The research activities carried out by the doctoral students are briefly described below, as self-certified and verified during their annual presentation.
Rahul Kumar
The main objective of this project is to analyse the performance of GaN based three phase VSI for EVs. The power ratings are chosen to be 50kVA with target efficiency of 97%. Hence, to achieve such power ratings, multiple GaN modules will be connected in parallel. At higher power levels, the amount of power dissipation increases causing the power transistors to generate more heat that requires an efficient cooling system. It is well defined in the literature that liquid cooling system have higher heat dissipation capacity, lower total thermal resistance, etc. compared to traditional air-cooling methods. Therefore, for the better thermal management, the liquid cooling method will be employed in this project.
This project is divided into few stages i.e., sizing stage, protection circuits design, layout design, experimental design, etc. At this moment, the focus is on the sizing stage. In the sizing stage, initially, the load parameters required for the 50kVA inverter are calculated. Besides, a comparison between different GaN switching devices is established to select the most suitable device for the specified application. The switching loss analysis is performed using DPT. Based on comparative analysis DC link capacitor is selected. Finally, the thermal resistance required for heatsink is calculated that will help in selecting the cold plate for experimental analysis.
Somayyeh Rakhshani
My research objective is to produce a new generation of active electrospun anion-exchange membranes (AEM) for hydrogen production from a manufacturing perspective to be cost-effective with desired properties and characterize them by fast reliable methods. In this regard, we developed a composite anion exchange membrane prepared by activating a commercial support structure (Celgard® 3401) with a commercially available functional group (Fumion® FAA-3) through a phase-inversion process, and the results were published and reported in the first-year activities. In the following, 4 other commercial membranes were examined in this experiment as a backbone for AEM to see how comparable they are to celgard3401 (which has already shown good performance) in terms of conductivity after activating with an ionomer (Fumion). These experiments were done on some available membranes to get an idea of what structure is better for the backbone to be produced in the next step by the electrospinning technique. Celgard® 2325, FS2190, and FS2226 (Freudenberg and co), and Glass Fiber (Whatman) were activated with Fumion ionomer solution in a phase inversion process but in two procedures. The first procedure is the one that was already suggested by Pisa University (and already tested on Celgard3401) and the second one was immersion. Results showed that the former procedure is more effective than immersion, so we chose this method for activating non-conductive membranes with ionomer solutions. Among those 4 commercial membranes FS2190, a polymeric membrane with a fibrous structure that is like electrospun mats was kept for more modifications. Since the structure was open and highly permeable, we impregnated Fumion inside the sample as much as possible by 3 times activation. A roll press was also used to laminate the membranes with different gap distances and then measured the air permeability with a Gurly precision device. Finally, I activated the sample which has the highest Gurly (the least air permeability). The measured ionic conductivity of FS2190 was 2.4 mScm-1 at 25°C in a four-point probe electrochemical cell which is comparable to Celgard which was 3.0 mScm-1.
The main objective of my project is to investigate the potential of electrospinning techniques for the synthesis of porous support such as Celgard or intrinsic AEM membranes such as Fumasep for water electrolyzers. Electrospinning is highly attractive to industry and academia because of its high production rate and simplicity of setup. The nanoscale fibers are generated by the application of a strong electric field on polymer solution or melt. During electrospinning, a high voltage is applied between the spinneret and collector. The polymer solution is extruded from the spinneret to produce a pendant droplet due to surface tension. An electrified droplet is formed into a Taylor cone because of electrostatic repulsion between surface charges of the same sign. As soon as electric force overcomes the surface tension jets extend straight ahead but then undergo vigorous whipping motions due to bending instabilities. The jet solidifies rapidly, resulting in solid fiber deposition on the grounded collector. In pursuit of our goal, we follow two approaches: first to fabricate an intrinsically anionic membrane like FAA-3-PK-130 (Fumasep), and second to fabricate an uncharged electrospun backbone that can be activated with a functional group that helps anion transportation. Polysulfone (PSU) as a high-performance polymer and both thermally and chemically stable, is used as a constituent of the membrane backbone in this work. PSU granules (Grade: Udel® P 1700) from Goodfellow, Cambridge, UK, N-Methyl-2-pyrrolidone: NMP (100% purity, VWR, Radnor, PA, USA) as a solvent, and Fumion® (FAA-3, 10% solution in NMP) from Fuma-Tech, Germany is used as an anion exchange ionomer that helps the hydroxide anions transport. We synthesized electrospun membranes using an electrospinning machine (Fluidnatek LE100, Bioinicia SI, Spain), which is equipped with a large stationary planar metallic collector (x-y plane) underneath a single scanning emitter that can be driven in both x and y directions, at controllable speed, to cover a desired deposition area on the collector. The distance between the collector and emitter along the z-axis is also adjustable. The emitter and the collector are connected to their high-voltage generator. The polymer solution was fed into the emitter at an adjustable rate controlled by a syringe pump. The relative humidity and temperature were recorded during the deposition process.
First approach: Electrospinning of a mixed solution of Polysulphone and Fumion.
A 24% w/w solution of PSU/NMP was made by pre-drying 32.6gr of pure PSU granules at 60°C, overnight and then stirring them until completely dissolved in 100 ml NMP. The final polymer solution for electrospinning was a mixed solution of PSU 24% with 1% (volume) Fumion (commercial solution). After several runs, we were able to electro-spin the mixed solution into a fibrous non-woven mat. As demonstrated by SEM, the fibrous membrane was synthesized successfully. The sample (labeled PSUFU-01) was fabricated with a thickness of 25±2 μm. The membrane appears to have different layers of intertwined fibers within its structure, with high porosity, and open pore architecture. Its air permeability confirms that the membrane structure is rather porous, indicating that a denser microstructure should be aimed for in the future to prevent the direct passage of water and solution across the cell. As an optimization, to address this issue, we decreased the distance between the emitter (d) and the collector and increased the flow rate (FR). This allowed the fibers to reach the collector quasi-wet and spread on the surface, thus closing porosity, and resulting in fibers coalescing together into nodes. The resulting lattice-like microstructure was endowed with a significantly denser arrangement, with zero air permeability. It was not possible to precisely measure permeability because the time for passing 100 cm3 of air through an aperture area of 0.64 cm2 was beyond the maximum testing time (>8h). While the microstructural and mechanical properties of the second membrane are quite interesting, the conductivity (σ) of such a membrane is still very low, as was expected from the small amount of ionomer inside the fibers. 1% Fumion solution, which itself has only a 10% content of ionomer (the ionomer content is only 0.15 % w/w in the mixed solution) is not enough to create a conductive percolating path inside the membrane. To increase the ionomer content and improve the conductivity of the membrane I tried to make different solutions with different concentrations of ionomer inside. The challenge we faced here was to combine PSU with Fumion to achieve a solution with high ionomer content as well as be spinnable. It is known that spinnability is affected by different factors including solution properties (concentration, solution viscosity, solution conductivity, and solvent) as well as the environmental parameters and electrospinning system settings. After many attempts, the final solution was made by dissolving PSU granules directly in Fumion solution. In such a way that 5.36 gr PSU granules that were dried at 60°C overnight, were dissolved in 20 ml commercial Fumion solution (10%) and left stirring for almost 2 days at room temperature to achieve a uniform solution that contains 20% PSU and 80% Fumion solution. In this combination, the ionomer content in the fabricated membrane will be 28.5%. The results of electrospinning samples (PSUFU) are uniform membranes, porous and cotton-like. The porosity is too high to put in the cell for conductivity measurement. To address this, I pressed two samples with a roll press to close the structure. However, even though the porosity decreased, it was still not enough to make the conductivity test with the cell. As the samples have a cotton-like texture and are very porous, it is very difficult to remove them from the substrate. Therefore, a 2-and-3-step procedure is planned to spin the multilayer membrane. In the two-step plan, a pure layer of Polysulphone was spun, and then the mixed solution PSUFU was spun over it. In the three-step plan, a pure layer of Polysulphone was spun, and then the mixed solution PSUFU was spun over it, followed by another layer of pure Polysulphone on top. Compared with the previous sample, these results have much better texture and are easier to remove from the substrate. The Air permeability of new samples seems to be okay for conductivity measurement. So, the samples were cut in a circle form with 36mm diameter, seated in NaCl solution 0.5M overnight, and their conductivity was measured in a 4-point prob cell. Table 1 shows the conductivity of these samples compared with the last sample (PSUFU-02: mixed solution of PSU and 1% Fumion inside) that we published the result in the EEEIC2023 conference. The results are significantly improved. The results are very promising at this stage. The texture and conductivity of the membrane are significantly improved, but the optimization continues to prepare a higher conductivity membrane with the desired texture and mechanical properties.
The second approach: activating the Polysulphone (PSU) membrane with different ionomers.
In this approach, the goal is to activate the electrospun PSU membrane with different ionomer solutions that don’t dissolve the PSU. The problem addressed here was that the selected commercially available ionomer solution, Fumion, is delivered in an NMP solution. Since PSU dissolves in NMP too, we could not simply attempt to impregnate the backbone with the ionomer, as previously done with Celgard3401. To address this issue, we extracted the Fumion polymer by precipitation of the commercial solution in THF. We received another 3 different ionomers (based on polyketone) which were prepared by Prof. Pucci at Pisa University. The fifth ionomer we already had was Polymer AP1- HNN8 (a dispersion powder) from Aemion. So, 5 different ionomer solutions were made by dissolving the above-mentioned ionomer polymers in ethanol. A Polysulfone membrane which was made of a 24% w solution of PSU in NMP with the electrospinning technique with 36.5µm thickness, was cut into small square shape samples (4 × 4 cm). They were activated by adding 0.5 ml of ionomer solution for each side and letting it dry. The first three samples that were activated by ionomer solution based on polyketone were not suitable for conductivity measurement. That’s because they are still too porous after activating easily passing the solution from one side to another side of the cell. It seems that the solution concentration is not enough to help close the structure of the membrane. But we have very good results on samples 4 and 7. Polysulfone electrospun membrane that was activated with Fumion solution (fumion polymer in ethanol) has conductivity comparable with Celgard membrane which had already been activated with Fumion solution.
Babar Ali
In this phase, a new research endeavor was undertaken which centered on the creation of a smart insole. A composite of graphene nanoplatelet polymer was spray-coated on a commercial insole to function as a pressure sensor. Subsequently, this sensor was subjected to morphological, electrical, and electromechanical characterization to confirm its viability as an effective pressure sensor for gait monitoring.
II trimestre
During this phase, work continued on the smart insole project established earlier. A lightweight, battery-powered wearable data acquisition and communication system was designed and tested. Alongside this, an Android-based application was developed for data visualization and logging. The outcomes of this research were later published in a peer-reviewed academic journal and presented at several conferences as invited talks.
III trimestre During this trimester, the exploration of dispense printing for flexible printable sensing applications took place. In addition, the development and characterization of various conductive inks were conducted for their potential use in the dispense printer.
IV trimestre This period was dedicated to an international mobility at York University in Canada, where the focus was on investigating the fabrication of multi-lead ECG electrodes on textiles utilizing advanced printing technologies.
Mohamed Yahya Mohamed Elhag
I trimester. Developed the SYNDEM Inverter code of the three-phase LCL filter system into PSIM software by considering the open and closed loop systems and improving the exact discrete-time model of The LCL Filters connected to a grid in stationary and synchronous reference frames.
II trimester. Implemented the three-phase LCL filter system for the PSIM software into the SYNDEM Inverter and tested the code under different parameters and power ratings.
III trimester. Designed the Uncertainty and Disturbance Estimator-Based Control of L and LCL-type grid-tied Inverters using PSIM software at the Illinois Institution of Technology in Chicago, United States, under the supervision of Prof. Qing-Chang Zhong.
IV trimester. Extended the exact discrete-time model of The LCL Filters connected to a grid to the synchronous reference frames and obtained the mathematical model block diagrams in reference frames.
Umar Farooq
I trimester. Literature review of current trends in thermoelectric properties of different materials and their preparation methods.
II trimester. The study of electrical and thermal characteristics of PVDF/GNP coated fabrics and their preparation.
III trimester. The graphene-based thermocouple has been studied. The thermocouple is made using PVDF/GNP nanocomposites, which was applied onto various fabrics while maintaining their flexibility. The proposed thermocouple has performance comparable to that of commercially available K-type, generating an output voltage of 33.9 μV /K and providing accurate temperature
measurement for various applications.
IV trimester. The study of PVDF/GNP nanocomposites which was cast on commercial textiles and their electrical and thermal capabilities as thermoelectric generator while retaining flexibility, chemical stability, and corrosion resistance. Additionally, the size investigation of the these generator is carried out.
Samira Lakouraj Mansouri
I trimester. During the first quarterer, a literature review was conducted to establish familiarity with the fabrication and characterization of graphene-based material and sensors. Furthermore, several lab activities were performed to get hands-on practice on the instruments required for morphological and electrical characterization.
II trimester. During the second quarter, developed graphene-coated textiles were prepared and characterized as pressure sensor for human movements such as breathing and walking patterns.
III trimester. In this period along with working on graphene-based pressure sensor I also cooperate with 3D form humidity sensor for breathing applications.
IV trimester. In this quarter characterized the final result of the sensors and submit a conference paper. Also I wrote the manuscript of my journal paper. In addition I participated in the Naotechnology and Materials Devices (NMDC) 2023.
Sara Taherinezhadtayebi
I trimester. I mostly dedicated my time to the literature review of the whole project and the state of the art of this research. Based on the main goals of the work and the bibliography review, I was drafting a review paper about “Waste Management of Wind Turbine Blades: A Comprehensive Review on Available Recycling Technologies to Overcome Potential Environmental Hazards Caused by Microplastics”. i attended two courses in Sapienza and participated in INSTM conference.
II trimester. I started guiding a master's student to write up his thesis on “Grinding technologies used for mechanical recycling of waste Wind Turbine Blades” title.
III trimester. I attended a training school in Jena, Germany related to Microplastics. I learned many experimental techniques and fabrication processes such as Density measurement, Morphological observations through Optical Microscope (OM) and Scanning Electron Microscope (SEM), Mechanical properties evaluation by Zwick-Roell machine, Water absorption (WA) percentage, Porosity percentage of Concrete-based materials, as well as composites Injection molding technique (IMT). I helped one master's student write his thesis ISI paper about the “Effect of MFC gel incorporation in Short Carbon fiber-reinforced Concrete: Property Evaluation.”
IV trimester. I produced a particular type of cement (Blast Furnace Slag Cement), which utilized a GF-reinforced type of blade waste as a feedstock for the clinker.
Mairaj Ahmad
This year, oxidation and hot corrosion testing of Rene-N4 and FSX-414 superalloys for 500, 1000, 2000, 3000, and 4000 hours in the air and water vapor environment with continuous flow 10L/min of air and 0.5bar water vapor pressure were performed and the characterization of were done by Weight gain or loss, Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffractometer (XRD). First of all, Rene-N4 and FSX-414 inform of barrs were aged at 982°C for two hours to remove the coating and oxide scale on the surface of barrs, then samples having 20mm diameter and 2mm thickness having a proper surface finish and surface roughness were cut by using Electric Discharge Machine (EDM). After that, These samples were acid-cleaned to remove dust and other second particles. To check the exact temperature inside the furnace, temperature profiling of the heating zone of the furnace was done by using a K-type thermocouple. After temperature profiling the high-temperature oxidation and corrosion tests were performed for 500, 1000, 2000, 3000, and 4000 hours at 982°C temperature with a continuous flow of air (10L/min) and water vapor (0.5bar pressure). Regularly the airflow and water vapor flow are provided by the evaporator. For both air and water vapor-based corrosion tests 12 samples were used, where after 500, 1000, 2000, 3000, and 4000 hours two samples were extracted from the furnace to perform characterization by SEM, EDS, and XRD. After 500, 1000, 2000, 3000, and 4000 hours of corrosion testing, all samples were removed from the furnace to weigh them, and two samples from these 12 samples were for further characterization by SEM, EDS, and XRD. To find the depth of the corrosion scale one sample were cut into half by the diamond precise cutting method and after grinding and polishing thickness of different oxide scale were calculated by SEM images. SEM, EDS, and XRD results show that the formation of Al2O3, TiO2, Ni3Al, Ni3Ti, Cr2O3, MnCr2O4and CoCr2O4 oxide scale takes place during oxidation and hot corrosion at 982°C. The weight of samples first increases due to the formation of the oxide scale but after 1000 hours decreases because of the removal of the oxide scale.
During the second PhD year I spent 4 months in company Baker Hughes where performed aging of Rene-N4 superalloys for 2 hours at 982°C and cutting of samples with 4.6mm thickness and 24mm diameter. Now, next, we have to perform low-temperature cyclic testing at 704, 760, 815, 870, 927, and 982°C temperatures for 750 cycles. Salt fog test of CC1 coated and naked turbine blades for 3, 6, and 12 months is under progress.
Naseer Ahmad
In this year, I develop of “Actual Design Space” (ADS), for the axial flux PM machine, it is observed that the creation of the ADS is an entirely analytical, non-iterative process, as that its computational cost is negligible compared to even one Finite Element (FE) iteration. The Actual Design Space denotes that it comprises only of machines that satisfy all the design constraints, e.g., maximum temperatures, and requirements, e.g., rated power. This property of the ADS having advantages to verify that the design is feasible and to get a better insight of the design problem and select the best solution/optimization algorithm.
Moreover, I developed a theoretical framework for the "Actual Design Space" (ADS) of the axial flux PM machine. I achieved this by identifying design variables and analyzing the geometry of the machine to establish equations for electromagnetic design variables. The developed theoretical framework, design and electromagnetic equations translated into MATLAB coding to verify the accuracy of the sizing equations for the ADS and working on verification of these equations through a case study. The coding ensures accurate theoretical calculations and a defined ADS. The obtained MATLAB code is currently under testing and the results are being compared to case studies available in the literature. Further validation is achieved through simulations using Finite Element Analysis (FEA), ensuring the practical applicability of the design parameters.
Detailed Overview
The concept of an "Actual Design Space" (ADS) in the context of design and engineering refers to a specifically defined area within the broader theoretical design space that is more likely to contain viable solutions to a specific design problem. the Actual Design Space is a strategic concept in design and engineering that helps focus resources and efforts on the most promising solutions within a larger set of potential designs. It's about efficiency and effectiveness in the design process, ensuring that time and effort are directed towards developing solutions that are most likely to meet the defined needs and constraints of the project.
ADS is both analytical and iterative. Initially, designers and engineers may consider a wide array of potential solutions, encompassing a diverse range of ideas and concepts. However, as the design process progresses, this broad spectrum is systematically narrowed down. This refinement is guided by specific criteria by different constraints. Consequently, the ADS becomes a focused arena of design exploration where the probability of finding successful solutions is maximized. This approach not only streamlines the design process but also enhances the quality and applicability of the resulting solutions, making the ADS a fundamental concept in efficient and effective design and engineering practices.
Internal Relationship (IR): ‘equation that relates two or more Design Variables to each other’.
Constraint (Cnt): ‘Limitation to the feasible values of one Design Variable, or a combination of Design Variables, that arises from any sort of physical limitation’,
Requirement (Rqm): ‘Limitation to the feasible values of one Design Variable, or a combination of Design Variables, that arises from any sort of demanded performance’.
External Relationship (ER): ‘inequation that limits or equation that fixes the feasible values of one or more Design Variable, due to either a Constraint or a Requirement’.
The term ‘External’ denotes the fact that this set of inequalities depends on ‘external’ factors, i.e. the specific applications.
The terms ‘Internal’ denotes the fact that these equations are given only by the characteristics of the device itself (e.g. by the specific class of electric machine). In other words, they are not at all related to the specific application, nor to the nameplate data.
ADS of An Axial Flux Pm Machine: Internal Stage
This Section is devoted to the description of the Internal Stage of an Axial Flux (AF) PM machine ADS determination. The main objective is the enumeration of the DVs that define the design of an AFPM machine, along with the IRs that link them to each other. The analysis considers the AFPM machine geometry and electromagnetic aspects.
Geometric Design Variables
This Section analyses the geometry of a standard AFPM machine. The stator geometry counts fifteen DVs and the fifteen stator DVs are linked to each other through the nine IRs given. Hence, the stator geometry provides six IDVs.
Rotor Geometry
Nine DVs characterize the AFPM rotor. The DVs of the rotor geometry are related to each other by four IR. Hence, the number of rotors IDVs is five.
Assembly Design Parameters
Four further DVs belong to the full machine assembly. The DVs of the assembly design parameters are related to each other by three IR. Hence, the number of assembly design parameters IDVs is one.
Electromagnetic Design Variables
That the magnetic circuit defines six DVs and five IRs, which result in one ‘electromagnetic’ IDV.
Following from the above, it is now possible to calculate the number of IDVs related to the electromagnetic design. Geometrical and electromagnetic aspects count 34 DVs interlinked by 21 IRs, which results in 13 IDVs.
It is important to highlight that the 15 IDVs that derive from the electromagnetic and geometric aspects are the only ones involved in the energy conversion process. We have a 13 degree of freedom.
ADS Representation
we have developed a MATLAB code that rigorously verifies the equations to our study, thereby ensuring the accuracy and reliability of our theoretical framework. Focusing on the electrical machine design, we have identified three key design variables within Independent Design Variables (IDVs) for effective result representation. DS0 forms the foundational set, encompassing all possible designs in electrical machine engineering. To refine this broad spectrum, we introduce a series of constraints, progressively narrowing down the design space from DS0 to more specific subsets. In representation IDVs when they are discretized. In this approach, the initial design space, conceptualized as a rectangular area, is divided into a finite set of points. Each of these points is then examined individually during the generation of the Actual Design Space (ADS).
Constraints: We define some limit according to the requirements
1st Constraint (DS1): In DS1 consist of all those electrical machine design that passed the 1st constraints and discarded all design that passed the 1st constraint and DS1 representation.
2nd Constraint (DS2): In DS2 consist of all those electrical machine design that passed the 1st constraint and 2nd constraint and DS2.
3rd Constraint (DS3): In DS3 consist of all those electrical machine design that passed the 1st constraint, 2nd constraint and 3rd constraint and DS3.
Simulation Results
We conducted a simulation result on the base of calculated design parameters. These simulations play a crucial role in validating the theoretical models and assumptions made during the design process. The comparison is essential as it the outcomes from different FEA and Design Equations, offering a comprehensive view of the design's performance under some assumptions.