New and fast route to black TiO2 based on hollow cathode H2 plasma

A. Godoy Jr; A. L. J. Pereira; M. C. Gome; R. S. Pessoa; D. M. G. Leite; G. Petraconi Filho; W. Miyakawa; A S. da Silva Sobrinho

arXiv · 1909.04623

New and fast route to black TiO2 based on hollow cathode H2 plasma

A. Godoy Jr·A. L. J. Pereira·M. C. Gome·R. S. Pessoa·D. M. G. Leite·G. Petraconi Filho·W. Miyakawa·A S. da Silva Sobrinho

View original source ↗Read source document ↗Export metadata ↓

Abstract

In this work, we demonstrate a new method to produce black TiO2 from pristine anatase TiO2 films. It consists on the immersion of TiO2 films in a hollow cathode H2 RF plasma for a few minutes, resulting in an efficient blackening of TiO2. In this study, the pristine anatase TiO2 films were grown by magnetron sputtering onto cover glass and c-Si substrates and then annealed at 450 °C for 2 h. Before and after the hollow cathode H2 plasma treatment, the samples were characterized by profilometry, UV-Vis spectrophotometry, X-ray diffraction, Raman spectroscopy, X-ray photoelectron spectroscopy, field emission scanning electron and atomic force microscopies, and four-point probe measurements. The results show that the obtained black TiO2 thin films have a significant light absorption on the whole solar spectrum, a very low sheet resistance, and also a relatively high surface area when compared to the pristine TiO2. All these characteristics lead to an important improvement on their photocatalytic activity, as measured by the degradation rate of methylene blue under UV irradiation.

Explore related subjects

physics.plasm-ph cond-mat.mtrl-sci physics.app-ph

Keep this discovery

Explore connections, maps & timelines

BibTeX RIS

A. Godoy Jr, A. L. J. Pereira, M. C. Gome, R. S. Pessoa, D. M. G. Leite, G. Petraconi Filho, W. Miyakawa, A S. da Silva Sobrinho. 2019-09-10. New and fast route to black TiO2 based on hollow cathode H2 plasma. https://arxiv.org/abs/1909.04623

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related papers

arXiv2026

Runaway electron interactions with whistler waves in tokamak plasmas: energy-dependent transport scaling

Resonant interactions between high energy runaway electrons (REs) and whistler waves are a promising mechanism for RE mitigation in tokamak plasmas. While prior studies have largely relied on quasi-linear diffusion models in simplified geometries, we present a first-principles-informed framework that models RE-whistler interactions in a 3D tokamak equilibrium. This is achieved by coupling AORSA, which computes whistler eigenmodes for a given tokamak plasma equilibrium, and KORC, a kinetic orbit code that tracks full orbit RE trajectories in prescribed wave fields. Our results demonstrate that REs undergo scattering to large pitch angles and exhibit anomalous diffusion in both pitch-angle and kinetic energy space. Crucially, we observe a transition between diffusive, sub-diffusive, and super-diffusive transport regimes as a function of initial RE energy - an effect not captured by existing quasi-linear models. This anomalous transport behavior represents a significant advancement in understanding RE dynamics in the presence of wave - particle interactions. By identifying the conditions under which anomalous diffusion arises, this work lays the theoretical foundation for designing targeted, wave-based mitigation strategies in future tokamak experiments.

physics.plasm-ph↗

arXiv2026

Geodesic Acoustic Modes in pair plasmas confined in tokamak magnetic fields

This paper is devoted to the derivation of the dispersion relation of the Geodesic Acoustic Mode in pair plasmas, i.e. assuming that ions and electrons have the same mass. Geodesic Acoustic Modes are plasma perturbations playing a crucial role in turbulence regulation, and therefore in the determination of the plasma confinement in tokamaks. Experiments with pair plasmas, like electron-positron plasmas, have been proposed with different kinds of confinements, and aim to study fundamental processes in plasma physics and understanding the formation of the early universe.

physics.plasm-ph↗

arXiv2026

Horizon-Aware Early Event Prediction for Tokamak Disruption Alarms

Reliable disruption prediction is essential for the safe operation of future tokamaks. Existing full-distribution survival methods model the complete residual time-to-disruption distribution, whereas operational decisions primarily depend on disruption risk within a finite prediction horizon. This mismatch motivates introducing Early Event Prediction (EEP) objectives into survival-based disruption prediction. We take Deep Survival Machines (DSM) as the full-distribution baseline and propose applying two established EEP methods to tokamak disruption prediction: Temporal Label Smoothing (TLS), which directly predicts disruption probability within a finite horizon, and survTLS, which additionally models the event-time distribution within that horizon. Using a common causal encoder, we compare these methods on DIII-D, Alcator C-Mod, and EAST. We distinguish threshold-free deadline ranking from validation-selected fixed-policy alarm performance and evaluate prediction horizons and encoder architectures. TLS achieves the best mean alarm performance on DIII-D and EAST, whereas all methods perform poorly on Alcator C-Mod. survTLS does not consistently outperform DSM, suggesting that directly learning horizon-level event probability is more effective than modeling detailed within-horizon event-time distributions in the present setting. Finally, the selected prediction horizons and encoder-ablation results vary across devices, reflecting differences in disruption characteristics.

physics.plasm-ph↗