Physicochemical, Mineralogical and Radiological Properties of Red Mud Samples as Secondary Raw Materials

The main goal of the presented research was the preliminary investigation of possibility of red mud - Hungarian dump sites Almasfuzito (sample A) and Ajka (sample B) - application as a pigment or as a raw material for use in the construction materials industry. Also, the aim of this work was the characterization of red mud as industrial waste generated by the Bayer process in the aluminum industry - which may cause environmental problems if appropriate treatment is not carried out. The main mineral phases of both red mud are hematite (Fe2O3), calcite (CaCO3), gibbsite (Al(OH)(3)) and they consists of particles of median particle size 2.1 mu m (sample A) and 2.5 mu m (sample B) and have a characteristic red color, which was the reason for its testing for use in the industry of building materials as a pigment for standard concrete mixtures. The radionuclides content in the samples was determined by gamma spectrometry, and the radiological hazards originating from U-238, Th-232, K-40 in the samples, were assessed through the radium equivalent activity, and the external radiation hazard index. The absorbed dose rate and the annual effective dose were calculated in accordance with the UNSCEAR 2010 report and the results are presented in this paper

Geopolymerisation behaviour of size fractioned fly ash

Fly ash is a fine powder residue resulted from combustion of pulverized coal in thermal power plants. Different size fractions of fly ash have different properties. Four size fractions (with characteristic particle diameter D-50 of 40.37, 23.64, 10.33 and 2.98 mu m respectively) collected from different fields of an electrostatic precipitator and representing the entire particle spectrum of fly ash has been selected for the study. These fractions have been characterized for their granulometry, chemistry, glass content and mineralogical phases. Geopolymerisation of size fractioned fly ash has been carried out at ambient (27 degrees C) and elevated (60 degrees C) temperature using isothermal conduction calorimetry (ICC) and the microstructure has been studied using X-ray diffractometry (XRD), scanning electron microscopy with X-ray microanalysis probe (SEM-EDS) and Fourier transform infrared spectroscopy (FTIR). Calorimetric studies showed that the heat flow curve during geopolymerisation has linear correlation with the glass content of fly ash. The compressive strength development at both ambient and elevated temperature was due to the combined effect of SiO2/Al2O3 ratio, particle size and glass content. SEM-EDS studies have shown more reaction product in finer fractions and unreacted particles in coarser fractions. Formation of more thermonatrite phase was due to poor reactivity of coarse size fraction resulting into free alkali which in presence of atmospheric carbon formed Na2CO3 center dot H2O. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

Mechanical activation of fly ash and its influence on micro and nano-structural behaviour of resulting geopolymers

Fly ash, mechanically activated up to 120 min, has been used to synthesize geopolymers at ambient temperature. Fourier transform infrared spectroscopy (FTIR), quantitative X-ray powder diffractometry (XRD) and transmission electron microscopy (TEM-EDS) have been used for the structural characterization. The decrease in characteristic particle diameter up to 60 min and then increase is related to particle breakage and aggregation/agglomeration respectively. The manifestation of mechanical activation (MA) during geopolymerisation resulted in enhanced dissolution and precipitation of Si and Al. The appearance of a new FTIR band in 1080-1096 cm (1) region in MA geopolymers is attributed to SiQ(n) (n = 3-4) structural units of quartz. The increment in amorphization in MA fly ash resulted in an increase in crystallinity of geopolymers. The shift in characteristic XRD amorphous hump towards lower d(angstrom) value in geopolymers is associated with incorporation of OH and Na resulting in structural changes in amorphous phase. TEM-EDS revealed that geopolymers from as received fly ash exhibited predominance of primary structures such as nano-crystalline mullite, microcrystalline quartz and alumino-silicate glass. Whereas geopolymers from MA fly ash has shown secondary features mainly N-A-S-H gel, whose nano-porosity increased due to changes in gel characteristic. Finally, a conceptual mechanism of reaction is presented. (c) 2016 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved

In-situ investigation of the decomposition process in cold-rolled Nb53Ti47 alloy

The multi-layer composite development primarily aims to develop and test the components of the next generation of hadron colliders (e.g., Large Hadron Collider - LHC) consisting of superconducting raw materials. Multilayer sheet is very similar to the commonly used NbTi wire products, a 2D version of the commercial wire. These composites consist of layers such as NbTi superconductor, Nb diffusion barrier (between NbTi and Cu) and Cu stabilizer. In β-NbTi superconducting alloys, α-Ti precipitates are primary flux pinning centers that maintain stable superconductivity. A multi-step series of heat treatments and cold-forming processes can develop the flux pinning centers. Practically, this process means three heat treatments of constant period and temperature and drawing or rolling between the heat treatments.The study aimed to describe the behavior of the cold-rolled (ε = 3.35) Nb53Ti47w% alloys during isothermal heating at 673 K as a function of heating time. The processes during the aging were investigated by the in-situ XRD method in the heating chamber. The X-ray diffraction patterns were evaluated by Rietveld refinement. The thermally activated spinodal decomposition and precipitation processes were described based on the phases identified at the individual heat treatment steps and their lattice parameters. The in-situ study also revealed an increase in α-Ti precipitation with time and decomposition that co-occurs. This is the basic study that prepares the applicability of the alloy

Phase Transformation and Morphology Evolution of Ti50Cu25Ni20Sn5 during Mechanical Milling

Nanocrystalline/amorphous powder was produced by ball milling of Ti50Cu25Ni20Sn5 (at.%) master alloy. Both laser diffraction particle size analyzer and scanning electron microscope (SEM) were used to monitor the changes in the particle size as well as in the shape of particles as a function of milling time. During ball milling, the average particle size decreased with milling time from >320 µm to ~38 µm after 180 min of milling. The deformation-induced hardening and phase transformation caused the hardness value to increase from 506 to 779 HV. X-ray diffraction (XRD) analysis was used to observe the changes in the phases/amorphous content as a function of milling time. The amount of amorphous fraction increased continuously until 120 min milling (36 wt % amorphous content). The interval of crystallite size was between 1 and 10 nm after 180 min of milling with 25 wt % amorphous fractions. Cubic Cu(Ni,Cu)Ti2 structure was transformed into the orthorhombic structure owing to the shear/stress, dislocations, and Cu substitution during the milling process

Physicochemical, mineralogical and radiological properties of red mud samples as secondary raw materials

The main goal of the presented research was the preliminary investigation of possibility of red mud - Hungarian dump sites Almasfuzito (sample A) and Ajka (sample B) - application as a pigment or as a raw material for use in the construction materials industry. Also, the aim of this work was the characterization of red mud as industrial waste generated by the Bayer process in the aluminum industry - which may cause environmental problems if appropriate treatment is not carried out. The main mineral phases of both red mud are hematite (Fe2O3), calcite (CaCO3), gibbsite (Al(OH)3) and they consists of particles of median particle size 2.1 mm (sample A) and 2.5 mm (sample B) and have a characteristic red color, which was the reason for its testing for use in the industry of building materials as a pigment for standard concrete mixtures. The radionuclides content in the samples was determined by gamma spectrometry, and the radiological hazards originating from 238U, 232Th, 40K in the samples, were assessed through the radium equivalent activity, and the external radiation hazard index. The absorbed dose rate and the annual effective dose were calculated in accordance with the UNSCEAR 2010 report and the results are presented in this paper. [Project of the Serbian Ministry of Education, Science and Technological Development, Grant no. III 45012 and Grant no. III 45005