scholarly journals Revealing particle growth mechanisms by combining high-surface-area catalysts made with monodisperse particles and electron microscopy conducted at atmospheric pressure

2016 ◽  
Vol 337 ◽  
pp. 240-247 ◽  
Author(s):  
Shuyi Zhang ◽  
Matteo Cargnello ◽  
Wei Cai ◽  
Christopher B. Murray ◽  
George W. Graham ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Surface Area ◽  
Atmospheric Pressure ◽  
High Surface ◽  
High Surface Area ◽  
Particle Growth ◽  
Growth Mechanisms ◽  
Monodisperse Particles

Carbons of high surface area. A study by adsorption and high resolution electron microscopy

Carbon ◽  
1982 ◽  
Vol 20 (5) ◽  
pp. 419-426 ◽  
Author(s):  
H Marsh ◽  
D Crawford ◽  
T.M O'Grady ◽  
A Wennerberg
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron

scholarly journals Synthesis and characterization of porous silica and polyaniline-porous silica composite materials with high surface area

2014 ◽  
Vol 49 (1) ◽  
pp. 1-8
Author(s):  
US Akhtar ◽  
MK Hossain ◽  
MS Miran ◽  
MYA Mollah
Keyword(s):  
Electron Microscopy ◽  
Pore Size ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Porous Silica ◽  
Nitrogen Adsorption ◽  
High Specific Surface Area ◽  
Molar Ratio ◽  
Cylindrical Pore

Porous silica materials were synthesized from tetraethyl orthosilicate (TEOS) using Pluronic P123 (non-ionic triblock copolymer, EO20PO70O20) as template under acidic conditions which was then used to prepare polyaniline (PAni) and porous silica composites (PAnisilica) at a fixed molar ratio. These materials were characterized by nitrogen adsorption-desorption isotherm measured by Barrett-Joyner- Halenda (BJH) method and pore size distribution from desorption branch and surface area measured by the Brunauer-Emmett-Teller (BET) method, scanning electron microscopy (SEM), transmission electron microscopy (TEM), TEM-energy dispersive X-ray (EDX) and Fourier transform infrared (FT-IR) spectroscopy. The composite maintains its structure even after the polymerization and the polymer is dispersed on the inorganic matrix. The rod-like porous silica was about 1?m to 1.5 ?m long and on an average the diameter was in the range of 300- 500 nm. The SEM and TEM images show well ordered 2d hexagonal pore, high specific surface area (850 m2g-1) and uniform pore size of ca. 6.5 nm in diameter. After incorporation of PAni inside the silica pore, framework of porous silica did not collapse and the surface area of the composite was as high as 434 m2g-1 which was 5.5 time higher than our previous report of 78.3 m2g-1. Due to shrinkage of the framework during the incorporation of aniline inside the silica, the pore diameter slightly increase to 7.5 nm but still showing Type IV isotherm and typical hysteresis loop H1 implying a uniform cylindrical pore geometry. DOI: http://dx.doi.org/10.3329/bjsir.v49i1.18847 Bangladesh J. Sci. Ind. Res. 49(1), 1-8, 2014

scholarly journals Metal-Free Counter Electrode for Efficient Dye-Sensitized Solar Cells through High Surface Area and Large Porous Carbon

2011 ◽  
Vol 2011 ◽  
pp. 1-4 ◽  
Author(s):  
Pavuluri Srinivasu ◽  
Surya Prakash Singh ◽  
Ashraful Islam ◽  
Liyuan Han
Keyword(s):  
Electron Microscopy ◽  
Surface Area ◽  
Mesoporous Carbon ◽  
Counter Electrode ◽  
High Surface ◽  
High Surface Area ◽  
Dye Sensitized Solar Cells ◽  
Nitrogen Adsorption ◽  
Dye Sensitized ◽  
Sensitized Solar Cells

Highly efficient, large mesoporous carbon is fabricated as a metal-free counter electrode for dye-sensitized solar cells. The mesoporous carbon shows very high energy conversion efficiency of 7.1% compared with activated carbon. The mesoporous carbon is prepared and characterized by nitrogen adsorption, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The nitrogen adsorption data reveals that the material possesses BET specific surface area ca.1300 m2/g and pore diameter 4.4 nm. Hexagonal rod-like morphology and ordered pore structure of mesoporous carbon are confirmed by electron microscopy data. The better performance of this carbon material is greatly benefited from its ordered interconnected mesoporous structure and high surface area.

One-Step Hydrothermal Synthesis of MoS2 Nano-Flowers with High Surface Area and Crystalline

2012 ◽  
Vol 531-532 ◽  
pp. 508-511 ◽  
Author(s):  
Yan Juan Li ◽  
Nan Li ◽  
Xiao Yan ◽  
Yue Chi ◽  
Qing Yuan ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Hydrothermal Synthesis ◽  
Surface Area ◽  
Ph Value ◽  
High Surface ◽  
High Surface Area ◽  
Ammonium Molybdate ◽  
Molar Ratio ◽  
Sulfur Source ◽  
One Step

One-step and controlled pH hydrothermal synthesis of transition metal disulfide using double molybdenum sources to synthesize MoS2 nano-flowers at low temperature was first reported. Anhydrous molybdenum pentachloride (MoCl5) and four sulfur ammonium molybdate ((NH4) 6Mo7O24•4H2O) were the molybdenum source and CS (NH2) 2 was the sulfur source. Through hydrothermal method, MoS2 was obtained at 180 °C. The pH value of system was controlled by adjusting the molar ratio of MoCl5 and (NH4) 6Mo7O24•4H2O. The products were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), surface area (BET) and transmission electron microscopy (TEM). The results show that the products were hexagonal MoS2 with a high crystalline and flower-like structure consisted of small particles. The thickness of petals is a few to tens of nanometers. By changing the molar ratio of molybdenum sources, the resultant phase from the mixed phase transited to the pure phase and the purity of synthetic MoS2 crystal increaseed.

Transmission Electron Microscopy Studies of Pd Encapsulation by Ceria-Zirconia Oxides

1998 ◽  
Vol 4 (S2) ◽  
pp. 724-725
Author(s):  
J. C. Jiang ◽  
X. Q. Pan ◽  
G. W. Graham ◽  
R. W. McCabe ◽  
J. Schwank
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Temperature ◽  
Surface Area ◽  
High Speed ◽  
High Surface ◽  
Silicon Crystal ◽  
High Surface Area ◽  
Thermal Environments ◽  
Transmission Electron

High-temperature catalysts containing Pd supported on high-surface area ceria-zirconia are optimum materials for fuel economy when automotive engines operate under high speed or load conditions. A prerequisite for developing such thermally stable catalysts is to gain a good understanding of the thermal deactivation modes contributing to the aging and degradation of catalysts in harsh thermal environments. It was discovered by X-ray diffraction that upon hightemperature aging, Pd may sinter into large (about 10 nm diameter) particles and become encapsulated in the ceria-zirconia. To confirm this conclusion, a prototype high-temperature catalyst containing Pd supported on high-surface area ceria-zirconia, aged at temperature above 1100 °C is studied by transmission electron microscopy (TEM).The ceria-zirconia supported Pd (0.25 wt%) catalyst was aged at 1105 °C and calcined at 700 °C for 2 h. For TEM sample preparations, first of all, a large-size aggregate with diameter about 1 mm was selected and sandwiched between by two pieces of silicon crystal.

scholarly journals The Role of Temperature on the Degree of End-Closing and Filling of Single-Walled Carbon Nanotubes

Nanomaterials ◽  
2021 ◽  
Vol 11 (12) ◽  
pp. 3365
Author(s):  
Magdalena Kierkowicz ◽  
Elzbieta Pach ◽  
Julio Fraile ◽  
Concepción Domingo ◽  
Belén Ballesteros ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Surface Area ◽  
Density Functional ◽  
Annealing Temperature ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Density Functional Theory Calculations ◽  
Nitrogen Adsorption

Carbon nanotubes (CNTs), owing to their high surface area-to-volume ratio and hollow core, can be employed as hosts for adsorbed and/or encapsulated molecules. At high temperatures, the ends of CNTs close spontaneously, which is relevant for several applications, including catalysis, gas storage, and biomedical imaging and therapy. This study highlights the influence of the annealing temperature in the range between 400 and 1100 °C on the structure and morphology of single-walled CNTs. The nitrogen adsorption and density functional theory calculations indicate that the fraction of end-closed CNTs increases with temperature. Raman spectroscopy reveals that the thermal treatment does not alter the tubular structure. Insight is also provided into the efficacy of CNTs filling from the molten phase, depending on the annealing temperature. The CNTs are filled with europium (III) chloride and analyzed by using electron microscopy (scanning electron microscopy and high-resolution transmission electron microscopy) and energy-dispersive X-ray spectroscopy, confirming the presence of filling and closed ends. The filling yield increases with temperature, as determined by thermogravimetric analysis. The obtained results show that the apparent surface area of CNTs, fraction of closed ends, and amount of encapsulated payload can be tailored via annealing.

High Surface Area Silicon Carbide Doped with Zirconium for use as Heterogeneous Catalyst Support

1996 ◽  
Vol 454 ◽  
Author(s):  
Marc J. Ledoux ◽  
Cuong Pham-Huu ◽  
Christophe Bouchy ◽  
Pascal Del Gallo ◽  
Claude Estournes ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Surface Area ◽  
High Surface ◽  
Catalyst Support ◽  
High Surface Area ◽  
X Ray Diffraction ◽  
Transmission Electron ◽  
Bet Method ◽  
Porosity Measurements

ABSTRACTHigh surface area (> 100 m2 · g−1) SiC doped with zirconium was prepared by the gas-solid reaction. The material was made up of three phases: β-SiC, covered by ZrO2 and an amorphous phase composed of Si, Zr and O. The characterization of the sample was performed by means of powder X-ray diffraction (XRD), surface area and porosity measurements by the BET method, scanning electron microscopy (SEM) and high-resolution transmission electron microscopy (HRTEM). Preliminary catalytic tests, the standard n-C7 isomerization on supported MoOxCy showed that this new support was at least as effective as pure SiC.

Hydrophobic Silica Aerogels by Ambient Pressure Drying

2015 ◽  
Vol 830-831 ◽  
pp. 476-479
Author(s):  
Srinivasan Nagapriya ◽  
M.R. Ajith ◽  
H. Sreemoolanadhan ◽  
Mariamma Mathew ◽  
S.C. Sharma
Keyword(s):  
Surface Area ◽  
Atmospheric Pressure ◽  
Polar Solvent ◽  
Ambient Pressure ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Sol Gel Process

Silica aerogels have been prepared through sol-gel process by polymerization of TEOS in the presence of NH4F and NH4OH as catalysts. The solvent present in the gel is replaced by ethanol followed by a non-polar solvent such as n-hexane prior to solvent modification step. Gels are made hydrophobic by treating them with HMDZ to prevent rupture during drying, which has been confirmed by FTIR. Gels are then washed and dried carefully in a PID controlled oven at atmospheric pressure. The ageing duration and solvent exchange combinations are optimized to yield crack-free gels prior to drying. Aerogels are characterized for density, specific surface area, pore volume, pore size, thermal stability and contact angle. Hydrophobic, high surface area (570 m2/g), low density (0.07 g/cm3) silica aerogels are synthesized by using optimized mole ratio of precursors and catalysts. Silica aerogel granules (1-3 mm) as well as monoliths (Ф~35 mm) could be produced through ambient pressure drying of gels.

scholarly journals High Photodegradation Performance of ZnO Nanoparticles Supported on Porous Zeolite Na-a: Effects of ZnO Loading

2021 ◽  
Author(s):  
Lawrence Kioko Munguti ◽  
Francis Birhanu Dejene
Keyword(s):  
Electron Microscopy ◽  
Surface Area ◽  
Zno Nanoparticles ◽  
Diffuse Reflectance Spectroscopy ◽  
High Surface ◽  
Sol Gel ◽  
High Surface Area ◽  
Textural Properties ◽  
Bonding Properties ◽  
Bet Technique

Abstract Zeolite Na-A supported ZnO nanocomposites (ZnO/Zeolite Na-A NCs) were synthesized at low temperature (70 ℃) via the sol-gel process and characterized by X-ray diffraction technique (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV-visible diffuse reflectance spectroscopy (UV-vis DRS) and Fourier transform infrared (FTIR) spectroscopy for structural, morphological, optical and bonding properties. The textural properties and porosity were obtained by Brunauer-Emmett-Teller (BET) technique. The obtained XRD and microscopy results indicated that the obtained nanopowders were crystalline in nature and no collapse of the structure of zeolite Na-A. In addition, the synthesized ZnO nanoparticles occurred mainly on the surface of the zeolite support. It is clear that the zeolite supported ZnO nanoparticles were more dispersed as compared to the pure ZnO with improved porosity and high surface area. Photocatalytic activity for the ZnO/zeolite Na-A was tremendously increased which was attributed to the synergetic combined effects of both ZnO and zeolite aluminosilicate network such as increased surface area (SBET), high adsorption and restrained charge recombination.

scholarly journals Green Synthesis of S- and N-Codoped Carbon Nanospheres and Application as Adsorbent of Pb (II) from Aqueous Solution

2020 ◽  
Vol 2020 ◽  
pp. 1-13 ◽  
Author(s):  
Nadia Hussain ◽  
Salam Alwan ◽  
Hassan Alshamsi ◽  
Ibrahim Sahib
Keyword(s):  
Electron Microscopy ◽  
Surface Area ◽  
Adsorption Process ◽  
High Surface ◽  
High Surface Area ◽  
Correlation Coefficients ◽  
Nitrogen Adsorption ◽  
Entropy Change ◽  
Standard Entropy ◽  
Carbon Nanospheres

In this paper, green and facile synthesis of sulfur- and nitrogen-codoped carbon nanospheres (CNs) was prepared from the extract of Hibiscus sabdariffa L by a direct hydrothermal method. Finally, sulfur-carbon nanospheres (CNs) were used as the adsorbent to remove Pb+2 ions from aqueous solutions because of the high surface area of S-CNs from CNs and N-CNs. The synthesized nanospheres were examined by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), field emission scanning electron microscopy, transmission electron microscopy (TEM), and nitrogen adsorption-desorption isotherms. The results show spherical shapes have a particle size of up to 65 nm with a high surface area capable of absorbing lead ions efficiently. Additionally, the factors affecting the process of adsorption that include equilibrium time, temperature, pH solution, ionic intensity, and adsorbent dose were studied. The equilibrium removal efficiency was studied employing Langmuir, Freundlich, and Temkin isotherm forms. The kinetic data were analyzed with two different kinetic models, and both apply to the adsorption process depending on the values of correlation coefficients. The thermodynamic parameters including Gibbs free energy (ΔG°), standard enthalpy change (ΔH°), and standard entropy change (ΔS°) were calculated for the adsorption process.

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