Mechanochemical synthesis of nanocrystalline lead selenide

Mechanochemical synthesis of lead selenide PbSe nanoparticles has been performed by high-energy milling of lead and selenium powder in a planetary ball mill Pulverisette 6 (Fritsch, Germany) and in an industrial eccentric vibratory mill ESM 654 (Siebtechnik GmbH, Germany). Structural properties of the synthesized lead selenide were characterized by X-ray diffraction, which confirms crystalline nature of PbSe nanoparticles (JCPDS 6-354). The average size of PbSe crystallites of 37 nm was calculated from XRD data by Williamson-Hall method. The methods of particle size distribution analysis, specific surface area measurement, scanning electron microscopy and transmission electron microscopy were used for characterization of surface, mean particle size, and morphology of PbSe. An application of industrial mill verified a possibility of the synthesis of a narrowband-gap semiconductor PbSe at ambient temperature and in a relatively short reaction time

Industrial control measurements of high chromium steel rolls heat treatment

In this paper, industrial control measurements of the heat treatment of high chromium steel (HCS) rolls is presented. Measurements of the gas fired car bottom chamber furnace Bosio PP- KP 70/1150 were carried out in the company Valji d. o. o., Štore, Slovenia. Temperature in the individual heating zones of the furnace, temperatures of the roll surface, furnace external walls, and gas consumption was monitored throughout the whole process of heat treatment. The temperature profile of the rolls cross-section was calculated using computer simulation. Periodical measurements of CO and NOx emissions were also carried out with the aim of combustion evaluation and ecological integrity. The successfulness of heat treatment was examined through microstructure observation, hardness measurement, and the amount of retained austenite in the heat treated rolls

Industrial control measurements of high chromium steel rolls heat treatment

In this paper, industrial control measurements of the heat treatment of high chromium steel (HCS) rolls is presented. Measurements of the gas fired car bottom chamber furnace Bosio PP- KP 70/1150 were carried out in the company Valji d. o. o., Štore, Slovenia. Temperature in the individual heating zones of the furnace, temperatures of the roll surface, furnace external walls, and gas consumption was monitored throughout the whole process of heat treatment. The temperature profile of the rolls cross-section was calculated using computer simulation. Periodical measurements of CO and NOx emissions were also carried out with the aim of combustion evaluation and ecological integrity. The successfulness of heat treatment was examined through microstructure observation, hardness measurement, and the amount of retained austenite in the heat treated rolls

Mechanochemical synthesis of multiferroic yttrium manganite

Multiferroic yttrium manganite (YMnO3) is known as a material that exhibits both ferromagnetic and ferroelectric properties making it interesting for various technological applications. In this work single-phased YMnO3 was prepared for the first time by mechanochemical synthesis in a planetary ball mill. The YMnO3 can be formed directly from the highly activated constituent oxides, Y2O3 and Mn2O3, after 60 min of milling time and subsequently grows during prolonged milling. The cumulative energy introduced into the system during milling for 60 min was 86 kJ/g. X-ray analysis indicates that the as-prepared samples crystallize majority with hexagonal (P63cm) and minorly with orthorhombic (Pnma) YMnO3 structure. The morphology, structure and chemical composition of the powder were investigated by SEM with EDS and TEM. The magnetic properties of the obtained YMnO3 powders were found to change as a function of milling time in a manner consistent with the variation in the nanocomposite microstructure

Spectroscopic and nanoscale characterization of blue-coloured smithsonite (ZnCO3) from Lavrion historical mines (Greece)

Spectroscopic and microscopic (particularly HRTEM) techniques were used to investigate the origin of the colour of natural blue Zn-carbonate (smithsonite). Blue smithsonite is rich in copper, but substitution of zinc cations by copper cations, as proposed in the past for the origin of the colour, is questionable considering the absence of anhydrous divalent copper carbonates in nature. In this work, optical microscopy, SEM-EDS, XRD and laser micro-Raman could not resolve distinct phases either than Zn-carbonate, while NIR spectra excluded known chromophore Cu-hydroxycarbonate minerals. HRTEM studies however could clearly resolve nano-sized (3-7 nm) Cu-rich inclusions (specifically Si/Ca/Cu/As-rich inclusions of at least one phase), which are organised in bands with no topotaxial relation to bulk smithsonite. Electron-beam sensitivity of the samples, even at low electron current densities, did not allow the exact identification of the inclusions. However, it can be safely suggested, for the first time in the literature, that they are the cause of the blue colour in smithsonite

In situ TEM study of κ→β and κ→γ phase transformations in Ga2O3

The temperature-driven phase transformation of metastable κ-Ga2O3 layers deposited on sapphire was studied by high resolution TEM. Annealing experiments up to 1000 °C were performed either in situ in vacuum within the TEM or ex situ in ambient air. This allowed for the detection of the atomistic mechanisms at the basis of κ to β phase transition. In the case of in situ TEM observations we could even record in real time the atomic rearrangement. We provide in this paper the relevant crystallographic relations between original κ and new β lattice. Surprisingly, the ex situ experiments demonstrated the additional formation of a γ-Ga2O3 intermediate phase at 820 °C. The remarkably different behavior between in situ and ex situ annealing experiments is explained in terms of ambient (ambient air or high vacuum) and heating rate. An extensive investigation of γ-Ga2O3, also a metastable phase, showed that it has a cubic defect spinel structure (Fd3¯m) with disordered vacancies. Repeated observations of the metastable γ-Ga2O3 after two months show that the vacancies tend to order, and that the vacancies are fully ordered after one year