Processing of waste slag of non-ferrous metallurgy for the purpose of its complex utilization as a secondary mineral raw material

This article provides an overview of the methods of processing slag from welting is given, different approaches and attempts of scientists from a number of countries aimed at processing such slags are considered. In the course of the review it was found that a huge number of the following methods and methods of processing from waelz slag, there is not a single option that has sufficient complexity of processing, and that at the moment are in the dumps toxins from waelz never found its use as a secondary raw material. The elemental chemical composition of the slag from welting, which is represented by compounds of calcium, silicon, iron, aluminum, carbon and heavy nonferrous metals in the form of zinc and lead, is determined. Thus, it is established that for many years, the slags from waelz that have not found their application and are in the dump at the moment continue to have a polluting effect on the environment. Ill. 1. Ref. 63.

Mechanism Analysis of the Influence of Delay Period on Mechanical Properties of Reactive Powder Concrete

In order to analyze the influence mechanism of delay period on the mechanical properties of reactive powder concrete (RPC), the compressive strength of RPC with delay periods of 18, 24, and 30 h was tested at the age of 7, 28, and 90 days, respectively. The results show that compared with the RPC with delay period of 18 h, the compressive strength of the RPC with delay periods of 24 and 30 h increases by 3.2 and 4.2%, respectively, and the long-term strength reduction ratio decreases by 22.8 and 71.9%, respectively. The constitutive model curves of RPC under different delay period show that the initial elastic modulus E increases with the delay period and the strength and rigidity of RPC increase with the extension of delay period. According to the non-evaporation water quantity test, it could be speculated that the quantities of hydration products of the RPC with delay periods of 24 and 30 h slightly increase compared with the RPC with delay period of 18 h. X-ray diffraction (XRD) analysis show that the delay periods of 24 and 30 h consume more 3CaO·SiO2 (C3S) and 2CaO·SiO2 (C2S) compared with delay period of 18 h. Seen from the scanning electron microscope (SEM) image, the structures of the three groups of samples are relatively dense and have no significant difference. Through energy dispersive X-ray spectroscopy (EDS) analysis, the calcium-silicon ratios of hydration products of the RPC with delay periods of 18, 24, and 30 h are 1.81, 1.56, and 1.54, respectively. The existence of C-S-H gel and Ca(OH)2 in hydration products is confirmed by thermogravimetric-differential scanning calorimetry (DSC-TG) analysis. An appropriate delay period (30 h in this paper) generates more hydration products, then improves the compactness of the internal structure and reduces the calcium-silicon ratio of hydration products, and it is conducive to the growth of RPC compressive strength and the stability of long-term compressive strength.

Hierarchically porous calcium–silicon nanosphere-enabled co-delivery of microRNA-210 and simvastatin for bone regeneration

Co-encapsulation and co-delivery of miR-210 and simvastatin based on dual-sized pore structure calcium–silicon nanospheres for bone regeneration.

Ca2Si5N8:Eu2+ phosphors synthesized in graphite crucibles for enhanced reducing atmosphere

We easily synthesized a pure calcium silicon nitride phosphor powder, Ca2Si5N8:Eu[Formula: see text] from starting materials stable in air, using a graphite crucible to provide reducing conditions at a comparatively lower calcination temperature (1400[Formula: see text]C) and shorter reaction time (8 h) under an atmospheric pressure. At 150[Formula: see text]C, the nitride phosphor still retained 77% of its original emission intensity at room temperature.

Analysis of thermodynamic properties of Ca – Si – Fe melt

The model of ideal associated solutions was used for the analysis of thermodynamic properties of the Ca – Si – Fe melt. Chemical equilibrium, as per the law of mass conservation between associates and monomers in the assumed model version, was performed without consideration of mole fractions of these particles in solution but with consideration of the absolute number of their moles. It allows taking account the changes in the associated solution mole composition depending on the concentration of its components. The understudied binary sub-system Ca – Si was analyzed most comprehensively. Using the latest data of temperature dependency of heat capacity for five types of intermetallics of this sub-system, types of stable associates in it were defined, i.e. Са2Si, СаSi in the solution range with low contents of silicon in solution and СаSi, СаSi2 in the solution range with high contents of silicon in solution. Thermodynamic properties of the corresponding intermetallics in the databases Terra, Astra and HSC notably differ from the computed properties of the associates. The reason of disagreement of experimental and reference data consists apparently in the inaccurate reference information based on the previous underestimated studies of intermetallics’ heat capacities. Analysis of mixing energy of Ca – Si alloy components has shown that concentration and temperature dependencies of excessive free energy closely follow the so-called pseudosubregular model of binary solutions. Only two types of stable associates were defined for the other sub-system Fe – Si, i.e. Fe3Si and FeSi. On the whole, energies of formation of these associates and respective intermetallics agree well. The third sub-system Ca – Fe was not considered because of the very limited mutual solubility of its components. Thus, only three associates, i.e. CaSi, CaSi2 , FeSi, are valid out of five possible in the triple system Ca – Si – Fe in the range with high concentrations of silicon. A calculation under this condition of thermodynamic properties of calcium silicon melts for CK10 – CK30 grades has shown that activity of silicon in them at temperature 1873 K constituted 0.6 – 0.7, whereas activities of other components do not exceed 0.01.

Mineralogy of C-S-H belite hydrates incorporating Zn-Al-Ti layered double hydroxides

Recently, the belitic cements with low alite content were the subject of several research works which aimed to replace the Ordinary Portland Clinker (OPC) for ecological reasons (reduction of CO2 emissions), so to understand the reactivity of this cement, the hydration study of the C2S “dicalcium silicate” phase is primordial research step. As well for a clean environment, the TiO2 photocatalyst has been extensively applied in the science of building materials because of its ability to degrade the cement surface pollutants. New photocatalyst based layered double hydroxides (LDH) associated with zinc, aluminium and TiO2 was introduced to increase the compatibility with mortars. The present work is subjected to investigate the effect of the layered double hydroxides on the hydration of C2S in following the evolution of hydration by X-ray diffraction at 2, 7, 28 and 90 days and analyzing the calcium/silicon ratio of different formed hydrates.