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The research on the impacts of modified TiO2 nanoparticles (NPs) on interfacial tension (IFT) is in its infancy. Our work focuses on the IFT of the modified TiO2 and Gemini surfactant N,N,N′,N′-tetramethyl-N,N′-dimyristyl-1,2-ethane diammonium dichlone (YND1233) complex solutions for reservoir stimulation purposes. The factors of YND1233, modified TiO2 NPs, temperature, aging stability, adsorption loss, and mineralized degree were explored with the comparison of unmodified TiO2 NPs and YND1233 as contrast samples. The results indicate that the dynamic IFTs decrease and then increase with the concentrations of YND1233 and modified TiO2 NPs, and the minimum IFT appears at 0.200 and 0.010 wt%, respectively. YND1233/modified TiO2 complex solutions show lower and more stable IFTs, better temperature resistance, longer aging time, and lower adsorption on the surface of quartz sand. The modified TiO2 NPs and YND1233 in the YND1233/modified TiO2 complex solution can be adsorbed to the interface and decrease the I...

In the binary system (1−x)Li2SO4–xNa2SO4, the solid–solid phase transitions and energy storage properties of Li2SO4, Na2SO4, the binary compound LiNaSO4 and two eutectoids (E1: 0.726Li2SO4–0.274Na2SO4; E2: 0.03Li2SO4–0.97Na2SO4) were investigated by X-ray diffraction and differential scanning calorimetry. Li2SO4 has a solid–solid phase transition at 578 °C with the transition enthalpy 252 J g−1. The binary compound LiNaSO4 gives a slightly lower enthalpy value, 214 J g−1 and its transition temperature is clearly reduced to 514 °C. The transition enthalpy of the eutectoid E1 is maintained to 177 J g−1 and its transition temperature is further reduced to 474 °C. Li2SO4, LiNaSO4 and the eutectoid E1 are applicable phase transition materials because of their large transition enthalpies. The enthalpies of Na2SO4 and the eutectoid E2 are not very high (∼45 J g−1), but their transition temperatures are quite low (∼250 °C); thus their transition properties may be applied at such low temperatures.

Barium orthotitanate (Ba2TiO4) was prepared by heating at 1250°C for 2 h. The thermal stability of Ba2TiO4 and the phase transformation between the low-temperature monoclinic polymorph (β-Ba2TiO4) and the high-temperature orthorhombic polymorph (α′-Ba2TiO4) were examined by X-ray diffraction. Ba2TiO4 can be corroded by CO2 below 700°C forming BaCO3 and BaTiO3, which is reversible above 750°C. A martensitic transformation from β-Ba2TiO4 to α′-Ba2TiO4 starts at ∼100°C and ends at ∼220°C in heating process. The transformation hysteresis loop is ∼200°C. α′-Ba2TiO4 can be stabilized to room temperature by doping small amount of aliovalent ion Nd3+ (1.5 mole%) or relatively large amount of isovalent ion Sr2+ (10 mole%). After annealing the doped samples at low temperatures (e.g., below 1100°C), for the Nd-doped sample, α′-Ba2TiO4 can be partially transformed to β-Ba2TiO4, whereas the Sr-doped sample is stably kept as α′-Ba2TiO4.

Three cadmium(II) coordination polymers, [CdBr2(L1)] n (1), [CdI2(L2)] n (2), and Cd2Br4(L3)2 (3), where L1 = 1,3-bis(5,6-dimethylbenzimidazole)propane, L2 = 1,4-bis(5,6-dimethylbenzimidazole)butane, and L3 = 1,6-bis(5,6-dimethylbenzimidazole)hexane, have been synthesized by hydrothermal methods and characterized by elemental analyses, IR spectra, TGA, PXRD, and X-ray crystallographic diffraction. Complex 1 contains a 1-D helical chain in which CdBr2 units are linked by L1. For 2, each CdI2 is connected by two different conformations of L2 to form a 1-D zigzag chain. For 3, each CdBr2 is linked by L3 bridges to afford a binuclear structure. These results indicate that the spacer length of the ligands play important roles in assembly of Cd(II) coordination polymers. Thermogravimetric analyses and solid-state luminescent properties of the complexes have also been investigated.

Compounds [CdLCl2] n (1) and {[Cd(L)2(ClO4)]·ClO4} n (2), where L = 1,3-bis(5,6-dimethylbenzimidazol-1-ylmethyl)benzene, have been synthesized by hydrothermal method, and characterized by element analysis, IR spectra, Powder XRD, and X-ray crystallographic diffraction. Cd(II) in 1 and 2 are both trigonal bipyramidal. Different cadmium salts of chloride and perchlorate lead to different configurations of [Cd2L2]2+, trans-form in 1 but trans and cis-forms in 2. The 1-D beaded chains of 1 are further linked to generate a 3-D supramolecular architecture by strong π–π stacking interactions as well as intermolecular C–H ··· Cl hydrogen bonds. In 2, the 1-D beaded chains are further assembled by intermolecular C–H ··· O hydrogen bonds to form a 2-D layer. Solid-state fluorescent properties of 1 and 2 were investigated at room temperature.

A novel Cu(II) mixed-ligand complex, {[Cu(sq)(L)(H2O)]· 0.9H2O}n (1) (sq = squarate dianion, L = 5,5′-dimethyl-2,2′-bipyridine), has been synthesized and characterized by elemental analyses, infrared (IR), and X-ray single-crystal diffraction. In 1, each copper(II) ion has a five-coordinated environment with square pyramidal geometry. A one-dimensional (1D) chain structure of the complex is constructed by squarate in μ-1,2-bis(monodentate) coordination mode and further forms a two-dimensional (2D) framework via “metal chelate–metal chelate ring” π–π stacking interactions between the adjacent chains. This unexpected π–π stacking interaction provides structural evidence for the metalloaromaticity of the Cu(II)-(aromatic α,α′-diimines) chelate rings.

Three new complexes, [Ni2(dpc)2(L1)2(H2O)2] · 4H2O (1), [Ni(dpc)(L2)1.5] n (2), and {[Ni(dpc)(L3)1.5] · 2H2O} n (3), where H2dpc = dipicolinic acid, L1 = 1,4-bis(2-methylimidazol-1-yl)butane, L2 = 4,4′-bis(2-methylimidazol-1-ylmethyl)biphenyl, and L3 = 1,4-bis(benzimidazol-1-yl)-2-butylene, have been synthesized by hydrothermal methods and characterized by elemental analyses, infrared spectra, thermogravimetric analysis, and X-ray crystallography. The common structural characteristic of the three complexes is that the Ni2+ is coordinated by tridentate dipicolinate through nitrogen of pyridine and oxygen of carboxylate, serving as a terminal ligand. In 1, two L1 link two [Ni(dpc)(H2O)] units to a discrete binuclear metallomacrocycle with a 22-membered ring, which is assembled through multiple O–H ··· O hydrogen bonds to form a 3-D supramolecular framework. Complex 2 exhibits a 1-D ladder-like chain structure constructed by cis/trans-conformation L2 linking metal centers; 3 displays a 2-D (6,3) topology, be...