scholarly journals Preventing Agglomeration of CuO-Based Oxygen Carriers for Chemical Looping Applications

2021 ◽  
Author(s):  
Qasim Imtiaz ◽  
Andac Armutlulu ◽  
Felix Donat ◽  
Muhammad Awais Naeem ◽  
Christoph Müller
Keyword(s):  
Thin Films ◽  
Focused Ion Beam ◽  
Pechini Method ◽  
Ion Beam ◽  
Oxygen Carrier ◽  
Structural Instability ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Promising Alternative ◽  
Main Challenge

Chemical looping combustion (CLC) is a promising alternative to the conventional combustion-based, fossil fuel conversion processes. In CLC, a solid oxygen carrier is used to transfer oxygen from air to a carbonaceous fuel. This indirect combustion route allows for effective CO<sub>2</sub> capture since a sequestrable stream of CO<sub>2 </sub>is inherently produced without any need for energy-intensive CO<sub>2</sub> separation. From a thermodynamic point of view, CuO is arguably one of the most promising oxygen carrier candidates for CLC. However, the main challenge associated with the use of CuO for CLC is its structural instability at the typical operating temperatures of chemical looping processes, leading to severe thermal sintering and agglomeration. To minimize irreversible microstructural changes during CLC operation, CuO is commonly stabilized by a high Tammann temperature ceramic, e.g., Al<sub>2</sub>O<sub>3</sub>, MgAl<sub>2</sub>O<sub>4</sub>, etc. However, it has been observed that a high Tammann temperature support does not always provide a high resistance to agglomeration. This work aims at identifying descriptors that can be used to characterize accurately the agglomeration tendency of CuO-based oxygen carriers. CuO-based oxygen carriers supported on different metal oxides were synthesized using a Pechini method. The cyclic redox stability and agglomeration tendency of the synthesized materials was evaluated using both a thermo-gravimetric analyser and a lab-scale fluidized bed reactor at 900 °C using 10 vol. % H<sub>2</sub> in N<sub>2</sub> as the fuel and air for re-oxidation. In order to study the diffusion of Cu(O) during redox reactions, well-defined model surfaces comprising thin films of Cu/CuO and two different supports, viz. ZrO<sub>2</sub> or MgO, were prepared via magnetron sputtering. Energy dispersive X-ray (EDX) spectroscopy on focused ion beam (FIB)-cut cross-sections of the thin films revealed that Cu atoms have a tendency to diffuse outward through most of the films of the support material under redox conditions. The support that inhibits the outward movement of Cu(O), i.e. avoiding the presence of low melting Cu on the oxygen carrier surface, is found to provide the highest agglomeration resistance. The support MgO was found to possesses such diffusion characteristics.

scholarly journals Preventing Agglomeration of CuO-Based Oxygen Carriers for Chemical Looping Applications

2021 ◽  
Author(s):  
Qasim Imtiaz ◽  
Andac Armutlulu ◽  
Felix Donat ◽  
Muhammad Awais Naeem ◽  
Christoph Müller
Keyword(s):  
Thin Films ◽  
Focused Ion Beam ◽  
Pechini Method ◽  
Ion Beam ◽  
Oxygen Carrier ◽  
Structural Instability ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Promising Alternative ◽  
Main Challenge

Chemical looping combustion (CLC) is a promising alternative to the conventional combustion-based, fossil fuel conversion processes. In CLC, a solid oxygen carrier is used to transfer oxygen from air to a carbonaceous fuel. This indirect combustion route allows for effective CO<sub>2</sub> capture since a sequestrable stream of CO<sub>2 </sub>is inherently produced without any need for energy-intensive CO<sub>2</sub> separation. From a thermodynamic point of view, CuO is arguably one of the most promising oxygen carrier candidates for CLC. However, the main challenge associated with the use of CuO for CLC is its structural instability at the typical operating temperatures of chemical looping processes, leading to severe thermal sintering and agglomeration. To minimize irreversible microstructural changes during CLC operation, CuO is commonly stabilized by a high Tammann temperature ceramic, e.g., Al<sub>2</sub>O<sub>3</sub>, MgAl<sub>2</sub>O<sub>4</sub>, etc. However, it has been observed that a high Tammann temperature support does not always provide a high resistance to agglomeration. This work aims at identifying descriptors that can be used to characterize accurately the agglomeration tendency of CuO-based oxygen carriers. CuO-based oxygen carriers supported on different metal oxides were synthesized using a Pechini method. The cyclic redox stability and agglomeration tendency of the synthesized materials was evaluated using both a thermo-gravimetric analyser and a lab-scale fluidized bed reactor at 900 °C using 10 vol. % H<sub>2</sub> in N<sub>2</sub> as the fuel and air for re-oxidation. In order to study the diffusion of Cu(O) during redox reactions, well-defined model surfaces comprising thin films of Cu/CuO and two different supports, viz. ZrO<sub>2</sub> or MgO, were prepared via magnetron sputtering. Energy dispersive X-ray (EDX) spectroscopy on focused ion beam (FIB)-cut cross-sections of the thin films revealed that Cu atoms have a tendency to diffuse outward through most of the films of the support material under redox conditions. The support that inhibits the outward movement of Cu(O), i.e. avoiding the presence of low melting Cu on the oxygen carrier surface, is found to provide the highest agglomeration resistance. The support MgO was found to possesses such diffusion characteristics.

scholarly journals Development of CuO-based oxygen carriers supported on diatomite and kaolin for chemical looping combustion

2021 ◽  
Vol 10 (4) ◽  
pp. e15110412831
Author(s):  
Romário Cezar Pereira da Costa ◽  
Rebecca Araújo Barros do Nascimento ◽  
Dulce Maria de Araújo Melo ◽  
Dener Silva Albuquerque ◽  
Rodolfo Luiz Bezerra de Araújo Medeiros ◽  
...  
Keyword(s):  
Reaction Rate ◽  
Direct Reduction ◽  
Oxygen Carrier ◽  
Chemical Looping Combustion ◽  
Chemical Looping ◽  
Impregnation Method ◽  
Oxygen Carriers ◽  
Fuel Gas ◽  
Promising Alternative ◽  
X Ray

Chemical Looping Combustion (CLC) technology has emerged as a promising alternative capable of restricting the effects of global warming due to anthropogenic gas emissions, especially CO2, through its inherent capture. This study aims to synthesize and evaluate Cu-based oxygen carriers supported on natural materials such as diatomite and kaolin, through the incipient wet impregnation method for CLC process applications. Oxygen carriers were characterized by X-ray diffraction (XRD), temperature-programmed reduction (TPR), and scanning electron microscopy with surface energy dispersive x-ray spectroscopy (SEM-EDS). The mechanical strength of the two oxygen carrier particles was determined after the sintering procedure resulting in high crushing force. Reactivity of oxygen carriers was evaluated in a thermobalance with CH4 and H2 gases. Different reaction pathways were attempted when undergoing the redox cycles: total direct reduction of CuO to Cu0 for Cu-K and partial reduction of CuO to Cu2O and CuO to Cu-D. However, the highest reactivity and reaction rate was achieved in Cu-D due to the pore structure of diatomite, the chemical composition and the resulting interaction between CuO and the support. H2 gas reactivity tests showed a higher conversion rate and greater stability between cycles for both oxygen carriers. Thus, the reducible CuO content present in Cu-Diatomite during the reactivity test with H2 as the fuel gas was ideal for achieving high solids conversion, tendency for greater stability and a higher reaction rate.

Mechanical Properties of Electroplated Copper Thin Films

1999 ◽  
Vol 594 ◽  
Author(s):  
R. Spolenak ◽  
C. A. Volkert ◽  
K. Takahashi ◽  
S. Fiorillo ◽  
J. Miner ◽  
...  
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Grain Size ◽  
Film Thickness ◽  
Yield Stress ◽  
Laser Scanning ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Cu Films ◽  
Electroplated Copper

AbstractIt is well known that the mechanical properties of thin films depend critically on film thickness However, the contributions from film thickness and grain size are difficult to separate, because they typically scale with each other. In one study by Venkatraman and Bravman, Al films, which were thinned using anodic oxidation to reduce film thickness without changing grain size, showed a clear increase in yield stress with decreasing film thickness.We have performed a similar study on both electroplated and sputtered Cu films by using chemical-mechanical polishing (CMP) to reduce the film thickness without changing the grain size. Stress-temperature curves were measured for both the electroplated and sputtered Cu films with thicknesses between 0.1 and 1.8 microns using a laser scanning wafer curvature technique. The yield stress at room temperature was found to increase with decreasing film thickness for both sets of samples. The sputtered films, however, showed higher yield stresses in comparison to the electroplated films. Most of these differences can be attributed to the different microstructures of the films, which were determined by focused ion beam (FIB) microscopy and x-ray diffraction.

Effects of P Content on Morphology of Nanocrystals Induced by FIB Irradiation in Ni-P Amorphous Alloy

2006 ◽  
Vol 960 ◽  
Author(s):  
Koji Sato ◽  
Chiemi Ishiyama ◽  
Masato Sone ◽  
Yakichi Higo
Keyword(s):  
Thin Films ◽  
Amorphous Alloy ◽  
Crystallographic Orientation ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
Orientation Relationships ◽  
Beam Direction ◽  
Precipitation Distribution ◽  
P Content

ABSTRACTWe studied the effects of phosphorus (P) on Ni nanocrystalline morphology formed by focused ion beam (FIB) irradiation for Ni-P amorphous alloy thin films. The P content in the amorphous alloy was varied from 8 to 12 wt.%. The nanocrystals induced by the FIB irradiation for Ni-11.8, 8.9, 7.9 wt.% amorphous alloy had an f.c.c. structure and showed unique crystallographic orientation relationships to the geometry of the focused ion beam, that is, {111}f.c.c. parallel to the irradiated plane and <110>f.c.c. parallel to the projected ion beam direction, respectively. The Ni nanocrystals precipitated like aggregates with decreasing of the P content. These results represent that the P content does not affect crystallographic orientation relationships, while influences the precipitation distribution of Ni nanocrystals generated by the FIB irradiation.

scholarly journals Reverse Water–Gas Shift Chemical Looping Using a Core–Shell Structured Perovskite Oxygen Carrier

Energies ◽  
2020 ◽  
Vol 13 (20) ◽  
pp. 5324
Author(s):  
Minbeom Lee ◽  
Yikyeom Kim ◽  
Hyun Suk Lim ◽  
Ayeong Jo ◽  
Dohyung Kang ◽  
...  
Keyword(s):  
Metal Oxide ◽  
Oxygen Carrier ◽  
Dark Field ◽  
Water Gas Shift ◽  
Unit Weight ◽  
Core Shell ◽  
Chemical Looping ◽  
Oxygen Carriers ◽  
Reverse Water Gas Shift ◽  
Water Gas

Reverse water–gas shift chemical looping (RWGS-CL) offers a promising means of converting the greenhouse gas of CO2 to CO because of its relatively low operating temperatures and high CO selectivity without any side product. This paper introduces a core–shell structured oxygen carrier for RWGS-CL. The prepared oxygen carrier consists of a metal oxide core and perovskite shell, which was confirmed by inductively coupled plasma mass spectroscopy (ICP-MS), XPS, and high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM) measurements. The perovskite-structured shell of the prepared oxygen carrier facilitates the formation and consumption of oxygen defects in the metal oxide core during H2-CO2 redox looping cycles. As a result, amounts of CO produced per unit weight of the core–shell structured oxygen carriers were higher than that of a simple perovskite oxygen carrier. Of the metal oxide cores tested, CeO2, NiO, Co3O4, and Co3O4-NiO, La0.75Sr0.25FeO3-encapsulated Co3O4-NiO was found to be the most promising oxygen carrier for RWGS-CL, because it was most productive in terms of CO production and exhibited long-term stability.

Review of Hydrogen Production from the Steam-Iron Process by Chemical-Looping Combustion

2014 ◽  
Vol 953-954 ◽  
pp. 966-969 ◽  
Author(s):  
Long Fei Wang ◽  
Shu Zhong Wang ◽  
Ming Luo
Keyword(s):  
Hydrogen Production ◽  
Solid Fuel ◽  
Process Development ◽  
Oxygen Carrier ◽  
Energy Conversion Efficiency ◽  
High Reactivity ◽  
Future Research ◽  
Pure Hydrogen ◽  
Chemical Looping ◽  
Oxygen Carriers

Chemical looping hydrogen production (CLH) is a promising method for pure hydrogen production, which not only can improve energy conversion efficiency and reduce environmental pollution, but also can separate carbon dioxide. This paper try to review the present chemical looping hydrogen process development on the screening of oxygen carrier particles of gaseous fuel and solid fuel, the design of proper reactors, and the system simulation. The design of solid fuel CLH system and the development of oxygen carriers with high reactivity and abrasion resistance for solid fuel at high temperature and pressure will be future research focuses.

Focused Ion-Beam (FIB) Nanomachining of Silicon Carbide (SiC) Stencil Masks for Nanoscale Patterning

2012 ◽  
Vol 717-720 ◽  
pp. 889-892 ◽  
Author(s):  
Hamidreza Zamani ◽  
Seung Wan Lee ◽  
Amir Avishai ◽  
Christian A. Zorman ◽  
R. Mohan Sankaran ◽  
...  
Keyword(s):  
Thin Films ◽  
Silicon Carbide ◽  
Focused Ion Beam ◽  
Ion Beam ◽  
High Quality ◽  
Nanoscale Patterning ◽  
Different Types ◽  
Thin Membranes ◽  
Amorphous Sic ◽  
Nanoscale Features

We report on experimental explorations of using focused ion beam (FIB) nanomachining of different types of silicon carbide (SiC) thin membranes, for making robust, high-quality stencil masks for new emerging options of nanoscale patterning. Using thin films and membranes in polycrystalline SiC (poly-SiC), 3C-SiC, and amorphous SiC (a-SiC) with thicknesses in the range of t~250nm−1.6μm, we have prototyped a series of stencil masks, with nanoscale features routinely down to ~100nm.

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