Papers by Keyword: Sodium

Abstract: The electronic structure of ultrathin Na/GaN interfaces was studied using photoelectron spectroscopy with synchrotron radiation in the photon energy range of 75–770 eV. The experiments were carried out in situ in ultrahigh vacuum of 5·10^–10 Torr with submonolayer sodium coverages on the gallium nitride surface. The photoemission spectra of the Ga 3d and N 1s core levels were studied at different excitation energies. It was found that Na adsorption causes a decrease in the intensity and a shift in the spectra of the Ga 3d and N 1s core levels towards higher binding energies. It was found that the sodium adsorption leads to some changes in the spectra due to charge transfer between the Na adlayer and the surface Ga or N atoms.

Abstract: The influence of different acidic medium, including hydrochloric acid, nitric acid and perchloric acid on the absorbance of sodium by flame atomic absorption spectrometry was studied. The results showed that the effects of acidic medium and water on the determination of sodium were as follows: hydrochloric acid > perchloric acid > nitric acid > water. Acid effect changed with the increase of acid concentration, however, the absorbance value of sodium element decreased when the concentration of acid was higher than 1%~2%. This effect was more obvious for high content of sodium. The detection limits, repeatability and recovery of the samples under the three acidic medium were compared. The optimum acid conditions were determined and the sensitivity of the method was improved.

Abstract: The new reconstructions formed by sodium adsorption on Pb-terminated Si (111) surface were obtained: 2x2+2sqrt3x2sqrt3, 4x1, 3x3 and others. These surface structures have been observed by low-energy electron diffraction (LEED) and phase diagram for 2D binary (Na,Pb)/Si (111) system has been obtained. The (Na,Pb)/Si (111) system is considered as a two-dimensional alloy layer with highly ordered structure. Influence of two-dimensional alloys on surface conductivity of Si (111) substrate has been studied in situ by four-point-probe method.

Abstract: Biological apatite presented in bone and teeth of mammals contains various ions in trace levels. Substitution of the ions into hydroxyapatite (HAp) can ensure higher bioactivity compared with stoichiometric HAp. It is known that sodium (Na) has been detected as an abundant trace element next to the presence of calcium and phosphorous in natural bone. The aim of this study is to examine the effect of substitution of Na on material properties of the HAp ceramics. Therefore, we have synthesized the sodium-substituted hydroxyapatite (NaAp) ceramics without carbonate ions by an ultrasonic spray-pyrolysis (USSP) technique. The USSP technique can obtain the desired powder by directly heating droplets of a sample solution with the target composition. Both NaAp powders with (Ca+Na)/P ratios of 1.67, 1.72 and 1.77 and their ceramics did not contain carbonate ions, and HAp single phase was maintained even after sintering. It was revealed that the substitution of Na enhanced the sinterability of HAp ceramics and improved the apatite-forming ability.

Abstract: This paper contains the continuation of basic research from 2012 - the molar ratio influence to water glass coatings basic properties (adhesion, diffusion properties, surface quality) was expanded with basic resistance (combination of sun, UV light and rain). Most silicate coatings for concrete protection are currently based on potassium water glass. Water glass matrix itself is, however, insufficient for coatings matrix and often is modified by polymer substances for the coating purpose. Combinations of water glass basic matrix (Sodium, Potassium, Lithium, Sodium - Lithium and Potassium - Lithium) with the appropriate polymer modifiers is also content of the presented paper. Polymer dispersions modification effect to basic properties and resistance to developed silicate coating binder is also part of paper.

Abstract: Relocation of alkali metals sodium, potassium and cesium during oxidation of 4H-SiC has been studied by secondary ion mass spectrometry. The alkali metal source has been introduced by ion implantation before oxidation into n-and p-type 4H-SiC samples. Dry oxidation of SiC has been performed at 1150 oC during 4, 8 and 16 h. In the formed oxide, the main part of the alkali metals diffuses out via the SiO₂ surface. Close to the moving SiO₂/SiC interface, a minor amount of alkali metals is retained. In the SiC material, the main amount of implanted alkali atoms is not redistributed during the oxidation, although a minor amount diffuses deeper into the samples. For p-type 4H-SiC, the diffusion deeper into the samples of the studied alkali metals decreases as the mass increases, Na⁺<K⁺<Cs⁺, but the sodium mobility is substantial already at 1150 °C.

Abstract: A new SPR sensor surface based onself-assembled-Calix [4] arene-derivative-monolayer was proposed for the detection of sodium in water. The immobisation of claixarene onto the gold surface was confirmed by impedance spectroscopy (EIS). Three alkaliions were used K⁺, Na⁺ and Ca²⁺ and the influence of pH on ions detection was studied and optimized. The Calix [4] arene-gold SPR sensor developed was characterized by low limit of detection (LOD) for about 10^-10 M, high sensitivity and wide linear detection range between 10^-6M and 10^-14M.

Abstract: The negative impact of soil salinity on agricultural yields is disturbing and significant, especially when related to agricultural plants, whose sensitivity to salinity is frequently, but not exclusively, associated with the abundance of Na⁺ in the soil, which in excess becomes toxic for plants. This work aims to propose an alternative for the control of Na⁺ present in waters from saline soils, by the possibility of applying bovine hydroxyapatite as a way to remedy this problematic. Hydroxyapatite powders were processed from bovine bone. The powders were characterized by X-ray diffraction analyses. Preliminary experiments were performed in batches at room temperature, adding together 5g hydroxyapatite and a dilute solution of sodium chloride. Liquid samples were analyzed by atomic absorption spectrophotometry. The results showed that the hydroxyapatite could be a promising alternative for the reduction of Na⁺ concentration in waters from saline soils.

Abstract: The powder of Li_1.4Al_0.4Ti_1.6 (PO₄) ₃ has been synthesized by a solid phase reaction between Li₂CO₃, Al₂O₃, TiO₂ and NH₄H₂PO₄. Sodium removal was studied in an extensive series of tests involving different ionic exchange process variables such as time and temperature. The results indicate that the Na/Li ion exchange reaction rate increased obviously with increasing temperature, and the Na/Li ion exchange kinetics process of Li_1.4Al_0.4Ti_1.6 (PO₄) ₃ in lithium chloride solution could be shown approximately by the equation of JMAK. Furthermore, it is concluded that the Na⁺-removed materials obtained from NASICON-type ceramics synthesized can serve as selective Na⁺ absorbent due to its high selectivity and larger ion exchange capacity.

Abstract:

In the Kroll and Hunter processes to produce titanium from TiCl₄, magnesium and sodium are used respectively as reducing agents. These processes are slow and very energy intensive and consequently much work was done over the years to improve the economics of producing these metals. In this regard, more success has been achieved with improving the economics of magnesium electrowinning than with alkali metal electrowinning. Magnesium electrowinning cells generally have electrodes with a planar shape and alkali metal electrolysis cells have electrodes with a cylindrical shape. Furthermore, recent advances in magnesium electrolysis allowed the introduction of bipolar electrodes, whereas such electrodes have not been introduced in alkali metal electrowinning cells. It is conceptually possible to replicate the advances in the construction of magnesium electrowinning cells to improve sodium or other alkali metal electrowinning cells. However, there are underlying fundamental reasons why it would be difficult to do so.In this paper the technologies for magnesium and alkali metal electrowinning cells are briefly reviewed. The reasons why it would be difficult to copy the improvements made in magnesium electrowinning technology to alkali metal electrowinning technology are then explained in terms of the implications of the underlying chemical and physical properties of the chemicals involved in the processes.