Preparation and Hydration Kinetics of Pure CaAl2O4

1991 ◽  
Vol 245 ◽  
Author(s):  
M. A. Gulgun ◽  
O. O. Popoola ◽  
I. Nettleship ◽  
W. M. Kriven ◽  
J. F. Young
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Single Phase ◽  
Hydration Kinetics ◽  
Phase Pure ◽  
Microscopy Techniques ◽  
Kinetics Of

ABSTRACTSingle phase, pure monocalcium aluminate (CaAl2O4) powders are chemically synthesized at temperatures as low as 900°C. The powders have a specific surface area of approximately 10 m2/g. The hydration kinetics of CaAl2O4 and the morphology of the hydrates are analyzed using electron microscopy techniques

Study on the kinetics of process for obtaining cobalt nanopowder by hydrogen reduction under isothermal conditions

2021 ◽  
Vol 1 (1) ◽  
pp. 49-56
Author(s):  
Hieр Nguyen Tien
Keyword(s):  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Hydrogen Reduction ◽  
Average Particle Size ◽  
Chemical Deposition ◽  
Average Particle ◽  
Isothermal Conditions ◽  
Electron Microscopes ◽  
Kinetics Of

The kinetics of metallic cobalt nanopowder synthesizing by hydrogen reduction from Co(OH)2 nanopowder under isothermal conditions were studied. Co(OH)2 nanopowder was prepared in advance by chemical deposition from aqueous solutions of Co(NO3)2 cobalt nitrate (10 wt.%) and NaOH alkali (10 wt.%) at room temperature, pH = 9 under continuous stirring. The hydrogen reduction of Co(OH)2 nanopowder under isothermal conditions was carried out in a tube furnace in the temperature range from 270 to 310 °C. The crystal structure and composition of powders was studied by X-ray phase analysis. The specific surface area of samples was measured using the BET method by low-temperature nitrogen adsorption. The average particle size of powders was determined by the measured specific surface area. Particles size characteristics and morphology were investigated by transmission and scanning electron microscopes. Kinetic parameters of Co(OH)2 hydrogen reduction under isothermal conditions were calculated using the Gray–Weddington model and Arrhenius equation. It was found that the rate constant of reduction at t = 310 °C is approximately 1.93 times higher than at 270 °C, so the process accelerates by 1.58 times for 40 min of reduction. The activation energy of cobalt nanopowder synthesizing from Co(OH)2 by hydrogen reduction is ~40 kJ/mol, which indicates a mixed reaction mode. It was shown that cobalt nanoparticles obtained by the hydrogen reduction of its hydroxide at 280 °C are aggregates of equiaxed particles up to 100 nm in size where individual particles are connected to several neighboring particles by contact isthmuses.

Synthesis and Characterization of Porous Mo-W Oxide Nanostructures

2008 ◽  
Vol 8 (12) ◽  
pp. 6445-6450
Author(s):  
F. Paraguay-Delgado ◽  
Y. Verde ◽  
E. Cizniega ◽  
J. A. Lumbreras ◽  
G. Alonso-Nuñez
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Synthesis Method ◽  
Atomic Ratio ◽  
High Specific Surface Area ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Before And After

The present study reports the synthesis method, microstructure characterization, and thermal stability of nanostructured porous mixed oxide (MoO3-WO3) at 550 and 900 °C of annealing. The material was synthesized using a hydrothermal method. The precursor was prepared by aqueous solution using ammonium heptamolibdate and ammonium metatungstate, with an atomic ratio of Mo/W = 1. The pH was adjusted to 5, and then the solution was transferred to a teflon-lined stainless steel autoclave and heated at 200 °C for 48 h. The resultant material was washed using deionized water. The specific surface area, morphology, composition, and microstructure before and after annealing were studied by N2 physisorption, scanning electron microscopy (SEM), analytical transmission electron microscopy (TEM), and X-Ray diffraction (XRD). The initial synthesized materials showed low crystallinity and high specific surface area around (141 m2/g). After thermal annealing the material showed higher crystallinity and diminished its specific surface area drastically.

scholarly journals Combination of mesoporous titanium dioxide with MoS2 nanosheets for high photocatalytic activity

2017 ◽  
Vol 19 (2) ◽  
pp. 56-60 ◽  
Author(s):  
Loghman Karimi
Keyword(s):  
Electron Microscopy ◽  
Titanium Dioxide ◽  
Photocatalytic Activity ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Dye Degradation ◽  
Hydrothermal Process ◽  
Bet Analysis ◽  
Mesoporous Titanium Dioxide

Abstract This study presents a facile approach for the preparation of MoS2 nanosheet decorated by porous titanium dioxide with effective photocatalytic activity. Mesoporous titanium dioxide nanostructures first synthesized by a hydrothermal process using titanium (III) chloride and then the MoS2/TiO2 were prepared through mixing of MoS2 nanosheet with mesoporous titanium dioxide under ultrasonic irradiation. The synthesized nanocomposite was characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), field emission scanning electron microscopy (FE-SEM), and Brunauer-Emmett-Teller (BET) analysis. The results showed that the nanocomposite has mesoporous structure with specific surface area of 176.4 m2/g and pore diameter of 20 nm. The as-prepared MoS2/TiO2 nanocomposites exhibited outstanding photocatalytic activity for dye degradation under sunlight irradiation, which could be attributed to synergistic effect between the molybdenum disulfide nanosheet and mesoporous titanium dioxide. The photocatalytic performance achieved is about 2.2 times higher than that of mesoporous TiO2 alone. It is believed that the extended light absorption ability and the large specific surface area of the 2D MoS2 nanosheets in the nanocomposite, leading to the enhanced photocatalytic degradation activity.

CVD Synthesis of Multi-Walled Carbon Nanotubes onto Different Catalysts at Low Temperature

NANO ◽  
2018 ◽  
Vol 13 (04) ◽  
pp. 1850036 ◽  
Author(s):  
Guiqiang Diao ◽  
Hao Li ◽  
Hao Liang ◽  
Iryna Ivanenko ◽  
Tetiana Dontsova ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Low Temperature ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Sol Gel ◽  
Lithium Ion ◽  
Multi Walled Carbon Nanotubes ◽  
Walled Carbon Nanotubes

Multi-walled carbon nanotubes (MWCNTs) were synthesized onto a series of individual and bimetallic catalysts by the chemical vapor deposition (CVD) of acetylene at low temperature (600[Formula: see text]C). The catalysts were prepared by two methods, i.e., precipitation and sol–gel, with two different carriers – MgO and Al2O3. The catalysts were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), thermal gravimetric (TG) analysis, low-temperature adsorption of nitrogen. The yield of the MWCNTs was calculated in two ways, while the highest yield of 800% was achieved onto the two-component NiO/Co2O3/MgO catalyst, SEM and transmission electron microscopy (TEM) results confirm that uniform tube-like structure MWCNTs with the yield of 410% were obtained onto Co2O3/Al2O3 catalyst. These MWCNTs are smooth and pointing in the same direction. Their tube diameter is about 20[Formula: see text]nm, which is the smallest around all observed MWCNTs. Moreover, nonuniform curved bamboo-like MWCNTs with nozzles in the yield of 760% were obtained onto NiO/V2O3/MgO catalyst. Their diameter ranges from 25[Formula: see text]nm to 50[Formula: see text]nm. Results show that single-component catalyst promotes the growth of uniform and smaller nanotubes. Among the as-grown nanotubes, their specific surface area increases and average pores diameter reduces after the treatment with concentrated nitric acid at reflux and washing condition. The largest specific surface area (305[Formula: see text]m2/g) and average pores diameter (26[Formula: see text]m2/g) are processed to MWCNTs grown onto the NiO/Co2O3/MgO catalyst. MWCNTs with such large structural adsorption characteristics and purity of more than 99% obtained with yield 800% show potential use for preparation of nanocomposites as anode materials in lithium ion batteries.

scholarly journals Towards the Continuous Hydrothermal Synthesis of ZnO@Mg2Al-CO3 Core-Shell Composite Nanomaterials

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 2052
Author(s):  
Ian Clark ◽  
Jacob Smith ◽  
Rachel L. Gomes ◽  
Edward Lester
Keyword(s):  
Composite Material ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Single Phase ◽  
Core Shell ◽  
Composite Nanomaterials ◽  
One Step ◽  
Double Hydroxide ◽  
Shell Composite

Core-shell Zinc Oxide/Layered Double Hydroxide (ZnO@LDH) composite nanomaterials have been produced by a one-step continuous hydrothermal synthesis process, in an attempt to further enhance the application potential of layered double hydroxide (LDH) nanomaterials. The synthesis involves two hydrothermal reactors in series with the first producing a ZnO core and the second producing the Mg2Al-CO3 shell. Crystal domain length of single phase ZnO and composite ZnO was 25 nm and 42 nm, respectively. The ZnO@LDH composite had a specific surface area of 76 m2 g−1, which was larger than ZnO or Mg2Al-CO3 when produced separately (53 m2 g−1 and 58 m2 g−1, respectively). The increased specific surface area is attributed to the structural arrangement of the Mg2Al-CO3 in the composite. Platelets are envisaged to nucleate on the core and grow outwards, thus reducing the face–face stacking that occurs in conventional Mg2Al-CO3 synthesis. The Mg/Al ratio in the single phase LDH was close to the theoretical ratio of 2, but the Mg/Al ratio in the composite was 1.27 due to the formation of Zn2Al-CO3 LDH from residual Zn2+ ions. NaOH concentration was also found to influence Mg/Al ratio, with lower NaOH resulting in a lower Mg/Al ratio. NaOH concentration also affected morphology and specific surface area, with reduced NaOH content in the second reaction stage causing a dramatic increase in specific surface area (> 250 m2 g−1). The formation of a core-shell composite material was achieved through continuous synthesis; however, the final product was not entirely ZnO@Mg2Al-CO3. The product contained a mixture of ZnO, Mg2Al-CO3, Zn2Al-CO3, and the composite material. Whilst further optimisation is required in order to remove other crystalline impurities from the synthesis, this research acts as a stepping stone towards the formation of composite materials via a one-step continuous synthesis.

Effects of dry grinding on pyrophyllite

Clay Minerals ◽  
1988 ◽  
Vol 23 (4) ◽  
pp. 399-410 ◽  
Author(s):  
J. L. Pérez-Rodríguez ◽  
L. Madrid Sánchez del Villar ◽  
P.J. Sánchez-Soto
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Grinding Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Dry Grinding ◽  
Scanning Electron ◽  
Area Data

AbstractDry grinding of pyrophyllite (Hillsboro, USA) has been studied by X-ray diffraction (XRD), specific surface area measurements (BET) and scanning electron microscopy (SEM). At the beginning of the grinding process, some effects such as delamination, gliding and folding of the layers, and decrease in particle size were detected by SEM and XRD, resulting in a large increase in specific surface area, up to a maximum of ∼60 m2·g−1. Marked changes in the structure take place between 30 and 32 mins grinding. Longer grinding times increase the degree of disorder and SEM and specific surface area data suggest that aggregation occurs. XRD results indicate that some residual order persists in the degraded structure.

scholarly journals Synthesis and Characterization of Uniform Spherical Nanoporous TiO2Aerogel Templated by Cellulose Alcohol-Gel with Enhanced Photocatalytic Activity

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Zhiming Liu ◽  
Peng Wu ◽  
Shaoli Yang ◽  
Haiying Wang ◽  
Chunde Jin
Keyword(s):  
Electron Microscopy ◽  
Photocatalytic Activity ◽  
Methyl Orange ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Thermal Method ◽  
X Ray ◽  
Double Beam ◽  
Methyl Orange Dye

The spherical nanoporous TiO2aerogels were prepared by a simple ethanol-thermal method, using spherical cellulose alcohol-gel as the template. The morphology, crystalline structure, pore size, specific surface area, and the photocatalytic activity of obtained TiO2aerogel were separately characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), N2adsorption-desorption isotherms, and double beam UV-VIS spectrophotometer. The characteristics of TiO2aerogels presented uniform sphere shape, good internal structural morphology, high specific surface area (ranging from 111.88 to 149.95 m2/g), and good crystalline anatase phase. Moreover, methyl orange dye was used as the target pollutant to characterize the photocatalytic activities and the adsorption performance. The photocatalytic experiment shows that the obtained spherical TiO2aerogels had a higher degradation ratio of 92.9% on methyl orange dye compared with aspherical TiO2aerogels prepared from other concentrations of tetrabutyl orthotitanate (TBOT).

scholarly journals Hydrothermal Synthesis of Co-Doped NiSe2 Nanowire for High-Performance Asymmetric Supercapacitors

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1468 ◽  
Author(s):  
Yun Gu ◽  
Le-Qing Fan ◽  
Jian-Ling Huang ◽  
Cheng-Long Geng ◽  
Jian-Ming Lin ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Energy Density ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Electrode Materials ◽  
Nickel Foam ◽  
High Energy ◽  
High Energy Density ◽  
Asymmetric Supercapacitor

Co@NiSe2 electrode materials were synthesized via a simple hydrothermal method by using nickel foam in situ as the backbone and subsequently characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, and a specific surface area analyzer. Results show that the Co@NiSe2 electrode exhibits a nanowire structure and grows uniformly on the nickel foam base. These features make the electrode show a relatively high specific surface area and electrical conductivity, and thus exhibit excellent electrochemical performance. The obtained electrode has a high specific capacitance of 3167.6 F·g−1 at a current density of 1 A·g−1. To enlarge the potential window and increase the energy density, an asymmetric supercapacitor was assembled by using a Co@NiSe2 electrode and activated carbon acting as positive and negative electrodes, respectively. The prepared asymmetrical supercapacitor functions stably under the potential window of 0–1.6 V. The asymmetric supercapacitor can deliver a high energy density of 50.0 Wh·kg−1 at a power density of 779.0 W·kg−1. Moreover, the prepared asymmetric supercapacitor exhibits a good rate performance and cycle stability.

Synthesis, Characterisation, and Photocatalytic Behaviour of Mesoporous ZnS Nanoparticles Prepared Using By-Product Templating

2017 ◽  
Vol 70 (10) ◽  
pp. 1099 ◽  
Author(s):  
Hosein B. Motejadded Emrooz ◽  
Ali R. Rahmani ◽  
Francisco J. Gotor
Keyword(s):  
Electron Microscopy ◽  
Specific Surface ◽  
Surface Area ◽  
Specific Surface Area ◽  
Diffuse Reflectance Spectroscopy ◽  
High Surface ◽  
Ultrasonic Waves ◽  
Soft Template ◽  
Bandgap Energy ◽  
Zns Nanoparticles

High surface area mesoporous ZnS nanoparticles (MZN) were obtained with the aid of the by-product of the synthesising reaction. This by-product, namely NaNO3, can be considered as a soft template responsible for the formation of pores. Ethanol and water were chosen as the synthesis media. Ultrasonic waves were used as an accelerator for the synthesis of MZNs. Photocatalytic activities of the synthesised samples for the degradation of methylene blue (MB) were investigated under ultraviolet irradiation. Synthesised specimens were characterised using field emission scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, diffuse reflectance spectroscopy, N2-physisorption, and FT-IR spectroscopy. Results indicated that the synthesis media has a pronounced effect on the surface properties of the final porous particles by several mechanisms. The specific surface area of the MZN samples synthesised in water and ethanol were determined to be 53 and 201 m2 g−1, respectively. The difference in the specific surface area was attributed to the weak solvation of S2− ions (Na2S·5H2O in ethanol) and also to the by-product of the synthesis reaction. The photocatalytic behaviour of the mesoporous ZnS nanoparticles synthesised in these two media were investigated and the results have been interpreted with the aid of effective surface area, pore volume, and bandgap energy of the specimens.

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