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Cement kiln dust accelerated carbonation in aqueous slurries at 25°C and 3 bar PCO2 was investigated by X-ray diffraction analysis, solution chemistry, scanning electron microscopy, and energy dispersive spectroscopy to better understand chemical and mineralogical processes governing CO2 uptake. Dissolution of lime, portlandite, and ettringite occurs primarily in the carbonation process. These provide Ca2+ ions to react with CO32− ions leading to calcite bulk precipitation from solution. Concomitantly, the dissolution of Ca-(Al)-silicate grains takes place but it is limited by the formation of a Si-rich and Ca-depleted rim which appears onto the grain surfaces due to an initial hydration step. The Si-rich decalcified rim hinders the diffusion of Ca2+ ions from the core of silicate grains to the bulk solution. The diffusion of Ca ions through the rim is then the rate limiting step for the carbonation of Ca-(Al)-silicate, that accounts for up to 4% of the carbonation potential. Achieved results elucidate the processes governing CO2 uptake by cement kiln dust, and are fundamental in the perspective of enhanced CO2 sequestration by cement kiln dust. © 2017 Society of Chemical Industry and John Wiley & Sons, Ltd.

This paper describes an e-learning platform developed in the context of the European Project CyTest (2014-1-IT01-KA202-002607), dedicated to Cytological Training at European Standard through Telepathology. The main, and novel, feature of our system is the deep integration between virtual microscopy and the training system: images are not simply there to be seen but they are active parts of testing, supporting quantitative measurement of image comprehension, for instance by evaluating the identification of relevant cellular structures by the position of markers put by the student on the image. The solution we developed offers a complete tool for easy creation and interactive access to questions related to images and fully integrates the components of virtual microscopy and teaching, based on state-of-the-art instruments for digital pathology images management, as OMERO, and for training course distribution, as Moodle. The system can be easily extended to support histopathological diagnosis. The software is distributed as Open Source and available on GitHub.

This paper presents an automatic alignment procedure for a four-source photometric stereo (PS) technique for reconstructing the depth map in the scanning electron microscope (SEM). PS, which is based on the so-called reflectance map, used several images of a surface to estimate the surface depth at each image point, in which the Lambertian reflectivity function is the simplest. In the SEM, the backscattered electron emission, which is one of the most important signals, is nearly Lambertian, and to simplify matters, SEM images are intrinsically grayscale maps. The possibility of having electron-PS at the SEM is assumed, taking advantage of one of the most exciting features of the technique, which returns true numerical 3-D models instead of some depth illusion from ordinary pictures.

Plants growing on polluted soils need to control the bioavailability of pollutants to reduce their toxicity. This study aims to reveal processes occurring at the soil-root interface of Pistacia lentiscus L. growing on the highly Zn-contaminated tailings of Campo Pisano mine (SW Sardinia, Italy), in order to shed light on possible mechanisms allowing for plant adaptation. The study combines conventional X-ray diffraction (XRD) and scanning electron microscopy (SEM) with advanced synchrotron-based techniques, micro-X-ray fluorescence mapping (μ-XRF) and X-ray absorption spectroscopy (XAS). Data analysis elucidates a mechanism used by P. lentiscus L. as response to high Zn concentration in soil. In particular, P. lentiscus roots take up Al, Si and Zn from the rhizosphere minerals in order to build biomineralizations that are part of survival strategy of the species, leading to formation of a Si-Al biomineralization coating the root epidermis. XAS analysis rules out Zn binding to organic molecules and indicates that Zn coordinates Si atoms stored in root epidermis leading to the precipitation of an amorphous Zn-silicate. These findings represent a step forward in understanding biological mechanisms and the resulting behaviour of minor and trace elements during plant-soil interaction and will have significant implications for development of phytoremediation techniques.

This paper presents failure modes observed in long-term aging of high-brightness GaN/InGaN LEDs. The blue LEDs submitted to DC aging test present large decrease of emitted optical power and increase of diode reverse leakage current. Increase of parasitic series resistance, suggesting contact degradation, has also been found in stressed sample, together with apparent carrier density increases and reduction of the junction depletion width. Furthermore stressed LEDs present modification of a specific trap property: trap activation energy decreases from 340 meV in the virgin sample down to 75 meV in the stressed sample. Generation of non-radiative recombination centers seems to be one of the dominant failure mechanisms responsible for the observed electrical and optical LED degradations.

In a general framework for exploiting the automation capabilities in modern SEM, two main branches has been investigated: the web-based remote microscopy [1] and the 3D metrology by Photometric Stereo (PS). Focusing on this second topic, in a previous paper [2] an Automatic Alignment Procedure for a 4-Source Photometric Stereo (PS) technique was presented for metrically reconstructing the third dimension in the Scanning Electron Microscope (SEM). The method, developed on a ESEM Quanta FEI-200 platform [3] equipped by standard ETH and solid state annular BSE detectors, has been completely automated, and made easily implemented on any standard equipped SEM.

This paper presents an experimental analysis of high brightness light emitting diodes (HBLEDs) performance and stability under dc and pulsed current bias. Three different families of HBLEDs from three leading manufacturers have been considered. The analysis was carried out by means of current-voltage, integrated optical power and electroluminescence measurements, and failure analysis. After an initial characterization of the electrical, optical and thermal behavior of the devices, a set of ageing tests was carried out, both under dc and pulsed bias conditions. Identified degradation modes were efficiency decrease, series resistance increase, leakage current increase, and modifications of the emitted spectrum. Characterization of devices behavior during stress indicated (i) generation of non-radiative components, (ii) degradation of the anode contacts and bonding wires, (iii) degradation of the phosphorous layer conversion efficiency and (iv) of the plastic package as possible responsible of the electrical and optical degradation of the LEDs. Comparison between dc and pulsed stress carried out using the same average current level and different duty cycle values showed that the use of pulsed bias can reduce the degradation rate with respect to dc bias. However, for duty cycles lower than 20 %, fast degradation and abrupt ruptures can take place, due to the high peak current levels.

This paper reports an analysis of InGaN/GaN LEDs degradation under dc and pulsed current conditions. The analysis was carried out by means of current-voltage and optical power measurements, scanning electron microscopy and EDS maps. Identified degradation modes were leakage and generation/recombination current increase, series resistance increase and output power decrease, related to the high temperatures reached by the devices during stress. Failure analysis revealed degradation of anode contacts and Ti-W reflector, which can be related to the measured series resistance increase. Comparison between dc and pulsed stress carried out with the same average current indicated that pulsed driving does not imply an acceleration in the degradation rate, except for the lowest duty cycles.

In this work, we report on the results of a reliability evaluation, in terms of electrical characteristics, stability and optical output power maintenance carried out on high brightness GaN/InGaN blue LEDs. Constant and pulsed bias where investigated over devices with and without heat sink in order to identify the influence of self-heating on the devices reliability. Several degradation modes have been identified such as increase of reverse and generation/recombination current, increase of the series resistance and decrease in the optical emitted power.

Extended abstract of a paper presented at Microscopy and Microanalysis 2008 in Albuquerque, New Mexico, USA, August 3 – August 7, 2008

Remote control of a scientific instrument is a topic gaining more and more attention between instrument users and operators. The project presented in this article reports results obtained from two distinct research efforts. The main outcome from the first research was the realization of an application to remote-control a Scanning Electron Microscope (SEM), while the main outcome from the second research was the implementation of a procedure to reconstruct 3D surfaces.