In this study, we systematically investigated the influence of residual water on the oxidation of titanium in an oxygen-free atmosphere at ambient pressure created using silane-doped argon. The study addresses a limitation of oxygen-free production: although molecular oxygen can be effectively scavenged by silane, residual moisture remains in the atmosphere and may act as an additional oxidising species for highly reactive metals. High-purity titanium samples (99.995%) were exposed for 10 min to oxygen-free atmospheres with controlled water concentrations ranging from 0.1 to 1.0 ppm. X-ray photoelectron spectroscopy (XPS) was used to analyse the resulting changes in the titanium chemical states and to determine the corresponding oxide thickness. In laboratory-scale reaction-chamber experiments, reducing the water concentration from 0.8 ppm to 0.2 ppm reduced the oxide thickness from 0.38 ± 0.09 nm to 0.12 ± 0.09 nm. In a glove box operated under comparable oxygen-free conditions, reducing the water concentration from 1.0 ppm to 0.1 ppm reduced the oxide thickness from 0.61 ± 0.09 nm to 0.23 ± 0.12 nm, corresponding to a reduction of approximately 62%. These results demonstrate that residual water causes measurable oxidation of titanium even after molecular oxygen has been removed and that moisture concentration is therefore an important process parameter for oxygen-free production. The findings show that further optimisation of oxygen-free atmospheres for highly reactive metals requires not only efficient oxygen scavenging but also stringent control of residual moisture.
The thickness of two-dimensional (2D) materials in atomic force microscopy (AFM) images is most commonly determined using single height profiles or the histogram method. A major limitation of these approaches is that the background topography and thickness are treated as independent quantities and estimated sequentially, causing errors in the background estimation to propagate into the calculated thickness. Here, we investigate a polynomial step-function fitting (PSFF) method that simultaneously performs background correction and thickness determination. In this approach, each terrace in an AFM image is represented as the sum of its thickness and a polynomial background. The polynomial, whose order can be selected according to the image characteristics, compensates for real surface features, including sample tilt, curvature, and other smooth, low-order variations, as well as instrumental image distortions such as scanner bow. Consequently, the fitting procedure simultaneously yields the thickness of all terraces and a leveled (flattened) AFM image by subtracting the fitted polynomial background from the raw AFM data. Using mechanically exfoliated graphene and chemical-vapor-deposition-grown molybdenum disulfide samples, we demonstrate thickness determination from both one-dimensional (1D) height profiles (1D PSFF) and two-dimensional (2D) AFM images (2D PSFF). We further demonstrate the advantages of 2D over 1D fitting for accurate thickness determination, compare the performance of PSFF with the histogram method while identifying the conditions under which the histogram method provides reliable results, and discuss the applicability of PSFF for accurate thickness determination and reliable layer counting of 2D materials.
Photocatalytic nitrate reduction is limited not simply by photon absorption, but by whether the reaction interface can store electrons, polarize nitrate, and sustain proton-coupled N-O bond cleavage against competing oxygen reduction. To address this limitation, a recoverable photovoltage-gated membrane microreactor is constructed from a cesium tungsten bronze/silver vanadate heterojunction confined in a polyacrylonitrile nanofiber scaffold and gated by a thin polyaniline interphase. The membrane preserves a surface-accessible oxide junction while creating a hydrated, near-neutral, anion-permissive reaction microenvironment. Multiscale photophysical measurements show that polyaniline converts the oxide/polymer boundary into an electron-buffering interface, thereby lowering charge-transfer resistance, amplifying the surface photovoltage, increasing the extracted photocurrent, and extending photoinduced-state persistence in complementary nanosecond TRPL/TAS and microsecond TRMC measurements. Under visible light, the optimized membrane reduces 20.0 mg L-1 NO3−-N by 97.8% within 180 min, reaching 0.44 mg L-1 residual NO3−-N and an apparent rate constant of 0.0198 min-1, while real-water tests retain 88.6% removal. Product-resolved 15N analysis directly identifies N2 as the dominant nitrogen product (79.6% selectivity), with minor N2O formation (2.7%) and nitrate-derived NH4+ (15.7%), while the combined gas/liquid inventory closes the endpoint nitrogen balance to approximately 100%. In situ Raman and photochromic spectroscopy track surface nitrate consumption, formation of the NOX intermediate, and reversible W5+ electron storage during the reaction. DFT predicts a multi-contact W/Ag/PANI nitrate-binding motif that is consistent with the experimentally observed surface-bound nitrate conversion and interfacial electron enrichment, and further indicates charge transfer to adsorbed nitrate, N-O bond elongation, weaker O2 competition, and a lower thermodynamic free-energy requirement for the NO → NOH step. These results demonstrate interfacial photovoltage gating within the present membrane architecture and define a testable design framework for evaluating electron-directed nitrate-conversion interfaces in other material systems.
The widespread application of copper additive manufacturing (AM) via laser is hindered by complex interactions between powder properties and energy sources. The optical response of copper powder is strongly influenced by its surface condition, making surface modification a promising approach to tailoring its laser absorptance. In this study, low-temperature oxidation in the range of100–200°C was employed to modify the powder surface and enhance laser absorptance. This work establishes the relationship between powder absorptance and oxidation behaviour of copper. The pre-oxidation treatment formed a thin cuprous oxide layer on the copper particle surfaces.Phase and surface morphology analyses were performed to clarify the oxidation behaviour of copper powder in the low-temperature range. After pre-oxidation at 150 °C for 300 min, the reflectivity at 1068 nm decreased from 53.1% for the as-received powder to 29.7%, while. the equivalent oxide layer thickness was estimated to be 343 nm based on UV–NIR spectroscopy and an optical oxide-layer model. . This study provides a promising route for controlling the oxidation state of copper powder to tailor its optical response, with potential applications for laser based additive manufacturing of copper.
For nearly a century, coating adhesion has been framed as a chemistry problem. This perspective assembles quantitative evidence showing this framing is largely wrong for metal-plated plastics: mechanical interlocking contributes an overwhelming nine-tenths of total adhesion strength, while chemistry mainly enables wetting and continuous coating formation. Although chemical adhesion indeed scales with true interfacial area, it is far too weak to provide the adhesion levels demanded by practical applications. Consequently, the field’s routine fixation on surface free energy and superhydrophilic water contact angles is often a distraction largely irrelevant to ultimate adhesion. The route to stronger adhesion is different – engineering interfacial geometry can double or even triple the coating quality beyond industrial benchmarks. The dominance of mechanical interlocking is generalizable across metal-plated systems and demand a shift from chemistry-first narratives to mechanics-first design.
