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Papers by Assiya Yermukhambetova

Doctoral thesis, UCL (University College London)., May 28, 2017

Nanostructured magnesium nickel oxide (Mg0.6Ni0.4O) was synthesized by a self-propagating high te... more Nanostructured magnesium nickel oxide (Mg0.6Ni0.4O) was synthesized by a self-propagating high temperature synthesis method followed by heat treatment. The particles of the resulting oxide were used as additives to prepare the sulfur/polyacrylonitrile/Mg0.6Ni0.4O (S/PAN/Mg0.6Ni0.4O) composite via wet ballmilling. The SEM observation revealed that the composite morphology was drastically changed by the addition of Mg0.6Ni0.4O, from smooth bulky particles of S/PAN to rough nanostructured agglomerates with two times the increase in the specific surface area, favouring the reactivity of the composite, and a homogeneous component distribution. Cyclic voltammetry, discharge–charge tests and ac impedance spectroscopy have shown improved conductivity and electrochemical properties of the composite by the addition of Mg0.6Ni0.4O, leading to high sulfur utilization and interfacial stabilization in a Li/S cell upon discharge–charge cycling. The cell demonstrated enhanced reversibility, resulti...

Journal of materials chemistry. A, Materials for energy and sustainability, 2013

Micromachines, Dec 23, 2022

Lithium–sulphur batteries are considered as a promising battery system due to its high theoretica... more Lithium–sulphur batteries are considered as a promising battery system due to its high theoretical capacity (1675 A h kg−1), high energy density (~2500 W h kg−1) and the natural abundance of sulphur. However, despite intensive research there are certain limitations to be overcome to bring Li/S to practical application; these limitations stem from the multiple reactions and phase changes in the sulphur cathode. Herein, for the first time to author’s knowledge, the effect of the cathode morphology as a function of charge cycles was studied by a multi-scale 3D in-situ X-ray tomography approach. The microstructural evolution within the same Li/S cell is studied without disrupting the contents and revealing significant changes to the electrode morphology. The uneven distribution of the sulphur phase fraction within the electrode thickness and sulphur agglomeration upon cycling were shown. The advantages of in-situ X-ray tomography are compelling, enabling a non-destructive imaging of bat...

Micromachines

Particle packing plays an essential role in industry and chemical engineering. In this work, the ... more Particle packing plays an essential role in industry and chemical engineering. In this work, the discrete element method is used to generate the cylindrical particles and densify the binary cylindrical particle mixtures under the poured packing conditions. The influences of the aspect ratio and volume fraction of particles on the packing structure are measured by planar packing fraction. The Voronoi tessellation is used to quantify the porous structure of packing. The cumulative distribution functions of local packing fractions and the probability distributions of the reduced free volume of Voronoi cells are calculated to describe the local packing characteristics of binary mixtures with different volume fractions. As a result, it is observed that particles with larger aspect ratios in the binary mixture tend to orient randomly, and the particles with smaller aspect ratios have a preferentially horizontal orientation. Results also show that the less dense packings are obtained for m...

In this study the microstructure features of ternary powder compacts of different size ratios and... more In this study the microstructure features of ternary powder compacts of different size ratios and various volume fractions are investigated. Particle compacts are generated by particle growth model using a discrete element method approach. The particles of three different sizes are placed randomly without overlap in a 3D box at given volume fractions. Then, the particle sizes increase to reach the desired particle size. The microstructural properties of powder compacts are analysed using a radical Voronoi tessellation. The obtained results confirm that microstructural characteristics of powder compacts are influenced by size ratios and volume fractions of large, medium and small components of the ternary mixture.

IOP Conference Series: Materials Science and Engineering, 2020

Fibers have been used to improve the mechanical properties of the asphalt paving mixture. It is k... more Fibers have been used to improve the mechanical properties of the asphalt paving mixture. It is known that the enhancement of powder compact mechanical properties is related to the compact packing microstructure. This study focuses on the evaluation of the packing microstructure of powder compacts produced from ternary mixtures of spherical particles and fibers. The discrete element method is employed to generate the compacts of particle mixtures of different compositions under gravity. The compact microstructure is quantitatively characterized by utilizing the developed image analysis technique to approximate the size distribution of voids among particles in X, Y and Z directions. As a result, the denser packing was obtained with a greater fraction of small spherical particles. The inclusion of fibers resulted in the high-density compact with uniform distribution of small size voids.

European Journal of Education

The spray drying processes are widely used in chemical, ceramic, food, and pharmaceutical industr... more The spray drying processes are widely used in chemical, ceramic, food, and pharmaceutical industries to produce both high‐volume and high‐value particulate products. Therefore, it is important to include a topic covering the spray drying process in the undergraduate curriculum of chemical and materials engineering students. In this article, we describe an Excel Visual Basic for Applications (VBA)‐based educational module developed to assist students in learning the spray drying process. The module consists of two Excel files with VBA macro programs and teaching materials. The module focuses on the design of spray drying process conditions to produce the particulate product with desired moisture content at required production rate while satisfying the process restrictions on the inlet slurry concentration and the exhaust air temperature. Students are also asked to carry out the energy performance analysis of spray dryer equipped with an air‐to‐air heat exchanger that recovers the exh...

Materials

Herein, an approach is proposed to analyze the tortuosity of porous electrodes using the radical ... more Herein, an approach is proposed to analyze the tortuosity of porous electrodes using the radical Voronoi tessellation. For this purpose, a series of particle compacts geometrically similar to the actual porous electrode were generated using discrete element method; the radical Voronoi tessellation was constructed for each compact to characterize the structural properties; the tortuosity of compact porous structure was simulated by applying the Dijkstra’s shortest path algorithm on radical Voronoi tessellation. Finally, the relationships were established between the tortuosity and the composition of the ternary particle mixture, and between the tortuosity and the radical Voronoi cell parameters. The following correlations between tortuosity values and radical Voronoi cell parameters were found: larger faces and longer edges of radical Voronoi cell leads to the increased fraction of larger values of tortuosity in the distribution, while smaller faces and shorter edges of radical Voron...

Computer Applications in Engineering Education

Materials Today: Proceedings

Computer Applications in Engineering Education

Journal of Electroanalytical Chemistry, 2015

Nanostructured magnesium nickel oxide (Mg 0.6 Ni 0.4 O) was synthesized by a self-propagating hig... more Nanostructured magnesium nickel oxide (Mg 0.6 Ni 0.4 O) was synthesized by a self-propagating high temperature synthesis method followed by heat treatment. The particles of the resulting oxide were used as additives to prepare the sulfur/polyacrylonitrile/Mg 0.6 Ni 0.4 O (S/PAN/Mg 0.6 Ni 0.4 O) composite via wet ballmilling. The SEM observation revealed that the composite morphology was drastically changed by the addition of Mg 0.6 Ni 0.4 O, from smooth bulky particles of S/PAN to rough nanostructured agglomerates with two times the increase in the specific surface area, favouring the reactivity of the composite, and a homogeneous component distribution. Cyclic voltammetry, discharge-charge tests and ac impedance spectroscopy have shown improved conductivity and electrochemical properties of the composite by the addition of Mg 0.6 Ni 0.4 O, leading to high sulfur utilization and interfacial stabilization in a Li/S cell upon discharge-charge cycling. The cell demonstrated enhanced reversibility, resulting in a discharge capacity of about 1223 mA h g À1 at the second cycle and retained about 100% of this value over 100 cycles. Furthermore, the S/PAN/Mg 0.6 Ni 0.4 O composite cathode exhibited a good rate capability with discharge capacities of 887, 710 and 445 mA h g À1 at 0.5, 0.7 and 1 C, respectively. Experimental The synthesis of Mg 0.6 Ni 0.4 O was carried out by the SHS method. 0.6 mol Mg(NO 3) 2 (Sigma-Aldrich, 98% purity), 0.4 mol

Powder Technology, 2013

ABSTRACT Keywords: Self-propagating high temperature synthesis Mg 0.6 Ni 0.4 O Sulfur cathode add... more ABSTRACT Keywords: Self-propagating high temperature synthesis Mg 0.6 Ni 0.4 O Sulfur cathode additive Lithium–sulfur battery Nanostructured magnesium nickel oxide Mg 0.6 Ni 0.4 O was successfully synthesized by self-propagating high temperature synthesis (SHS) followed by heat treatment. The effect of the precursor composition and calci-nation temperature on the Mg 0.6 Ni 0.4 O powder properties was investigated. These particles were used as an additive to prepare S/Mg 0.6 Ni 0.4 O composite via ball-milling with sulfur. The composite preparation condi-tions were optimized to achieve the higher specific surface area without compromising the sample crystallin-ity. The SEM observation revealed that the sulfur morphology was drastically changed by the Mg 0.6 Ni 0.4 O addition, from smooth to rough agglomerated particles. This change has enhanced the electrochemical performance of the composite cathode. Cyclic voltammetry and charge–discharge tests demonstrated en-hanced reversibility and high sulfur utilization in a Li/S cell with S/Mg 0.6 Ni 0.4 O cathode, delivering about 850 mAh g −1 of reversible capacity at the initial cycle. The effect of the Mg 0.6 Ni 0.4 O heat treatment temper-ature on the S/Mg 0.6 Ni 0.4 O cycling performance was also investigated. The cathode with Mg 0.6 Ni 0.4 O calcined at 700 °C exhibited enhanced capacity retention which could be due to its high specific surface area and nanosized structure. © 2012 Published by Elsevier B.V.

Doctoral thesis, UCL (University College London)., May 28, 2017

Nanostructured magnesium nickel oxide (Mg0.6Ni0.4O) was synthesized by a self-propagating high te... more Nanostructured magnesium nickel oxide (Mg0.6Ni0.4O) was synthesized by a self-propagating high temperature synthesis method followed by heat treatment. The particles of the resulting oxide were used as additives to prepare the sulfur/polyacrylonitrile/Mg0.6Ni0.4O (S/PAN/Mg0.6Ni0.4O) composite via wet ballmilling. The SEM observation revealed that the composite morphology was drastically changed by the addition of Mg0.6Ni0.4O, from smooth bulky particles of S/PAN to rough nanostructured agglomerates with two times the increase in the specific surface area, favouring the reactivity of the composite, and a homogeneous component distribution. Cyclic voltammetry, discharge–charge tests and ac impedance spectroscopy have shown improved conductivity and electrochemical properties of the composite by the addition of Mg0.6Ni0.4O, leading to high sulfur utilization and interfacial stabilization in a Li/S cell upon discharge–charge cycling. The cell demonstrated enhanced reversibility, resulti...

Journal of materials chemistry. A, Materials for energy and sustainability, 2013

Micromachines, Dec 23, 2022

Lithium–sulphur batteries are considered as a promising battery system due to its high theoretica... more Lithium–sulphur batteries are considered as a promising battery system due to its high theoretical capacity (1675 A h kg−1), high energy density (~2500 W h kg−1) and the natural abundance of sulphur. However, despite intensive research there are certain limitations to be overcome to bring Li/S to practical application; these limitations stem from the multiple reactions and phase changes in the sulphur cathode. Herein, for the first time to author’s knowledge, the effect of the cathode morphology as a function of charge cycles was studied by a multi-scale 3D in-situ X-ray tomography approach. The microstructural evolution within the same Li/S cell is studied without disrupting the contents and revealing significant changes to the electrode morphology. The uneven distribution of the sulphur phase fraction within the electrode thickness and sulphur agglomeration upon cycling were shown. The advantages of in-situ X-ray tomography are compelling, enabling a non-destructive imaging of bat...

Micromachines

Particle packing plays an essential role in industry and chemical engineering. In this work, the ... more Particle packing plays an essential role in industry and chemical engineering. In this work, the discrete element method is used to generate the cylindrical particles and densify the binary cylindrical particle mixtures under the poured packing conditions. The influences of the aspect ratio and volume fraction of particles on the packing structure are measured by planar packing fraction. The Voronoi tessellation is used to quantify the porous structure of packing. The cumulative distribution functions of local packing fractions and the probability distributions of the reduced free volume of Voronoi cells are calculated to describe the local packing characteristics of binary mixtures with different volume fractions. As a result, it is observed that particles with larger aspect ratios in the binary mixture tend to orient randomly, and the particles with smaller aspect ratios have a preferentially horizontal orientation. Results also show that the less dense packings are obtained for m...

In this study the microstructure features of ternary powder compacts of different size ratios and... more In this study the microstructure features of ternary powder compacts of different size ratios and various volume fractions are investigated. Particle compacts are generated by particle growth model using a discrete element method approach. The particles of three different sizes are placed randomly without overlap in a 3D box at given volume fractions. Then, the particle sizes increase to reach the desired particle size. The microstructural properties of powder compacts are analysed using a radical Voronoi tessellation. The obtained results confirm that microstructural characteristics of powder compacts are influenced by size ratios and volume fractions of large, medium and small components of the ternary mixture.

IOP Conference Series: Materials Science and Engineering, 2020

Fibers have been used to improve the mechanical properties of the asphalt paving mixture. It is k... more Fibers have been used to improve the mechanical properties of the asphalt paving mixture. It is known that the enhancement of powder compact mechanical properties is related to the compact packing microstructure. This study focuses on the evaluation of the packing microstructure of powder compacts produced from ternary mixtures of spherical particles and fibers. The discrete element method is employed to generate the compacts of particle mixtures of different compositions under gravity. The compact microstructure is quantitatively characterized by utilizing the developed image analysis technique to approximate the size distribution of voids among particles in X, Y and Z directions. As a result, the denser packing was obtained with a greater fraction of small spherical particles. The inclusion of fibers resulted in the high-density compact with uniform distribution of small size voids.

European Journal of Education

The spray drying processes are widely used in chemical, ceramic, food, and pharmaceutical industr... more The spray drying processes are widely used in chemical, ceramic, food, and pharmaceutical industries to produce both high‐volume and high‐value particulate products. Therefore, it is important to include a topic covering the spray drying process in the undergraduate curriculum of chemical and materials engineering students. In this article, we describe an Excel Visual Basic for Applications (VBA)‐based educational module developed to assist students in learning the spray drying process. The module consists of two Excel files with VBA macro programs and teaching materials. The module focuses on the design of spray drying process conditions to produce the particulate product with desired moisture content at required production rate while satisfying the process restrictions on the inlet slurry concentration and the exhaust air temperature. Students are also asked to carry out the energy performance analysis of spray dryer equipped with an air‐to‐air heat exchanger that recovers the exh...

Materials

Herein, an approach is proposed to analyze the tortuosity of porous electrodes using the radical ... more Herein, an approach is proposed to analyze the tortuosity of porous electrodes using the radical Voronoi tessellation. For this purpose, a series of particle compacts geometrically similar to the actual porous electrode were generated using discrete element method; the radical Voronoi tessellation was constructed for each compact to characterize the structural properties; the tortuosity of compact porous structure was simulated by applying the Dijkstra’s shortest path algorithm on radical Voronoi tessellation. Finally, the relationships were established between the tortuosity and the composition of the ternary particle mixture, and between the tortuosity and the radical Voronoi cell parameters. The following correlations between tortuosity values and radical Voronoi cell parameters were found: larger faces and longer edges of radical Voronoi cell leads to the increased fraction of larger values of tortuosity in the distribution, while smaller faces and shorter edges of radical Voron...

Computer Applications in Engineering Education

Materials Today: Proceedings

Computer Applications in Engineering Education

Journal of Electroanalytical Chemistry, 2015

Nanostructured magnesium nickel oxide (Mg 0.6 Ni 0.4 O) was synthesized by a self-propagating hig... more Nanostructured magnesium nickel oxide (Mg 0.6 Ni 0.4 O) was synthesized by a self-propagating high temperature synthesis method followed by heat treatment. The particles of the resulting oxide were used as additives to prepare the sulfur/polyacrylonitrile/Mg 0.6 Ni 0.4 O (S/PAN/Mg 0.6 Ni 0.4 O) composite via wet ballmilling. The SEM observation revealed that the composite morphology was drastically changed by the addition of Mg 0.6 Ni 0.4 O, from smooth bulky particles of S/PAN to rough nanostructured agglomerates with two times the increase in the specific surface area, favouring the reactivity of the composite, and a homogeneous component distribution. Cyclic voltammetry, discharge-charge tests and ac impedance spectroscopy have shown improved conductivity and electrochemical properties of the composite by the addition of Mg 0.6 Ni 0.4 O, leading to high sulfur utilization and interfacial stabilization in a Li/S cell upon discharge-charge cycling. The cell demonstrated enhanced reversibility, resulting in a discharge capacity of about 1223 mA h g À1 at the second cycle and retained about 100% of this value over 100 cycles. Furthermore, the S/PAN/Mg 0.6 Ni 0.4 O composite cathode exhibited a good rate capability with discharge capacities of 887, 710 and 445 mA h g À1 at 0.5, 0.7 and 1 C, respectively. Experimental The synthesis of Mg 0.6 Ni 0.4 O was carried out by the SHS method. 0.6 mol Mg(NO 3) 2 (Sigma-Aldrich, 98% purity), 0.4 mol

Powder Technology, 2013

ABSTRACT Keywords: Self-propagating high temperature synthesis Mg 0.6 Ni 0.4 O Sulfur cathode add... more ABSTRACT Keywords: Self-propagating high temperature synthesis Mg 0.6 Ni 0.4 O Sulfur cathode additive Lithium–sulfur battery Nanostructured magnesium nickel oxide Mg 0.6 Ni 0.4 O was successfully synthesized by self-propagating high temperature synthesis (SHS) followed by heat treatment. The effect of the precursor composition and calci-nation temperature on the Mg 0.6 Ni 0.4 O powder properties was investigated. These particles were used as an additive to prepare S/Mg 0.6 Ni 0.4 O composite via ball-milling with sulfur. The composite preparation condi-tions were optimized to achieve the higher specific surface area without compromising the sample crystallin-ity. The SEM observation revealed that the sulfur morphology was drastically changed by the Mg 0.6 Ni 0.4 O addition, from smooth to rough agglomerated particles. This change has enhanced the electrochemical performance of the composite cathode. Cyclic voltammetry and charge–discharge tests demonstrated en-hanced reversibility and high sulfur utilization in a Li/S cell with S/Mg 0.6 Ni 0.4 O cathode, delivering about 850 mAh g −1 of reversible capacity at the initial cycle. The effect of the Mg 0.6 Ni 0.4 O heat treatment temper-ature on the S/Mg 0.6 Ni 0.4 O cycling performance was also investigated. The cathode with Mg 0.6 Ni 0.4 O calcined at 700 °C exhibited enhanced capacity retention which could be due to its high specific surface area and nanosized structure. © 2012 Published by Elsevier B.V.