scholarly journals Comparative Study of the Reactivity of the Tungsten Oxides WO2 and WO3 with Beryllium at Temperatures up to 1273 K

2019 ◽  
Vol 4 (3) ◽  
pp. 82 ◽  
Author(s):  
Martin Köppen
Keyword(s):  
Photoelectron Spectroscopy ◽  
Gas Turbines ◽  
Functional Materials ◽  
Power Devices ◽  
Tungsten Oxides ◽  
First Case ◽  
Catastrophic Failures ◽  
Experimental Step ◽  
Modern Technologies ◽  
Tungsten Substrate

Tungsten oxides play a pivotal role in a variety of modern technologies, e.g., switchable glasses, wastewater treatment, and modern gas sensors. Metallic tungsten is used as armor material, for example in gas turbines as well as future fusion power devices. In the first case, oxides are desired as functional materials; while in the second case, oxides can lead to catastrophic failures, so avoiding the oxidation of tungsten is desired. In both cases, it is crucial to understand the reactivity of tungsten oxides with other chemicals. In this study, the different reactivities of tungsten oxides with the highly-oxophilic beryllium are studied and compared. Tungsten-(IV)-oxide and tungsten-(VI)-oxide layers are prepared on a tungsten substrate. In the next step, a thin film of beryllium is evaporated on the samples. In consecutive steps, the sample is heated in steps of 100 K from room temperature (r. t.) to 1273 K. The chemical composition is investigated after each experimental step by high-resolution X-ray photoelectron spectroscopy (XPS) for all involved core levels as well as the valence band. A model is developed to analyze the chemical reactions after each step. In this study, we find that tungsten trioxide was already reduced by beryllium at r. t. and started to react to form the ternary compounds BeWO3 and BeWO4 at temperatures starting from 673 K. However, tungsten dioxide is resistant to reduction at temperatures of up to 1173 K. In conclusion, we find WO2 to be much more chemically resistant to the reduction agent Be than WO3.

scholarly journals Comparative Study of the Reactivity of the Tungsten Oxides WO2 and WO3 with Beryllium at Temperatures up to 1273 K

2019 ◽  
Author(s):  
Martin Köppen
Keyword(s):  
Photoelectron Spectroscopy ◽  
Gas Turbines ◽  
Functional Materials ◽  
Power Devices ◽  
Tungsten Oxides ◽  
First Case ◽  
Catastrophic Failures ◽  
Experimental Step ◽  
Modern Technologies ◽  
Tungsten Substrate

Tungsten oxides play a pivotal role in a variety of modern technologies e.g., switchable glasses, wastewater treatment, and modern gas sensors. Metallic tungsten is used as armor material, for e.g., gas turbines as well as future fusion power devices. In the first case, oxides are desired as functional materials, while in the second case, oxides can lead to catastrophic failures, so avoiding the oxidation of tungsten is desired. In both cases, it is crucial to understand the reactivity of tungsten oxides with other chemicals. In this study, the different reactivities of tungsten oxides with the highly-oxophilic beryllium are studied and compared. Tungsten-(IV)-oxide and tungsten-(VI)-oxide layers are prepared on a tungsten substrate. In the next step, a thin film of beryllium is evaporated on the samples. In consecutive steps, the sample is heated in steps of 100 K from r. t. to 1273 K. The chemical composition is investigated after each experimental step by high-resolution X-ray photoelectron spectroscopy (XPS) of all involved core levels as well as the valence band. A model is developed to analyze the chemical reactions after each step. In this study, we find that tungsten trioxide was already reduced by beryllium at r. t. and started to react to form the ternary compounds BeWO3 and BeWO4 at temperatures starting from 673 K. However, tungsten dioxide is resistant to reduction at temperatures of up to 1173 K. In conclusion, we find WO2 to be much more chemically resistant to the reduction agent Be than WO3.

scholarly journals Comparative Study of The Reactivity of the Tungsten Oxides WO2 And WO3 With Beryllium at Temperatures up to 1273 K

2019 ◽  
Author(s):  
Martin Köppen
Keyword(s):  
Photoelectron Spectroscopy ◽  
Gas Turbines ◽  
Power Devices ◽  
Tungsten Oxides ◽  
First Case ◽  
Catastrophic Failures ◽  
Experimental Step ◽  
Valence Bands ◽  
The Stability ◽  
Tungsten Substrate

Tungsten oxides play a pivotal role in a variety of modern devices e.g. switchable glasses, wastewater treatment and modern gas sensors and metallic tungsten is used as armour material for e.g. gas turbines and future fusion power devices. In the first case you want to keep the oxide as functional material, while in the second case oxides can lead to catastrophic failures and you want avoid oxidation of tungsten. In both cases it is crucial to understand the stability of the tungsten oxides against chemicals. In this study the different reactivity of tungsten oxides towards the highly oxophilic beryllium is studied and compared. Tungsten--(IV)--oxide and tungsten--(VI)--oxide layers are prepared on a tungsten substrate. In the next step a thin film of beryllium is evaporated on the samples. In consecutive steps the sample is heated in steps of 100 K from r.t. to 1273 K. The chemical composition is investigated after each experimental step by high resolution X-ray photoelectron spectroscopy (XPS) of all involved core levels as well as the valence bands. A model is developed to analyse the chemical reactions after each step. In this study, we found the tungsten trioxid is reduced already by beryllium at r.t. and starts to react towards the ternary compounds BeWO_3 and BeWO_4 at temperatures starting from 673 K. However, the tungsten dioxide sample is reduction resistant to tempartures up to 1173 K. In conclusion, we found the WO_2 surface to be much more chemical resistant towards the reduction agent Be than WO_3.

scholarly journals Elucidation of the Crystal Growth Characteristics of SnO2 Nanoaggregates Formed by Sequential Low-Temperature Sol-Gel Reaction and Freeze Drying

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1738
Author(s):  
Saeid Vafaei ◽  
Alexander Wolosz ◽  
Catlin Ethridge ◽  
Udo Schnupf ◽  
Nagisa Hattori ◽  
...  
Keyword(s):  
Crystal Growth ◽  
Low Temperature ◽  
Photoelectron Spectroscopy ◽  
High Performance ◽  
Freeze Drying ◽  
Sno2 Nanoparticles ◽  
Sol Gel ◽  
Functional Materials ◽  
Cost Effective ◽  
High Concentration

SnO2 nanoparticles are regarded as attractive, functional materials because of their versatile applications. SnO2 nanoaggregates with single-nanometer-scale lumpy surfaces provide opportunities to enhance hetero-material interfacial areas, leading to the performance improvement of materials and devices. For the first time, we demonstrate that SnO2 nanoaggregates with oxygen vacancies can be produced by a simple, low-temperature sol-gel approach combined with freeze-drying. We characterize the initiation of the low-temperature crystal growth of the obtained SnO2 nanoaggregates using high-resolution transmission electron microscopy (HRTEM). The results indicate that Sn (II) hydroxide precursors are converted into submicrometer-scale nanoaggregates consisting of uniform SnO2 spherical nanocrystals (2~5 nm in size). As the sol-gel reaction time increases, further crystallization is observed through the neighboring particles in a confined part of the aggregates, while the specific surface areas of the SnO2 samples increase concomitantly. In addition, X-ray photoelectron spectroscopy (XPS) measurements suggest that Sn (II) ions exist in the SnO2 samples when the reactions are stopped after a short time or when a relatively high concentration of Sn (II) is involved in the corresponding sol-gel reactions. Understanding this low-temperature growth of 3D SnO2 will provide new avenues for developing and producing high-performance, photofunctional nanomaterials via a cost-effective and scalable method.

Deposition of gold nanoparticles on organo-kaolinite — Application in electrocatalysis for carbon monoxide oxidation

2011 ◽  
Vol 89 (7) ◽  
pp. 845-853 ◽  
Author(s):  
Sadok Letaief ◽  
Wendy Pell ◽  
Christian Detellier
Keyword(s):  
Carbon Monoxide ◽  
Gold Nanoparticles ◽  
Photoelectron Spectroscopy ◽  
Fine Particles ◽  
Raw Materials ◽  
Carbon Monoxide Oxidation ◽  
Functional Materials ◽  
Metallic State ◽  
Oxidation Reactions ◽  
X Ray

The clay mineral kaolinite was used as support of gold nanoparticles for heterogeneous catalysis of oxidation reactions, particularly of carbon monoxide oxidation. The application of clay minerals in the preparation of new functional materials provides an alternative approach for the use of these abundant raw materials. To improve the physicochemical properties of kaolinite, as well as to ensure a strong immobilization of the adsorbed species, kaolinite was functionalized by grafting 2-amino-2-methyl-1,3-propanediol on the internal and external surfaces of the octahedral sheets by reaction with the aluminol groups. Gold nanoparticles were then deposited on the external surfaces of the fine particles of the functionalized kaolinite. The resulting gold kaolinite nanohybrid material was characterized by various physicochemical techniques. X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and energy-dispersive X-ray spectrometry confirmed that gold was effectively reduced to the metallic state during adsorption onto the external surfaces of the modified kaolinite. The gold nanoparticles have a narrow size distribution: more than 88% are less than 4 nm in diameter. Gold nanoparticles deposited on kaolinite catalyze the electro-oxidation of carbon monoxide in alkaline solution at room temperature.

scholarly journals Adsorption of hexavalent chromium by polyacrylonitrile-based porous carbon from aqueous solution

2018 ◽  
Vol 5 (1) ◽  
pp. 171662 ◽  
Author(s):  
Bin Feng ◽  
Wenzhong Shen ◽  
Liyi Shi ◽  
Shijie Qu
Keyword(s):  
Aqueous Solution ◽  
Adsorption Capacity ◽  
Porous Carbon ◽  
Photoelectron Spectroscopy ◽  
Ph Value ◽  
Functional Materials ◽  
High Specific Surface Area ◽  
Maximum Adsorption Capacity ◽  
Elementary Analysis ◽  
Initial Adsorption

Owing to the unique microporous structure and high specific surface area, porous carbon could act as a good carrier for functional materials. In this paper, polyacrylonitrile (PAN)-based porous carbon materials (PPC-0.6-600, PPC-0.8-600, PPC-0.6-800 and PPC-0.8-800) were prepared by heating KOH at 600°C and 800 o C for the removal of Cr(VI) from aqueous solution. The adsorbent was characterized by the techniques of Fourier transform infrared spectroscopy (FT-IR), elementary analysis, scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and N 2 adsorption techniques. The results showed that the adsorption capacity increased with decreasing pH value of the initial solution. The adsorption capacity of Cr(VI) on PPC-0.8-800 was much greater than that on other materials, and maximum adsorption capacity were calculated to be 374.90 mg g −1 . Moreover, PPC-0.8-800 had superior recyclability for the removal of Cr(VI) from wastewater, about 82% of its initial adsorption capacity was retained even after five cycles. The result of kinetic simulation showed that the adsorption of Cr(VI) on the PAN-based porous carbon could be described by pseudo-second-order kinetics. The adsorption process was the ionic interaction between protonated amine groups of PPC and HCrO 4 - ions.

An Efficient Simple Hydrothermal Method to Synthesis FeS2 Microspheres and their Optical Property

2016 ◽  
Vol 847 ◽  
pp. 72-77
Author(s):  
Yu Xuan Liang ◽  
Peng Peng Bai ◽  
Shu Qi Zheng
Keyword(s):  
Photoelectron Spectroscopy ◽  
Low Cost ◽  
Wave Length ◽  
Functional Materials ◽  
Optical And Electrical Properties ◽  
X Ray Diffraction ◽  
Synthetic Sample ◽  
X Ray ◽  
New Type ◽  
Good Uniformity

Pyrite (FeS2) is an important semiconductor material which shows various excellent optical and electrical properties and extensive applied prospect as a new-type, photoelectrical functional materials. In this study, a low cost and efficient simple hydrothermal two-step synthetic method was given to obtain FeS2 microspheres with 2-3 μm in diameter. The obtained products were characterized with X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet and visible spectrophotometer (UV-Vis). XRD showed that the synthetic sample consisted of two crystal structures of FeS2, pyrite and marcasite. SEM observation indicated that FeS2 microspheres were well crystallized and had good uniformity. UV-Vis spectrum had a strong optical absorption in the region of 200-400 nm wave length. The reaction temperature had an impact on the size of FeS2 microspheres. A possible mechanism for the size of the FeS2 microspheres generated at high temperature is smaller than that at low temperature is discussed.

Active Control of Combustion Instabilities in a Matrix Burner Using Primary and Pilot Fuel and Acoustic Forcing

2010 ◽  
Author(s):  
Dieter Bohn ◽  
Nils Ohlendorf ◽  
Frank Weidner ◽  
James F. Willie
Keyword(s):  
Heat Release ◽  
Mass Flow ◽  
Gas Turbines ◽  
Open Loop ◽  
Nox Emissions ◽  
Combustion Instabilities ◽  
Loop Control ◽  
First Case ◽  
Pilot Fuel ◽  
Acoustic Forcing

Lean premixed flames applied in modern gas turbines leads to reduce NOx emissions, but at the same time they are more susceptible to combustion instabilities than diffusion flames. These oscillations cause pressure fluctuations with high amplitudes and unacceptable noise as well as the risk of component or even engine failure. They can lead to pockets of fuel being formed in the mixing chamber and to bad mixing, which leads to increase in emissions. This paper reports the successful decoupling of the pressure and heat release inside the combustion chamber of a matrix burner using two actuation techniques. This led to the successful attenuation of the dominant instability modes occurring inside the combustor of the matrix burner. In the first case, acoustic forcing was used to decouple the pressure and the heat release inside the combustor. This was achieved by using a loudspeaker to modulate the primary air mass flow. This was followed by using acoustic forcing in CFD to decouple the pressure and heat release inside the combustor. For the action of the loudspeaker, sinusoidal forcing was used to mimic the modulation action of the diaphragm of the loudspeaker. In the second case, a fast gaseous “on-off” injector was used to modulate the primary fuel mass flow. After this, pilot fuel modulation was used to stabilize the flame. The control law governing the primary and pilot fuel modulation is discussed in details. The effect of open loop control on NOx emissions in the burner is also reported and discussed.

Palladium Nanoparticles Synthesized by Bio-Templates for Suzuki Coupling Reaction

2015 ◽  
Vol 1118 ◽  
pp. 14-19 ◽  
Author(s):  
Yu Hui Wei ◽  
Lan Jie Wang ◽  
Xiu Hua Zhao ◽  
Chun Cao Li ◽  
Li Xia Kong ◽  
...  
Keyword(s):  
Photoelectron Spectroscopy ◽  
Palladium Nanoparticles ◽  
Amyloid Fibrils ◽  
Coupling Reaction ◽  
Functional Materials ◽  
Palladium Chloride ◽  
Chemical Compositions ◽  
Layer By Layer ◽  
Suzuki Coupling Reaction ◽  
Insulin Fibrils

Palladium nanoparticles (Pd NPs) are the most widely used functional materials for a variety of catalytic reactions. In this work, we synthesized the size-controlled Pd NPs using amyloid fibrils as bio-templates. First, 1mg/ml insulin peptides were incubated at 80°Cfor 3 days to form protein fibrils. Then, layer-by-layer technology was used to prepare Pd-insulin fibrils multilayer film as catalyst by alternatively depositing insulin fibrils and palladium chloride which has been aged at several different temperatures for two days. The chemical compositions of Pd-insulin film were also characterized by X-ray photoelectron spectroscopy (XPS). The Pd-insulin film demonstrated high isolated yield in promoting Suzuki cross-coupling reaction. In addition, the effect of Pd NPs size on the catalytic activity was also discussed.

XPS and Electrochemical Studies on Tungsten-Oxidizer Interaction in Chemical Mechanical Polishing

1999 ◽  
Vol 566 ◽  
Author(s):  
Dnyanesh Tamboli ◽  
Sudipta Seal ◽  
Vimal Desai
Keyword(s):  
Photoelectron Spectroscopy ◽  
Chemical Mechanical Polishing ◽  
Material Removal ◽  
Electrochemical Measurements ◽  
Electrochemical Studies ◽  
Removal Mechanism ◽  
Tungsten Oxides ◽  
X Ray ◽  
Static Solutions

Electrochemical interaction between the oxidizer and the metal is believed to play a key role in material removal in tungsten CMP. In this study, we use X-ray Photoelectron Spectroscopy (XPS) in conjunction with electrochemical measurements in both in-situ polishing conditions as well as in static solutions, to identify the passivation and dissolution modes of tungsten. Dissolution of tungsten oxides was found to be the primary non-mechanical tungsten removal mechanism in CMP.

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