ABSTRACT
Second-generation thin-film Cu(In, Ga)Se2 (CIGS) solar cells are a well-established photovoltaic technology with a record power conversion efficiency of 23.6%. However, their reliance on critical raw materials, such as In and Ga, requires new approaches to reduce the amount of critical raw materials employed. The micro-concentrator concept involves the combination of thin-film photovoltaic technology with concentrator photovoltaic technology. This approach reduces the size of the solar cell to the micrometer range and uses optical concentration to collect sunlight from a larger area, focusing it onto micro solar cells. This work is devoted to the development of a process for manufacturing pre-structured substrates with regular arrays of holes with 200 and 250 µm diameters inside a SiOx insulating matrix. Subsequently, a Cu-In-Ga precursor is deposited by sputtering, followed by photoresist lift-off and the application of a Cu-In-Ga thermal annealing at 500 °C to improve precursor quality and assess pre-structured substrate stability under elevated temperatures. Finally, a two-stage selenization process leads to the formation of CIGS absorber micro-dots. This study presents in detail the fabrication process and explores the feasibility of a bottom-up approach using pre-structured substrates, addressing challenges encountered during fabrication and providing insights for future improvements in CIGS absorber materials.
ABSTRACT
This research presents a dual-pronged bibliometric and systematic review of the integration of phase change materials (PCM) in asphalt pavements to counteract the urban heat island (UHI) effect. The bibliometric approach discerns the evolution of PCM-inclusion asphalt research, highlighting a marked rise in the number of publications between 2019 and 2022. Notably, Chang'an University in China has emerged as a leading contributor. The systematic review addresses key questions like optimal PCM types for UHI effect mitigation, strategies for PCM leakage prevention in asphalt, and effects on mechanical properties. The findings identify polyethylene glycols (PEGs), especially PEG2000 and PEG4000, as prevailing PCM due to their wide phase-change temperature range and significant enthalpy during phase transitions. While including PCM can modify asphalt's mechanical attributes, such mixtures typically stay within performance norms. This review emphasises the potential of PCM in urban heat management and the need for further research to achieve optimal thermal and mechanical balance.
ABSTRACT
Aging by oxidation of asphalt roadway material promotes changes in its physical, chemical, and rheological properties, affecting its hardening and accelerating the degradation of its corresponding asphalt mixture. Titanium dioxide (TiO2) has been applied in engineering investigations to promote anti-aging and photocatalytic properties. In this study, a commercial binder was modified with nano-TiO2 (using contents of 0.1, 0.25, 0.5, 1, 2, 3, and 6%). It was evaluated by physicochemical and rheological tests (penetration, softening point, mass loss, dynamic viscosity, rheology, and Fourier transform infrared spectroscopy-FTIR) before and after aging by rolling thin-film oven test (RTFOT) and pressure aging vessel (PAV). The results indicated that incorporating nano-TiO2 mitigates binder aging, pointing out 0.25% as an optimum modification content for the investigated asphalt binder.
ABSTRACT
This work describes the development of a capacitive-type sensor created from nanoporous anodic aluminium oxide (NP-AAO) prepared by the one-step anodization method conducted in potentiostatic mode and performed in a low-cost homemade system. A series of samples were prepared via an anodization campaign carried out on different acid electrolytes, in which the anodization parameters were adjusted to investigate the effect of pore size and porosity on the capacitive sensing performance. Two sensor test cases are investigated. The first case explores the use of highly uniform NP-AAO structures for humidity sensing applications while the second analyses the use of NP-AAO as a capacitive touch sensor for biological applications, namely, to detect the presence of small "objects" such as bacterial colonies of Escherichia Coli. A mathematical model based on equivalent electrical circuits was developed to evaluate the effect of humidity condensation (inside the pores) on the sensor capacitance and also to estimate the capacitance change of the sensor due to pore blocking by the presence of a certain number of bacterial microorganisms. Regarding the humidity sensing test cases, it was found that the sensitivity of the sensor fabricated in a phosphoric acid solution reaches up to 39 (pF/RH%), which is almost three times higher than the sensor fabricated in oxalic acid and about eight times higher than the sensor fabricated in sulfuric acid. Its improved sensitivity is explained in terms of the pore size effect on the mean free path and the loss of Brownian energy of the water vapour molecules. Concerning the touch sensing test case, it is demonstrated that the NP-AAO structures can be used as capacitive touch sensors because the magnitude of the capacitance change directly depends on the number of bacteria that cover the nanopores; the fraction of the electrode area activated by bacterial pore blocking is about 4.4% and 30.2% for B1 (E. Coli OD600nm = 0.1) and B2 (E. Coli OD600nm = 1) sensors, respectively.
Subject(s)
Escherichia coli , Touch , Aluminum Oxide , Electrodes , HumidityABSTRACT
Transparent binder is used to substitute conventional black asphalt binder and to provide light-colored pavements, whereas nano-TiO2 has the potential to promote photocatalytic and self-cleaning properties. Together, these materials provide multifunction effects and benefits when the pavement is submitted to high solar irradiation. This paper analyzes the physicochemical and rheological properties of a transparent binder modified with 0.5%, 3.0%, 6.0%, and 10.0% nano-TiO2 and compares it to the transparent base binder and conventional and polymer modified binders (PMB) without nano-TiO2. Their penetration, softening point, dynamic viscosity, master curve, black diagram, Linear Amplitude Sweep (LAS), Multiple Stress Creep Recovery (MSCR), and Fourier Transform Infrared Spectroscopy (FTIR) were obtained. The transparent binders (base and modified) seem to be workable considering their viscosity, and exhibited values between the conventional binder and PMB with respect to rutting resistance, penetration, and softening point. They showed similar behavior to the PMB, demonstrating signs of polymer modification. The addition of TiO2 seemed to reduce fatigue life, except for the 0.5% content. Nevertheless, its addition in high contents increased the rutting resistance. The TiO2 modification seems to have little effect on the chemical functional indices. The best percentage of TiO2 was 0.5%, with respect to fatigue, and 10.0% with respect to permanent deformation.
ABSTRACT
The antimicrobial functionality of composites constituted by chitosan with silver-doped zeolites was developed and characterized. A composite with chitosan particles and silver-doped zeolites was synthesized using an ionic gelation process with sodium tripolyphosphate. The chitosan silver-doped zeolites composite obtained presented sizes up to 5 µm, while the silver-doped zeolites had an average size between 0.5 µm and 3.3 µm. The synthesized chitosan silver-doped zeolites composites, as well as the silver-doped zeolites and the chitosan dissolution, were characterized through X-ray diffraction, Fourier Transform Infrared spectroscopy and scanning electron microscopy. The electro kinetic behaviour of chitosan, silver-doped zeolites and chitosan silver-doped zeolites composite was evaluated under different pH conditions. The antimicrobial activity of the composites was evaluated in terms of minimum inhibitory concentrations and minimum lethal concentrations and the results suggest that the chitosan silver-doped zeolites composites show antimicrobial activity against gram-negative and gram-positive bacteria, Escherichia coli and Staphylococcus aureus, respectively and against Candida albicans. The results here presented support the potential application of the composite of chitosan with silver-doped zeolites in the functionalization of textiles with antimicrobial properties.