Oxford Instruments plc is a United Kingdom manufacturing and research company that designs and manufactures tools and systems for industry and research. The company is headquartered in Abingdon, Oxfordshire, England, with sites in the United Kingdom, United States, Europe, and Asia. It is listed on the London Stock Exchange and is a constituent of the FTSE 250 Index.
Pitting potential (Ep) and stress corrosion cracking potential (ESCC) of super duplex stainless steel (SDSS) grade (UNS S32760) were determined using potentiodynamic polarization and slow strain rate test (SSRT) methods at 1300 C. SSRT tests were conducted at controlled applied potentials (EAPP) from + 0 to + 1200 mV (Ag/AgCl) in 15 and 1000 ppm chloride to determine the stress corrosion cracking (SCC) resistance response of SDSS material. Potentiodynamic polarization tests were also conducted at 130C in chloride concentration from 15, 100, 1000, 10,000 22,000 ppm, showed pitting resistance of SDSS material decrease with increase in chloride concentration. SSRT results indicate that isolated microcracks initiate at applied potentials below 500 mV, with crack coalescence occurring near ESCC ( 500 mV) and rapid degradation dominated by localized galvanic and pitting corrosion at higher potentials. Microstructural characterization using SEM and EBSD revealed that damage below Ep and ESCC is associated with short cracks and selective phase attack, whereas at potentials exceeding Ep by 200 mV, pit–crack interactions become dominant. Grain size distribution, phase morphology, and phase continuity particularly along the rolling direction were found to influence pit growth and crack propagation.
Accurate identification and classification of a material based on energy dispersive spectrometry (EDS) has always been a challenge, down to the variability between systems, acquisition conditions, spectrum processing methods and accuracy in quantitative analysis results. Traditional methods rely on template spectra from known chemical compositions to match against an unknown spectrum. The spectrum matching algorithm assumes that template spectra are acquired with the same system and under the same conditions, which poses difficulties and in some cases is impossible. In this paper, a different approach is proposed based on quantitative analysis results as the basis for matching. Quantification-based matching removes the ambiguity introduced by different systems and acquisition conditions. Databases can be created based on the nominal composition of compounds without acquiring a spectrum from known samples. This paper explains the details of the matching algorithm and presents three examples to demonstrate the performance.
Force distance curves (FCs) are direct probes of tip sample interactions in atomic force microscopy, but their dynamic content is often suppressed by filtering, averaging and quasistatic analysis. Indeed, in the forty years since the invention of the AFM, this hidden dynamic signal has been largely ignored, with exceptions restricted to the large oscillations associated with relatively large adhesive separations (snap from contact) or to time averaged approaches that carry their own challenges. Using high bandwidth interferometric detection, we directly measure fast FCs, including short lived cantilever oscillations during snap in, contact and pull off. Two excitation mechanisms coexist: thermal fluctuations and transients generated by rapid changes in the tip sample boundary condition. Cycle resolved frequency and amplitude estimators provide time local observables of the evolving cantilever and sample system within single FCs, creating a pixel by pixel mechanical contrast channel that requires no external broadband excitation, resonant tracking or multi pass imaging. A state dependent harmonic oscillator model incorporating van der Waals attraction, hysteretic capillary bridge formation and rupture, hydration mediated damping and repulsive contact stiffness partitions each FC into five interaction regimes and reproduces the observed responses. In repulsive contact, frequency shifts yield stiffness maps consistent with contact-mechanics estimates, enabling high throughput stiffness mapping and localization of transient tip sample events from individual pixels. More broadly, this hitherto hidden signal may pave the way for new ways of studying and exploiting Brownian motion in a variety of systems, providing the capability to follow time resolved (non) Markovian and (non) ergodic dynamics mediated by the tip sample interaction, including single event dynamics.
Contact-resonance atomic force microscopy (CR-AFM) provides nanoscale maps of contact stiffness, dissipation, and electromechanical response, but conventional piezoacoustic excitation can obscure the cantilever resonance with actuator and sample-holder modes. Pure Brownian excitation avoids this transfer-function background, yet its small amplitude generally requires averaging that is incompatible with routine imaging. We introduce interferometric dual-AC resonance tracking (iDART), which combines quadrature-phase differential interferometry with two-frequency resonance tracking. By positioning the interferometric spot near the displacement maximum of the first contact-resonance mode, the detector noise floor is reduced below the off-resonance thermal displacement of the cantilever. Brownian spectra identify the contact mode and define the tracking frequencies, while active electrical excitation provides the signal-to-noise ratio required for pixel-resolved imaging. Simultaneous low-frequency and resonant measurements show that both electrical and photothermal drive increases contrast in the amplitude and phase channels without appreciably shifting the contact resonance. These results establish a practical route to resonance-enhanced, drive free nanomechanical imaging at conventional AFM scan rates.
Nanoscale microstructure has a significant impact on the properties of materials, defining the high-temperature mechanical properties of metal alloys for aerospace and automotive applications. Quantifying the three-dimensional composition of a material across interfaces within such microstructure is therefore essential. Here, we report three-dimensional (3D) nanoscale composition quantification across interfaces in an Mg-Al-Ca alloy using scanning transmission electron microscopy-based X-ray energy dispersive spectroscopy. We use this demonstration to evaluate two 3D quantification approaches: (1) absolute quantification employing experimentally calibrated ionization cross-sections and compressed sensing tomography based on second order total variation regularisation and (2) relative quantification based on physical parameters extracted from the MC X-ray programme and tomography using the simultaneous iterative reconstruction technique (SIRT). X-ray absorption and shadowing corrections were integrated with both reconstruction methods. The results offer a methodological demonstration of absorption correction with absolute quantification as well as insight into the differences in absorption correction for CS-TV2 and SIRT. In turn, these findings reveal composition changes immediately at the interfaces between the α-Mg matrix and the intermetallic skeleton microstructure characteristic of Mg-Al-Ca alloys. These advances in microscopy methodology to probe 3D compositional fluctuations at buried interfaces establish a route for quantitative analysis of alloys and materials with surface oxides as well as samples containing several elements with overlapping X-ray absorption edges.
