Band 116, Heft 2

Al matrix composites are the most promising candidate for light-weight components in the aerospace and automotive industries. Graphene has numerous applications across various fields due to its exceptional mechanical, electrical, and thermal properties. The incorporation of graphene into aluminium (Al) matrix composites shows significantly improved mechanical and physical properties compared with pure Al. This review article summarizes the properties and applications of graphene in various areas. This article covers the processing route and effect of different fractions of graphene in aluminium matrix. Moreover, the article evaluates the advancement in mechanical and microstructural properties in Al/graphene composites with various fractions of graphene content.

Upconversion luminescence materials hold significant promise for various applications, including lasers, solar cells, anti-counterfeiting technology, biological labeling, and sensor technology. GdPO 4 stands out as a highly promising upconversion host material thanks to its exceptional chemical and thermal stability. While the upconversion luminescence properties of Er 3+ and Yb 3+ co-doped materials are indeed influenced by the crystal environment of rare earth ions within the matrix, the fundamental understanding of how pH and the high concentration of Yb 3+ can ultimately affect these luminescence properties is still lacking. In this paper, we synthesized a series of GdPO 4 :Er 3+ , Yb 3+ upconversion phosphors by a hydrothermal process followed by heat treatments at 900 °C for 2 h. The results of X-ray diffraction and scanning electron microscopy indicate that pH of the initial solution and doping concentration of Yb 3+ can indeed affect crystal growth of samples. Spectroscopic studies reveal that the structure, size and morphology can influence the properties of upconversion emission in GdPO 4 :Er 3+ , Yb 3+ by affecting the local environment of rare earth ions, the surface of sample and the relaxation processes in the samples. The color coordinates calculation illustrates that these implications can ultimately alter the emission color of the samples. This research enhances our comprehension of the role played by the pH of initial solution and the concentration of Yb 3+ ions in the synthesis of Er 3+ , Yb 3+ ions co-doped upconversion materials, specifically in fine-tuning the emission color for the final upconversion materials.

Graphene has gained tremendous attention in the field of photonics and electronics because of its numerous outstanding properties including zero bandgap, exceptionally high crystal and electronic quality, high mechanical strength, and electrical conductivity. At the cutting edge of technology, graphene oxide–molybdenum disulphide hybrid structures have drawn tremendous attention for the development of high efficiency infrared (IR) detectors, where MoS 2 film is used for generation of photoelectrons, and reduced graphene oxide is used to enhance the carrier mobility. The production of graphene oxide (GO) in this work is done using a modified version of Hummer’s process, in which GO is thermally reduced for an hour at 350 °C to produce reduced graphene oxide (rGO). The appearance of X-ray diffraction peak, corresponding to (001) and (002) for GO and rGO, respectively confirms the crystalline nature of the materials. The Raman spectra of GO and rGO exhibit distinctive peaks located at 1,358 cm −1 and 1,597 cm −1 , which correspond to the D bands and G bands, respectively. The layered structure of rGO is examined by scanning electron microscopy. On the other hand, MoS 2 film was grown by the sulphonation of sputtered Mo film on silicon substrate. The characteristic peak of MoS 2 , corresponding to (002) plane, is observed around 2 θ = 14.1° whereas Raman characteristic bands are observed at 386 cm −1 (E 1 2g ) and 408 cm −1 (A 1g ). Afterwards, rGO layer was deposited on MoS 2 thin film. The highest current On/Off ratio of 45.8 was found under illumination of 1,060 nm IR source. Under illumination at a 1,060 nm IR wavelength, the device demonstrates a responsivity of 0.21 A W −1 and detectivity of 1.83 × 10 9  Jones.

Carbon dots are regarded as a brand new class of nanostructures in the carbonaceous family that have piqued the curiosity of researchers in a wide range of bio applications. This work focuses on the synthesis and characterization of carbon dots, as well as their latent fingerprint detection and antibacterial/antifungal capabilities. Highly luminous carbon dots were prepared by optimizing simple hydrothermal carbonization settings at 180 °C for 12 h using lemon juice as a raw precursor. The resulting product was examined using Fourier transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray analysis, X-ray diffractometery, and ultraviolet–visible spectrophotometer. The as-prepared carbon dots were found to be extremely bright when excited under ultraviolet light ( λ = 365 nm). The presence of carbon and oxygen functionalities on the surface of the carbon dots was revealed by infrared spectrocopy. The diffraction pattern confirmed the amorphous structure of the carbon dots, with an average size of 7 nm determined using the Scherrer equation. The surface morphology analysis revealed that the carbon dots exhibited an aggregated form with irregular spherical shapes. The chemical structure examination validated the elemental makeup of the prepared lemon juice-based carbon dots. The detection of latent fingerprints on carbon dots under ultraviolet light yielded positive results. In addition, the obtained carbon dots displayed antifungal and antibacterial activity against tested pathogenic fungal and bacterial strains.

Bright blue cobalt aluminate powders were prepared using ultrasonic-assisted co-precipitation and hydrothermal methods. In addition, triethylamine (TEA), butyrolactam (BL), and n-cetyl-n,n,n-trimethylammonium bromide (CTAB) surfactants were used during synthesis to enhance the sample characteristics. The prepared compounds were compared based on their photocatalytic characteristics and the degradation of Congo Red (CR). From X-ray diffraction, the synthesised compounds were identified as CoAl 2 O 4 with a spinel structure. Scanning electron microscopy revealed that polygonal particles were obtained in the ultrasonic-assisted co-precipitation method whereas rounded particles were obtained in the ultrasonic-assisted hydrothermal method. The most homogeneous morphology was seen in the co-precipitation sample using TEA, and the smallest particles were observed in the hydrothermal samples using BL. The highest CR removal was achieved in the co-precipitation and hydrothermal samples prepared using TEA, with 46.15 % and 39 % removal, respectively. The determination of the optimal experimental parameters was effective in enhancing the photocatalytic properties of spinel CoAl 2 O 4 .

The dissolution of a nickel nanoparticle in aluminium under the conditions of the crystalline and amorphous state of aluminium and nickel, which can be achieved, in particular, with severe plastic deformation of the powders of the initial mixture (mechanoactivation), was studied by means of molecular dynamics. It is shown that the state of the aluminium structure (crystalline or amorphous) has a relatively small effect on the intensity of mutual diffusion of Ni and Al up to the melting temperature of aluminium. This is due to the formation of a crystalline aluminium layer around the crystalline particle, which repeats the Ni lattice. In the case of the amorphous state of the nickel particle and the aluminium matrix, dissolution occurred much faster than in the crystalline state of nickel. That is, mutual diffusion occurs significantly more strongly in the case of the amorphous state of nickel compared to the case of amorphous aluminium at the same constant temperature. The diameter of the nickel nanoparticle in the considered range from 4 to 12 nm did not affect the temperature at which the mutual diffusion of Ni and Al sharply accelerated with varying temperature. This was due to the fact that the melting point of aluminium did not change when simulating particles of different sizes.

With two different Zr content Ti–Zr microalloyed low-carbon steels, isothermal relaxation tests at 875–950 °C were conducted using a Gleeble-3500 thermal simulation testing machine. Based on the Avrami equation, the thermodynamic and kinetic model for the precipitation of Ti ( k 1 + m 1 ) Zr ( k 2 + m 2 ) C ( k 1 + k 2 ) N ( m 1 + m 2 ) ${\text{Ti}}_{\left({k}_{1}+{m}_{1}\right)}{\text{Zr}}_{\left({k}_{2}+{m}_{2}\right)}{\mathrm{C}}_{\left({k}_{1}+{k}_{2}\right)}{\mathrm{N}}_{\left({m}_{1}+{m}_{2}\right)}$ in austenite was established. The results indicate that the microalloyed elements in Ti–Zr microalloyed low-carbon steel will form composite precipitates through replacement and heterogeneous mechanisms, and nucleate and precipitate at grain boundaries and dislocations in the form of (Ti, Zr) (C, N). For the nucleation and precipitation of carbonitrides at dislocations in 0.035Zr steel and 0.091Zr steel, their nucleation rate–temperature curves (NrT) and Precipitation–time–temperature (PTT) curves intersect at a certain point. The increase in Zr content suppresses the precipitation of carbonitrides from austenite, reducing the strain-induced precipitation in Ti–Zr microalloyed low-carbon steel during rolling process.

The microstructures and martensitic transformation of a Ti-rich Ti 50.5 Ni 33.5 Cu 11.5 Pd 4.5 alloy aged at 500 °C for durations ranging from 15 min to 25 h were systematically investigated. With increasing aging time, the precipitates exhibit continuous growth; however, their quantity initially increases and subsequently decreases. The morphology of the precipitates evolves from granular to lamellar forms. Post-aging treatment, the transformation sequence transitions from a one-stage (B2–B19) to a two-stage process (B2 1 –B19 1 and B2 2 –B19 2 ) due to the precipitation of Ti 2 Cu-type particles, maintaining near-zero hysteresis. The two-stage martensitic transformation originates from the combined effects of stress distribution heterogeneities and variations in Ni content induced by aging precipitation.

This study’s main goal is to investigate how the properties of pure copper are impacted by the addition of silicon carbide–graphite reinforcement. Here in this research a powder metallurgy procedure is used to make copper matrix composites with different amounts of silicon carbide–graphite reinforcement (2 %, 5 %, 8 %, and 10 %) by weight. The microstructure, phases present, wear analysis, and X-ray diffraction analysis were all thoroughly examined, while scanning electron microscopy was used for imaging the microstructure of materials. The absence of any intermediate phases between the reinforcing materials and the copper matrix, according to X-ray diffraction data, suggests a strong interfacial interaction between them. A microstructural analysis of the copper matrix indicated a consistent dispersion of silicon carbide–graphite. The amount of reinforcement employed was found to have an impact on the wear characteristics of these copper matrix composites. Notably, the softness of graphite caused the hardness to drop when it was added. The 5 % reinforcement composite material outperformed the other evaluated composite materials in terms of wear rate, which was calculated in term of specific wear rate by using a pin-on-disc testing machine. This implies that this specific composite could be useful for tribological applications.