclic pyrano[2,3‐d]pyrimidine skeleton. The X‐ray crystal structures of products are confirmed, and the possible mechanism is provided in this paper.

Synthesis and gas-sensing properties of the silicon nanowires/vanadium oxide nanorods composite

As air pollution is becoming more and more serious in recent years, gas-sensing devices have attracted intensive attention. In particular, NO2 is one of the most toxic gases in the atmosphere, which tends to produce acid rain and photochemical smog. Thus, there is a strong demand of cheap, reliable and sensitive gas sensors targeting NO2. Gas sensors fabricated on silicon substrates with room-temperature operation are very promising in power saving, integrated circuit processing and portable detectors. More important, the silicon nanowires (SiNWs)-based devices are compatible with very large scale integration processes and complementary metal oxide semiconductor technologies. In the present work, the novel nanocomposite structure of (SiNWs)/vanadium oxide (V2O5) nanorods for NO2 detection is successfully synthesized. The SiNWs are fabricated by a combination of nanosphere lithography and metal-assisted chemical etching. Vanadium films are deposited on SiNWs by DC magnetron sputtering, and then V2O5 nanorods are synthesized with subsequent thermal annealing process for full oxidation in air. The morphology and crystal structure of product obtained are characterized by field-emission scanning electron microscopy and X-ray diffraction. The characterization results indicate that V2O5 nanorods are uniformly distributed on the surfaces of SiNWs. The increased specific surface area of SiNWs/V2O5 nanocomposite provides more adsorption sites and diffusion conduits for gas molecules. Therefore, the novel structure of the nanocomposite is conducive to gas-sensing. In addition, the sputtering time has an obvious influence on the morphology of vanadium oxide. With the increase of the sputtering time, the specific surface area and the number of p-n heterojunctions formed in the nanocomposite are both less than those of nanocomposite with appropriate sputtering time. The gas-sensing properties are examined by measuring the resistance change towards 0.5-4 ppm NO2 gas at room temperature by the static volumetric method. Results show that the nanocomposite with shorter deposition time has better gas-sensing properties to low-concentration NO2 gas than those of bare SiNWs and nanocomposite with longer deposition time. On the contrary, the responses of the nanocomposite to other high-concentration reducing gases are very low, indicating good selectivity. The enhancement in gas sensing properties may be attributed to the change in width of the space charge region, which is similar to the behavior of p-n junction under forward bias, in the high-density p-n heterojunction structure formed between SiNWs and V2O5 nanorods. In conclusion, these results demonstrate that the SiNWs/V2O5 nanocomposite has great potential for future NO2 gas detection applications with low consumption and good performance.

Hydrothermal synthesis and up-conversion luminescence properties of NaYF4:Yb3+,Tm3+ phosphors

An up-conversion luminescent material, NaYF4 doped with rare-earth (RE), possessed a high luminescence efficiency and excellent stability. As described herein, a series of hexagonal nano-prismatic NaYF4:Yb3+,Tm3+ up-conversion phosphors had successfully been synthesized through mild hydrothermal method. The influence of hydrothermal time, the content of sodium tartrate, activator, sensitizer and ammonium fluoride on the luminescence properties of the target product were systematically investigated by means of single factor experiments. Based on the single factor experiments, the orthogonal method was used to obtain the optimal preparation conditions of the sodium tartrate/RE mole ratio, the sensitizer Yb3+ ions content, the NH4F/RE mole ratio, and the hydrothermal time which were 0.5, 23%, 11, 13 h, respectively. The fluorescent emission spectra analysis results showed that the strongest blue up-conversion luminescence emission peaks (1G4→3H6 transition of Tm3+ ion) of the NaYF4:Yb3+,Tm3+ phosphors using sodium tartrate as complexing agent was located at 477 nm under 980 nm near infrared (NIR) laser diode excitation. Finally the target products using different complexing agent were prepared at optimum preparation condition, and characterized by X-ray diffraction, scanning electron microscope. The crystal structure of products using tartaric acid and citric acid as complexing agent was hexagonal, consisting of spheres with 100 nm diameter.

Synthesis and characterization of sol–gel derived ZrV2O7 fibers with negative thermal expansion property

Novel ZrV2O7 fibers with negative thermal expansion were prepared via combination of sol–gel process and thermal decomposition. The as-prepared fibers were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy and Raman spectroscopy. The results showed that the synthetic pH value had little influence on the crystal structure of products while showed significant effect on morphology. The fibers obtained at pH = 9 exhibited cylindrical morphology and its mean diameter was about 1 μm. The thermal expansion property of the as-prepared fibers was investigated by in situ XRD and thermal mechanical analyzer. All of the as-prepared fibers showed positive thermal expansion first and then negative thermal expansion, resulting from a phase transition from 3 × 3 × 3 superstructure to 1 × 1 × 1 cubic structure. The macro thermal expansion coefficients of ZrV2O7 ceramic rods increased with decreasing of fiber diameter. The mechanism of the phase transition was also discussed.

Synthesis of Alumina-Grafted Manganese Oxide Particles Using Surfactants through Coprecipitation Method and Their Thermal Properties

Alumina particles were grafted onto the surface of manganese oxide particles via the coprecipitation process using surfactant and cosurfactant. The phase of Mn/Al salts (Phase I) and the phase of precipitation agent (Phase II) were prepared in aqueous surfactant solution, separately. Phase II was added into Phase I and the reaction was performed to form the precursors of composites through hydrogen bonding between <TEX>$Mn(OH)_2$</TEX> and <TEX>$Al(OH)_3$</TEX> prepared by the reaction of Mn/Al salts with the precipitation agent. The alumina-grafted manganese oxide particles were obtained as a final product after calcination. The concentrations of Al salt and surfactant were varied to investigate their effects on the formation and the crystallinity of composites. In addition, the crystal structure of products could be controlled by changing the calcination temperature. Through thermal analyses, it was found that the thermal stability of manganese oxide was improved by the introduction of alumina on its surface.

IN SITUPREPARATION AND INHIBITORY ACTIVITY OF HYDROXYAPATITE/SILVER NANOCOMPOSITE

The hydroxyapatite (HAP) assembled microsphere chains/silver ( Ag ) nanocomposites were prepared by a facile in situ preparation method under hydrothermal condition. The crystal structure of products was characterized by X-ray diffraction (XRD) and the morphologies of products were investigated by transmission electron microscopy (TEM). The nanocomposites own large surface area and can hydrogen-bond to other substances by the hydroxyl group on the surface. The nanocomposites have good structural stability under the electrostatic effect of the silver nanoparticles and strong adsorbability of the HAP microsphere chains. The two substances combine to form special nanocomposite spheres. Specially, the HAP/ Ag nanocomposites have high inhibitory activity and can be applied in the environment and medicine fields. The nanocomposite structures can save the consumption of Ag materials.

Co-evaporation of transition metal salt and SiO powder toward copper(or nickel)/silicon-contained composite nanostructures

We demonstrate that several novel copper(or nickel)/silicon-contained composite nanostructures were successfully synthesized by co-evaporating SiO powder and corresponding transition metal salts (transition metal organic salt and transition metal inorganic salt), including nickel formate, cobalt acetate, and copper sulfate. The morphologies, compositions, and crystal structures of products were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectrometry (EDS), transmission electron microscopy (TEM) and high resolution transmission electron microscopy (HRTEM). The results indicate that the morphology and composition of formed copper(or nickel)/silicon-contained composite nanostructures are dramatically influenced by the distance between SiO powder and transition metal salts, or by the pre-sintering temperature of the reactants. The possible formation mechanisms of these composite nanostructures were discussed on the basis of experimental observations.

Crystal structures and growth mechanisms of octahedral and decahedral Au@Ag core-shell nanocrystals prepared by a two-step reduction method

Octahedral and decahedral Au@Ag core-shell nanocrystals have been prepared in high yields using a two-step reduction method. In the first step, octahedral or decahedral Au core seeds were prepared by reducing HAuCl4·4H2O in tetraethylene glycol (TEG) under microwave (MW) heating or in diethylene glycol (DEG) under oil-bath heating, respectively, in the presence of polyvinylpyrrolidone (PVP) as a polymer surfactant. In the second step, Ag shells were overgrown on these Au seeds in N,N-dimethylformamide (DMF) in the presence of PVP under oil-bath heating for three hours or MW heating for ten minutes. Crystal structures of products were characterized using TEM, TEM–EDS, and SEM. Under oil-bath heating, octahedral or decahedral Au@Ag nanocrystals covered by uniform Ag shells were prepared. On the other hand, decahedral Au@Ag core-shell particles are formed through stepwise growth of tetrahedral units after covering thin Ag shells over decahedral Au cores under fast MW heating. Since the growth rate of Ag shells on corners having defects is slower than that on flat {111} facets, non-uniform Ag shells were formed under fast MW heating. Optical properties of each nanocrystal were determined by measuring extinction spectra.

Preparation of CdTe nanostructures with different crystal structures and morphologies

CdTe nanorods and various branched nanostructures with different crystal structures were have successfully prepared via the catalyst-assisted vacuum thermal evaporation (CVTE) technique using various experimental parameters. SEM and XRD studies were carried out on the as-prepared CdTe nanostructures. The results show that the morphologies and crystal structures of the products were strongly influenced by the growth conditions and the mole ratios of Bi and CdTe. In the high mole ratio (0.08:1) of Bi and CdTe, CdTe branched nanostructures of CdTe were obtained, while nanorods of CdTe were formed at a lower mole ratio of 0.05:1. The crystal structure of products is either Zinc blende or a two-phase mixture of zinc blende and wurtzite. The content of the wurtzite phase were found to increase with increasing growth temperature. Our results also reveal that high growth temperature tends to form the wurtzite phase, and stacking faults may exist in materials grown in higher temperatures. These nanostructures grow following the vapor–liquid–solid (VLS) mechanism.

Hydrothermal Synthesis and Gas Sensing Properties of α-Fe2O3 Hollow Microspheres and Nanorods

α-Fe2O3 hollow microspheres and nanorods were synthesized via a hydrothermal method using glucose and ethylenediaminetetraacetic acid (EDTA) as morphology controlled agents, followed by calcination at 500 °C for 4 h in air. The crystal structures of products were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show that the hollow microspheres with diameters of 1-2 μm are consist of nanoparticles (80-100 nm), and the nanorods have a structure in the diameter of 80-100 nm and length about 1 μm. Furthermore, the α-Fe2O3 hollow microspheres show higher gas response to ethanol than that of nanorods and nanoparticles.

Formation of 1-D ZnTe nanocrystals by aerosol-assisted spray pyrolysis

One-dimensional (1-D) ZnTe nanowires were prepared by aerosol-assisted spray pyrolysis using a mixture of ZnO (1 mmol)/OA (4 mL)/TOPO (0.8 g)/ODE (4 mL) as Zn precursor and Te/TOP (3 mL of 0.75M) as Te precursor. The shape, size, and crystal structure of products were characterized by means of transmission electron microscope (TEM) and X-ray diffraction (XRD). The shape evolution of ZnTe nanocrystals from nanodots to nanowires was achieved by controlling the reaction temperature. ZnTe nanodots with average diameter of 8.3 nm were synthesized at 300 °C. “Earthworm-like” shaped ZnTe (linear ZnTe aggregates) consisting of primary ZnTe nanodots of about 16 nm in diameter were obtained at 400 °C. In addition, 1-D ZnTe nanowires were prepared at reaction temperature higher than 450 °C. Those experimental results suggest that ZnTe nanowires with zinc blende structure are formed from ZnTe nanodots by the oriented attachment due to insufficient surface capping of surfactant molecules and by strong dipole-dipole interaction of nanodots, followed by self-organization of linear aggregates at higher reaction temperatures. The linear ZnTe aggregates consisting of primary ZnTe nanodots may be an intermediate stage in the formation process of nanowires from nanodots.

The Effect of Organic Compounds on the Crystal Structure of Zinc Hydroxystannate

The polyhedral crystals, octahedral crystals and cube crystals of Zinc hydroxystannate (ZHS) were prepared by the homogeneous precipitation synthesis method. The organic compounds, PEG-400, β-cyclodextrin (β-CD) and L-alanine were added in the reaction systems to control the crystal structure. The crystal structure and morphology of products were characterized by SEM and XRD. The crystal structure of all products could be attributed to the cubic ZnSn(OH)6 by the XRD analysis. The SEM pictures of the products were different with the change of organic compounds. The FTIR spectrum indicated the ZHS without organic residual and the possible formation mechanism was discussed.

Crystal Structures and Growth Mechanisms of Icosahedral Au@Ag Core−Shell and Au/Ag Twin Nanocrystals Prepared by PVP-Assisted N,N-Dimethylformamide Reduction

Icosahedral Au@Ag core−shell nanocrystals have been prepared using a two-step reduction method. In the first step, icosahedral Au core seeds were prepared by reducing HAuCl4·4H2O in tetraethylene glycol (TEG) under microwave (MW) heating in the presence of polyvinylpyrrolidone (PVP) as a polymer surfactant. In the second step, Ag shells were overgrown on icosahedral Au seeds in N,N-dimethylformamide (DMF) in the presence of PVP under oil-bath heating for 3 h or MW heating for 10 min. Crystal structures of products were characterized using TEM, TEM-EDS, and SEM. Under oil-bath heating, Au@Ag icosahedral nanocrystals nearly fully covered by Ag shells were prepared, whereas those partially covered by tetrahedral units of Ag shells were formed under MW heating. On the basis of these findings, it was concluded that icosahedral Au@Ag core−shell particles are formed through stepwise growth of tetrahedral units, as observed in the crystal growth of monometallic icosahedral Ag crystals in DMF. There were minor Au/...