Pub Date : 2021-02-26DOI: 10.15587/2706-5448.2021.225328
Andrei Torsky, A. Volnenko, L. Plyatsuk, L. Hurets, D. Zhumadullayev, Аbay Abzhabparov
The object of research is the efficiency of dust collection of fine dust in an apparatus with an intense turbulent mode of phase interaction. One of the most problematic areas of the existing dust and gas cleaning equipment is the low efficiency of collecting fine dust. Effective cleaning of exhaust gases from dust involves the use of multi-stage cleaning systems, including wet and dry dust cleaning devices, which entails high capital and operating costs. These disadvantages are eliminated in the developed design of the cyclone-vortex dust collector with two contact zones. The device implements both dry and wet dust collection mechanisms, which allows for high efficiency of dust removal at high productivity. The conducted studies of the total and fractional efficiency of dust collection when changing the operating parameters of the developed device showed that the efficiency of collecting fine dust is 98–99 %. The increase in the efficiency of dust collection in the dry stage of the device is due to an increase in centrifugal force. In the wet stage of contact, the efficiency reaches its maximum values due to the vortex crushing of the liquid in the nozzle zone of the apparatus. Studies of the fractional efficiency of the apparatus show that with an increase in the diameter of the captured particles, the efficiency of the dust collection process for dry and wet stages, as well as the overall efficiency, increases. With an increase in the density of irrigation, the overall efficiency of dust collection in the apparatus increases. It has been established that an increase in the efficiency of capturing highly dispersed particles occurs due to turbulent diffusion, the value of which is determined by the frequency of turbulent pulsations and the degree of entrainment of particles during the pulsating motion of packed bodies. To describe the results obtained, a centrifugal-inertial model for a dry contact stage and a turbulent-diffusion model of solid particle deposition for a wet contact stage are proposed, which make it possible to calculate the dust collection efficiency of the contact stages, as well as the overall efficiency of the cyclone-vortex apparatus. The results obtained show the prospects of using devices of this design at heat power plants and other industries.
{"title":"Study of Dust Collection Effectiveness in Cyclonic-Vortex Action Apparatus","authors":"Andrei Torsky, A. Volnenko, L. Plyatsuk, L. Hurets, D. Zhumadullayev, Аbay Abzhabparov","doi":"10.15587/2706-5448.2021.225328","DOIUrl":"https://doi.org/10.15587/2706-5448.2021.225328","url":null,"abstract":"The object of research is the efficiency of dust collection of fine dust in an apparatus with an intense turbulent mode of phase interaction. One of the most problematic areas of the existing dust and gas cleaning equipment is the low efficiency of collecting fine dust. Effective cleaning of exhaust gases from dust involves the use of multi-stage cleaning systems, including wet and dry dust cleaning devices, which entails high capital and operating costs. These disadvantages are eliminated in the developed design of the cyclone-vortex dust collector with two contact zones. The device implements both dry and wet dust collection mechanisms, which allows for high efficiency of dust removal at high productivity.\u0000The conducted studies of the total and fractional efficiency of dust collection when changing the operating parameters of the developed device showed that the efficiency of collecting fine dust is 98–99 %. The increase in the efficiency of dust collection in the dry stage of the device is due to an increase in centrifugal force. In the wet stage of contact, the efficiency reaches its maximum values due to the vortex crushing of the liquid in the nozzle zone of the apparatus. Studies of the fractional efficiency of the apparatus show that with an increase in the diameter of the captured particles, the efficiency of the dust collection process for dry and wet stages, as well as the overall efficiency, increases. With an increase in the density of irrigation, the overall efficiency of dust collection in the apparatus increases. It has been established that an increase in the efficiency of capturing highly dispersed particles occurs due to turbulent diffusion, the value of which is determined by the frequency of turbulent pulsations and the degree of entrainment of particles during the pulsating motion of packed bodies. To describe the results obtained, a centrifugal-inertial model for a dry contact stage and a turbulent-diffusion model of solid particle deposition for a wet contact stage are proposed, which make it possible to calculate the dust collection efficiency of the contact stages, as well as the overall efficiency of the cyclone-vortex apparatus.\u0000The results obtained show the prospects of using devices of this design at heat power plants and other industries.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"74982738","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Twinning is found to impart favorable mechanical, physical and chemical properties to nanostructured materials. One important twinning mode, deformation twinning, prevails in coarse-grained hexagonal close-packed (HCP) crystalline materials and body-centered cubic (BCC) and face-centered cubic (FCC) nanomaterials under high-stress conditions. In FCC structures, the {111} deformation twinning is traditionally believed to nucleate and grow through layer-by-layer emission of 1/6 Shockley partial dislocations on consecutive {111} planes. Here, we report that by conducting high-resolution transmission electron microscopy (HRTEM) observation, deformation twinning is, for the first time, found to occur in nanocrystalline (Fe, Nb)23Zr6 particles with a Mn23Th6-type FCC structure that is composed of a Zr-octahedron-based FCC network connected by alloying elements Fe and Nb like the large FCC structure such as metal-organic-framework (MOF). Based on direct atomic-scale observations, we discover a new mechanism for the {111} deformation twinning in FCC structures. To form a [112]/(111) twin, for example, short ( (‾1‾11) planes within two adjacent (111) plane layers in the repeated three-layer sequence of (111) planes are shear deformed continuously by a shear-force dipole along the [112] direction like a domino effect, whereas the other (111) plane in the repeated sequence remains intact. Through this route, a small energy for twinning is expected because only 2/3 (111) planes need to be transformed to form a twin. In addition, a loading criterion for deformation twinning of a FCC NP under uniaxial compression is proposed based on our results. Our work here not only provides a fundamental understanding on deformation twinning in FCC structures, but also opens up studies of deformation behaviors in a class of Mn23Th6-type FCC materials.
{"title":"Deformation Twinning in Octahedron-Based Face-Centered Cubic Metallic Structures: Localized Shear-Force Dipoles Drive Atomic Displacements","authors":"Hengfei Gu, Ph.D, Chengze Liu, Ph.D, Fusen Yuan, Ph.D, Fuzhou Han, Ph.D, Yingdong Zhang, Ph.D, Muhammad Ali, Wenbin Guo, Jie Ren, Lifeng Zhang, Songquan Wu, Geping Li, Ph.D.","doi":"10.2139/ssrn.3788457","DOIUrl":"https://doi.org/10.2139/ssrn.3788457","url":null,"abstract":"Twinning is found to impart favorable mechanical, physical and chemical properties to nanostructured materials. One important twinning mode, deformation twinning, prevails in coarse-grained hexagonal close-packed (HCP) crystalline materials and body-centered cubic (BCC) and face-centered cubic (FCC) nanomaterials under high-stress conditions. In FCC structures, the {111} deformation twinning is traditionally believed to nucleate and grow through layer-by-layer emission of 1/6 Shockley partial dislocations on consecutive {111} planes. Here, we report that by conducting high-resolution transmission electron microscopy (HRTEM) observation, deformation twinning is, for the first time, found to occur in nanocrystalline (Fe, Nb)23Zr6 particles with a Mn23Th6-type FCC structure that is composed of a Zr-octahedron-based FCC network connected by alloying elements Fe and Nb like the large FCC structure such as metal-organic-framework (MOF). Based on direct atomic-scale observations, we discover a new mechanism for the {111} deformation twinning in FCC structures. To form a [112]/(111) twin, for example, short ( (‾1‾11) planes within two adjacent (111) plane layers in the repeated three-layer sequence of (111) planes are shear deformed continuously by a shear-force dipole along the [112] direction like a domino effect, whereas the other (111) plane in the repeated sequence remains intact. Through this route, a small energy for twinning is expected because only 2/3 (111) planes need to be transformed to form a twin. In addition, a loading criterion for deformation twinning of a FCC NP under uniaxial compression is proposed based on our results. Our work here not only provides a fundamental understanding on deformation twinning in FCC structures, but also opens up studies of deformation behaviors in a class of Mn23Th6-type FCC materials.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"85318349","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
For many contemporary powdermetallurgical applications, spherical powders are preferred. Spherical particles have a lower oxygen content, a better flowability and their behaviour is - compared to irregular particles - better predictable. The powder production process via melt atomization can be divided into the steps a. primary breakup into ligaments, b. ligament breakup and c. secondary breakup and/or spheroidisation, while simultaneously cooling and freezing take place. Apart from thermodynamic conditions during the process, melt properties such as viscosity, density, surface tension, heat capacity and thermal conductivity will influence the processes around spheroidisation. As a first step, a 4-force model (viscosity, surface tension, external dynamic and inertia forces) is applied on the melt droplet to predict the influence of the melt properties on spheroidisation separately. Secondly, the spheroidisation process is calculated for different materials such as Copper, Iron or Titanium for existing atomisation systems. Finally, suggestions are presented which may help to produce more spherical particles.
{"title":"Influence of Material Properties on Spheroidisation of Gas Atomization Process","authors":"Martin Dopler","doi":"10.2139/ssrn.3785861","DOIUrl":"https://doi.org/10.2139/ssrn.3785861","url":null,"abstract":"For many contemporary powdermetallurgical applications, spherical powders are preferred. Spherical particles have a lower oxygen content, a better flowability and their behaviour is - compared to irregular particles - better predictable. The powder production process via melt atomization can be divided into the steps a. primary breakup into ligaments, b. ligament breakup and c. secondary breakup and/or spheroidisation, while simultaneously cooling and freezing take place. Apart from thermodynamic conditions during the process, melt properties such as viscosity, density, surface tension, heat capacity and thermal conductivity will influence the processes around spheroidisation. As a first step, a 4-force model (viscosity, surface tension, external dynamic and inertia forces) is applied on the melt droplet to predict the influence of the melt properties on spheroidisation separately. Secondly, the spheroidisation process is calculated for different materials such as Copper, Iron or Titanium for existing atomisation systems. Finally, suggestions are presented which may help to produce more spherical particles.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"72675466","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Anika Langebeck, A. Bohlen, R. Rentsch, F. Vollertsen
A manifold variety of additive manufacturing techniques has a significant positive impact on many industry sectors. Large components are often manufactured via laser metal deposition (LMD) instead of using powder bed based processes. The advantages of LMD process are a high build-up rate with values up to 300 cm³/h and a nearly limitless build-up volume. In combination with the lightweight material aluminium it is possible to manufacture large lightweight components with geometries adapted to customer requirements in small batches. This contributes the pursuit of higher efficiency of machines through lightweight materials as well as lightweight design. A low-defect additive manufacturing of high strength aluminium EN AW-7075 powder via LMD is an important challenge to concern. During the process a considerable proportion of pores can build which weakens the mechanical properties. Additionally, the heat input affects the hardness of the manufactured part. A significant reduction of pore volume can be achieved by a higher laser power and an improved shielding gas flow. Therefore, a shielding gas shroud was developed to keep atmospheric hydrogen away from the process zone. The combination of the improved shielding gas flow with a high laser power led to a decrease of pore volume from over 7% to lower than 1.5%.
{"title":"Low-Defect AM of High Strength Aluminium Alloy by LMD","authors":"Anika Langebeck, A. Bohlen, R. Rentsch, F. Vollertsen","doi":"10.2139/ssrn.3785871","DOIUrl":"https://doi.org/10.2139/ssrn.3785871","url":null,"abstract":"A manifold variety of additive manufacturing techniques has a significant positive impact on many industry sectors. Large components are often manufactured via laser metal deposition (LMD) instead of using powder bed based processes. The advantages of LMD process are a high build-up rate with values up to 300 cm³/h and a nearly limitless build-up volume. In combination with the lightweight material aluminium it is possible to manufacture large lightweight components with geometries adapted to customer requirements in small batches. This contributes the pursuit of higher efficiency of machines through lightweight materials as well as lightweight design. A low-defect additive manufacturing of high strength aluminium EN AW-7075 powder via LMD is an important challenge to concern. During the process a considerable proportion of pores can build which weakens the mechanical properties. Additionally, the heat input affects the hardness of the manufactured part. A significant reduction of pore volume can be achieved by a higher laser power and an improved shielding gas flow. Therefore, a shielding gas shroud was developed to keep atmospheric hydrogen away from the process zone. The combination of the improved shielding gas flow with a high laser power led to a decrease of pore volume from over 7% to lower than 1.5%.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"83818336","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pd40 Ni40P20 (at.%) samples with different enthalpy states and relaxation behaviors were fabricated through high-pressure torsion or sub-Tg annealing of the as-cast state. Subsequently, the underlying structural relaxation was studied by investigating the modulus and thermal characteristics using in-situ shear modulus measurement and modulated differential scanning calorimetry. The results show that high-pressure torsion leads to shear modulus softening and an increase of the irreversible exothermic enthalpy, indicating a significant structural rejuvenation, while sub-Tg annealing causes shear modulus hardening and a decrease of the irreversible exothermic enthalpy. Besides, the reversible endothermic effect which reflects the heat capacity was found to be almost identical for all samples, independent on deformation or thermal history. The total heat flow can be well correlated to the shear modulus within the framework of interstitialcy theory. Furthermore, we demonstrate that the structural relaxation below Tg decouples into the internal stress relaxation and β-relaxation. The former is an irreversible process of releasing internal stress, accompanied by an exothermic effect and modulus hardening. The latter is a complex process involving kinetic and thermodynamic components, accompanied by an endothermic effect and modulus softening. Shadow glass transition and glass transition overshoot are related to the activation (cage-breaking) processes in the kinetics of β-relaxation and α-relaxation, respectively. This work indicates that β-relaxation and α-relaxation are kinetically and thermodynamically identical but occur in distinct temperature or frequency domains. Internal stress relaxation as a universal mechanism plays a significant role in the structural relaxation, and simultaneously modulates the diffusive relaxation spectrum.
{"title":"On the Shear Modulus and Thermal Effect During Structural Relaxation in a Model Metallic Glass: Correlation and Thermal Decoupling","authors":"Hongbo Zhou, V. Khonik, G. Wilde","doi":"10.2139/ssrn.3784439","DOIUrl":"https://doi.org/10.2139/ssrn.3784439","url":null,"abstract":"Pd40 Ni40P20 (at.%) samples with different enthalpy states and relaxation behaviors were fabricated through high-pressure torsion or sub-Tg annealing of the as-cast state. Subsequently, the underlying structural relaxation was studied by investigating the modulus and thermal characteristics using in-situ shear modulus measurement and modulated differential scanning calorimetry. The results show that high-pressure torsion leads to shear modulus softening and an increase of the irreversible exothermic enthalpy, indicating a significant structural rejuvenation, while sub-Tg annealing causes shear modulus hardening and a decrease of the irreversible exothermic enthalpy. Besides, the reversible endothermic effect which reflects the heat capacity was found to be almost identical for all samples, independent on deformation or thermal history. The total heat flow can be well correlated to the shear modulus within the framework of interstitialcy theory. Furthermore, we demonstrate that the structural relaxation below Tg decouples into the internal stress relaxation and β-relaxation. The former is an irreversible process of releasing internal stress, accompanied by an exothermic effect and modulus hardening. The latter is a complex process involving kinetic and thermodynamic components, accompanied by an endothermic effect and modulus softening. Shadow glass transition and glass transition overshoot are related to the activation (cage-breaking) processes in the kinetics of β-relaxation and α-relaxation, respectively. This work indicates that β-relaxation and α-relaxation are kinetically and thermodynamically identical but occur in distinct temperature or frequency domains. Internal stress relaxation as a universal mechanism plays a significant role in the structural relaxation, and simultaneously modulates the diffusive relaxation spectrum.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-12","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"88814713","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jutta Luksch, A. Jung, C. Pauly, R. Derr, Patrick Grünewald, M. Laub, M. Klaus, C. Genzel, C. Motz, F. Mücklich, F. Schaefer
Nickel(Ni)/aluminium(Al) hybrid foams are Al base foams coated with Ni by electrodeposition. Hybrid foams offer an enhanced energy absorption capacity. To ensure a good adhering Ni coating, necessary for a shear resistant interface, the influence of a chemical pre-treatment of the base foam was investigated by a combination of an interface morphology analysis by focused ion beam (FIB) tomography and in situ mechanical testing. The critical energy for interfacial decohesion from microbending fracture tests in the scanning electron microscope (SEM) were contrasted to depth-resolved measurements of the evolving stresses in the Ni coating during three-point bending tests at the energy-dispersive diffraction (EDDI) beamline at the synchrotron BESSY II. Such an assessment of the interface decohesion resistance with respect to the interface morphology provides a strategy for further improvement of the interface morphology.
{"title":"Ni/Al-Hybrid Foams: An Interface Study by Combination of 3D-Phase Morphology Imaging, Microbeam Fracture Mechanics and in situ Synchrotron Stress Analysis","authors":"Jutta Luksch, A. Jung, C. Pauly, R. Derr, Patrick Grünewald, M. Laub, M. Klaus, C. Genzel, C. Motz, F. Mücklich, F. Schaefer","doi":"10.2139/ssrn.3782840","DOIUrl":"https://doi.org/10.2139/ssrn.3782840","url":null,"abstract":"Nickel(Ni)/aluminium(Al) hybrid foams are Al base foams coated with Ni by electrodeposition. Hybrid foams offer an enhanced energy absorption capacity. To ensure a good adhering Ni coating, necessary for a shear resistant interface, the influence of a chemical pre-treatment of the base foam was investigated by a combination of an interface morphology analysis by focused ion beam (FIB) tomography and in situ mechanical testing. The critical energy for interfacial decohesion from microbending fracture tests in the scanning electron microscope (SEM) were contrasted to depth-resolved measurements of the evolving stresses in the Ni coating during three-point bending tests at the energy-dispersive diffraction (EDDI) beamline at the synchrotron BESSY II. Such an assessment of the interface decohesion resistance with respect to the interface morphology provides a strategy for further improvement of the interface morphology.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-09","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79770382","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Because of surface structural constraint and thermal management requirement, visible - infrared compatible camouflage is still a great challenge. In this study, we introduce a 2D periodic aperture array into ZnO/Ag/ZnO film to realize visible-infrared compatible camouflage with a performance of thermal management by utilizing the extraordinary optical transmission in a dielectric/metal/dielectric (D/M/D) structure. Because of the high visible transmittance of the D/M/D structure, when applied on a visible camouflage coating, the beneath coating can be observed, realizing arbitrary visible camouflage. Due to the perforated Ag layer, both low emittances in 3~5 μm, 8~14 μm for infrared camouflage and high emittance in 5~8 μm for heat dissipation by radiation are achieved theoretically and experimentally. The fabricated photonic crystal exhibits high-temperature infrared camouflage in two atmospheric windows. With the same heating power of 0.40 W/cm2, this photonic crystal is 12.2 ℃ cooler than a sample with a low-emittance surface. The proposed visible - infrared compatible camouflage photonic crystal with the performance of thermal management provides a guideline on coordinated control of light and heat, indicating a potential application in energy & thermal technologies.
{"title":"A Visible - Infrared Compatible Camouflage Photonic Crystal with Enhanced Emission in 5~8 μm","authors":"Saichao Dang, Hong Ye","doi":"10.2139/ssrn.3783256","DOIUrl":"https://doi.org/10.2139/ssrn.3783256","url":null,"abstract":"Because of surface structural constraint and thermal management requirement, visible - infrared compatible camouflage is still a great challenge. In this study, we introduce a 2D periodic aperture array into ZnO/Ag/ZnO film to realize visible-infrared compatible camouflage with a performance of thermal management by utilizing the extraordinary optical transmission in a dielectric/metal/dielectric (D/M/D) structure. Because of the high visible transmittance of the D/M/D structure, when applied on a visible camouflage coating, the beneath coating can be observed, realizing arbitrary visible camouflage. Due to the perforated Ag layer, both low emittances in 3~5 μm, 8~14 μm for infrared camouflage and high emittance in 5~8 μm for heat dissipation by radiation are achieved theoretically and experimentally. The fabricated photonic crystal exhibits high-temperature infrared camouflage in two atmospheric windows. With the same heating power of 0.40 W/cm2, this photonic crystal is 12.2 ℃ cooler than a sample with a low-emittance surface. The proposed visible - infrared compatible camouflage photonic crystal with the performance of thermal management provides a guideline on coordinated control of light and heat, indicating a potential application in energy & thermal technologies.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"91159740","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Fatemeh Razmjooei, T. Morawietz, E. Taghizadeh, E. Hadjixenophontos, Lukas Mues, B. Wood, C. Harms, A. Gago, S. Ansar, K. Friedrich
Anion exchange membrane water electrolysis (AEMWE) for generation of hydrogen from water is an emerging technology with high potential to surpass peer electrolyzers. However, current AEMWEs exhibit significant overpotential loss. Almost all the reported improvements in AEMWE performance have been confined to development and optimization of the conductive membranes and active electrodes to address issues regarding the ohmic and activation loss in AEMWE. However, coming from a different perspective, the strong effect of other cell components, which directly influence interfacial contact and transport phenomenon, is an important aspect to further improve the AEMWE performance and should not be neglected . Here, for the first time we report a solution to solve this missing piece of the puzzle with a highly conductive novel multifunctional liquid/gas diffusion layers (LGDLs), which consisted of well-tuned pores to asynchronously transport electrons, heat and liquid/gas while minimizing ohmic, mass transport and interfacial losses. The ohmic and mass transfer losses were reduced by 48% and 58%, respectively, thanks to the developed multifunctional LGDL and as a result the performance increased by 13 % at 0.5 A cm-2 in water, which places AEMWE close in effectiveness to more mainstream alkaline electrolyzers but without the need of using corrosive alkaline solutions as electrolyte. This multifunctional LGDL, called NiMPL-PTL, was developed by introducing nickel based micro porous layers (MPLs) using atmospheric plasma spray (APS) technique on the top of a porous transport layer (PTL) substrate. The low tortuosity of this novel porous NiMPL-PTL can reduce capillary pressure and bubble point, which can efficiently remove the unavoidable gas bubbles formed at electrode surface. Moreover, this NiMPL-PTL can decrease the contact resistance, since it increases the contact area between PTL and membrane electrode assembly (MEA) by reducing the aperture size of the PTL. Therefore, a significant mitigation of mass transport issues at high current densities and an improvement in interfacial contact resistance (ICR) were achieved by implementing NiMPL-PTL in the AEMWE operated in water. Electrochemical results showed that for AEMWE cell with well-tuned NiMPL-PTLs, the operating voltage required at the current density of 0.5 A cm-2 is as low as 1.90 V with an operating efficiency of 76%HHV, which was 290 mV lower than that of cell with the uncoated PTLs , which could only reach to efficiency of 65%HHV. To the best of our knowledge, there has been no such a genuine design of multifunctional coated backing layer PTL to improve the AEMWE performance in water.
阴离子交换膜电解水制氢技术是一项极具发展潜力的新兴技术。然而，目前的AEMWEs表现出明显的过电位损失。几乎所有报道的AEMWE性能的改进都局限于导电膜和活性电极的开发和优化，以解决AEMWE中的欧姆和活化损耗问题。然而，从另一个角度来看，直接影响界面接触和传输现象的其他电池组分的强效应是进一步提高AEMWE性能的重要方面，不可忽视。在这里，我们首次报道了一种解决方案，用一种高导电性的新型多功能液/气扩散层(lgdl)来解决这个缺失的难题，lgdl由精心调整的孔组成，可以异步传输电子、热量和液/气，同时最大限度地减少欧姆、质量传输和界面损失。由于开发了多功能LGDL，欧姆和传质损失分别降低了48%和58%，因此在0.5 a cm-2的水中性能提高了13%，这使得AEMWE的效率接近更主流的碱性电解槽，但不需要使用腐蚀性碱性溶液作为电解质。这种多功能LGDL被称为NiMPL-PTL，是通过在多孔传输层(PTL)衬底上使用大气等离子体喷涂(APS)技术引入镍基微孔层(MPLs)而开发的。这种新型多孔NiMPL-PTL具有较低的弯曲度，可以降低毛细压力和气泡点，有效地去除电极表面不可避免形成的气泡。此外，该NiMPL-PTL通过减小PTL的孔径尺寸，增加了PTL与膜电极组件(MEA)之间的接触面积，从而降低了接触电阻。因此，通过在水中运行的AEMWE中实施NiMPL-PTL，可以显著缓解高电流密度下的质量传输问题，并改善界面接触电阻(ICR)。电化学结果表明，在0.5 A cm-2的电流密度下，nimpl - ptl的工作电压低至1.90 V，工作效率为76%，比未涂覆ptl的电池低290 mV，工作效率仅为65%。据我们所知，目前还没有这样一种真正设计的多功能涂层衬底层PTL来提高AEMWE在水中的性能。
{"title":"Increasing the Performance of Anion Exchange Membrane Water Electrolyzer Operating in Neutral pH","authors":"Fatemeh Razmjooei, T. Morawietz, E. Taghizadeh, E. Hadjixenophontos, Lukas Mues, B. Wood, C. Harms, A. Gago, S. Ansar, K. Friedrich","doi":"10.2139/ssrn.3778363","DOIUrl":"https://doi.org/10.2139/ssrn.3778363","url":null,"abstract":"Anion exchange membrane water electrolysis (AEMWE) for generation of hydrogen from water is an emerging technology with high potential to surpass peer electrolyzers. However, current AEMWEs exhibit significant overpotential loss. Almost all the reported improvements in AEMWE performance have been confined to development and optimization of the conductive membranes and active electrodes to address issues regarding the ohmic and activation loss in AEMWE. However, coming from a different perspective, the strong effect of other cell components, which directly influence interfacial contact and transport phenomenon, is an important aspect to further improve the AEMWE performance and should not be neglected . Here, for the first time we report a solution to solve this missing piece of the puzzle with a highly conductive novel multifunctional liquid/gas diffusion layers (LGDLs), which consisted of well-tuned pores to asynchronously transport electrons, heat and liquid/gas while minimizing ohmic, mass transport and interfacial losses. The ohmic and mass transfer losses were reduced by 48% and 58%, respectively, thanks to the developed multifunctional LGDL and as a result the performance increased by 13 % at 0.5 A cm-2 in water, which places AEMWE close in effectiveness to more mainstream alkaline electrolyzers but without the need of using corrosive alkaline solutions as electrolyte. This multifunctional LGDL, called NiMPL-PTL, was developed by introducing nickel based micro porous layers (MPLs) using atmospheric plasma spray (APS) technique on the top of a porous transport layer (PTL) substrate. The low tortuosity of this novel porous NiMPL-PTL can reduce capillary pressure and bubble point, which can efficiently remove the unavoidable gas bubbles formed at electrode surface. Moreover, this NiMPL-PTL can decrease the contact resistance, since it increases the contact area between PTL and membrane electrode assembly (MEA) by reducing the aperture size of the PTL. Therefore, a significant mitigation of mass transport issues at high current densities and an improvement in interfacial contact resistance (ICR) were achieved by implementing NiMPL-PTL in the AEMWE operated in water. Electrochemical results showed that for AEMWE cell with well-tuned NiMPL-PTLs, the operating voltage required at the current density of 0.5 A cm-2 is as low as 1.90 V with an operating efficiency of 76%HHV, which was 290 mV lower than that of cell with the uncoated PTLs , which could only reach to efficiency of 65%HHV. To the best of our knowledge, there has been no such a genuine design of multifunctional coated backing layer PTL to improve the AEMWE performance in water.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"79764054","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Rajaa Farran, Y. Mekmouche, Nhat Tam Vo, C. Herrero, Annamaria Quaranta, Marie Sircoglou, F. Banse, P. Rousselot‐Pailley, A. Simaan, A. Aukauloo, T. Tron, W. Leibl
Photobiocatalysis is an interesting approach to use light to perform specific chemical transformations in a selective and efficient way. The intention is to couple a photoredox cycle with an enzyme performing multielectronic catalytic activity. Laccase, a robust multicopper oxidase, can be envisioned as a tool to use dioxygen as a clean electron sink when coupled to an oxidation photocatalyst. Here, we provide a detailed study of the coupling of a [Ru(bpy)3]2+ photosensitizer to laccase. We demonstrate that efficient laccase reduction requires using an electron relay like methyl viologen. In the presence of dioxygen, electrons transiently stored in superoxide ions (O2●–) are scavenged by laccase leading to formation of water instead of H2O2. The net result is the photo accumulation, in an essentially irreversible way, of highly oxidizing [Ru(bpy)3]3+. This study provides a global scheme for the future use of laccase, in tandem with a light-driven oxidative process, using O2 as both a one-electron transfer relay and a 4-electron substrate to become the sustainable final electron acceptor in a such a hybrid photocatalytic process.
{"title":"Tracking Light-Induced Electron Transfer Towards O 2 in a Hybrid Photoredox-Laccase System","authors":"Rajaa Farran, Y. Mekmouche, Nhat Tam Vo, C. Herrero, Annamaria Quaranta, Marie Sircoglou, F. Banse, P. Rousselot‐Pailley, A. Simaan, A. Aukauloo, T. Tron, W. Leibl","doi":"10.2139/ssrn.3778327","DOIUrl":"https://doi.org/10.2139/ssrn.3778327","url":null,"abstract":"Photobiocatalysis is an interesting approach to use light to perform specific chemical transformations in a selective and efficient way. The intention is to couple a photoredox cycle with an enzyme performing multielectronic catalytic activity. Laccase, a robust multicopper oxidase, can be envisioned as a tool to use dioxygen as a clean electron sink when coupled to an oxidation photocatalyst. Here, we provide a detailed study of the coupling of a [Ru(bpy)3]2+ photosensitizer to laccase. We demonstrate that efficient laccase reduction requires using an electron relay like methyl viologen. In the presence of dioxygen, electrons transiently stored in superoxide ions (O2●–) are scavenged by laccase leading to formation of water instead of H2O2. The net result is the photo accumulation, in an essentially irreversible way, of highly oxidizing [Ru(bpy)3]3+. This study provides a global scheme for the future use of laccase, in tandem with a light-driven oxidative process, using O2 as both a one-electron transfer relay and a 4-electron substrate to become the sustainable final electron acceptor in a such a hybrid photocatalytic process.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-02-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"80660703","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Himanshu Raghav, L. Konathala, N. Mishra, Bhanu Joshi, R. Goyal, Ankit Agrawal, Bipul Sarkar
In the past few years, the production olefin from various resources, particularly from carbon-rich sources, such as crude oil, natural gas, coal, and biomass, has received considerable attention. This study presented the production of light olefins by conducting CO2 hydrogenation through reverse water-gas shift and modified Fischer–Tropsch synthesis by employing a Fe-decorated large surface molybdenum carbide catalyst. A novel strategy was adopted for the synthesis of large surface mesoporous molybdenum carbide by using a hard template. A theoretical loading limit of Fe nanoparticles, calculated using density functional theory, was decorated over β-Mo2C through simple wetness impregnation. The trans isomers of Fe-doped β-Mo2C exhibited higher symmetry and were energetically slightly more stable for the hydrogenation of CO2 into light olefins than the cis isomers. Under the optimized condition, Fe(0.5)-Mo2C showed 7.3% CO2 conversion with 79.4% C2= olefins.
{"title":"Direct Conversion of CO 2 into Ethylene Over Fe-Decorated Hierarchical Molybdenum Carbide: Tailoring Activity and Stability","authors":"Himanshu Raghav, L. Konathala, N. Mishra, Bhanu Joshi, R. Goyal, Ankit Agrawal, Bipul Sarkar","doi":"10.2139/ssrn.3765613","DOIUrl":"https://doi.org/10.2139/ssrn.3765613","url":null,"abstract":"In the past few years, the production olefin from various resources, particularly from carbon-rich sources, such as crude oil, natural gas, coal, and biomass, has received considerable attention. This study presented the production of light olefins by conducting CO2 hydrogenation through reverse water-gas shift and modified Fischer–Tropsch synthesis by employing a Fe-decorated large surface molybdenum carbide catalyst. A novel strategy was adopted for the synthesis of large surface mesoporous molybdenum carbide by using a hard template. A theoretical loading limit of Fe nanoparticles, calculated using density functional theory, was decorated over β-Mo2C through simple wetness impregnation. The trans isomers of Fe-doped β-Mo2C exhibited higher symmetry and were energetically slightly more stable for the hydrogenation of CO2 into light olefins than the cis isomers. Under the optimized condition, Fe(0.5)-Mo2C showed 7.3% CO2 conversion with 79.4% C2= olefins.","PeriodicalId":9858,"journal":{"name":"Chemical Engineering (Engineering) eJournal","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2021-01-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"87393059","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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