Papers by Keyword: Nitrates

Abstract: Layered Double Hydroxide (LDH) is ionic clay that is characterized by the union of metal cations and OH^- hydroxides. LDH composites exhibit considerably high releasing and recharging capacity and have applications as bioactive cements. They can be prepared by direct co-precipitation of metal salts at controlled pH. The preparation is carried out from an acid solution of Zn (NO₃)₂.6H₂O, Al (NO₃)₃.9H₂O and a basic solution of Na₂CO₃ and NaOH, with a Zn/Al ratio = 3, the pH is stabilized between 9 and 9.5 at a constant temperature of 45°C. The objective of this study is to incorporate Zinc and Aluminum elements at different percentages in dicalcium silicate phase to produce C₂S phase incorporating LDH composite. The characterizations of the developed phases by XRD and SEM indicate the formation of stoichiometric LDH phases Zn₆Al₂(OH)₁₆CO₃.4H₂O and non-stoichiometric Zn_0.61Al_0.39 (OH)₂(CO₃)_0.195.xH₂O, the incorporation of Zn in the belitic C₂S phase and not Al. The obtained micrographs by SEM(EDAX) analysis show new morphology of the stabilized composite.

Abstract: The 110 Ksi tubing failed in use when reservoir acidification reconstruction and production testing were performed in an oil well, which were longitudinal cracking of coupling. Failure analysis was conducted on the coupling. The failure zone was studied by means of macroscopic analysis, metallographic, scanning electronic microscope,energy dispersive spectrometer and X-ray diffraction analysis etc. The results indicated that the failure of the coupling is caused by stress corrosion cracking (SCC). SCC initiated from the exterior surface of coupling and displayed the fracture feature of intergranular crack propagation. The corrosion products at the grain boundaries were found to be mainly some oxides. The failure was in connection with the completion fluid composition, which are mainly nitrates.

Abstract: A new technologies and materials stand at front of thescientific interest. Their development leads to technological potential increasing at various fields of industry.Progressive new materials are based on the development of nanotechnologies and nanomaterials, which have a widerange of the applications in manufacturing, medicine and the environment protection. There sult of the hugeefforts in the development of nanostructured materials, the amount of new material sthat are the building blocks of nanoparticles with defineds tructures and properties. Progress in the use of nanotechnologies and nanomaterials has been noticed in the area of water protection, because they develop a modern, economically viable and environmentally more acceptable sewage processes and materials. At this sphere new zeolite products are developing with modified external surface.

Abstract: The calorimetric measurements together with microscopic observations and analyses relating to the interaction of cement paste with sulfate and nitrate solutions of various concentration were carried out. These salts modify the rate of cement hydration at early age. In the presence of sulfates the formation of some well crystallized calcium sulfates or calcium sulfoaluminates can be found. In case of nitrates there is no additional products. However, one can observe that the calcium silicate phase becomes less fibrous but more compact, with very small individual particles, as the nucleation from the liquid phase is disturbed. There are the accompanying cations incorporated in this product.