Crystallographic studies on the site selectivity of Ca<Superscript>2+</Superscript>, K<Superscript>+</Superscript>, and Rb<Superscript>+</Superscript> ions within zeolite Y (Si/Al = 1.56)

The single-crystals of Ca²⁺, K⁺-exchanged zeolite Y, and Ca²⁺, Rb⁺-exchanged zeolite Y were prepared by using flow method with mixed ion-exchange solution, whose Ca(NO₃)₂:KNO₃ mole ratios were 1:1 (crystal 1) and 1:100 (crystal 2), and Ca(NO₃)₂:RbNO₃ mole ratios were 1:1 (crystal 3) and 1:100 (crystal 4), respectively, with a total concentration of 0.05 M. They were fully dehydrated by vacuum dehydration at 723 K and 1 × 10^?6 Torr for 2 days. Their crystals were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group \(Fd \overline{3}\) m, respectively, and were refined to the final error indices R ₁/wR ₂ = 0.057/0.196, 0.073/0.223, 0.055/0.188, and 0.049/0.175 for crystals 1, 2, 3, and 4, respectively. In the structure of crystal 1 (|Ca₂₃K₂₉|[Si₁₁₇Al₇₅O₃₈₄]-FAU), 23 Ca²⁺ ions per unit cell occupy sites I, II′, and II; 29 K⁺ ions per unit cell are at sites II′, II, and III′. In the structure of crystal 2 (|Ca_18.5K₃₈|[Si₁₁₇Al₇₅O₃₈₄]-FAU), 18.5 Ca²⁺ ions per unit cell occupy sites I, I′, and II; 38 K⁺ ions are at sites I′, II, and III′. In the structure of crystal 3 (|Ca₂₇Rb₂₁|[Si₁₁₇Al₇₅O₃₈₄]-FAU), 27 Ca²⁺ ions per unit cell occupy sites I, II′, and II; 21 Rb⁺ ions per unit cell are at sites II′, II, and III. In the structure of crystal 4 (|Ca₁₈Rb₃₉|[Si₁₁₇Al₇₅O₃₈₄]-FAU), 18 Ca²⁺ ions per unit cell occupy sites I and II; 39 Rb⁺ ions per unit cell are at sites I′, II′, II, III, and III′. In the four crystals, the Ca²⁺ ion which has much smaller size and higher charge than other cations such as K⁺ and Rb⁺ energetically preferred at site I and so the first to be filled on it. Unlike Ca²⁺ ion, no K⁺ and Rb⁺ ions are found at site I, which are clearly less favorable for K⁺ and Rb⁺ ions.     

Hydrothermal Synthesis of Mn–Fe Nano Oxides and Their Composite for Removal of Zn<Superscript>2+</Superscript>, Ni<Superscript>2+</Superscript> and Co<Superscript>2+</Superscript> from Simulated Radioactive Waste

A study on the sorption of Zn²⁺, Ni²⁺ and Co²⁺ onto mixed oxide of Mn and Fe obtained at different hydrothermal conditions and its organic hybrid film modified with polyacrylamide (Mn–Fe oxide/PAM) has been examined. The characterization of inorganic oxides and its composite samples were performed using XRD, SEM, FTIR, XRF and DTA-TGA techniques. The percent sorption of Zn²⁺, Ni²⁺ and Co²⁺ on Mn–Fe oxide at pH 4.5 was 97, 11.85 and 10 % respectively with selectivity order Zn²⁺ ? Ni²⁺ > Co²⁺. The sorption value of Zn²⁺ at pH 4.5 onto Fe–Mn oxide reached nearly the same value of Zn²⁺ onto its composite. So, the new compound of Fe–Mn oxide has promising uses for separation of zinc ions while its composite can be used for removal all of these cations.     

An EPR study of Cu adsorption by clinoptilolite from Cl<Superscript>−</Superscript>, NO<Stack><Subscript>3</Subscript><Superscript>−</Superscript></Stack> and SO<Stack><Subscript>4</Subscript><Superscript>2−</Superscript></Stack> solutions

The concentration and the type of Cu²⁺ species adsorbed on a natural zeolite (Clinoptilolite) was measured and studied by using Electron Paramagnetic Resonance Spectroscopy (EPR). The EPR results together with macroscopic sorption data indicate that the solution ionic strength as well as, the type of electrolyte anion (Cl⁻, NO₃⁻ and SO₄²⁻ ions were examined) affect the amount of Cu adsorbed and the type of Cu surface complexes. The increasing in solution pH affects Cu adsorption quantitatively whereas; the type of surface complexes formed depends mainly on solution ionic strength. For low solution ionic strength, when the inhibition from solution species is limited, the adsorbed Cu is characterized by more than one type of chemical environment. On the contrary, for high solution ionic strength the Cu adsorption is inhomogeneous and EPR spectra show only one type of surface complex. When the anions of the background electrolytes are different, but of equal normality, the results indicate that in the presence of SO₄²⁻ discernible Cu surface complexes are formed whereas, for Cl⁻ and NO₃⁻ these surface formations are obtained only for high Cu adsorbed concentrations.     

Studies of Bone-Bonding Ability and Antibacterial Properties of Ag<Superscript>+</Superscript>, Cu<Superscript>2+</Superscript> or Zn<Superscript>2+</Superscript> ions Doping within Hench’s Bioglass and Glass-Ceramic Derivatives

Derived Hench’s bioglasses with specific ionic dopants Ag⁺, Cu²⁺, or Zn²⁺ have been prepared. The bone-boding ability or bioactivity behavior for the prepared glasses and their glass-ceramic derivatives has been investigated after immersion in phosphate solution for two weeks. Collective Fourier transform infrared absorption spectra (FTIR) and scanning electron microscopic (SEM) studies were conducted in order to study the in-vitro bioactivity behavior. X-ray diffraction (XRD) analysis was carried out to identify the crystallized phases upon thermal heat treatment through a two-step regime. The glasses and their glass-ceramic derivatives were tested to study their antibacterial or antifungal efficiency responding to the doped metal ions. FTIR spectra revealed the generation of two split peaks at about 560 and 605 cm^?1, after immersion in (0.2 M) sodium phosphate solution (Na₃PO₄), signifying the formation of a crystalline calcium phosphate phase, leading to hydroxyapatite formation. SEM examinations show characteristic rounded or nodular microcrystals for hydroxyapatite which support the FTIR data. X-ray diffraction analysis indicated crystallization of the main soda-lime silicate phase (1Na₂O.2CaO.3SiO₂) besides a secondary silicon phosphate phase (SiO₂.P₂O₅) in the studied glass ceramics. The route of crystallization is discussed on the basis of the presence of 6% P₂O_5; which facilitates the formation of phase separation and voluminous bulk crystallization of the main soda-lime silicate phase. The introduction of dopants is identified to cause no changes in the precipitated phases, with only minor changes in the percent of the crystalline phases. Experimental data indicate that the glass-ceramic samples are effective in bioactivity and antimicrobial efficiency.     

Binary and Ternary Heterometallic (La<Superscript>3+</Superscript>, Gd<Superscript>3+</Superscript>, Y<Superscript>3+</Superscript>)–Eu<Superscript>3+</Superscript> Functionalized SBA-15 Mesoporous Hybrids: Chemically Bonded Assembly and Photoluminescence

A novel kind of organic–inorganic monomer SUASi has been achieved by modifying 5-sulfosalicylic acid (SUA) with 3-aminopropyltrimethoxysilane (APS), subsequently binary and ternary Eu³⁺ mesoporous hybrid materials with 5-sulfosalicylic acid (SUA)-functionalized SBA-15 and 1,10-phenanthroline (phen) are synthesized by co-condensation of SUASi and TEOS in the presence of Eu³⁺ complex and Pluronic P123 as a template. Finally, luminescent hybrid mesoporous materials consisting of active rare earth ions (Eu³⁺)—inert rare earth ions (Y³⁺, La³⁺, Gd³⁺) complex covalently bonded to the mesoporous materials network have been obtained via this sol–gel approach. The physical characterization and photoluminescence of all these resulting materials are studied in detail. Especially the luminescent behavior has been studied with the different ratios of Eu³⁺–(Y³⁺, La³⁺, Gd³⁺), which suggests that the existence of inert rare earth ions can enhance the luminescence intensity of Eu³⁺. This may be due to the intramolecular energy transfer between Y³⁺, La³⁺, Gd³⁺, and Eu³⁺ through the covalently bonded mesoporous framework.     

Conversion of two-micron radiation into visible light using glass and ceramics based on ZBLAN: Но<Superscript>3+</Superscript> and ZBLAN: Ho<Superscript>3+</Superscript> + Yb<Superscript>3+</Superscript>

Visualization of infrared radiation of Tm:YLF-laser at the wavelength of 1908 nm has been investigated in the glass and ceramics samples with compositions of 53ZrF₄ · 20 BaF₂ · 1HoF₃ · 3YbF₃ · 3AlF₃ · 20NaF and 53ZrF₄ · 20BaF₂ · 3LaF₃ · 1HoF₃ · 3AlF₃ · 20NaF (mol %). In luminescence spectra of ZBLAN samples doped with Но³⁺, the bands at the wavelengths of 480, 540, and 650 nm were observed, which correspond to ⁵ F ₃ → ⁵ I ₈, ⁵ S ₂, ⁵ F ₄ → ⁵ I ₈, and ⁵ F ₅ → ⁵ I ₈ electron transitions in Но³⁺ ions with the maximum intensity of the red band (650 nm). Occupancy of the ⁵ S ₂ and ⁵ F ₄ levels in the ZBLAN: 1% Но³⁺ samples is related to the sequential absorption of the exciting radiation quanta. The level of ⁵ F ₅ is filled mainly due to the ionic interaction. Additional doping with the Yb³⁺ ions led to the change of the luminescence color to green and a decrease in the threshold radiation power density of the Tm:YLF-laser in ceramic samples up to 2 W/cm².     

A Novel Gd<Superscript>3+</Superscript>–Pb<Superscript>2+</Superscript> Doped LiSrPO<Subscript>4</Subscript> Phosphor for Phototherapy Lamp Applications

The phosphors LiSrPO₄:Gd³⁺ and LiSrPO₄:Gd³⁺, Pb²⁺ with different concentration of Gd³⁺ and Pb²⁺ were synthesized by combination of re-crystallization and modified solid state diffusion method. The synthesized phosphors were characterized using XRD, SEM and PL spectroscopies. The PL excitation spectra of LiSrPO₄:Gd³⁺ phosphor exhibit peak at 275 nm due to the ⁸S_7/2 →⁴I_J transition of Gd³⁺ ions and gave narrow UVB emission at 312 nm. The effect of Pb²⁺ ions on the PL properties of LiSrPO₄:Gd³⁺have also been investigated. Upon the addition of Pb²⁺ ions, the excitation of phosphors shows broad peak with maximum at 247 nm, overlapping the Hg 253.7 nm line. This addition of Pb²⁺ ions improved the emission intensity of narrow band UVB i.e. 312 nm under the excitation of 247 nm. The phosphor could be good candidate as phototherapy lamp phosphor material.     

Structure of Ca–Sr–Ba Sodium–Borosilicate Glasses according to <Superscript>11</Superscript>B and <Superscript>29</Superscript>Si NMR Spectroscopy

The structure of borosilicate glasses is studied with ¹¹B and ²⁹Si NMR spectroscopy in order to investigate the influence of replacement of Na₂O by oxides of alkali earth metals on their local structure. The quantitative data are analyzed with respect to their correspondence to the criterion of the average charge of the structural unit. The reasons for the deviation between the experimental results and this criterion are considered. It is shown that, in the case of glass devoid of borate structural units with nonbridging oxygen atoms, the corrected contents of these units are consistent with the predictions of thermodynamic modeling of the structure and properties of oxide glasses.     

Crystallization and Luminescence Properties of Sm<Superscript>3+</Superscript>-Doped SrO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> Glass-Ceramics

Sm³⁺-doped SrO–Al₂O₃–SiO₂ glass-ceramics with excellent luminescence properties were prepared by batch melting and heat treatment. The crystallization behavior and luminescent properties of the glass-ceramics were investigated. The results indicate that the crystal phase in this system is monocelsian (SrAl₂Si₂O₈). Under the excitation with blue light (475 nm) the Sm³⁺-doped SrO–Al₂O₃–SiO₂ glass-ceramics emit green, orange and red lights centered at 565, 605, 650 and 715 nm, which can be assigned to the ⁴G_5/2 → ⁶H_J/2 (J = 5, 7, 9, 11) electron transitions in Sm³⁺ ions, respectively. With the increase of nucleation/crystallization temperature, the crystallite part rises from 66 to 79%. Besides, by increasing crystallization temperature or concentration of Sm³⁺, the samples emission located at 565, 605 and 650 nm is intensified significantly. We envision that, by fine controlling and combining of these three (green, orange and red) lights in an appropriate proportion, the Sm³⁺-doped glass-ceramics are promising luminescence materials for white light-emitting diodes devices.     

Mechanistic Study of the NO + NH<Subscript>4</Subscript>NO<Subscript>3</Subscript> Reaction on H- and Fe/H-BEA Zeolites Using <Superscript>15</Superscript>N and <Superscript>18</Superscript>O Labeled Species

Reduction of NO by NH₃ over metal-promoted zeolites represents the principal reaction in the selective catalytic reduction (SCR) technology for NOx removal from Diesel engine exhausts. It has been established that addition of ammonium nitrate (AN) to the reaction mixture substantially enhances the rate of this reaction, decreasing the temperature necessary for an efficient deNOx process. Nevertheless, the nature of this effect has not been completely elucidated. To investigate the NO?+?AN reaction mechanism, we have used individual reactants labeled with either ¹⁵N or ¹⁸O (or both isotopes), thus obtaining an experimental background for proposing the route of the SCR accelerated by AN addition. For this study, we have used as the catalysts H-BEA and Fe/H-BEA zeolites with various Si/Al ratios and various amounts and states of the iron species.     

Zn<Superscript>2+</Superscript>-exchange kinetics and antimicrobial properties of synthetic zirconium umbite (K<Subscript>2</Subscript>ZrSi<Subscript>3</Subscript>O<Subscript>9</Subscript>·H<Subscript>2</Subscript>O)

Zirconium umbite, K₂ZrSi₃O₉·H₂O, is a microporous framework ion exchanger whose potential as a carrier for Zn²⁺ ions in antimicrobial formulations has not yet been investigated. Accordingly, batch Zn²⁺-exchange kinetics of synthetic zirconium umbite (K-UM) and the subsequent antimicrobial action of the zinc-bearing phase (Zn-UM) against Staphylococcus aureus and Escherichia coli are reported. Nonstoicheiometric over-exchange of Zn²⁺ for K⁺ was observed and attributed to hydrolysis and complexation reactions of Zn²⁺ within the umbite framework. The exchange process, which was described by a simple pseudo-first-order model (k ₁ = 2.69 × 10⁻⁴ min⁻¹, R ² = 0.992), did not achieve equilibrium within 120 h at 25 °C, by which time the uptake of zinc was found to be 1.04 mmol g⁻¹. The minimal bactericidal concentrations of Zn-UM for E. coli and S. aureus were found to be >10 g cm³ and <1.0 g cm³, respectively.     

Composite WSi<Subscript>2</Subscript>–<Emphasis Type="Italic">Me</Emphasis><Superscript>V</Superscript>B<Subscript>2</Subscript> materials in W–Si–<Emphasis Type="Italic">Me</Emphasis><Superscript>V</Superscript>–B systems

Sections are constructed for WSi₂–Me ^VB₂ of the quaternary systems W–Si–(V, Nb, Ta)–B described by eutectic diagrams of state with T _eut (1940 ± 20), (1980 ± 20) and (2020 ± 30)°C and a boride content in the eutectics of 35, 20 and 15 mol.% respectively. Translated from Novye Ogneupory, No. 3, pp. 41 – 44, March 2009.     

Effect of amino acids containing sulfur on the corrosion of mild steel in phosphoric acid solutions containing Cl<Superscript>−</Superscript>, F<Superscript>−</Superscript> and Fe<Superscript>3+</Superscript> ions: Behavior under polarization conditions

The effect of cysteine (RSH), methionine (CH₃SR), cystine (RSSR) and N-acetylcysteine (ACC) on the corrosion behavior of mild steel in 40% H₃PO₄ solution without and with Cl⁻, F⁻, Fe^3‰+ and their ternary mixture was studied using both potentiostatic and electrochemical impedance (EIS) techniques under anodic and cathodic polarization conditions. The inorganic additives stimulate the overall corrosion reaction while the amino acids inhibit it with a predominant effect on the dissolution of iron. Both RSH and ACC are adsorbed according to Temkin’s isotherm while adsorption of RSSR and CH₃SR follows Frumkin and Langmuir isotherms respectively. The standard free energy of adsorption (ΔG ) was found to be in the order: RSSR > RSH ≅ ACC > CH₃SR. The binary mixtures of Cl⁻ or F⁻ with RSH or CH₃SR are the best inhibitors (IE > 90%) while those containing ferric ions or blend I and amino acids are not good corrosion inhibitors. EIS measurements showed that the cathodic reaction, hydrogen evolution, is charge transfer controlled while the anodic one, iron dissolution, is a complex process.     

Production and use of vibrocast products from the company “Promresurs”<Superscript>1</Superscript>

An assortment of products made by the young company “Promresurs” for casting steel is presented. It is noted that the products are made with high-quality raw materials, modern technologies, and high-quality equipment. Results are presented from tests of the products at the Nizhniy Tagil Metallurgical Combine.     

Formation of carbamates and cross-linking of microbial poly(ε-<Emphasis Type="SmallCaps">l</Emphasis>-lysine) studied by <Superscript>13</Superscript>C and <Superscript>15</Superscript>N solid-state NMR

Formation of carbamates by amino groups of poly(ε-l-lysine) (ε-PL) and cross-linking of ε-PL were studied by using ¹³C and ¹⁵N solid-state NMR. It is a characteristic found in ε-PL cast from basic aqueous solution exposed to the air or gaseous CO₂. It is not observed in ε-PL cast from acidic aqueous solution and ε-PL cast from degassed aqueous solution under CO₂ free environment. The carboxyl carbon and amide nitrogen appear at 164 ppm in ¹³C spectrum and 92 ppm in ¹⁵N spectrum, respectively, which arise when some amino groups of ε-PL react with gaseous CO₂ to make carbamates. In addition to these peaks a peak at 171 ppm appears. We assigned it to amide C=O carbons which can not make intermolecular hydrogen bondings since there exist bulky carbamates groups close to these C=O groups. Self-assembly of ionic pairs of ammonium groups and carbamate anions leads to cross-linking of ε-PL.     

Kinetics and latex particles analysis on styrene emulsion polymerization induced by <Superscript>60</Superscript>Co γ rays in presence of anionic polymerizable emulsifier

⁶⁰Co γ rays induced styrene emulsion polymerizations were carried out with sodium undec-10-enoate (UDNa) as emulsifier at room temperature and the different kinetics was discussed. The influence of absorbed dose rate, monomer concentration and emulsifier concentration on kinetics and latex particles was studied. The polymerization kinetics relation was found as R _P ∝ D ^0.37 · M ^0.75 · E ^0.70 (R _P , maximum polymerization rate; D, absorbed dose rate; M, monomer concentration; E, emulsifier concentration). The particles’ diameter increases and particle size distribution (PSD) becomes narrower with the decrease of absorbed dose rate and increase of monomer content. The effect of UDNa content on particles’ diameter and particle size distribution is the same as that of emulsifier in conventional emulsion system. This type of emulsion polymerization can easily form monodisperse particles.     

Optimization of Enzymatic Synthesis of Cetyl 2-Ethylhexanoate by Novozym<Superscript>®</Superscript> 435

Waxes are esters obtained from long-chain fatty acids and long-chain alcohols which are biodegradable, biocompatible and nontoxic. Seafowl feather oil is a natural wax ester that exists on seafowl feathers. Cetyl 2-ethylhexanoate is the major ingredient of seafowl feather oil. Cetyl 2-ethylhexanoate is widely used in cosmetics as a base oil because of its lubricity, moisture retention and non-toxic properties. An optimal production of cetyl 2-ethylhexanoate by direct esterification of cetyl alcohol with 2-ethylhexanoic acid was developed using an immobilized lipase (Novozym^® 435) as a catalyst in n-hexane. Response surface methodology (RSM) and 5-level-4-factor central composite rotatable design (CCRD) were employed to evaluate the effects of reaction time, reaction temperature, substrate molar ratio, and enzyme amount on the yield of cetyl 2-ethylhexanoate. The results show that reaction time, reaction temperature, substrate molar ratio, and enzyme amount have significant effects on the yield of the esterification reaction. On the basis of ridge-max analysis, the optimum conditions were as follows: a reaction time of 2.65 days, a reaction temperature of 56.18 °C, a substrate molar ratio of 2.55:1, and an enzyme amount of 251.39%. The predicted and experimental values of molar conversion were 91.95 and 89.75 ± 1.06%, respectively.