Influence of Mechanochemical Activation of Concrete Components on the Properties of Vibro-Centrifugated Heavy Concrete

One of the crucial problems in current construction is energy, resource, and material efficient technologies in both industrial and civil engineering, associated with new material manufacturing and building construction. This article is devoted to developing comprehensive technology for activation effects on concrete made by various production techniques: vibration, centrifugation, and vibro-centrifugation. The possibility of a significant improvement in the microstructure of concrete and obtaining materials with increased specified characteristics, depending on its manufacturing technology, were studied during the complex activation effect exposed to this concrete and its components. Chemical activation of water and mechanical activation of cement were considered. The urgency and prospects of double, complex mechanochemical activation of concrete mixture components were substantiated. It was proven that the complex mechanochemical activation of the concrete mixture components gives a synergistic effect in obtaining concrete composition with an improved structure and improved characteristics. Furthermore, the relationship between concrete production technology and the technology of activation of its components was established. It was revealed that the most effective is the complex mechanochemical activation of vibro-centrifuged concrete, which gives an increase in strength up to 30%. The study results indicate a further direction of development associated with an increase in variatropic characteristics using both prescription and technological factors.

Binding of Gold(III) from Solutions by the [Ag6{S2CN(CH2)6}6] Cluster: Synthesis, Thermal Behavior, and Self-Organization of the Supramolecular Structure of the Double Complex [Au{S2CN(CH2)6}2]2[AgCl2]Cl·2CHCl3 (Role of Secondary Au⋅⋅⋅Cl, Ag⋅⋅⋅S, and Cl⋅⋅⋅Cl Interactions)

The capability of silver(I) cyclo-hexamethylenedithiocarbamate to concentrate gold(III) from solutions characterized by a high level of salinity (5.15 M NaCl) into the solid phase has been established. The double chloroform-solvated Au(III)–Ag(I) complex [Au{S2CN(CH2)6}2]2[AgCl2]Cl·2CHCl3 (I) was preparatively isolated as an individual form of binding of [AuCl4]– anions. The composition of the ionic structural units of compound I indicates that gold(III) binding from a solution to the solid phase is accompanied by the complete redistribution of the HmDtc ligands between the coordination spheres of Ag(I) and Au(III). Complex I characterized by IR spectroscopy, simultaneous thermal analysis, and X-ray structure analysis (CIF file CCDC no. 2051654) exhibits the supramolecular structure containing two oppositely charged pseudo-polymeric subsystems. Complex cations [Au{S2CN(CH2)6}2]+ and anions [AgCl2]– (in a ratio of 2 : 1) form a complicatedly organized cation-anionic pseudo-polymeric ribbon ({[Au(HmDtc)2]⋅⋅⋅[AgCl2]⋅⋅⋅[Au(HmDtc)2]}+)n due to secondary interactions Ag⋅⋅⋅S (3.2613 Å) and Au⋅⋅⋅Cl (3.2765 Å). The pseudo-polymeric ribbon consists of two rows of cations and a row of anions. The outer-sphere chloride ions combine the solvate chloroform molecules by two equivalent hydrogen bonds Cl⋅⋅⋅H–C yielding anion-molecular triads [Cl3CH⋅⋅⋅Cl⋅⋅⋅HCCl3]–, which are involved in the formation of the supramolecular ribbon due to the secondary Cl⋅⋅⋅Cl interactions (3.4058 Å) between the nonequivalent chlorine atoms of the nearest solvate molecules. The study of the thermal behavior of complex I makes it possible to determine the character of thermolysis and conditions for the quantitative regeneration of bound gold.

Crystal Structure and Infrared Spectroscopy of trans-[Cr(NCS)2(Me2tn)2][Cr(NCS)4(Me2tn)] Moiety

A novel double complex, trans-[Cr(NCS)2(Me2tn)2][Cr(NCS)4(Me2tn)]·NaSCN·i-PrOH, (1) (Me2tn = 2,2-dimethyl-1,3-propanediamine, C5H14N2; i-PrOH = isopropyl alcohol), was prepared and its structure was determined by single-crystal X-ray diffraction at 95 K. The complex 1 crystallized in the space group P1 of the triclinic system with two nuclear formula units in a cell of dimensions a = 13.220(3), b = 13.699(3), c = 15.087(3) Å and α = 116.193(3), β = 102.73(3) and γ = 104.48(3)°. X-ray structural analysis revealed two crystallo-graphically independent Cr(III) complex cations in the complex 1. The asymmetric unit contains two halves of trans-[Cr(NCS)2(Me2tn)2]+ cations (2 and 3), one cis-[Cr(NCS)4(Me2tn)]− anion (4), one NaSCN salt and one isopropyl alcohol molecule. In two independent complex cations, the chromium(III) ions are coordinated by four N atoms of two chelating Me2tn and two NCS groups in a distorted octahedral geometry while the chromium(III) ion in cis-[Cr(NCS)4(Me2tn)]- has a distorted octahedral coordination with two N atoms of one Me2tn and four NCS groups. The two six-membered rings in trans-[Cr(NCS)2(Me2tn)2]+ cations adopt both anti chair-chair conformations. The Cr–N(Me2tn) bond lengths range from 2.0624(18) to 2.0877(16) Å, while the Cr–N(NCS) bond lengths range from 2.0718(16) to 2.0428 (16) Å. The crystal lattice is stabilized by hydrogen bonding interactions among the NH groups of the Me2tn ligand, OH group of i-PrOH and the S atoms of the NCS groups. The infrared spectral properties are also described.

Thermal decomposition of double complex compounds of 3D metals.

The paper is devoted to the study of thermolysis of double complex compounds (DCС) of metalsin the I transition series. 30 DCСwith various combinations of metal-central atoms (Co-Fe, Cu-Fe, Ni-Fe Cr-Fe, Cr-Co,) and ligands (ammonia, urea (ur), ethylenediamine (en), 1,3-diaminopropane (tn), cyanide, oxalate and nitrite anions) were synthesized and characterized. A complete study of the thermal proper-ties of these DCCs in three atmospheres was carried out: oxidizing (air), inert (Ar, N2, partly He) and re-ducing (H2), in the temperature range of 20–1000°Cand at constant heating rate of 10°C/min. The solid and gaseous thermolysis products were studied. In the air solid thermolysis products are represented by mixtures of central ions oxides or mixed oxides of the MIMII2O4type. The main gaseous products of thermolysis underthe temperature below 300°Cinclude NH3, HNCO (for urea DCС) and HCN (for cya-nocomplexes), and above 300°C —СО2. In addition, undecomposed ligands, CO, nitrogen oxides and probably nitrogen are presented in the gas phase. Thermolysis of the studied DCCgoesin the most com-plex way in inert atmospheres. Solid thermolysis products are heterogeneous mixtures of metals (Cu, Fe), solid solutions of CoxFe1-x, Ni3Fe intermetallic compounds, oxides, carbides and nitrides of central ions and amorphous carbon; the content of the latter reaches 58% of the initial content in the complex. The gaseous products of thermolysis include the same compounds, except for CO2, as in the atmosphere of air, but also in different ratios. In an H2atmosphere, all studied DCCs, except Cr-containing ones, are re-duced to the sum of central ions —Cu + Fe or solid solutions Co-Fe and Ni-Fe, practically free of carbon. Gaseous products are the same as in an inert atmosphere, butan increased yield of NH3and a reduced yield of CO2and/or HCN speak in favor of partial hydrogenation of the ligands to hydrocarbons. A review of the catalytic properties of solid products of DCC thermolysis (~170 samples) showed that about 1/3 of themare active in model reactions (catalytic decomposition of hydrogen peroxide, thermal decomposi-tion of ammonium perchlorate).