Hydrothermal SiO2 Nanopowders: Obtaining Them and Their Characteristics

The technological mode of obtaining amorphous SiO2 nanopowders based on hydrothermal solutions is proposed in this study. Polycondensation of orthosilicic acid as well as ultrafiltration membrane separation, and cryochemical vacuum sublimation were used. The characteristics of nanopowders were determined by tunneling electron microscopy, low-temperature nitrogen adsorption, X-ray diffraction, and small-angle X-ray scattering. The scheme allows to adjust density, particle diameters of nanopowders, specific surface area, as well as diameters, area and volume of the pore. Thus, the structure of nanopowders is regulated—the volume fraction of the packing of spherical particles in aggregates and agglomerates, the size of agglomerates, and the number of particles in agglomerates. The pour densities of the nanopowders depend on the SiO2 content in sols, which were 0.02 to 0.3 g/cm3. Nanoparticles specific surface area was brought to 500 m2/g by low temperature polycondensation. Nanoparticle aggregates specific pore volume (0.2–0.3 g/cm3) weakly depend on powders density. The volume fraction of the packing of SiO2 nanoparticles in aggregates was 0.6–0.7. Solid samples of compacted nanopowders had a compressive strength of up to 337 MPa. Possible applications of hydrothermal SiO2 nanopowders are considered.

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Structural and Morphological Quantitative 3D Characterisation of Ammonium Nitrate Prills by X-Ray Computed Tomography

Materials ◽

10.3390/ma13051230 ◽

2020 ◽

Vol 13 (5) ◽

pp. 1230

Author(s):

Fabien Léonard ◽

Zhen Zhang ◽

Holger Krebs ◽

Giovanni Bruno

Keyword(s):

Computed Tomography ◽

Specific Surface ◽

Ammonium Nitrate ◽

Surface Area ◽

Specific Surface Area ◽

Volume Fraction ◽

Fuel Oil ◽

X Ray ◽

Oil Retention ◽

X Ray Computed

The mixture of ammonium nitrate (AN) prills and fuel oil (FO), usually referred to as ANFO, is extensively used in the mining industry as a bulk explosive. One of the major performance predictors of ANFO mixtures is the fuel oil retention, which is itself governed by the complex pore structure of the AN prills. In this study, we present how X-ray computed tomography (XCT), and the associated advanced data processing workflow, can be used to fully characterise the structure and morphology of AN prills. We show that structural parameters such as volume fraction of the different phases and morphological parameters such as specific surface area and shape factor can be reliably extracted from the XCT data, and that there is a good agreement with the measured oil retention values. Importantly, oil retention measurements (qualifying the efficiency of ANFO as explosives) correlate well with the specific surface area determined by XCT. XCT can therefore be employed non-destructively; it can accurately evaluate and characterise porosity in ammonium nitrate prills, and even predict their efficiency.

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Low-Temperature Synthesis of Monolithic Titanium Carbide/Carbon Composite Aerogel

Nanomaterials ◽

10.3390/nano10122527 ◽

2020 ◽

Vol 10 (12) ◽

pp. 2527

Author(s):

Tingting Niu ◽

Bin Zhou ◽

Zehui Zhang ◽

Xiujie Ji ◽

Jianming Yang ◽

...

Keyword(s):

Titanium Dioxide ◽

Electron Microscope ◽

Low Temperature ◽

Titanium Carbide ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Carbon Composite ◽

Composite Aerogel ◽

X Ray

Resorcinol-formaldehyde/titanium dioxide composite (RF/TiO2) gel was prepared simultaneously by acid catalysis and then dried to aerogel with supercritical fluid CO2. The carbon/titanium dioxide aerogel was obtained by carbonization and then converted to nanoporous titanium carbide/carbon composite aerogel via 800 °C magnesiothermic catalysis. Meanwhile, the evolution of the samples in different stages was characterized by X-ray diffraction (XRD), an energy-dispersive X-ray (EDX) spectrometer, a scanning electron microscope (SEM), a transmission electron microscope (TEM) and specific surface area analysis (BET). The results showed that the final product was nanoporous TiC/C composite aerogel with a low apparent density of 339.5 mg/cm3 and a high specific surface area of 459.5 m2/g. Comparing to C aerogel, it could also be considered as one type of highly potential material with efficient photothermal conversion. The idea of converting oxide–carbon composite into titanium carbide via the confining template and low-temperature magnesiothermic catalysis may provide new sight to the synthesis of novel nanoscale carbide materials.

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A rapid analytical method for the specific surface area of amorphous sio2 based on X-Ray diffraction

Journal of Non-Crystalline Solids ◽

10.1016/j.jnoncrysol.2019.119841 ◽

2020 ◽

Vol 531 ◽

pp. 119841

Author(s):

Xiumei Ke ◽

Zhenfeng Wu ◽

Junzhi Lin ◽

Fang Wang ◽

Pan Li ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Analytical Method ◽

X Ray Diffraction ◽

Amorphous Sio2 ◽

X Ray

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Preparation of Zirconia Nanofibers by Electrospinning and Calcination with Zirconium Acetylacetonate as Precursor

Polymers ◽

10.3390/polym11061067 ◽

2019 ◽

Vol 11 (6) ◽

pp. 1067 ◽

Cited By ~ 5

Author(s):

Vyacheslav V. Rodaev ◽

Svetlana S. Razlivalova ◽

Andrey O. Zhigachev ◽

Vladimir M. Vasyukov ◽

Yuri I. Golovin

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Heterogeneous Catalysts ◽

Tetragonal Zirconia ◽

Nitrogen Adsorption ◽

Average Diameter ◽

High Specific Surface Area ◽

X Ray ◽

Adsorption Analysis

For the first time, zirconia nanofibers with an average diameter of about 75 nm have been fabricated by calcination of electrospun zirconium acetylacetonate/polyacrylonitrile fibers in the range of 500–1100 °C. Composite and ceramic filaments have been characterized by scanning electron microscopy, thermogravimetric analysis, nitrogen adsorption analysis, energy-dispersive X-ray spectroscopy, and X-ray diffractometry. The stages of the transition of zirconium acetylacetonate to zirconia have been revealed. It has been found out that a rise in calcination temperature from 500 to 1100 °C induces transformation of mesoporous tetragonal zirconia nanofibers with a high specific surface area (102.3 m2/g) to non-porous monoclinic zirconia nanofibers of almost the same diameter with a low value of specific surface area (8.3 m2/g). The tetragonal zirconia nanofibers with high specific surface area prepared at 500 °C can be considered, for instance, as promising supports for heterogeneous catalysts, enhancing their activity.

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Study of Heating Effect on Specific Surface Area, and Changing Optical Properties of ZnO Nanocrystals

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.403-408.1205 ◽

2011 ◽

Vol 403-408 ◽

pp. 1205-1210

Author(s):

Jaleh Babak ◽

Ashrafi Ghazaleh ◽

Gholami Nasim ◽

Azizian Saeid ◽

Golbedaghi Reza ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Energy Gap ◽

Sol Gel ◽

X Ray Diffraction ◽

X Ray ◽

Zno Nanocrystals ◽

Transmission Electron ◽

Zno Nanocrystal

In this work ZnO nanocrystal powders have been synthesized by using Zinc acetate dehydrate as a precursor and sol-gel method. Then the products have been annealed at temperature of 200-1050°C, for 2 hours. The powders were characterized using X-ray diffraction (XRD), UV-vis absorption and photoluminescence (PL) spectroscopy. The morphology of refrence ZnO nanoparticles have been studied using Transmission Electron Microscope (TEM). During the annealing process, increase in nanocrystal size, defects and energy gap quantitative, and decrease in specific surface area have been observed.

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Preparation of Nitrogen-Deficient Graphitic Carbon Nitride with a Large Specific Surface Area by Melt Pretreatment and Its Photocatalytic Performance

NANO ◽

10.1142/s1793292020500794 ◽

2020 ◽

Vol 15 (06) ◽

pp. 2050079

Author(s):

Xuelei Li ◽

Jinfeng Bai ◽

Jiaqi Li ◽

Chao Li ◽

Junru Zhang ◽

...

Keyword(s):

Visible Light ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Carbon Nitride ◽

Mesoporous Structure ◽

Graphitic Carbon ◽

Graphitic Carbon Nitride ◽

Large Specific Surface Area ◽

X Ray

In this study, nitrogen-deficient graphitic carbon nitride (M-LS-g-C3N4) with a mesoporous structure and a large specific surface area was obtained by calcination after melt pretreatment using urea as a precursor. X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, X-ray photoelectron spectroscopy (XPS), UV-Vis, ESR and photoluminescence (PL) were used to characterize the structure, morphology and optical performance of the samples. The TEM results showed the formation of a mesoporous structure on the 0.1[Formula: see text]M-LS-g-C3N4 surface. The porous structure led to an increase in the specific surface area from 41.5[Formula: see text]m2/g to 124.3[Formula: see text]m2/g. The UV-Vis results showed that nitrogen vacancies generated during the modification process reduced the band gap of g-C3N4 and improved the visible light absorption. The PL spectra showed that the nitrogen defects promoted the separation of photogenerated electron–hole pairs. In the visible light degradation of methyl orange (MO), the reaction rate constant of 0.1[Formula: see text]M-LS-g-C3N4 reached 0.0086[Formula: see text][Formula: see text], which was 5.05 times that of pure g-C3N4. Superoxide radicals and photogenerated holes were found to be the main active species in the reaction system. This study provides an efficient, green and convenient means of preparing graphitic carbon nitride with a large specific surface area.

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Electrochemical Properties of Supercapacitors Using Boron Nitrogen Double-Doped Carbon Nanotubes as Conductive Additive

NANO ◽

10.1142/s1793292019500802 ◽

2019 ◽

Vol 14 (07) ◽

pp. 1950080

Author(s):

Hao Hu ◽

Xiaogang Sun ◽

Wei Chen ◽

Jie Wang ◽

Xu Li ◽

...

Keyword(s):

Specific Surface ◽

Surface Area ◽

Double Layer ◽

Specific Surface Area ◽

Electric Double Layer ◽

X Ray ◽

Nitrogen Doped ◽

Conductive Additive ◽

Double Layer Capacitors ◽

Boron Nitrogen

Carbon nanotubes (CNTs) were doped by ammonium borate as the sources of nitrogen and boron. Under the protection of Ar gas, boron-nitrogen doped CNTs were prepared through nitriding and boronization at high temperature. It is a conductive additive. Then, the obtained CNTs were mixed with activated carbon (AC), SP, sodium dodecyl sulfate (SDS), and cellulose fiber to prepare electrodes. With all the materials, a symmetric electric double-layer supercapacitor (EDLC) was assembled. Next, the materials and electrodes were also characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The factors, chemical connections, and specific surface area of the CNTs were analyzed by X-ray energy spectrum analysis (EDS), X-ray photoelectron spectroscopy (XPS), as well as a specific surface area and porosimetry analyzer (BET). In addition, the electrochemical performances of electric double-layer capacitors were tested with the help of cyclic voltammetry, constant-current charging and discharging, and so on. From the results, we can make a conclusion, that is, both B and N atoms were added into the CNTs and formed bonds successfully with carbon atoms mutually. Besides, the specific surface area is about 1.5 times than that of the CNT. When the charge/discharge current density reaches 50[Formula: see text]mA/g, we can find that the mass specific capacitance of the capacitor can run up to 32.19[Formula: see text]F/g. Also, we observe that the maximum power density is close to 220[Formula: see text]W/kg (700[Formula: see text]mA/g), and the energy density can arrive 9.31[Formula: see text]Wh/kg (50[Formula: see text]mA/g). Based on the impedance test, the electrodes are characterized with low impedance. After 2000 cycles, the boron-nitrogen doped double-layer capacitors maintain a capacitance retention ratio of above 95%. Its power density can still achieve 220[Formula: see text]W/kg when the energy density keeps at 3.46[Formula: see text]Wh/kg. In other words, the electrochemical performance functions of the electric double-layer capacitors are enhanced while the CNTs serve as the electrodes.

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The Carbon Deposition during Iron Ore Reduction in Carbon Monoxide

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.625.243 ◽

2012 ◽

Vol 625 ◽

pp. 243-246

Author(s):

Shu Hua Geng ◽

Wei Zhong Ding ◽

Shu Qiang Guo ◽

Xiong Gang Lu

Keyword(s):

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Iron Ore ◽

Iron Reduction ◽

Carbon Deposition ◽

Reduction Process ◽

Ore Reduction ◽

X Ray ◽

Iron Ore Reduction

Iron ore reduction and carbon deposition in pure CO was investigated by using thermogravimetric (TG) method over the temperature range of 0-1200°C. The results of the work may be summarized as follows: in CO stream, carbon deposition occurred below 900°C, no carbon deposition was found above 1000°C. X-Ray analysis of the reacted sample indicated that the carbon deposition occurred with the iron was reduced. The iron reduction process and carbon deposition occurred simultaneously. The rate of carbon deposition changed with the transformation of iron oxides. The specific surface area and pore structure of reduced samples were analyzed. The specific surface area changed with the amount of carbon deposition.

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