High Absorption Values Research Articles

Use of Modified Organic and Inorganic Phase Change Materials for the Development of Personal Cooling Device

The human body needs comfort in every condition. Human health is significantly impacted by heat. The ambient air temperature rises in hot weather, which causes the human body to become fatigued and exhausted. Phase Change Materials (PCM) can solve this problem with high latent heat absorption values and a wide range of phase change temperatures. The objective is to develop a PCM-based cooling device that is safe, readily available, and easy to use in normal routine life. A personal cooling system, such as a cooling vest using PCM, can assist in preventing heat-related issues. In this study, Polyethylene Glycol-600 (PEG-600) and modified glauber salt are selected as thermal energy storage materials with melting temperatures of 18–22°C and 27°C, respectively. Graphene Oxide (GO) nanoparticles were synthesised and mixed into the PEG-600 to enhance its thermal conductivity and latent heat of fusion. GO nanoparticles were prepared by Modified Hummer’s method (MHM) and characterised by Fourier’s Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD), and Scanning Electron Microscopy (SEM). The latent heats and melting ranges of GO/PEG-600 and modified glauber salt were investigated by Differential Scanning Calorimetry (DSC). The addition of 0.6 wt.% GO to PEG-600 results in an increase in thermal conductivity of 6.1% and latent heat of 8%. The PCMs are encapsulated in aluminium packs, sealed, and kept in a cooling device. The developed cooling vest provides cooling for up to 95 minutes. The cooling vest is recharged by keeping it below 10°C for 20 minutes. The developed personal cooling device provides a passive, inexpensive, and safe cooling system by extracting heat from the human body.

Amplifying the photovoltaic properties of tetrathiafulvalenes based materials by incorporation of small acceptors: a density functional theory approach

Currently, polycyclic aromatic compounds in organic solar cells (OSCs) have gained substantial consideration in research communities due to their promising characteristics. Herein, polycyclic aromatic hydrocarbons (PAHs) core-based chromophores (TTFD1-TTFD6) were designed by structural modifications of peripheral acceptor groups into TTFR. The density functional theory (DFT) and time dependent density functional theory (TD-DFT) calculations were carried out at B3LYP/6-311G (d, p) functional to explore insights for their structural, electronic, and photonic characteristics. The structural modulation unveiled notable electronic impact on the HOMO and LUMO levels across all derivatives, leading to decreased band gaps. All the designed compounds exhibited band gap ranging from 2.246 to 1.957 eV, along with wide absorption spectra of 897.071-492.274 nm. An elevated exciton dissociation rate was observed due to the lower binding energy values (Eb = 0.381 to 0.365 eV) calculated in the derivatives compared to the reference (Eb = 0.394 eV). Furthermore, data from the transition density matrix (TDM) and density of states (DOS) also corroborated the effective charge transfer process. Comparable results of Voc for reference and designed chromophores were obtained via HOMOdonor−LUMOPC71BM. The declining Voc order values was noted as TTFD5 > TTFD6 > TTFD4 > TTFD3 > TTFD2 > TTFD1 > TTFR. Interestingly, TTFD5 was found with the smallest energy gap and highest absorption value, resulting in better charge transference among all the derivatives. The results illustrated that the modification in indenofluorene based chromophores with end-capped small acceptors proved to be a significant approach in achieving favorable photovoltaic properties.

Elasticity and modal effects on the optimal performance of micro-perforated multi-layered absorbers

Multi-layered wall-treatments with thin lightweight micro-perforated panels offer a potential solution to achieve broadband noise absorption while complying with mass saving and compactness. This study examines how vibrational effects, often neglected, may impede the wideband acoustical performance of such partitions, made up of a distribution of either periodic or graded micro-perforated membranes or panels. The impedance translation method and a scattering matrix analysis have been implemented. It is found that the elasticity behavior of thin micro-perforated membranes has a beneficial effect on the acoustical efficiency of the partitions. The contributions of the individual acoustical resonances tend to merge if the elasticity effects are accounted for. If the partition is optimized, near-constant high absorption and low transmission values are obtained over a wide frequency range. A more robust design involves partitions made up of micro-perforated panels. It was observed that the first volumetric volumetric mode of the panels modifies the absorption properties of the partition. It cross-couples with the acoustical resonances and redistributes their spectral locations. This structural resonance sets an upper frequency bound, below which the partition achieves a high broadband performance. It should be accounted for when setting the frequency limits of the total dissipation to be optimized.

Studies on hydrogen storage properties of TiVFeNi, (TiVFeNi)95Zr5 and (TiVFeNi)90Zr10 high entropy alloys

The major issues associated with High Entropy Alloys (HEAs) as hydrogen storage material are the activation of these alloys and low storage capacity. The aim of the present investigation is to reduce the activation process and increase the hydrogen storage capacity of TiVFeNi-based HEAs. We investigated the effect of different Zr content on the hydrogen storage properties of TiVFeNi-based HEAs. Four different Ti25V25Fe25Ni25, (TiVFeNi)95Zr5, (TiVFeNi)90Zr10, and (TiVFeNi)80Zr20 HEAs were synthesized through mechanical alloying. The as-synthesized Ti25V25Fe25Ni25 alloy possessed a mixture of bcc and fcc phases. However, the as-synthesized (TiVFeNi)95Zr5 and (TiVFeNi)90Zr10 HEAs possessed bcc and fcc phases with a ZrFe2 intermetallic phase. We found that as the Zr content increases, alloys' hydrogenation behavior, improves due to the better activation process. Among the studied HEAs, in present studies, the highest hydrogen storage capacity is found to be 2.86 wt% at RT with 10 atm of hydrogen pressure for (TiVFeNi)90Zr10 HEA after 15 activation cycles at different temperatures. The high absorption value was found due to the formation of intermetallic ZrFe2, which acts as a bridging entity on the surface of the synthesized bcc and fcc phases. The present study provides a detailed insight into how the presence of the ZrFe2 phase reduces the activation process as well as enhances the hydrogenation properties of TiVFeNi-based HEAs.

The application of copper sulfate mixed with Caesalpinia sappan L. extract to increase colorfastness in pressed blush products

This study aims to increase the colorfastness of pressed blush products by combining copper sulfate with Caesalpinia sappan L. extract. This experiment consisted of four conditions used for color extraction: 70% w w-1, 95% w w-1, 70% w w-1 with 10% w w-1 copper sulfate, and 95% w w-1 with 10% w w-1 copper sulfate. The highest yield percentage of crude extract was found at 70% w w-1, with the highest absorption value (λmax) at 70% methanol with 10% w w-1 copper sulfate. The darkest shade of red was found at 70% w w-1 with 10% w w-1 copper sulfate. The development of pressed blush occurred when corn starch was mixed with more white color and smell than arrowroot flour. The highest red color was achieved at 4.5% w w-1, with the highest red - purple intensity. The microbial contamination test showed no microbial contamination in pressed blush products. GRAPHICAL ABSTRACT HIGHLIGHTS Caesalpinia sappan L. was extracted using maceration methods with methanol solvent. Phytochemical screening revealed pink anthraquinone and anthocyanidins. The chemical properties showed a pH range of 5.31–5.74, maximum light absorption, and mordant increased absorption. A compress blush was developed with corn starch and arrowroot flour, suitable for the cosmetic industry.

A tunable graphene dual mode absorber for efficient terahertz radiation absorption and sensing applications

This paper presents a novel plasmonic graphene absorber designed for the terahertz frequency range, utilizing a dual mode optical filter configuration. The absorber consists of a layered periodic array comprising gold, SiO₂ and graphene. Key components include a graphene disk and four strategically positioned graphene stripes on a SiO₂ substrate. An underlying gold layer enhances the absorption efficiency by serving as a reflector. The structure is numerically simulated using the 3D finite difference time domain (FDTD) method. A comprehensive parametric study has been conducted to optimize the absorber's performance. The simulation results demonstrate near perfect absorption at 4.16 THz and 5.88 THz. This innovative design enables efficient absorption of terahertz radiation due to the plasmonic resonance effects of the graphene components. Additionally, the absorption frequency can be dynamically adjusted by altering the chemical potential of graphene through applying an external bias voltage. The tailored geometry and material composition result in a compact absorber with high absorption values and tunability. Detailed performance analysis through numerical simulations demonstrates the absorber's potential for applications in sensing, imaging, and communication systems operating in the terahertz frequency range.

Microwave-Assisted Hydrothermal Synthesis of Nanosheet Layered Hexagonal Spinel Ferrites for Efficient Electromagnetic Wave Absorbing.

A microwave-induced combustion method has been utilized to prepare nanosized powders of hexagonal spinel ferrites using urea and glycine as fuel. The structural and electromagnetic absorption of these products was investigated using X-ray diffraction (XRD). From the (3,1,1) and (1013) peaks in XRD measurements, it was seen that the samples we synthesized were nanosized spinel and y-phase hexagonal ferrite. In addition, Fourier-transform infrared measurements showed that the synthesized samples had high absorption values showing Fe-O, which is between 878 to 4000 cm-1, and metal-oxygen transitions, which are between the 700 and 2500-3000 cm-1 in the spinel and hexagonal phases. From the scanning electron microscope image of the particles, it is seen that they are homogeneous, filled structures with ∼35-40 nm. It appears from vector network analyzer measurements that the synthesized 1.5 mm thick composite materials have very high electromagnetic absorption properties and that these composites can also be used in electromagnetic interference, Wi-Fi applications, and health.

Photoresponse in sequentially stacked antimony selenide thin films

Antimony selenide (Sb2Se3), a binary semiconducting compound has widespread research attention due to its excellent optoelectronic properties in the visible region and usefulness in applications such as solar cells, photosensors and photoelectrodes. The presented study explores the thickness dependent photoresponse in Sb2Se3 thin films, prepared by reactive selenization of antimony films having thickness values of ∼938 nm and ∼1879 nm when stacked second time. Growth orientation along [001] direction was achieved through carefully optimized selenization conditions to enable favourable charge transport in anisotropic Sb2Se3. Predominant Sb2Se3 formation was inferred from x-ray diffraction, Raman spectroscopy, secondary electron microscopy and energy-dispersive X-ray analyses. High optical absorption coefficient values of about 1 × 105 cm−1 and 5.7 × 104 cm−1 were observed for ∼938 nm and ∼1879 nm thick Sb2Se3 thin films. Further, the optoelectronic properties were elucidated through current–voltage and transient photoresponse measurements under dark and illumination conditions. The measurements were done under zero and different bias voltages. Sb2Se3 films having∼ 938 nm thickness exhibited self-driven photoresponse with a responsivity of 4.3×10−8 A W−1 and detectivity of 3.5 × 106 jones respectively, under AM 1.5 G illumination conditions.

Exploaration of the influence of end-capped structural modification on photovoltaic properties of selenopheno-thiophene core based non-fullerene chromophores: A DFT study

In current study, six novel selenopheno-thiophene (ST) core-based chromophores (SePTD1- SePTD6) with A-D-A configuration were designed via structural tailoring with terminal acceptors of SePTR. The optoelectronic and photovoltaic properties of SePTD1-SePTD6 were explored through TDDFT/DFT approaches. The B3LYP/6–31 G(d,p) level was chose through benchmarked study with the help of DFT and experimental UV-Vis values of SePTR. All tailored chromophores exhibited a comparatively smaller band gap (2.144–2.003 eV), along with a significant bathochromic shift (676.8–724.2 nm) and an increased rate of charge transference then reference chromophore (2.119 eV and 686.6 nm). Among all derivatives, SePTD2 exhibited some unique characteristics such as, least HOMO/LUMO energy gap (2.003 eV), highest absorption values (665.4 nm in gas and 724.2 nm in solvent), least binding energy (0.291 eV) and also significant value of open circuit voltage (1.860 V). The aforementioned findings suggest that employing molecular engineering with extended acceptors enhances the photovoltaic performance of non-fullerene materials, thereby encouraging experimentalists to develop highly efficient photovoltaic devices.

Competing effects of ultrasound absorption and scattering in porous bone

The mechanisms and effects of ultrasonic attenuation in porous cortical bone are poorly understood, and it is necessary to better understand them to evaluate bone porosity noninvasively using ultrasound. A finite-difference time domain numerical study was conducted in which ultrasound propagation was simulated in human femur cross-sections obtained via scanning acoustic microscopy. The effect of absorption on overall attenuation was studied by varying the nominal absorption level attributed to the solid matrix. Ultrasound pulses were emitted with a central frequency of 8 MHz in through-transmission and backscattering configurations. From these data, the respective extinctions lengths due to overall attenuation, scattering, and absorption were obtained. Two regimes seem to exist depending on the nominal absorption value. At low absorption values, scattering dominates overall attenuation, scattering and absorption appear to have a synergistic effect on overall attenuation, and the diffusion constant decreases with increasing average pore diameter. At high absorption values, absorption dominates overall attenuation, the extinction length for scattering increases with pore diameter, and the diffusion constant increases with increasing average pore diameter. These regimes affect how ultrasound parameters, such as the extinction lengths due to scattering, absorption, and overall attenuation, should be used to evaluate the porosity of cortical bone.

Optimizing piezoresistivity in SiTiOC through modulus-tunable Re-entrant structures

Piezoresistive ceramic materials have significant advantages in terms of high sensitivity and stability, but their inherent high stiffness limits macroscopic deformation and detection range. Modulus-optimizable SiTiOC re-entrant structures have been presented to enhance the detection limit of piezoresistive polymer-derived ceramic (PDC) through geometric adjustments, and the relationship between piezoresistive performance and structural geometric parameters was investigated. By modifying the inner folding angles of 30°, 45°, 60° and fix-connected, the deformation behavior and mechanical performance of the structures can be flexibly controlled, resulting in variable sensing properties with a highly sensitive load range tuned from 30 to 100 N. The SiTiOC material obtained showed an optimized sensitivity coefficient of 0.14 MPa−1, which was attributed to an innovative modification of SiOC ceramics by introducing 2 wt% titanium acetylacetonate, creating impurity carrier accumulation regions and evenly dispersed conductive phases, forming percolation networks. Furthermore, the SiTiOC re-entrant structures exhibited long-term cyclic stability, maintaining a steady signal output under different loading degrees and frequencies. This was attributed to the excellent mechanical performance of the structures, with a high compressive strength and energy absorption value reaching 32.6 MPa and 125.44 kJ m−3, respectively, which ensured sufficient load-bearing capacity and the preservation of internal percolation networks. This study demonstrates the effectiveness of piezoresistivity tuning in PDC structures through geometric adjustments, thus expanding their application range. The one-step manufacturing of structuralized sensing materials by 3D printing provides a straightforward approach for the customized design of piezoresistive devices.

Thin metamaterial using acoustic black hole profiles for broadband sound absorption

The multi-pancake absorber is a thin acoustic metamaterial composed of periodically arranged thin annular cavities separated by the plates and connected by a main pore, enabling low frequency sound absorption. However, with a constant main pore radius, this structure exhibits tonal absorption behavior characterized by narrow peaks with varying amplitudes due to an imbalance in losses between the modes. This work investigates a geometric variation of the main pore, focusing on the designs with a gradually decreasing radius known as acoustic black hole profiles, to achieve broadband absorption. An analytical model based on the transfer matrix approach and lumped elements is proposed to predict the acoustic properties. Validation is conducted through thermo-visco-acoustic finite element simulations and impedance tube measurements. Multiple main pore profiles are investigated and the complex frequency plane representation is used to improve the balance of losses. An understanding of the influence of the main pore radius at the entrance and backing of the sample, allows design of a decreasing main pore radius profile that results in a high absorption coefficient value across a broad frequency range. Non-linear decreasing main pore profiles can be used, if necessary, to accentuate losses and achieve absorption peaks of similar amplitude.

Diversity, Vegetation Structure, Estimated Biomass and Carbon Stock in The Site of Limboto Lake of Gorontalo Regency

The development of Limboto Lake Site as the pilot area of Gorontalo Geopark is one step in rescuing the lake. This research aims to analyzed the vegetation structure, estimate biomass, and assess the carbon stock value of the vegetatio at the Limboto Lake site. This study employed a purposive sampling method. Important Value Index, a measure used to evaluate plant vegetation structure, was calculated based on Realtive Density, Relative Dominance, and Relative Frequency values. Biomass estimation and carbon stock assessment were conducted using allometric equations. The study’s finding showed that the vegetation surrounding Soekarno's landing area exhibited the highest IVI (sawlogs) scores for Swietenia mahagoni tree at 82.86%, Leucaena leucocephala saplings at 79.56%, and Manihot esculenta seedlings at 46.33%. Leucaena leucocephala consistently achieved the highest IVI score within the Limboto Lake area with a score as high as 76.90%, followed by Leucaena leucocephala on the sapling level with a score as high as 70.03%, and Nauclea orientalis on the seedling level with a score as high as 53.06%. Swietenia mahagoni, Samanea saman, and Leucaena leucocephala are three species with stems that predominate at the sawlog level and sapling, and these stems have high carbon absorption values.

Green Synthaesis Nanomaterial Zinc Oxide with Anthocyanin Extract Hylocereus polyrhizus for DSSC Application

Photovoltaic technology as an alternative to dye-sensitized third-generation solar cells is known as Dye-Sensitized Solar Cell (DSSC). DSSC is a device that can convert solar energy into electrical energy. Natural dye is used because it is relatively cheap and environmentally friendly. The type colour commonly used in DSSC are chlorophyll and anthocyanin. In this study the anthocyanin extract Hylocereus polyrhizus was used because it has a high absorption value. Nanoparticles ZnO is used because it has a relatively large energy gap value and can absorb sunlight optimally. The method used in this research is a spin coating, this method uses the procedure of making a thin film on the substrate. The characterizations were carried out using X-ray diffraction (XRD) to determine the crystal size of the ZnO nanoparticles, to know morphology nanoparticle can use scanning electron microscope (SEM), ultraviolet visible (UV-Vis) spectrometerer is used to determine the value of the band gap energy and solar cell simulator test to determine the efficiency value. The XRD result had a crystal size 30.74 nm. The SEM results that the shape of the particles is oval and homogeneous by agglomeration. The band gap value is 3.67 eV. The efficiency in the solar cell simulator test for the DSSC nanomaterial ZnO with anthocyanin extract Hylocereus polyrhizus was 0,29%.

Processing of nanocrystalline thin films of selenium and formation of FTO/p-Se/n-CdS/In heterojunctions for photovoltaic response

Thin films of nanocrystalline selenium (Se) of different thicknesses were grown on annealing from 323 to 398 K. The crystallinity of the layers increased with annealing temperatures (TA). The temperature thickness correlations were established. The layers exhibited spherical-shaped particles at higher annealing temperatures. The grown layers possess hexagonal crystal system with space group P3121(152); it shows prominent planes along the a-axis. The bandgap (Eg) decreases from 2.18 to 1.94 eV, 2.12 to 1.82 eV, and 2.13 to 1.84 eV with changes in TA of 700, 270, and 150 nm thick layers, respectively. The high absorption coefficient (α) values ∼ 1 × 105 cm−1 observed in all films makes it suitable as an absorber layer in a solar cell structure and an optical sensor. The FTO/p-Se/n-CdS/In heterojunction diodes provide zero-bias barrier height (фbo) of 0.788(7) eV. The open circuit voltage (Voc) of FTO/p-Se (150 nm)/n-CdS(200 nm)/In a photovoltaic cell was observed to be 55 mV.

In-vitro antioxidant, antidiabetic, anticholinergic activity of iron/copper nanoparticles synthesized using Strobilanthes cordifolia leaf extract

The Strobilanthes cordifolia plant, a member of the Acanthaceae family, has been extensively studied due to its wide range of biological properties. This particular research focused on the green synthesis of FeNPs/CuNPs and evaluated the effectiveness of the experiment through various characterization techniques, including UV, FTIR, XRD, and SEM with EDAX. The UV analysis provided valuable insights, showing that the synthesized nanoparticles had the highest absorption values at 462nm for FeNPs and 438nm for CuNPs. FTIR analysis confirmed the presence of different functional groups, while XRD measurements validated their crystalline nature. SEM data revealed the diverse shapes of the nanoparticles, including rods and spherical shapes. Additionally, EDAX analysis confirmed the presence of Fe and Cu elements in the biosynthesized nanoparticles. The antibacterial activity of FeNPs and CuNPs against Staphylococcus aureus and Escherichia coli showed significant inhibition. Moreover, the nanoparticles demonstrated strong antioxidant activity, as evidenced by their effective inhibition in DPPH and ABTS assays. Their potential as anti-diabetic agents was also explored, with assessments of their inhibitory effects on α-Amylase and α-Glucosidase enzymes. Additionally, the nanoparticles displayed inhibitory effects on anti-cholinergic enzymes such as AChE and BChE. Furthermore, comprehensive toxicological studies revealed a higher level of mosquito larvicidal activity against Aedes aegypti, Anopheles stephensi, and Culex quinquefasciatus. Among these, the FeNPs exhibited a larval mortality rate of 95% in Cx. Quinquefasciatus, while the CuNPs showed a rate of 93%. In conclusion, this study demonstrated that FeNPs/CuNPs possess favorable characteristics and significant potential for various biomedical applications.

Dual-band absorption due to simultaneous excitation of TE and TM modes in ITO-ES metamaterial for IR stealth technology

We proposed a plasmonic based Indium Tin Oxide Embedded Silver (ITO-ES) infrared dual-band perfect absorber for the utilization in IR stealth technology. The proposed structure comprised of nano size Ag ring and desk embedded in ITO. The optical losses in optical regime of nanoscale plasmonic Ag were incorporated in terms of collision frequency using the modified Drude model. The optical response of the proposed structure was predicted by exciting it with a planwave using full wave vector frequency domain solver by employing Finite Element Method (FEM) in Computer Simulation Technology (CST) Microwave Studio. The simultaneous excitation of higher order transverse electromagnetic (TE and TM) modes in the proposed structure lead to high values of both absorption and Front to Back ratio (FTBR). The controlled and selective wavelength multiband absorption is crucial for IR stealth technology. The proposed metamaterial structures exhibit dual-bands IR absorption at wavelengths λ = 1.40 μm and 6.4 μm. First absorption peak suppresses the back scattering of the laser used by laser guided devices for detection, while the second peak suppresses the IR signature of the structure due thermal radiation which can be used by tracking devices to detect warm/hot objects.

Ozone deterioration over North China plain caused by light absorption of black carbon and organic carbon

Previous studies have revealed that the light absorption effect of black carbon (BC) aerosol could influence ozone concentrations via absorbing sunlight and modulating photolysis rates, the so-called aerosol-photolysis interaction (API). However, few studies have quantified the API effect of organic carbon (OC) aerosol, which has recently been found to contribute to about 10%–40% of the total light absorption at 300 nm wavelength. This study tried to quantify and compare the OC and BC aerosols' influence on ozone concentrations through a case study over North China Plain (NCP) in Oct. 2018. By modulating OC's absorption index based on field measurements, we quantified the OC and BC API effect on surface ozone by the WRF-Chem model. The API effect and its uncertainties of OC aerosols were evaluated using the high and low absorption values that have been reported in previous studies. Results showed that, in terms of the pollution periods in NCP, removing all the OC aerosol from the atmosphere could increase the daytime maximum daily average 8-h (MDA8) O3. In this episode, the average (extreme) MDA8 O3 increased by 0.7–2.4 ppb (1.1–3.7 ppb), accounting for 1.5%–5.3% (2.4%–8.8%) of ozone concentration, comparable to that by BC of 2.0 ppb (3.3 ppb), accounting for 4.4% (7.8%), which means the OC's API effect was 35%–120% of BC's API effect on surface ozone in this case. The results also indicated a fact that, though OC has a lower light absorption rate than BC, the API efficiency of OC on surface ozone when reducing aerosols could be compensated by a higher portion of OC aerosols and higher light absorption efficiency due to much more OC was distributed on higher altitude (especially 1–3 km) than BC aerosols, which result in larger ozone changes in both the low troposphere and surface.

Petrographic and Geotechnical Features of Dir Volcanics as Dimension Stone, Upper Dir, North Pakistan

The utilization of dimension stone in construction has been prevalent since ancient times; however, its application in modern construction has gained significant attention over the last few decades. This research aimed to assess the physical and strength properties of volcanic rocks from the Kohistan Island Arc for their potential use as dimension stone. Five types of andesites (MMA, PMA-1, PMA-2, CMA, and FMA) and two types of agglomerates (AG-1 and AG-2) were identified based on their composition, color, and texture. The samples were characterized in terms of their petrography (compositional and textural), physical properties (specific gravity, water absorption, and porosity), and strength properties (unconfined compressive strength and unconfined tensile strength). Two non-destructive tests (ultrasonic pulse velocity test and Schmidt hammer) were conducted, and the degree of polishing was evaluated. Correlation analyses were carried out to establish possible relationships among these parameters. The presence of chlorite, epidote, sericite, and recrystallized quartz indicated signs of low-grade metamorphism in andesites. The study revealed that feldspar, amphibole, and quartz imparted good physical and strength properties to samples MMA, CMA, FMA, AG1, and AG2. On the other hand, PMA-1 and PMA-2 exhibited reduced physical and strength properties due to the abundance of alteration products like chlorite, sericite, and epidote. The unconfined compressive strength exhibited a strong correlation with ultrasonic pulse velocity, skeletal density, porosity, and water absorption. Weathering grade considerably affected the values of ultrasonic pulse velocity and Schmidt hammer. Consequently, samples PMA-1 and PMA-2 are not recommended for load-bearing masonry units and outdoor applications due to their high water absorption and low strength values. On the other hand, samples FMA and MMA exhibited excellent properties like high strength and good polishing, indicating their potential use as decorative and facing stones, external pavement, ashlar, rubbles, and load-bearing masonry units.

Photovoltaic and thermoelectric properties of Ag2MnGeS4_Kesterite: First-principal investigations

The electro-optical and thermoelectric properties of the Ag2MnGeS4_Kesterite were investigated via the density functional theory DFT. N-type direct semiconductor in the Г point with a value of 1.44 eV was observed through the calculated bandgap structure. The N-type semiconductor was proved by the negative sign of the Seebeck coefficient. High absorption values of about 74 % and 66 % in the UV region and low values of about 20 % and 21 % in the visible range, were noticed for [100] and [001] directions, respectively. The optical bandgap energy was about 1.61 eV and 1.53 eV, following [100] and [001] directions, respectively. A large transmittance spectrum is presented by the studied semiconductor that collects the entire spectrum of sunlight, allowing this material to be a promising candidate for photovoltaic, as an absorber donor active layer, and for coating materials. Additionally, the thermoelectric results obtained in this study make Ag2MnGeS4_Kesterite a good material for direct temperature gradient-to-electricity conversion and electricity-to-temperature gradient conversion.