Christos Mytafides - Academia.edu (original) (raw)

Uploads

Papers by Christos Mytafides

Research paper thumbnail of Additive manufacturing of highly conductive carbon nanotube architectures towards carbon-based flexible thermoelectric generators

Energy advances, 2024

Moving the fabrication of electronics from the conventional 2D orientation to 3D space, necessita... more Moving the fabrication of electronics from the conventional 2D orientation to 3D space, necessitates the use of sophisticated additive manufacturing processes which are capable to deliver multifunctional materials and devices with exceptional spatial resolution. In this study, it is reported the nozzle-guided 3D-printing of highly conductive, epoxy-dispersed, single-walled carbon nanotube (SWCNT) architectures with embedded thermoelectric (TE) properties, capable to exploit significant waste thermal energy from the environment. In order to achieve high-resolution and continuous printing with the SWCNTbased paste through a confined nozzle geometry, i.e. without agglomeration and nozzle clogging, a homogeneous epoxy resin-dispersed SWCNT paste was produced. As a result, various 3D-printed structures with high SWCNT concentration (10 wt%) were obtained via shear-mixing processes. The 3D printed p-and n-type epoxy-dispersed SWCNT-based thermoelements exhibit high power factors of 102 and 75 mW mK À2 , respectively. The manufactured 3D carbon-based thermoelectric generator (3D-CTEG) has the ability to stably operate at temperatures up to 180 1C in ambient conditions (1 atm, relative humidity: 50 AE 5% RH), obtaining TE values of an open-circuit voltage V OC = 13.6 mV, shortcircuit current I SC = 1204 mA, internal resistance R TEG = 11.3 Ohm, and a generated power output P max = 4.1 mW at DT = 100 K (with T Cold = 70 1C). The approach and methodology described in this study aims to increase the flexibility of integration and additive manufacturing processes for advanced 3D-printed conceptual devices and the development of multifunctional materials.

Research paper thumbnail of A hierarchically modified fibre-reinforced polymer composite laminate with graphene nanotube coatings operating as an efficient thermoelectric generator

Materials advances, 2024

In this study, a multifunctional, hierarchically modified glass fiber-reinforced polymer composit... more In this study, a multifunctional, hierarchically modified glass fiber-reinforced polymer composite laminate (GFRP) capable of harvesting thermoelectric energy is fabricated and demonstrated. The fibrous reinforcements were hierarchically patterned with alternate n-and p-type graphene nanotube (singlewalled carbon nanotube-SWCNT) aqueous dispersions, which were printed via ink dispensing processes. The optimal n-and p-type resin-impregnated printed films demonstrate high power factors of 82 and 96 mW m À1 K À2 , respectively, and excellent stability in air. The manufactured GFRP-based graphene thermoelectric generator (GTEG) has the capability to stably function up to 125 1C under ambient conditions (1 atm, RH: 50 AE 5% RH). Printed SWCNT-based thermoelectric (TE) modules were successfully designed and fabricated onto a glass fiber fabric substrate with remarkable properties of ntype and p-type TE thin films resulting in exceptionally high performance. The thermoelectrically functionalized GFRP exhibits excellent stability during operation with obtained TE values of an open circuit voltage V OC = 1.01 V, short circuit current I SC = 850 mA, internal resistance R TEG = 1188 Ohm, and a generated power output P max = 215 mW at DT = 100 1C with T C = 25 1C. The novelty of this work is that it demonstrates for the first time a multilayered hierarchically modified carbon-based energyharvesting structural composite, capable of powering electronic devices such as a LED light from the power it generates when exposed to a temperature difference, and the overall results are among the highest ever presented in the field of energy-harvesting structural composites and printed carbon-based thermoelectrics. Both experimental measurements and simulations validated the TE performance. In addition, GFRP-GTEG showed a bending strength of 310 MPa and a flexural modulus of 21.3 GPa under room temperature (RT) and normal conditions (25 1C), retaining to a significant extent its mechanical properties while simultaneously providing the energy-harvesting capability. The aforementioned functional composite may be easily scaled-up, delivering potential for industrial-scale manufacturing of high-performance TEG-enabled structural composites.

Research paper thumbnail of Carbon fiber/epoxy composite laminates as through-thickness thermoelectric generators

Composites Science and Technology

Research paper thumbnail of A high performance flexible and robust printed thermoelectric generator based on hybridized Te nanowires with PEDOT:PSS

Research paper thumbnail of Automated detection-classification of defects on photo-voltaic modules assisted by thermal drone inspection

MATEC Web of Conferences

A new computational procedure is proposed for the automated detection-classification of defects o... more A new computational procedure is proposed for the automated detection-classification of defects on photovoltaic (PV) modules-panels. Thermal imaging or IR thermography is an important and powerful non-destructive technique for the investigation of structural or operational defects on PV modules and when it is combined with drones can provide a fully automated inspection, detection and defect classification procedure. The aforementioned image processing approach adopts pre- and post-processing tools and methodologies assisting the infrared (IR) thermography for the evaluation of a photovoltaic (PV) module performance. In particular, the passive approach of IR thermography was adopted, a portable thermal imager was used for the in-situ acquisition of images that show the distribution of infrared luminance of the PV panel surface. The acquired images are processed and analyzed for the detection and classification of defects and hot spots on the module’s surface that are potential candi...

Research paper thumbnail of Advanced Glass Fiber Polymer Composite Laminate Operating as a Thermoelectric Generator: A Structural Device for Micropower Generation and Potential Large-Scale Thermal Energy Harvesting

This study demonstrates for the first time a structural glass fiber-reinforced polymer (GFRP) com... more This study demonstrates for the first time a structural glass fiber-reinforced polymer (GFRP) composite laminate with efficient thermal energy harvesting properties as a thermoelectric generator (TEG). This TEG laminate was fabricated by stacking unidirectional glass fiber (GF) laminae coated with p- and n-type single-wall carbon nanotube (SWCNT) inks via a blade coating technique. According to their thermoelectric (TE) response, the p- and n-type GF-SWCNT fabrics exhibited Seebeck coefficients of +23 and -29 μV/K with 60 and 118 μW/m·K2 power factor values, respectively. The in-series p-n interconnection of the TE-enabled GF-SWCNT fabrics and their subsequent impregnation with epoxy resin effectively generated an electrical power output of 2.2 μW directly from a 16-ply GFRP TEG laminate exposed to a temperature difference (ΔT) of 100 K. Both experimental and modeling work validated the TE performance. The structural integrity of the multifunctional GFRP was tested by three-point bending coupled with online monitoring of the steady-state TE current (Isc) at a ΔΤ of 80 K. Isc was found to closely follow all transitions and discontinuities related to structural damage in the stress/strain curve, thus showing its potential to serve the functions of power generation and damage monitoring.

Research paper thumbnail of Printed Single-Wall Carbon Nanotube-Based Joule Heating Devices Integrated as Functional Laminae in Advanced Composites

ACS Applied Materials & Interfaces

This work reports the design and fabrication of novel printed single-wall carbon nanotube (SWCNT)... more This work reports the design and fabrication of novel printed single-wall carbon nanotube (SWCNT) electrothermal Joule heating devices. The devices are directly deposited on unidirectional (UD) glass fiber (GF) fabrics. The GF-SWCNT Joule heaters were integrated during manufacturing as "system" plies in carbon fiber reinforced polymer (CFRP) composite laminates. Specific secondary functions were imparted on the composite laminate endowing thus a multifunctional character. The efficient out-of-oven curing (OOC) of a CFRP laminate was demonstrated using a sandwich configuration comprising top/bottom GF-SWCNT system plies. A total power consumption of ca. 10.5 kWh for the efficient polymerization of the thermoset matrix was required. Infrared thermography (IR-T) monitoring showed a uniform and stable temperature field before and after impregnation with epoxy resin. Quasi-static three-point bending and dynamic mechanical analysis (DMA) revealed a minor knock-down effect of the OOC-CFRP laminates properties compared to oven cured CFRPs, whereas the glass transition temperature (Tg) was almost identical. The OOC-CFRP laminates were efficient in providing additional functions such as deicing and self-sensing that are highly sought in the energy and transport sectors, i.e., wind turbine blades or aircraft wings. The novel modular design provides unique opportunities for large-area applications via multiple interconnected arrays of printed devices.

Research paper thumbnail of Fully printed and flexible carbon nanotube-based thermoelectric generator capable for high-temperature applications

Research paper thumbnail of High-Power All-Carbon Fully Printed and Wearable SWCNT-Based Organic Thermoelectric Generator

ACS Applied Materials & Interfaces

Research paper thumbnail of An Approach toward the Realization of a Through-Thickness Glass Fiber/Epoxy Thermoelectric Generator

Materials

The present study demonstrates, for the first time, the ability of a 10-ply glass fiber-reinforce... more The present study demonstrates, for the first time, the ability of a 10-ply glass fiber-reinforced polymer composite laminate to operate as a structural through-thickness thermoelectric generator. For this purpose, inorganic tellurium nanowires were mixed with single-wall carbon nanotubes in a wet chemical approach, capable of resulting in a flexible p-type thermoelectric material with a power factor value of 58.88 μW/m·K2. This material was used to prepare an aqueous thermoelectric ink, which was then deposited onto a glass fiber substrate via a simple dip-coating process. The coated glass fiber ply was laminated as top lamina with uncoated glass fiber plies underneath to manufacture a thermoelectric composite capable of generating 54.22 nW power output at a through-thickness temperature difference οf 100 K. The mechanical properties of the proposed through-thickness thermoelectric laminate were tested and compared with those of the plain laminates. A minor reduction of approximate...

Research paper thumbnail of Epoxy/Glass Fiber Nanostructured p- and n-Type Thermoelectric Enabled Model Composite Interphases

Applied Sciences

This experimental study is associated with the modification of glass fibers with efficient, organ... more This experimental study is associated with the modification of glass fibers with efficient, organic, functional, thermoelectrically enabled coatings. The thermoelectric (TE) behavior of the coated glass fiber tows with either inherent p semiconductor type single wall carbon nanotubes (SWCNTs) or the n-type molecular doped SWCNTs were examined within epoxy resin matrix in detail. The corresponding morphological, thermogravimetric, spectroscopic, and thermoelectric measurements were assessed in order to characterize the produced functional interphases. For the p-type model composites, the Seebeck coefficient was +16.2 μV/K which corresponds to a power factor of 0.02 μW/m∙K2 and for the n-type −28.4 μV/K which corresponds to power factor of 0.12 μW/m∙K2. The p–n junction between the model composites allowed for the fabrication of a single pair thermoelectric element generator (TEG) demonstrator. Furthermore, the stress transfer at the interphase of the coated glass fibers was studied b...

Research paper thumbnail of Hierarchical Reinforcing Fibers for Energy Harvesting Applications - A Strength Study

Key Engineering Materials

This work is concerned with the study of the strength of nanocoated reinforcing fibers. In more d... more This work is concerned with the study of the strength of nanocoated reinforcing fibers. In more detail, glass fibers were coated with an efficient thermoelectric (TE) ink in order to create multifunctional reinforcing fibers for advanced composite structural applications. The main scope is to evaluate the fracture properties of the TE-enabled hierarchical glass fibers. The hybrid nanocrystal TE ink was synthesized via a solvothermal reaction and further fully characterized in coating form. The morphology and wetting properties of the TE ink deposition onto glass fibers were evaluated via SEM and contact angle measurements. Enhanced values by 19.4% in tensile strength for the coated glass fibers compared to the reference are being reported, measured at single fiber level. The evaluated multifunctional glass fiber strength will be utilised during ongoing research for the interfacial shear strength determination.

Research paper thumbnail of Transformation of a university building into a zero energy building in Mediterranean climate

Research paper thumbnail of Transformation of a university building into a zero energy building in Mediterranean climate

Research paper thumbnail of Evaluation of Thermal Comfort Conditions in the New City Hall of Xanthi, Greece

The purpose of this study is to evaluate the thermal comfort conditions in the new City Hall of X... more The purpose of this study is to evaluate the thermal comfort conditions in the new City Hall of Xanthi and the energy performance of the building in general. The study includes field survey, which was conducted in a frequency of twice a day, once per week, for a period of two months between the heating and cooling season. The measurements were to determine the temperature, humidity and air velocity, inside and out side of the building. Measurements were also performed to determine the values of the heat capacity of building envelope materials and to assess the intensity of nonvisible radiation inside the building. Alongside, social research was conducted, in order to correlate measurement data with the subjective feeling of thermal comfort of the building users. As for the detected weaknesses, upgrading interventions were proposed.

Research paper thumbnail of Additive manufacturing of highly conductive carbon nanotube architectures towards carbon-based flexible thermoelectric generators

Energy advances, 2024

Moving the fabrication of electronics from the conventional 2D orientation to 3D space, necessita... more Moving the fabrication of electronics from the conventional 2D orientation to 3D space, necessitates the use of sophisticated additive manufacturing processes which are capable to deliver multifunctional materials and devices with exceptional spatial resolution. In this study, it is reported the nozzle-guided 3D-printing of highly conductive, epoxy-dispersed, single-walled carbon nanotube (SWCNT) architectures with embedded thermoelectric (TE) properties, capable to exploit significant waste thermal energy from the environment. In order to achieve high-resolution and continuous printing with the SWCNTbased paste through a confined nozzle geometry, i.e. without agglomeration and nozzle clogging, a homogeneous epoxy resin-dispersed SWCNT paste was produced. As a result, various 3D-printed structures with high SWCNT concentration (10 wt%) were obtained via shear-mixing processes. The 3D printed p-and n-type epoxy-dispersed SWCNT-based thermoelements exhibit high power factors of 102 and 75 mW mK À2 , respectively. The manufactured 3D carbon-based thermoelectric generator (3D-CTEG) has the ability to stably operate at temperatures up to 180 1C in ambient conditions (1 atm, relative humidity: 50 AE 5% RH), obtaining TE values of an open-circuit voltage V OC = 13.6 mV, shortcircuit current I SC = 1204 mA, internal resistance R TEG = 11.3 Ohm, and a generated power output P max = 4.1 mW at DT = 100 K (with T Cold = 70 1C). The approach and methodology described in this study aims to increase the flexibility of integration and additive manufacturing processes for advanced 3D-printed conceptual devices and the development of multifunctional materials.

Research paper thumbnail of A hierarchically modified fibre-reinforced polymer composite laminate with graphene nanotube coatings operating as an efficient thermoelectric generator

Materials advances, 2024

In this study, a multifunctional, hierarchically modified glass fiber-reinforced polymer composit... more In this study, a multifunctional, hierarchically modified glass fiber-reinforced polymer composite laminate (GFRP) capable of harvesting thermoelectric energy is fabricated and demonstrated. The fibrous reinforcements were hierarchically patterned with alternate n-and p-type graphene nanotube (singlewalled carbon nanotube-SWCNT) aqueous dispersions, which were printed via ink dispensing processes. The optimal n-and p-type resin-impregnated printed films demonstrate high power factors of 82 and 96 mW m À1 K À2 , respectively, and excellent stability in air. The manufactured GFRP-based graphene thermoelectric generator (GTEG) has the capability to stably function up to 125 1C under ambient conditions (1 atm, RH: 50 AE 5% RH). Printed SWCNT-based thermoelectric (TE) modules were successfully designed and fabricated onto a glass fiber fabric substrate with remarkable properties of ntype and p-type TE thin films resulting in exceptionally high performance. The thermoelectrically functionalized GFRP exhibits excellent stability during operation with obtained TE values of an open circuit voltage V OC = 1.01 V, short circuit current I SC = 850 mA, internal resistance R TEG = 1188 Ohm, and a generated power output P max = 215 mW at DT = 100 1C with T C = 25 1C. The novelty of this work is that it demonstrates for the first time a multilayered hierarchically modified carbon-based energyharvesting structural composite, capable of powering electronic devices such as a LED light from the power it generates when exposed to a temperature difference, and the overall results are among the highest ever presented in the field of energy-harvesting structural composites and printed carbon-based thermoelectrics. Both experimental measurements and simulations validated the TE performance. In addition, GFRP-GTEG showed a bending strength of 310 MPa and a flexural modulus of 21.3 GPa under room temperature (RT) and normal conditions (25 1C), retaining to a significant extent its mechanical properties while simultaneously providing the energy-harvesting capability. The aforementioned functional composite may be easily scaled-up, delivering potential for industrial-scale manufacturing of high-performance TEG-enabled structural composites.

Research paper thumbnail of Carbon fiber/epoxy composite laminates as through-thickness thermoelectric generators

Composites Science and Technology

Research paper thumbnail of A high performance flexible and robust printed thermoelectric generator based on hybridized Te nanowires with PEDOT:PSS

Research paper thumbnail of Automated detection-classification of defects on photo-voltaic modules assisted by thermal drone inspection

MATEC Web of Conferences

A new computational procedure is proposed for the automated detection-classification of defects o... more A new computational procedure is proposed for the automated detection-classification of defects on photovoltaic (PV) modules-panels. Thermal imaging or IR thermography is an important and powerful non-destructive technique for the investigation of structural or operational defects on PV modules and when it is combined with drones can provide a fully automated inspection, detection and defect classification procedure. The aforementioned image processing approach adopts pre- and post-processing tools and methodologies assisting the infrared (IR) thermography for the evaluation of a photovoltaic (PV) module performance. In particular, the passive approach of IR thermography was adopted, a portable thermal imager was used for the in-situ acquisition of images that show the distribution of infrared luminance of the PV panel surface. The acquired images are processed and analyzed for the detection and classification of defects and hot spots on the module’s surface that are potential candi...

Research paper thumbnail of Advanced Glass Fiber Polymer Composite Laminate Operating as a Thermoelectric Generator: A Structural Device for Micropower Generation and Potential Large-Scale Thermal Energy Harvesting

This study demonstrates for the first time a structural glass fiber-reinforced polymer (GFRP) com... more This study demonstrates for the first time a structural glass fiber-reinforced polymer (GFRP) composite laminate with efficient thermal energy harvesting properties as a thermoelectric generator (TEG). This TEG laminate was fabricated by stacking unidirectional glass fiber (GF) laminae coated with p- and n-type single-wall carbon nanotube (SWCNT) inks via a blade coating technique. According to their thermoelectric (TE) response, the p- and n-type GF-SWCNT fabrics exhibited Seebeck coefficients of +23 and -29 μV/K with 60 and 118 μW/m·K2 power factor values, respectively. The in-series p-n interconnection of the TE-enabled GF-SWCNT fabrics and their subsequent impregnation with epoxy resin effectively generated an electrical power output of 2.2 μW directly from a 16-ply GFRP TEG laminate exposed to a temperature difference (ΔT) of 100 K. Both experimental and modeling work validated the TE performance. The structural integrity of the multifunctional GFRP was tested by three-point bending coupled with online monitoring of the steady-state TE current (Isc) at a ΔΤ of 80 K. Isc was found to closely follow all transitions and discontinuities related to structural damage in the stress/strain curve, thus showing its potential to serve the functions of power generation and damage monitoring.

Research paper thumbnail of Printed Single-Wall Carbon Nanotube-Based Joule Heating Devices Integrated as Functional Laminae in Advanced Composites

ACS Applied Materials & Interfaces

This work reports the design and fabrication of novel printed single-wall carbon nanotube (SWCNT)... more This work reports the design and fabrication of novel printed single-wall carbon nanotube (SWCNT) electrothermal Joule heating devices. The devices are directly deposited on unidirectional (UD) glass fiber (GF) fabrics. The GF-SWCNT Joule heaters were integrated during manufacturing as "system" plies in carbon fiber reinforced polymer (CFRP) composite laminates. Specific secondary functions were imparted on the composite laminate endowing thus a multifunctional character. The efficient out-of-oven curing (OOC) of a CFRP laminate was demonstrated using a sandwich configuration comprising top/bottom GF-SWCNT system plies. A total power consumption of ca. 10.5 kWh for the efficient polymerization of the thermoset matrix was required. Infrared thermography (IR-T) monitoring showed a uniform and stable temperature field before and after impregnation with epoxy resin. Quasi-static three-point bending and dynamic mechanical analysis (DMA) revealed a minor knock-down effect of the OOC-CFRP laminates properties compared to oven cured CFRPs, whereas the glass transition temperature (Tg) was almost identical. The OOC-CFRP laminates were efficient in providing additional functions such as deicing and self-sensing that are highly sought in the energy and transport sectors, i.e., wind turbine blades or aircraft wings. The novel modular design provides unique opportunities for large-area applications via multiple interconnected arrays of printed devices.

Research paper thumbnail of Fully printed and flexible carbon nanotube-based thermoelectric generator capable for high-temperature applications

Research paper thumbnail of High-Power All-Carbon Fully Printed and Wearable SWCNT-Based Organic Thermoelectric Generator

ACS Applied Materials & Interfaces

Research paper thumbnail of An Approach toward the Realization of a Through-Thickness Glass Fiber/Epoxy Thermoelectric Generator

Materials

The present study demonstrates, for the first time, the ability of a 10-ply glass fiber-reinforce... more The present study demonstrates, for the first time, the ability of a 10-ply glass fiber-reinforced polymer composite laminate to operate as a structural through-thickness thermoelectric generator. For this purpose, inorganic tellurium nanowires were mixed with single-wall carbon nanotubes in a wet chemical approach, capable of resulting in a flexible p-type thermoelectric material with a power factor value of 58.88 μW/m·K2. This material was used to prepare an aqueous thermoelectric ink, which was then deposited onto a glass fiber substrate via a simple dip-coating process. The coated glass fiber ply was laminated as top lamina with uncoated glass fiber plies underneath to manufacture a thermoelectric composite capable of generating 54.22 nW power output at a through-thickness temperature difference οf 100 K. The mechanical properties of the proposed through-thickness thermoelectric laminate were tested and compared with those of the plain laminates. A minor reduction of approximate...

Research paper thumbnail of Epoxy/Glass Fiber Nanostructured p- and n-Type Thermoelectric Enabled Model Composite Interphases

Applied Sciences

This experimental study is associated with the modification of glass fibers with efficient, organ... more This experimental study is associated with the modification of glass fibers with efficient, organic, functional, thermoelectrically enabled coatings. The thermoelectric (TE) behavior of the coated glass fiber tows with either inherent p semiconductor type single wall carbon nanotubes (SWCNTs) or the n-type molecular doped SWCNTs were examined within epoxy resin matrix in detail. The corresponding morphological, thermogravimetric, spectroscopic, and thermoelectric measurements were assessed in order to characterize the produced functional interphases. For the p-type model composites, the Seebeck coefficient was +16.2 μV/K which corresponds to a power factor of 0.02 μW/m∙K2 and for the n-type −28.4 μV/K which corresponds to power factor of 0.12 μW/m∙K2. The p–n junction between the model composites allowed for the fabrication of a single pair thermoelectric element generator (TEG) demonstrator. Furthermore, the stress transfer at the interphase of the coated glass fibers was studied b...

Research paper thumbnail of Hierarchical Reinforcing Fibers for Energy Harvesting Applications - A Strength Study

Key Engineering Materials

This work is concerned with the study of the strength of nanocoated reinforcing fibers. In more d... more This work is concerned with the study of the strength of nanocoated reinforcing fibers. In more detail, glass fibers were coated with an efficient thermoelectric (TE) ink in order to create multifunctional reinforcing fibers for advanced composite structural applications. The main scope is to evaluate the fracture properties of the TE-enabled hierarchical glass fibers. The hybrid nanocrystal TE ink was synthesized via a solvothermal reaction and further fully characterized in coating form. The morphology and wetting properties of the TE ink deposition onto glass fibers were evaluated via SEM and contact angle measurements. Enhanced values by 19.4% in tensile strength for the coated glass fibers compared to the reference are being reported, measured at single fiber level. The evaluated multifunctional glass fiber strength will be utilised during ongoing research for the interfacial shear strength determination.

Research paper thumbnail of Transformation of a university building into a zero energy building in Mediterranean climate

Research paper thumbnail of Transformation of a university building into a zero energy building in Mediterranean climate

Research paper thumbnail of Evaluation of Thermal Comfort Conditions in the New City Hall of Xanthi, Greece

The purpose of this study is to evaluate the thermal comfort conditions in the new City Hall of X... more The purpose of this study is to evaluate the thermal comfort conditions in the new City Hall of Xanthi and the energy performance of the building in general. The study includes field survey, which was conducted in a frequency of twice a day, once per week, for a period of two months between the heating and cooling season. The measurements were to determine the temperature, humidity and air velocity, inside and out side of the building. Measurements were also performed to determine the values of the heat capacity of building envelope materials and to assess the intensity of nonvisible radiation inside the building. Alongside, social research was conducted, in order to correlate measurement data with the subjective feeling of thermal comfort of the building users. As for the detected weaknesses, upgrading interventions were proposed.