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A newly discovered quenched form of carbon, widely known as Q-carbon, thin films are synthesized by the direct conversion of the amorphous carbon layer using the nanosecond pulsed laser annealing technique, and its corrosion-resistant properties, that is, potentiodynamic polarization (PDP) and electrochemical impedance spectroscopy technique, are investigated. The unique microstructure and the existence of defects (sp 2 content) in sp 3 -rich Q-carbon are highly desirable for efficient corrosion-resistant performance. The sp 3 percentage of the as-grown Q-carbon is measured to be ∼80.5% from the D and G peaks of the Raman and C-1S X-ray photoelectron spectrum. The anti-corrosion properties with inhibition durability of Q-carbon thin films are systematically investigated in various concentrations of Na 2 SO 4 solutions, and the corrosion potential, corrosion current, and corrosion rate of Q-carbon are determined to be -253 V, 30.1 × 10 -5 A/cm 2 , and 0.00528, respectively, for 1 M Na 2 SO 4 solution. Both series and contact resistance decrease from 5498.6 and 821.1 Ω to 698.8 and 124.3 Ω with an increase of Na 2 SO 4 concentration from 0.1 to 1 M, respectively. The small shift of PDP curves toward more negative potential, the shrinkage of the radius of semicircular arcs in the Nyquist plot ( Z″ vs Z' ), and negligible loss in corrosion resistance (∼78%) are observed for Q-carbon thin film at the immersion time up to 48 h. The unique sp 2 -sp 3 ratio, shorter bond length, compact atomic arrangement, and minimum porosity, along with the high adhesion strength, due to the ultrafast solid-liquid-solid growth route, of Q-carbon thin film on the substrate signify it as a better alternative compared to the existing corrosion-resistant materials.

In this report, we propose a novel technique for identifying and analyzing diverse nanoscale carbon allotropes using scanning electron micrographs. By precisely controlling the quenching rates of undercooled molten carbon through laser irradiation, we achieved the formation of microdiamonds, nanodiamonds, and Q-carbon films. However, standard laser irradiation without proper undercooling control leads to the formation of sparsely located diverse carbon polymorphs, hindering their discovery and classification through manual analyses. To address this challenge, we applied transfer-learning approaches using convolutional neural networks and computer vision techniques to achieve allotrope discovery even with sparse spatial presence. Our method achieved high accuracy rates of 92% for Q-carbon identification and 94% for distinguishing it from nanodiamonds. By leveraging scanning electron micrographs and precise undercooling control, our technique enables the efficient identification and characterization of nanoscale carbon structures. This research significantly contributes to the advancement of the field, providing automated tools for Q-materials and carbon polymorph identification. It opens up new opportunities for the further exploration of these materials in various applications.

Here, we aimed to achieve exposure of a nanodiamond layer to a high-energy excimer laser. The treatment was realized in high-vacuum conditions. The carbon, in the form of nanodiamonds (NDs), underwent high-temperature changes. The induced changes in carbon form were studied with Raman spectroscopy, X-ray photoelectron spectroscopy, and X-ray diffraction (XRD) and we searched for the Q-carbon phase in the prepared structure. Surface morphology changes were detected by atomic force microscopy (AFM) and scanning electron microscopy (SEM). NDs were exposed to different laser energy values, from 1600 to 3000 mJ cm -2 . Using the AFM and SEM methods, we found that the NDs layer was disrupted with increasing beam energy, to create a fibrous structure resembling Q-carbon fibers. Layered micro-/nano-spheres, representing the role of diamonds, were created at the junction of the fibers. A Q-carbon structure (fibers) consisting of 80% sp 3 hybridization was prepared by melting and quenching the nanodiamond film. Higher energy values of the laser beam (2000 and 3000 mJ cm -2 ), in addition to oxygen bonds, also induced carbide bonds characteristic of Q-carbon. Raman spectroscopy confirmed the presence of a diamond (sp 3 ) phase and a low-intensity graphitic (G) peak occurring in the Q-carbon form samples.

The main aim of this study was to describe the treatment of carbon sheet with a high-energy excimer laser. The excimer modification changed the surface chemistry and morphology of carbon. The appearance of specific carbon forms and modifications have been detected due to exposure to laser beam fluencies up to 8 J cm -2 . High fluence optics was used for dramatic changes in the carbon layer with the possibility of Q-carbon formation; a specific amorphous carbon phase was detected with Raman spectroscopy. The changes in morphology were determined with atomic force microscopy and confirmed with scanning electron microscopy, where the partial formation of the Q-carbon phase was detected. Energy dispersive spectroscopy (EDS) was applied for a detailed study of surface chemistry. The particular shift of functional groups induced on laser-treated areas was determined by X-ray photoelectron spectroscopy. For the first time, high-dose laser exposure successfully induced a specific amorphous carbon phase.

The versatility of the arrangement of C atoms with the formation of different allotropes and phases has led to the discovery of several new structures with unique properties. Carbon nanomaterials are currently very attractive nanomaterials due to their unique physical, chemical, and biological properties. One of these is the development of superconductivity, for example, in graphite intercalated superconductors, single-walled carbon nanotubes, B-doped diamond, etc. Not only various forms of carbon materials but also carbon-related materials have aroused extraordinary theoretical and experimental interest. Hybrid carbon materials are good candidates for high current densities at low applied electric fields due to their negative electron affinity. The right combination of two different nanostructures, CNF or carbon nanotubes and nanoparticles, has led to some very interesting sensors with applications in electrochemical biosensors, biomolecules, and pharmaceutical compounds. Carbon materials have a number of unique properties. In order to increase their potential application and applicability in different industries and under different conditions, they are often combined with other types of material (most often polymers or metals). The resulting composite materials have significantly improved properties.

Q-carbon is a densely packed metastable phase of carbon formed by ultrafast quenching of carbon melt in a super-undercooled state. After quenching, diamond tetrahedra are randomly packed with >80% packing efficiency. This discovery has opened a pathway to fabricate various interesting heterostructures following the highly nonequilibrium route of nanosecond pulsed laser annealing. In the present work, we demonstrate the evolution of Q-carbon/α-carbon and Q-carbon/diamond heterostructures with atomically sharp interfaces, controlled via varying solidification rates of the undercooled C melt. This structure consists of ultrahard Q-carbon (∼80% sp 3 and rest sp 2 ) with an overlayer of soft α-carbon (∼40% sp 3 ) on the inert c-Al 2 O 3 substrate. Using high-resolution scanning transmission electron microscopy and Raman spectroscopy analysis, we present the formation of the highly dense Q-carbon/α-carbon bilayer structure with distinctly different atomic and electronic structures. The laser-solid interaction simulations coupled with atomistic ab initio modeling further confirm the conversion of C melt into Q-carbon by achieving maximum undercooling near the substrate and further into α-carbon with a decrease in regrowth velocity (<6 m/s) away from the substrate. We present details of the evolution of heterointerfaces formed from carbon melt for designing heterostructures far from equilibrium for various functional applications by using pulsed laser processing.

We have achieved a superconducting transition temperature (T c ) of 55 K in 27 at% B-doped Q-carbon. This value represents a significant improvement over previously reported T c of 36 K in B-doped Q-carbon and is the highest T c for conventional BCS (Bardeen-Cooper-Schrieffer) superconductivity in bulk carbon-based materials. The B-doped Q-carbon exhibits type-II superconducting characteristics with H c2 (0) ∼ 10.4 T, consistent with the BCS formalism. The B-doped Q-carbon is formed by nanosecond laser melting of B/C multilayered films in a super undercooled state and subsequent quenching. It is determined that ∼67% of the total boron exists with carbon in a sp 3 hybridized state, which is responsible for the substantially enhanced T c . Through the study of the vibrational modes, we deduce that higher density of states near the Fermi level and moderate to strong electron-phonon coupling lead to a high T c of 55 K. With these results, we establish that heavy B doping in Q-carbon is the pathway for achieving high-temperature superconductivity.