scholarly journals A Comparison of “Bottom-Up” and “Top-Down” Approaches to the Synthesis of Pt/C Electrocatalysts

Processes ◽  
2020 ◽  
Vol 8 (8) ◽  
pp. 947
Author(s):  
Alexandra Kuriganova ◽  
Nikita Faddeev ◽  
Mikhail Gorshenkov ◽  
Dmitri Kuznetsov ◽  
Igor Leontyev ◽  
...  
Keyword(s):  
Alternating Current ◽  
X Ray Diffraction ◽  
Platinum Nanoparticle ◽  
X Ray ◽  
Transmission Electron ◽  
Electrochemically Active ◽  
Electrochemical Dispersion ◽  
The Stability ◽  
Nanoparticle Sizes

Three 40 wt % Pt/C electrocatalysts prepared using two different approaches—the polyol process and electrochemical dispersion of platinum under pulse alternating current—and a commercial Pt/C catalyst (Johnson Matthey prod.) were examined via X-ray diffraction (XRD) and transmission electron microscopy (TEM). The stability characteristics of the Pt/C catalysts were studied via long-term cycling, revealing that, for all cycling modes, the best stability was achieved for the Pt/C catalyst with the largest platinum nanoparticle sizes, which was synthesized via electrochemical dispersion of platinum under pulse alternating current. Our results show that the mass and specific electrocatalytic activities of Pt/C catalysts toward ethanol electrooxidation are determined by the value of the electrochemically active Pt surface area in the catalysts.

scholarly journals Facile Organometallic Synthesis of Fe-Based Nanomaterials by Hot Injection Reaction

Nanomaterials ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1141
Author(s):  
Georgia Basina ◽  
Hafsa Khurshid ◽  
Nikolaos Tzitzios ◽  
George Hadjipanayis ◽  
Vasileios Tzitzios
Keyword(s):  
Room Temperature ◽  
Colloidal Particles ◽  
Iron Pentacarbonyl ◽  
Vibrating Sample Magnetometer ◽  
X Ray Diffraction ◽  
Organometallic Synthesis ◽  
X Ray ◽  
Transmission Electron ◽  
Hot Injection ◽  
The Stability

Fe-based colloids with a core/shell structure consisting of metallic iron and iron oxide were synthesized by a facile hot injection reaction of iron pentacarbonyl in a multi-surfactant mixture. The size of the colloidal particles was affected by the reaction temperature and the results demonstrated that their stability against complete oxidation related to their size. The crystal structure and the morphology were identified by powder X-ray diffraction and transmission electron microscopy, while the magnetic properties were studied at room temperature with a vibrating sample magnetometer. The injection temperature plays a very crucial role and higher temperatures enhance the stability and the resistance against oxidation. For the case of injection at 315 °C, the nanoparticles had around a 10 nm mean diameter and revealed 132 emu/g. Remarkably, a stable dispersion was created due to the colloids’ surface functionalization in a nonpolar solvent.

Synthesis of Trilaminar Core–Shell Au/α-Fe2O3@SnO2Nanocomposites and their Application for Nonenzymatic Dopamine Electrochemical Sensing

NANO ◽  
2019 ◽  
Vol 14 (11) ◽  
pp. 1950138 ◽  
Author(s):  
Sai Zhang ◽  
Shijun Yue ◽  
Jiajia Li ◽  
Jianbin Zheng ◽  
Guojie Gao
Keyword(s):  
Electron Microscopy ◽  
High Sensitivity ◽  
Electrochemical Sensing ◽  
Synthesis Process ◽  
Core Shell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Long Term Stability ◽  
Transmission Electron

Au nanoparticles anchored on core–shell [Formula: see text]-Fe2O3@SnO2 nanospindles were successfully constructed through hydrothermal synthesis process and used for fabricating a novel nonenzymatic dopamine (DA) sensor. The structure and morphology of the Au/[Formula: see text]-Fe2O3@SnO2 trilaminar nanohybrid film were characterized by scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), transmission electron microscopy (TEM) and X-ray diffraction (XRD). The electrochemical properties of the sensor were investigated by cyclic voltammetry and amperometry. The experimental results suggest that the composites have excellent catalytic property toward DA with a wide linear range from 0.5[Formula: see text][Formula: see text]M to 0.47[Formula: see text]mM, a low detection limit of 0.17[Formula: see text][Formula: see text]M (S/[Formula: see text]) and high sensitivity of 397.1[Formula: see text][Formula: see text]A[Formula: see text]mM[Formula: see text][Formula: see text]cm[Formula: see text]. In addition, the sensor exhibits long-term stability, good reproducibility and anti-interference.

scholarly journals Joint crystallization of KCuAl[PO4]2 and K(Al,Zn)2[(P,Si)O4]2: crystal chemistry and mechanism of formation of phosphate-silicate epitaxial heterostructure

2020 ◽  
Vol 76 (3) ◽  
pp. 483-491
Author(s):  
Olga Yakubovich ◽  
Galina Kiriukhina ◽  
Larisa Shvanskaya ◽  
Anatoliy Volkov ◽  
Olga Dimitrova
Keyword(s):  
Crystal Structures ◽  
Active Material ◽  
Structure Type ◽  
Structural Features ◽  
X Ray Diffraction ◽  
X Ray ◽  
Electrochemically Active ◽  
Phosphate Silicate ◽  
The Stability ◽  
Small Channels

Two novel phases, potassium copper aluminium bis(phosphate), KCuAl[PO4]2 (I), and potassium zinc aluminium bis(phosphate-silicate), K(Al,Zn)2[(P,Si)O4]2 (II), were obtained in one hydrothermal synthesis experiment at 553 K. Their crystal structures have been studied using single-crystal X-ray diffraction. (I) is a new member of the A + M 2+ M 3+[PO4]2 family. Its open 3D framework built by AlO5 and PO4 polyhedra includes small channels populated by columns of CuO6 octahedra sharing edges, and large channels where K+ ions are deposited. It is assumed that the stability of this structure type is due to the pair substitution of Cu/Al with Ni/Fe, Co/Fe or Mg/Fe in different representatives of the series. From the KCuAl[PO4]2 structural features, one may suppose it is a potentially electrochemically active material and/or possible low-temperature antiferromagnet. In accordance with results obtained from X-ray diffraction data, using scanning electron microscopy, microprobe analysis and detailed crystal chemical observation, (II) is considered as a product of epitaxial intergrowth of phosphate KAlZn[PO4]2 and silicate KAlSi[SiO4]2 components having closely similar crystal structures. The assembly of `coherent intergrowth' is described in the framework of a single diffraction pattern.

Gelatin as an ecofriendly natural polymer for preparing colloidal silver@gold nanobranches

2016 ◽  
Vol 5 (5) ◽  
Author(s):  
Phuong Phong Nguyen Thi ◽  
Dai Hai Nguyen
Keyword(s):  
Ph Value ◽  
Component Ratio ◽  
X Ray Diffraction ◽  
Ag Nps ◽  
Au Nps ◽  
X Ray ◽  
Transmission Electron ◽  
Uv Visible ◽  
The Stability ◽  
Maximum Absorption Wavelength

AbstractWe report star-shaped silver@gold (Ag@Au) nanoparticles (NPs) in gelatin suspensions for the purpose of enhancing the stability of Ag@Au NPs. In this case, Ag NPs were designed as nucleating agents, whereas gelatin was used as a protecting agent for Au development. Especially, variable gelatin concentrations were also prepared to explore its ability to increase the stability of Ag@Au NPs. The obtained samples were then characterized by UV-visible spectroscopy, transmission electron spectroscopy (TEM), X-ray diffraction, and Fourier transform infrared spectroscopy. The maximum absorption wavelength of all samples (566–580 nm) indicated that branched Ag@Au@gelatin NPs were successfully synthesized. In addition, our TEM results revealed that the size of branched Ag@Au@gelatin NPs was found to be between 20 and 45 nm as influenced by the component ratio and the pH value. These results can provide valuable insights into the improvement of Ag@Au NP stability in the presence of gelatin.

Characterization, Optical and Impedance Study of ZnSe Nanostructure

2013 ◽  
Vol 699 ◽  
pp. 490-495
Author(s):  
Ramna Tripathi ◽  
Akhilesh Kumar
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Impedance Spectroscopy ◽  
Zinc Selenide ◽  
Relaxation Times ◽  
Complex Impedance ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Stability

Zinc selenide nanoparticle has been synthesized using soft chemical routes. The particles were capped using 2-mercaptoethanol to achieve the stability and avoid the coalescence. The as-obtained particles were characterized by X-ray diffraction (XRD), Transmission electron microscopy (TEM), UV–VIS absorption and photoluminescence (PL) spectra. The impedance studies were carried out as a function of frequency (100 Hz–1 MHz) and temperature (298–373 K) by impedance spectroscopy. An analysis of the complex impedance (z' and z") with frequency is performed assuming a distribution of relaxation times.

An Inexpensive, Stable and Highly Efficient Photocatalyst for Degradation of Organic Dyes in Water: Core-Shell Montmorillonite-TiO2 Colloids

2013 ◽  
Vol 864-867 ◽  
pp. 404-407
Author(s):  
Shi Zhao Kang ◽  
Tan Wu ◽  
Xiang Qing Li ◽  
Yi Lun Zhou ◽  
Jin Mu
Keyword(s):  
Photocatalytic Activity ◽  
Methyl Orange ◽  
Organic Dyes ◽  
Hydrothermal Process ◽  
Core Shell ◽  
X Ray Diffraction ◽  
X Ray ◽  
Highly Efficient ◽  
Transmission Electron ◽  
The Stability

Core-shell montmorillonite-TiO2 colloids were prepared in a hydrothermal process and characterized with transmission electron microscope, powder X-ray diffraction analysis, Brunauer-Emmett-Teller analysis and UV-vis spectra. Afterwards, their photocatalytic activity was investigated under UV irradiation using methyl orange as a model contaminant. In addition, the stability of the core-shell montmorillonite-TiO2 colloids was investigated by repeatedly performing methyl orange photocatalytic degradation experiments. The results indicate the as-prepared core-shell montmorillonite-TiO2 colloids are a highly efficient photocatalyst for the degradation of organic dyes in water. And this photocatalytic activity remains almost unchanged after eight successive cycles.

500℃ high-temperature reliability of Ni/Nb Ohmic contact on n-type 4H-SiC

2021 ◽  
Author(s):  
Vuong Van Cuong ◽  
Tadashi Sato ◽  
Takamichi Miyazaki ◽  
Tetsuya Meguro ◽  
Seiji Ishikawa ◽  
...  
Keyword(s):  
High Temperature ◽  
Ohmic Contact ◽  
Chemical Compounds ◽  
Etching Process ◽  
X Ray Diffraction ◽  
X Ray ◽  
Ohmic Behavior ◽  
Transmission Electron ◽  
Current Voltage ◽  
The Stability

Abstract The reliability of Ni/Nb ohmic contact on n-type 4H-SiC at 500℃ was investigated. The current-voltage characteristics showed that, while the Ni(50)/Nb(50)/4H-SiC sample without applying the CF4:O2 etching process degraded just after 25-hour and lost ohmic behavior after 50-hour aging, the Ni(75)/Nb(25)/4H-SiC contact undergone CF4:O2 surface treatment still showed excellent stability after aging for 100 hours at 500℃. Though X-ray diffraction results indicated that the chemical compounds remained stable during the aging process, transmission electron microscopy showed that there was a redistribution of the chemical compounds at the interface of the contact after 500℃ aging. The depth distribution of the elements and energy dispersive X-ray analyses revealed that the contribution of carbon agglomeration at the interface accounted for the degradation of the sample without applying the etching process. Whereas the well-controlled excess carbon atoms of the contact undergone CF4:O2 treatment ensured the stability of this contact when operating at high-temperature ambient.

Multicomponent metastable phase formed by crystallization of Ti–Ni–Cu–Sn–Zr amorphous alloy

1999 ◽  
Vol 14 (11) ◽  
pp. 4426-4430 ◽  
Author(s):  
Dmitri V. Louzguine ◽  
Akihisa Inoue
Keyword(s):  
Metastable Phase ◽  
Exothermic Reaction ◽  
Primary Crystallization ◽  
Lattice Parameter ◽  
Body Centered Cubic ◽  
X Ray Diffraction ◽  
X Ray ◽  
Unknown Phase ◽  
Transmission Electron

Crystallization of the Ti45Ni20Cu25Sn5Zr5 alloy has been studied by means of scanning differential calorimetry, x-ray diffraction, and conventional and high-resolution transmission electron microscopy. The first stage at about 750–800 K is related to the primary crystallization of the Ti8Ni3Cu3SnZr metastable phase having Im3m body-centered-cubic structure with a lattice parameter of a = 0.3069 nm followed by precipitation of the secondary dotlike phase precipitates on its boundaries. The activation energy for the first exothermic reaction determined by Kissinger analysis was found to be 310 kJ/mol. CuTi, Ni2TiZr, and an unknown phase are formed during long-term annealing at high (more than 850 K) temperature.

scholarly journals Crystallization Process and Microstructural Evolution of Melt Spun Al-RE-Ni-(Cu) Ribbons

Metals ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 443
Author(s):  
Francisco G. Cuevas ◽  
Sergio Lozano-Perez ◽  
Rosa María Aranda ◽  
Raquel Astacio
Keyword(s):  
Crystallization Process ◽  
Primary Crystallization ◽  
Amorphous Structure ◽  
Intermetallic Phases ◽  
X Ray Diffraction ◽  
Scanning Calorimetry ◽  
X Ray ◽  
Transmission Electron ◽  
Melt Spun ◽  
The Stability

The crystallization process, both at the initial and subsequent stages, of amorphous Al88-RE4-Ni8 alloys (RE = Y, Sm and Ce) has been studied. Additionally, the consequences of adding 1 at.% Cu replacing Ni or Al were studied. The stability of the amorphous structure in melt spun ribbons was thermally studied by differential scanning calorimetry, with Ce alloys being the most stable. The effect of Cu to reduce the nanocrystal size during primary crystallization was analyzed by transmission electron microscopy. This latter technique and x-ray diffraction showed the formation of intermetallic phases at higher temperatures. A clear difference was observed for the Ce alloy, with a simpler sequence involving the presence of Al3Ni and Al11Ce3. However, for the Y and Sm alloys, a more complex evolution involving metastable ternary phases before Al19RE5Ni3 appears, takes place. The shape of the intermetallics changes from equiaxial in the Ce alloys to elongate for Y and Sm, with longer particles for Sm and, in general, when Cu is added to the alloy.

Effect of Thermomechanical Processing on the Microstructure and Retained Austenite Stability during In Situ Tensile Testing Using Synchrotron X-Ray Diffraction of NbMoAl TRIP Steel

2011 ◽  
Vol 172-174 ◽  
pp. 741-746 ◽  
Author(s):  
Elena V. Pereloma ◽  
Lai Chang Zhang ◽  
Klaus Dieter Liss ◽  
Ulf Garbe ◽  
Jonathan Almer ◽  
...  
Keyword(s):  
Tensile Testing ◽  
Retained Austenite ◽  
Thermomechanical Processing ◽  
Critical Role ◽  
High Energy ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
The Stability

In this work we compare and contrast the stability of retained austenite during tensile testing of Nb-Mo-Al transformation-induced plasticity steel subjected to different thermomechanical processing schedules. The obtained microstructures were characterised using optical metallography, transmission electron microscopy and X-ray diffraction. The transformation of retained austenite to martensite under tensile loading was observed by in-situ high energy X-ray diffraction at 1ID / APS. It has been shown that the variations in the microstructure of the steel, such as volume fractions of present phases, their morphology and dimensions, play a critical role in the strain-induced transition of retained austenite to martensite.

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