High-resolution monitoring of water temperature and oxygen concentration in Lake Murten (Switzerland)

Lake Murten is located in the Lake District in western Switzerland and so far, it has been poorly investigated. The Environmental Service of Fribourg (SEn) has monitored this lake once a month for several years by water profiles (water temperature, pH, dissolved oxygen, conductivity) at its deepest part. The SEn identified the stratification of water masses as one of the main causes for oxygen consumption in the hypolimnion. In the present study, a Lander System was deployed in Lake Murten from April to September 2015 at 20 m depth at the northwestern part of the lake to monitor water temperature and dissolved oxygen at higher resolution (30 s interval). These records were compared with time series of atmospheric parameters like atmospheric temperature, wind speed and precipitation. A clear correlation of lake temperatures with wind speed was observed during the Spring and Autumn. The water mass stratification evolved through the season and reached its peak during Summer, preventing surface turbulences to reach the deeper part (20 m) of the water column and to partially oxygenate the metalimnion

Ba_0.5Sr_0.5Co_0.8Fe_0.2O_{3−<em>δ</em>} (BSCF) feedstock development and optimization for thermoplastic forming of thin planar and tubular oxygen separation membranes

This paper presents the processing steps for producing thin planar and tubular oxygen separation membranes by thermoplastic forming of Ba0.5Sr0.5Co0.8Fe0.2O3−δ (BSCF) with polystyrene (PS) and stearic acid (SA) as binder. The influence of powder content on the shape stability of thin membranes (tubular and planar structures) during the thermoplastic processing route was investigated. The effect of powder content on mixing torque and the rheological behavior were investigated. The effect of the powder content could be analytically described using the model proposed by Frankel and Acrivos. The deformation of free standing green bodies was investigated using disks. The result showed that increasing the powder content is remarkably effective to minimize the deformation of the membrane during the thermal debinding step. By using a high powder content (60 vol. %) and a multicomponent binder system composed of PS, SA and paraffin wax (PW), it was possible to achieve disks and thin wall tubular structures without deformation after sintering. Using capillary rheometer an unexpected decrease in the total extrusion pressure was measured for the feedstock containing PW. The change in apparent activation energy between 800–1000 °C was not related to the membrane properties

Efficient and stable inorganic perovskite solar cells manufactured by pulsed flash infrared annealing

Organic–inorganic perovskite solar cells have achieved impressive power conversion efficiency over the past years, yet operational stability remains the key concern. One strategy to improve long‐term stability is to replace the thermally unstable organic with inorganic cations comprising the perovskite lattice. Here, for the first time, pulsed infrared light is used to drive the crystallization of inorganic mixed halide CsPbIxBr(3−x) perovskite films in solar cells with a power conversion efficiency exceeding 10%. By varying the iodide–bromine ratio systematically, it is found that to keep the inorganic perovskite black phase stable at the room temperature, the iodine content needs to be limited to lower than 60% – bromine content higher than 40%. The finding revises previous reports claiming stable compositions with higher iodine contents, which is systematically exploited to reduce the perovskite bandgap with the aim to enlarge the light absorption spectra and thus to boost the device efficiency. It is demonstrated that the newly defined stable compositional range enables devices that retain 90% of the efficiency after stressing the perovskite at 200 °C for 1 h. This result demonstrates that inorganic halide perovskites are stable materials for high‐ temperature applications such as concentrated photovoltaics

A model based two-stage classifier for airborne particles analyzed with Computer Controlled Scanning Electron Microscopy

Computer controlled scanning electron microscopy (CCSEM) is a widely-used method for single airborne particle analysis. It produces extensive chemical and morphological data sets, whose processing and interpretation can be very time consuming. We propose an automated two-stage particle classification procedure based on elemental compositions of individual particles. A rule-based classifier is applied in the first stage to form the main classes consisting of particles containing the same elements. Only elements with concentrations above a threshold of 5 wt% are considered. In the second stage, data of each main class are isometrically log-ratio transformed and then clustered into subclasses, using a robust, model-based method. Single particles which are too far away from any more densely populated region are excluded during training, preventing these particles from distorting the definition of the sufficiently populated subclasses. The classifier was trained with over 55,000 single particles from 83 samples of manifold environments, resulting in 227 main classes and 465 subclasses in total. All these classes are checked manually by inspecting the ternary plot matrix of each main class. Regardless of the size of training data, some particles might belong to still undefined classes. Therefore, a classifier was chosen which can declare particles as unknown when they are too far away from all classes defined during training

Temperature evolution inside a pot during experimental surface (bonfire) firing

Time–temperature evolutions of different parts inside a pot were recorded during three experimental surface (bonfire) firings. The experimental vessels were shaped from a calcareous clay, tempered with 30% vol. of oolithic limestone. The temperature–time recording showed: (1) Tmax. was reached after 12–22 min and differed between the firings as well as inside individual vessels; (2) the range of the thermal variation within one single firing was found to be as high as 390 °C, and up to 220 °C on a specific cross-section; (3) the lowest temperature was not systematically recorded in the core of the object, as is generally expected. Under the polarizing microscope, no textural and mineralogical changes were observed in the ceramic bodies. This is sustained by powder X-ray diffraction analyses evidencing no dolomite or calcite breakdown. The presence or absence of specific illite and chlorite peaks can be generally related to Tmax. and soaking time, but equivalent firing temperature estimations do not match the measured temperatures

Scanning electron microscope images of uncoated microfossils: applications, perspectives and limitations

We present a recently developed method using a field emission scanning electron microscope (FEG) to view and photograph microfossil specimens that are not coated by conductive material. The FEG microscope provides high electron flux and offers the option to capture images at low beam voltage. Balancing incident energy with absorbed energy from the detector leads to charge-free images of non-conductive material. As an example of the application, we show images of planktonic foraminifers and ostracods obtained with this method and compare them with those obtained on the same specimens after gold coating. The method is particularly useful for illustrating holotypes, neotypes and topotypes of microfossils when an environmental scanning electron microscope is not available

Antimonate opaque glaze colours from the faience manufacture of Le Bois d'Épense (19th century, Northeastern France)*

Three types of antimony-based, opaque ceramic colours were used in the faience workshop of Le Bois d'Épense during the first decades of the 19th century; that is, yellow, tawny and green. Yellow is generated by lead antimonate crystals (Naples Yellow), which are incorporated into an uncoloured glass matrix. According to SEM–EDS measurements, these pigments contain iron. The tawny colour is the optical result of the combined presence of similar yellow, iron-bearing lead antimonate particles in a Fe-rich, brownish glass matrix. The green opaque colour is produced by the combination of a blue cobalt glass and yellow Pb–Sn–Fe-antimonate crystals. Cores of zoned pigments lighten the recipes, according to which the pigments were produced. First, they were synthesized by calcination, ground and then mixed with a colourless, brown or blue glass powder. The resulting powder mixture was added to a liquid agent and used as high-temperature ceramic colour

Nanowire formation by gold nano-fragment coalescence on quantized vortices in He II

We demonstrate that laser ablation of a gold target immersed in superfluid and normal fluid helium leads to the formation of elongated gold nano-fragments. In the superfluid phase these nano-fragments aggregate into filaments with extremely large aspect ratios displaying metallic electric conductivity. We attribute this unusual structure to the coalescence of gold particles trapped on quantized vortices. Our observations suggest new ways to visualize the structure of quantized vortex bundles and a new approach for producing centimeter-long metal nanowires

Contrasting recipes for the kiln furnitures of the faience manufacture Granges-le-Bourg (Haute Saône, France)

Thirty-nine samples of kiln furniture or technical ceramic (firing plate, saggars, spacers, props, wads) and six samples of building ceramics (bricks, tiles) from the manufacture of Granges-le-Bourg were studied by optical microscopy, X-ray fluorescence, X-ray diffraction and scanning electron microscopy. The kiln furniture is chemically inhomogeneous and belong to a CaO- + MgO-poor (firing plate, saggars) or a CaO- + MgO-rich (props, spacers, wads) group. Bricks and tiles pertain to the first group which was manufactured using decarbonatized top layers of local Triassic dolomitic marls. For the second group, the deeper layers were used. Plate and saggars are covered with a tin oxide opacified glassy coating with no significant reaction zone to the body

Contrasting recipes for the kiln furnitures of the faience manufacture Granges-le-Bourg (Haute Saône, France)

Thirty-nine samples of kiln furniture or technical ceramic (firing plate, saggars, spacers, props, wads) and six samples of building ceramics (bricks, tiles) from the manufacture of Granges-le-Bourg were studied by optical microscopy, X-ray fluorescence, X-ray diffraction and scanning electron microscopy. The kiln furniture is chemically inhomogeneous and belong to a CaO- + MgO-poor (firing plate, saggars) or a CaO- + MgO-rich (props, spacers, wads) group. Bricks and tiles pertain to the first group which was manufactured using decarbonatized top layers of local Triassic dolomitic marls. For the second group, the deeper layers were used. Plate and saggars are covered with a tin oxide opacified glassy coating with no significant reaction zone to the body