11 research outputs found
Disclosing mechanical and specific structural characteristics of thick and adherent nanodiamond composite hard coating deposited on WC−Co substrates.
Get PDFNanodiamond composite (NDC) films, with a notable hardness of 65 GPa and a substantial thickness of 10 µm, were successfully fabricated on unheated WC−Co substrates using cathodic arc plasma deposition (CAPD) technology. Raman and synchrotron-based structural analysis, comparing NDC films with similarly hard tetrahedral amorphous carbon (ta-C) films and chemical vapor deposition (CVD) diamond, unveiled distinctive features. Visible Raman spectroscopy highlighted NDC's unique nanostructured composition, characterized by nanodiamond grains embedded in an amorphous carbon matrix, resulting in a high fraction of C−C sp3 bonds (70%) and intense σ* C−C resonance contributing to its observed hardness. The small size of diamond crystals induced numerous grain boundaries, as evident through intense t-PA Raman peaks, effectively suppressing internal stress to 2.77 GPa and enabling the deposition of an impressive thickness (10 µm), surpassing the thinness of hard ta-C (< 1 µm). Despite the substantial thickness, NDC films demonstrated remarkable films-substrate adhesion, with no delamination and minimal spallation, in contrast to observed buckling and delamination in CVD diamond during Rockwell testing at various loads (60 Kg and 100 Kg). Additionally, NDC films maintained a stable and low coefficient of friction (≤ 0.1) against an Al2O3 counter-body, compared to the higher coefficient (≥ 0.25) of the bare WC-Co substrate. Furthermore, NDC deposition boasted a rapid rate (3.5 µm/hr), significantly exceeding both ta-C and diamond coatings, enhancing its practical applicability. Significantly, the deposition process for NDC films stands out for its environmental friendliness and cost-effectiveness, involving no external heating, chemical reactions, chemical etching of Co, or nanodiamond seeding. The findings underscore the exceptional potential of NDC as a strong competitor to hard ta-C and CVD diamond coatings, especially in advanced cutting tool applications
Investigating the physical and electrical properties of La2O3 via annealing of La(OH)3
No full textAbstract A simple technique was utilized to fabricate pure hexagonal La2O3 nanorods by utilizing lanthanum(III) nitrate hexahydrate (La(NO3)3·6H2O) and ammonia (NH4OH). The La2O3 nanoparticles were analyzed using XRD, TGA, Raman, SEM, FTIR, TEM, PL spectroscopy, and Mott–Schottky techniques. The XRD analysis confirmed the production of La(OH)3 nanorods under appropriate conditions, which were then successfully converted into La2O2CO3 and finally into La2O3 nanorods through annealing. The TGA analysis showed that the total weight loss was due to water evaporation and the dissolution of minimal moisture present in the environment. The FTIR analysis confirmed the presence of functional groups. The SEM analysis revealed changes in morphology. The TEM analysis to determine the particle size. The PL findings showed three emission peaks at 390, 520, and 698 nm due to interband transitions and defects in the samples. The Mott–Schottky analysis demonstrated that the flatband potential and acceptor density varied with annealing temperature, ranging from 1 to 1.2 V and 2 × 1018 to 1.4 × 1019 cm−3, respectively. Annealing at 1000 °C resulted in the lowest resistance to charge transfer (Rct)
Correlation between positron annihilation lifetime and photoluminescence measurements for calcined Hydroxyapatite
No full textAbstract Hydroxyapatite (HAp) Ca10(PO4)6(OH)2 is a compound that has stable chemical properties, composition, and an affinity for human bone. As a result, it can be used in odontology, cancer treatment, and orthopedic grafts to repair damaged bone. To produce calcined HAp at 600 °C with different pH values, a wet chemical precipitation method was employed. All synthesized HAp samples were characterized by X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier-transform infrared spectroscopy (FTIR), photoluminescence (PL), Zeta potential, and positron annihilation lifetime spectroscopy (PALS). The XRD results revealed that all calcined HAp samples were formed in a hexagonal structure with a preferred (002) orientation at different pH values. The crystal size of the samples was determined using the Scherrer equation, which ranged from 16 to 25 nm. The SEM and TEM results showed that the morphology of the samples varied from nanorods to nanospheres and rice-like structures depending on the pH value of the sample. The PL measurements indicated that the blue and green emission peaks of HAp were due to defects (bulk, surface, and interface) in the samples, which created additional energy levels within the band gap. According to Zeta potential measurements, the charge carrier changed from a positive to negative value, ranging from 3.94 mV to − 2.95 mV. PALS was used to understand the relationship between the defects and the photoluminescence (PL) properties of HAp. Our results suggest that HAp nanoparticles have excellent potential for developing non-toxic biomedical and optical devices for phototherapy
One step to fabricate vertical submicron ZnO rod arrays by hydrothermal method without seed layer for optoelectronic devices
No full textEco-friendly thick and wear-resistant nanodiamond composite hard coatings deposited on WC–Co substrates.
No full textNanodiamond composite (NDC) films, synthesized using an environmentally friendly PVD coaxial arc plasma deposition technique on commercial cemented carbide (Co6 wt%) substrates without the need for substrate heating, chemical etching of Co, and chemical gases. These NDC coatings, crafted under specific discharge power conditions (5.2 J/pulse, 120 V, and 1 Hz), with or without a substrate biasing (−100V, 40kHz, and 35% duty cycle), exhibit a distinctive nanostructure characterized by nanodiamond grains embedded in an amorphous carbon (a-C) matrix. Highlighting remarkable mechanical characteristics attributed to highly energetic ejected carbon ion. The coatings boast high hardness (H = 65–82 GPa), Young's modulus (E = 688–780 GPa), plasticity index (H/E = 0.094–0.105), and brittle fracture resistance (H3/E2 = 0.58–0.9 GPa). Additionally, these NDC films manifest a substantial thickness of 7 μm due to low internal stress, along with superior adhesion, anti-wear resistance, and a low friction coefficient (0.1–0.09) through dry sliding against an Al2O3 counterpart. Raman analysis substantiates the nanocomposite structure of the film, underscoring the influential role of biasing in enhancing the characteristics of these environmentally friendly and wear-resistant NDC coatings. Nevertheless, the application of a negative bias led to increased internal stress levels (1.28 to 4.53 GPa), adversely impacting the adhesion between the film and substrate, resulting in a decrease from HF3 to HF6 as per Rockwell C indentation. NDC coatings hold significant potential for extending the lifespan of cutting tools and improving overall machining performance
Enhancement of Structural, Optical and Photoelectrochemical Properties of n−Cu<sub>2</sub>O Thin Films with K Ions Doping toward Biosensor and Solar Cell Applications
No full textn-type Cu2O thin films were grown on conductive FTO substrates using a low-cost electrodeposition method. The doping of the n−Cu2O thin films with K ions was well identified using XRD, Raman, SEM, EDX, UV-vis, PL, photocurrent, Mott–Schottky, and EIS measurements. The results of the XRD show the creation of cubic Cu2O polycrystalline and monoclinic CuO, with the crystallite sizes ranging from 55 to 25.2 nm. The Raman analysis confirmed the presence of functional groups corresponding to the Cu2O and CuO in the fabricated samples. Moreover, the samples’ crystallinity and morphology change with the doping concentrations which was confirmed by SEM. The PL results show two characteristic emission peaks at 520 and 690 nm which are due to the interband transitions in the Cu2O as well as the oxygen vacancies in the CuO, respectively. Moreover, the PL strength was quenched at higher doping concentrations which reveals that the dopant K limits e−/h+ pairs recombination by trapped electrons and holes. The optical results show that the absorption edge is positioned between 425 and 460 nm. The computed Eg for the undoped and K−doped n−Cu2O was observed to be between 2.39 and 2.21 eV. The photocurrent measurements displayed that the grown thin films have the characteristic behavior of n-type semiconductors. Furthermore, the photocurrent is enhanced by raising the doped concentration, where the maximum value was achieved with 0.1 M of K ions. The Mott–Schottky measurements revealed that the flat band potential and donor density vary with a doping concentration from −0.87 to −0.71 V and 1.3 × 1017 to 3.2 × 1017 cm−3, respectively. EIS shows that the lowest resistivity to charge transfer (Rct) was attained at a 0.1 M concentration of K ions. The outcomes indicate that doping n−Cu2O thin films are an excellent candidate for biosensor and photovoltaic applications
Unveiling a 72.5 GPa peak hardness in sustainable nanodiamond composite hard coatings via discharge energy control: a nanoindentation-Raman approach.
Get PDFSustainable nanodiamond composite (NDC) films hold promise for high-performance hard coatings thanks to coaxial arc plasma deposition (CAPD). This eco-friendly technique eliminates the need for external heating, chemical reactions, or Co substrate pre-treatment. CAPD boasts lower energy consumption and faster deposition rates, making it a sustainable solution for the growing demand for high-quality, environmentally friendly coatings. This study investigates the influence of discharge energy on the nanostructure and mechanical properties of these NDC films. Optimal discharge energy, ranging from 2.3 to 12 J/pulse, was meticulously explored. A combined nanoindentation-Raman approach reveals a significant correlation between discharge energy and film properties. Remarkably, at 7 J/pulse, a peak hardness of 72.5 GPa is achieved, surpassing other energy levels. Raman spectroscopy confirms maximum nanodiamond content at this energy level (evidenced by maximized Adia/AG ratio, indicating a higher diamond-to-graphite ratio), along with minimal graphitization. Additionally, the presence of trans-polyacetylene (t-PA) peaks (denoted as At-PA) revealed the existence of maximum grain boundaries ratio (At-PA/AG), contributing to enhanced mechanical properties. Optimizing discharge energy tailors NDC film nanostructure, enhancing mechanical performance for advanced hard coatings
Impact of substrate type on the surface and properties of electrodeposited Cu2O nanostructure films as an absorber layer for solar cell applications
No full textNumerical simulation based performance enhancement approach for an inorganic BaZrS3/CuO heterojunction solar cell
No full textAbstract One of the main components of the worldwide transition to sustainable energy is solar cells, usually referred to as photovoltaics. By converting sunlight into power, they lessen their reliance on fossil fuels and the release of greenhouse gases. Because solar cells are decentralized, distributed energy systems may be developed, which increases the efficiency of the cells. Chalcogenide perovskites have drawn interest due to their potential in solar energy conversion since they provide distinctive optoelectronic characteristics and stability. But high temperatures and lengthy reaction periods make it difficult to synthesise and process them. Therefore, we present the inaugural numerical simulation using SCAPS-1D for emerging inorganic BaZrS3/CuO heterojunction solar cells. This study delves into the behaviour of diverse parameters in photovoltaic devices, encompassing efficiency (η) values, short-circuit current density (Jsc), fill factor (FF), and open-circuit voltage (Voc). Additionally, we thoroughly examine the impact of window and absorber layer thickness, carrier concentration, and bandgap on the fundamental characteristics of solar cells. Our findings showcase the attainment of the highest efficiency (η) values, reaching 27.3% for our modelled devices, accompanied by Jsc values of 40.5 mA/cm2, Voc value of 0.79 V, and FF value of 85.2. The efficiency (η) values are chiefly influenced by the combined effects of Voc, Jsc, and FF values. This optimal efficiency was achieved with CuO thickness, band gap, and carrier concentration set at 5 µm, 1.05 eV, and above 1019 cm−3, respectively. In comparison, the optimal parameters for BaZrS3 include a thickness of 1 µm, a carrier concentration below 1020 cm−3, and a band gap less than 1.6 eV. Therefore, in the near future, the present simulation will simultaneously provide up an entirely novel field for the less defective perovskite solar cell
Fabrication and characterization of flexible solar cell from electrodeposited Cu2O thin film on plastic substrate
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