Thermochemistry of triboactivated natural and NH<Subscript>4</Subscript>-exchanged clinoptilolite mixed with Tunisian apatite

Mechanical tribo- and thermo-chemical methods applied for remodeling phosphate raw materials manifest a number of advantages over the conventional technologies. They are related to the reduction of soil contamination and minimization of the released gas emissions in the environment and generate solid wastes. In this work, natural and NH₄-exchanged clinoptilolite are used for increasing the transition of P₂O₅ into assimilated by plants form during tribochemical activation (TCA). Better nutrients assimilation as well as green production could be achieved by applying such a treatment based on the ion-exchange reactions taking place in the soil. The occurring upon TCA structural changes and phase transformations of the used Tunisian phosphorite, natural and NH₄-exchanged clinoptilolite as well as their mixtures are investigated by means of X-ray powder diffraction, IR spectroscopy, and thermal analysis. The thermal method gives evidence for solid phase reactions and increased reactivity as a result of the tribochemical treatment. This treatment leads also to minimization of the size of crystallites, amorfization of the samples, and increasing amount of hydroxyl and carbonate ions in the apatite structure. Treated samples are highly soluble. In addition, conditions for almost complete solubility of P₂O₅ were found. This study shows that some of the produced compositions are suitable for fertilizers or soil conditioners.     

Adsorption of RDX and TATP on IRMOF-1: an ab initio study

The adsorption of 1,3,5-trinitro-s-triazine (RDX) and triacetone triperoxide (TATP) on representative fragments of metal organic framework (IRMOF-1) was studied at the B3LYP/6-31G(d) level of theory. For examined adsorbates several possible adsorption positions toward the IRMOF-1 fragments were found. The adsorption strength of the adsorbate on IRMOF-1 is largely affected by the geometry of the active site of IRMOF-1 which controls the orientation of the target molecule with respect to the IRMOF-1 fragment. The calculations show that the adsorption on these fragments occurs due to the formation of hydrogen bonds between the molecular C–H groups and the oxygen atoms of IRMOF-1. The RDX and TATP molecules are the most strongly adsorbed on the linker fragment of IRMOF-1. This type of adsorption results in the polarization of RDX and TATP on the IRMOF-1 fragments. The interaction energy of two most stable RDX-, and TATP-IRMOF-1 adsorption systems are ?9.8 and ?12.8 kcal/mol, respectively. It can be concluded that the 1,4-benzenedicarboxylate site of IRMOF-1 shows the stronger molecular adsorption of RDX and TATP than the site containing [Zn₄O(CO₂)₆] and also it is characterized by higher reactivity than the other considered sites. The binding of studied explosive molecules to IRMOF-1 consists of interplay between attractive interactions between the target molecule and MOF as well as the shielding by the IRMOF-1 fragment induced by the molecular adsorption. The relative importance of these effects depends on the chemical nature, the size, and the shape of the molecule and MOF. Small-size molecules require smaller space for the adsorption and also they are less shielded by the sizeable adsorbent. So they interact better when adsorbed on larger IRMOF-1 fragment. On the other side, larger molecules show higher adsorption strength with small fragments of IRMOF-1.     

Molding thermoplastic materials for aerospace industry

Properties of thermoplastic polymers for decorative structural, structural, and special applications (thermoelastoplastics) are described. These materials completely meet domestic (AP-25) and international (FAR-25) requirements for fire safety.     

Crystal structure of a new small-pore zirconosilicate Na2ZrSi2O7·H2O and its relation to stoichiometrically and topologically similar compounds

The small-pore zirconosilicate Na₂ZrSi₂O₇·H₂O crystallizes in monoclinic system with space group C2/c, a = 5.4715(4); b = 9.4111(6); c = 13.0969(8) Å, β = 92.851(7)°. Its framework consists of layers built of ZrO₆ octahedra and SiO₄ tetrahedra and forming condensed [Si₂O₇] pyrogroups by connection. The sodium ions and water molecules are placed in channels set up between the layers. The stoichiometric and structural similarities of the studied phase with anhydrous compounds having general chemical formula A₂₍₃₎MT₂O₇ (A = Na,K; M = Zr,Lu,Sc; T = Si,Ge) are discussed. The topological relationship of their structures is interpreted in the light of spatial combination of silicon and zirconium polyhedra as basic building units into larger composite building units and their three-dimensional arrangement.     

Gas-phase electron diffraction and quantum chemical study of the structure of the 4-nitrobenzene sulfonyl chloride molecule

A combined gas-phase electron diffraction and quantum chemical (B3LYP/6-311+G**, B3LYP/cc-pVTZ, MP2/6-31G*, and MP2/cc-pVTZ) study of the structure of the 4-nitrobenzene sulfonyl chloride molecule is performed. It is found that at a temperature of 391(3) K only one conformer with C _s symmetry is present in the gas phase. The following experimental values of structural parameters are obtained: r _h1(C-H)_av = 1.086(6) Å, r _h1(C-C)_av = 1.395(3) Å, r _h1(C1-S) = 1.773(4) Å, r _h1(S=O) = 1.423(3) Å, r _h1(S-Cl) = 2.048(4) Å, r _h1(N-O) = 1.224(3) Å, r _h1(N-C4) = 1.477(3) Å, ∠(C1-S=O) = 109.0(4)°, ∠(Cl-S-O) = 106.7(2)°, ∠C1-S-Cl = 100.2(13)°, ∠O=S=O = 122.9(11)°, ∠O=N=O = 123.6(5)°. The C2-C1-S-Cl torsion angle that characterizes the position of the S-Cl bond relative to the benzene ring plane is 89(4)°. The NO₂ group lies in the benzene ring plane. Internal rotation barriers calculated by B3LYP/6-311+G** and MP2/6-31G* methods are: V ₁ = 4.7 kcal/mol and 5.3 kcal/mol for the sulfonyl chloride group; V ₂ = 4.9 kcal/mol and 6.0 kcal/mol for the nitro group.     

Crystal structure and conduction of BICUTIVOX

Existence boundaries, structure, and transport parameters were studied for Bi₄V_{2 ? x} Cu _x/2Ti _x/2O_{11 ? x} solid solutions. Doping levels within x = 0.025–0.15 distort the C2/m crystal lattice (this lattice is characteristic of individual the Bi₄V₂O₁₁ phase) and lowers its symmetry to triclinic. The solid solutions with 0.25 ≤ x ≤ 0.30 crystallize in tetragonal space group I4/mmm. High-temperature X-ray diffraction and dilatometry measurements for Bi₄V_{2 ? x} Cu _x/2Ti _x/2O_{11 ? x} (x ≤ 0.35) solid solutions verified the existence of three structural varieties within 298–1023 K. Electrical conductivity of BICUTIVOX was studied by impedance spectroscopy as a function of temperature, composition, and oxygen partial pressure. Equivalent circuits of cells were analyzed. Features of electrical conductivity versus temperature for the structural varieties are noted. Above 873 K, the solid solutions samples with x = 0.05 have the highest conductivity. At lower temperatures, higher conductivities are in the solid solutions that retain the γ phase in the low-temperature region. The dominant oxygen-ion conduction mechanism was discovered in the solid solutions.     

Structure, conformation and hydrogen bonding of two amino-cycloalkanespiro-5-hydantoins

The crystal structures of 3-amino-cycloheptanespiro-4′-imidazolidine-2′,5′-dione (I) {systematic name: 3-amino-1,3-diazaspiro[4.6] undecane-2,4-dione} and 3-amino-cyclooctanespiro-4′-imidazolidine-2′,5′-dione (II) {systematic name: 3-amino-1,3-diazaspiro[4.7] dodecane-2,4-dione}, have been determined. In both compounds the polar hydantoin groups cause molecules to aggregate via N-H...O and N-H...N interactions, forming a layer structure, in which the cycloalkane rings project outwards from the central, more polar, region. The observed molecular structure is compared with that calculated by density functional theory methods.      

Surface preparation for gluing

The methods of surface preparation for gluing in relation to substrates from aluminium alloys, constructional and corrosion-resistant steels, and polymer composites are described. The technological parameters of surface preparation are specified. The potential backlashes for the gluing process and the quality of adhesive structures due to deviations from the assigned technological parameters are shown.     

Application of Validated TLC—Densitometric Method for Simultaneous Identification and Determination of Losartan Potassium,Telmisartan, and Valsartan in Tablets

JPC – Journal of Planar Chromatography – Modern TLC - The antihypertensive effect of sartans is a result of inhibition of the binding of angiotensin (AT) II to the AT1 receptor in...