Vibrational spectroscopy of the borate mineral henmilite Ca₂Cu[B(OH)₄]₂(OH)₄.
Henmilite is a triclinic mineral with the crystal structure consisting of isolated B(OH)(4) tetrahedra, planar Cu(OH)(4) groups and Ca(OH)(3) polyhedra. The structure can also be viewed as having dimers of Ca polyhedra connected to each other through 2B(OH) tetrahedra to form chains parallel to the C axis. The structure of the mineral has been assessed by the combination of Raman and infrared spectra. Raman bands at 902, 922, 951, and 984 cm(-1) and infrared bands at 912, 955 and 998 cm(-1) are assigned to stretching vibrations of tetragonal boron. The Raman band at 758 cm(-1) is assigned to the symmetric stretching mode of tetrahedral boron. The series of bands in the 400-600 cm(-1) region are due to the out-of-plane bending modes of tetrahedral boron. Two very sharp Raman bands are observed at 3559 and 3609 cm(-1). Two infrared bands are found at 3558 and 3607 cm(-1). These bands are assigned to the OH stretching vibrations of the OH units in henmilite. A series of Raman bands are observed at 3195, 3269, 3328, 3396, 3424 and 3501 cm(-1) are assigned to water stretching modes. Infrared spectroscopy also identified water and OH units in the henmilite structure. It is proposed that water is involved in the structure of henmilite. Hydrogen bond distances based upon the OH stretching vibrations using a Libowitzky equation were calculated. The number and variation of water hydrogen bond distances are important for the stability off the mineral.
The role of ferrite-cementite interface in formation of hierarchical film on carbon steel in CO2-saturated brine
Abstract Carbon steels with ferrite-pearlite structures are commonly used materials in many industrial operations, and their protection against corrosion often relies on preventative inhibition measures. Film-forming corrosion inhibitors are known to provide protection to carbon steels in oil and gas productions lines for decades. However, the mechanisms of how these protect against corrosion are not known. Corrosion inhibitor films with hierarchical structures can be protective to the steel surface due to their large surface area and interconnected hierarchical porosity. The compounds that contribute to the formation of hierarchical morphology can be components of corrosion inhibitor formulations. This study demonstrates solution deposition of a hierarchically structured film derived from sodium thiosulphate. The film forms on an AISI 1030 carbon steel (UNS G10300) substrate in CO2-saturated sodium chloride containing solution under ambient conditions. We identified that the hierarchical film derived from sodium thiosulphate occurs originally at the interface of ferrite-cementite phase in pearlite and elucidate the role of oxygen in the formation of the hierarchical structures. These findings are expected to facilitate developments of novel corrosion inhibition strategies, through a controlled growth of surface films at metallic substrates for specific applications, including corrosion protection in oil and gas industry, catalysis and energy-storage applications.
Neutronenbeugungsmessungen an SrBr2 · H2O und Srl2 · H2O, symmetrisch und asymmetrisch gebundene Kristallwasser-moleküle
An den isotypen Hydraten SrBr2 · H2O und SrI2 · H2O (Raumgruppe Pnma) wurden Einkristallneutronenbeugungsmessungen vorgenommen. Die Bindungslangen sowie die Anordnung der verzweigten Wasserstoffbrucken werden mit Raman- und IR-spektroskopischen Daten korreliert. Die zwei- bzw. dreifach verzweigten Wasserstoffbrucken sind insgesamt signifikant starker als gleich lange lineare Brucken zu Br−-und I−-Ionen. Die von den beiden Wasserstoffatomen des SrI2 · H2O gebildeten H-Brucken sind, wie die entsprechenden OH-Schwingungsfrequenzen zeigen, trotz der unterschiedlichen H…I-Abstande gleich stark (H2O symmetrisch). Das Kristallwassermolekul des SrBr2 · H2O ist asymmetrisch gebunden (unterschiedlich starke H-Brucken). 
 
 
 
Neutron Diffraction Studies of SrBr2 · H2O and SrI2 · H2O, Symmetrically and Asymmetrically Bonded Water Molecules 
 
 
 
Single crystal neutron diffraction studies were performed on the isostructural (space group Pnma) SrBr2 · H2O and SrI2 · H2O. Lengths and structure of the hydrogen bonds are correlated with Raman and IR spectroscopic data. The bifurcated and trifurcated H-bonds present are altogether significantly stronger than linear ones with similar H…Br and H…I distances, respectively. In the case of SrI2 · H2O, the H-bonds of the two hydrogen atoms of the water molecules exhibit equal strength (symmetric water molecule) as shown by the respective OH vibrational energies despite the different H…I distances. The water molecule of SrBr2 · H2O is asymmetrically bonded (different strength of the H-bonds).