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.     

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.     

Structural and Magnetic Properties of Cu<Superscript>2+</Superscript> Substituted Co–Zn Ferrite Nanoparticles,Synthesized by Sol–Gel Combustion Method

In this work, the effect of Cu content on structural and magnetic properties of Cobalt–Zinc Ferrite nanoparticles synthesized by sol–gel combustion method have been investigated. All the samples exhibit cubic spinel structure and the lattice constant decreases linearly with increasing Cu-content. Average crystallite sizes calculated from Debye–Scherrer formula are in the range of 51–100 nm. The broadening of X-ray diffraction peaks decrease with increasing Cu content ‘x’ suggest that crystallite size increases with increasing ‘x’. Cation distribution estimated form X-ray line intensity calculations show that Cu ions simultaneously occupy tetrahedral (A) and octahedral (B) sites with different ratio and Zn and Co ions occupies A and B sites respectively. With increasing Cu content a fraction of Co ions migrate to A site when x?>0.2. Grain sizes estimated from SEM are found to be increase with increasing Cu content. Particle size calculated using TEM for the undoped Co–Zn ferrites is about 55 nm. Saturation magnetization (Ms), Coercivity (Hc) and remanent magnetization (Mr) that varies significantly with Cu-Content. Saturation magnetization decreases from 90.7 emu/g (x?=?0.0) to 51 emu/g (x?=?0.4). The proposed cation distribution supports the variation in saturation magnetization and Coercivity with increasing Cu content.     

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.     

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.     

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.     

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.     

Preparation and Luminescent Properties of Tb<Superscript>3+</Superscript>-doped SrO–Al<Subscript>2</Subscript>O<Subscript>3</Subscript>–SiO<Subscript>2</Subscript> Glass–Ceramics for white Light-Emitting Diode

Tb³⁺-doped SrO–Al₂O₃–SiO₂ glass-ceramics are prepared by melting under ambient atmosphere and followed by two-step heat treatment approach. Extensive differential thermal analysis, X-ray diffraction and scanning electron microscope characterizations are applied to investigate thermal properties, crystal structure, and morphology of these glass-ceramics. The results indicate that the optimal ratio of two nucleation agents (TiO₂ and ZrO₂) is 3:1 (molar fraction) in glass-ceramics. In addition, several heat treatment schedules are developed to study the influence of treatment temperature on luminescence properties of Tb³⁺- doped glass-ceramics. The results demonstrate that there are four emission bands located at 489, 547, 588 and 623 nm under 376 nm ultraviolet excitation, corresponding to ⁵D₄ → ⁷F_j (j = 6, 5, 4, 3) transitions of Tb³⁺, respectively. At last, the corresponding chromaticity coordinates are calculated and constructed, which indicates that the Tb³⁺ glass-ceramic can emit approximate white light under 376 nm ultraviolet excitation when they nucleated at 950°C and crystallized at 1050°C. The white immersion approached standard illuminant C as the crystallization temperature increased.     

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.     

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.     

Synthesis,Characterization and Ion Exchange Behavior of Polyaniline Stannic Silicomolybdate,an Organic–Inorganic Composite Material: Quantitative Separation of Pb<Superscript>2+</Superscript> Ions from Industrial Effluents

Polyaniline stannic silicomolybdate, an organic–inorganic composite material was synthesized by mixing polyaniline, an electrically conducting organic polymer into the matrices of inorganic precipitate of stannic silicomolybdate. The experimental parameters such as mixing volume ratio and pH were established for the synthesis of the material. The material was found granular, thus suitable for column operations. Polyaniline stannic silicomolybdate shows better ion exchange capacity and thermal stability. The exchanger was characterized on the basis of instrumental techniques such as FTIR, TGA, DTA XRD and SEM. The X-ray diffraction study showed semi-crystalline nature. The elution behavior of the material was also examined. The SEM micrographs show the difference in surface morphology of inorganic component and the composite material. Distribution coefficient studies were performed for different metal ions in varied solvent systems such as Triton X-100, trichloroacetic acid and acetic acid. The effect of temperature on the distribution coefficient was also studied. It was found that 40 °C appeared to be the most suitable temperature. The material was found to be selective for Pb²⁺ ion. On the basis of distribution coefficient values, some analytically important binary separations of metal ions viz. Mg²⁺–Pb²⁺, Zn²⁺–Pb²⁺, Cd²⁺–Pb²⁺ and Mg²⁺–Cu²⁺ were achieved on polyaniline stannic silicomolybdate columns. The practical utility of polyaniline stannic silicomolybdate was explored by achieving quantitative separation of Pb²⁺ in industrial waste effluents from battery manufacturing units.     

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.     

Electrical and Dielectric Properties of Non-magnetic Al<Superscript>3+</Superscript> Substituted Ni–Zn Nano Ferrites for High Frequency Applications

The effect of Al substitution on electrical and dielectric parameters of Ni–Zn ferrite has been discussed in the present work. The phase identification, surface morphology was studied using X-ray diffractometer (XRD), scanning electron microscope (SEM), respectively. The XRD patterns confirm the single-phase formation of these ferrites. With Al³⁺, substitution lattice parameter decreases due to smaller Al³⁺ ions replacing Fe³⁺ ions. The average grain size obtained from SEM results are in the range of 390–27 nm. The DC resistivity was observed to increase with increasing Al³⁺ ions concentration due to the unavailability of Fe³⁺ ions. Dielectric constant (\(\upvarepsilon ^{\prime }\)) and dielectric loss tangent (tan δ) have been studied as a function of frequency (1 kHz–10 MHz) and temperature (50–300 °C). The observed results are explained on the basis of interfacial polarization as predicted by Maxwell and Wagner.     

Effects of dietary supplementation of rapeseed oil on metabolism of [1-<Superscript>14</Superscript>C]18∶1n−9, [1-<Superscript>14</Superscript>C]20∶3n−6, and [1-<Superscript>14</Superscript>C]20∶4n−3 in atlantic salmon heaptocytes

Atlantic salmon were fed fish meal-based diets supplemented with either 100% fish oil (FO) or 100% rapeseed oil (RO) from an initial weight of 85 g to a final average weight of 280 g. The effects of these diets on the capacity of Atlantic salmon hepatocytes to elogate, desaturate, and esterify [1-¹⁴C]18∶1n−9 and the immediate substrates for the Δ⁵ desaturase, [1-¹⁴C]20∶3 n−6 and [1-¹⁴C]20∶4n−3, were investigated. Radiolabeled 18∶1n−9 was mainly esterified into cellular TAG, whereas the more polyunsaturated FA, [1-¹⁴C]20∶3n−6 and [1-¹⁴C]20∶4n−3, were primarily esterified into cellular PL. More of the elongation product, [1-¹⁴C]20∶1n−9, was produced from 18∶1n−9 and more of the desaturation and elongation products, 22∶5n−6 and 22∶6n−3, were produced from [1-¹⁴C]20∶3n−6 and [1-¹⁴C]20∶4n−3, respectively, in RO hepatocytes than in FO hepatocytes. Further, we studied whether increased addition of [1-¹⁴C]18∶1n−9 to the hepatocyte culture media would affect the capacity of hepatocytes to oxidize 18∶1n−9 to acid-soluble products and CO₂. An increase in exogenous concentration of 18∶1n−9 from 7 to 100 μM resulted in a nearly twofold increase in the amount of 18∶1n−9 that was oxidized. The conversion of 20∶4n−3 and 20∶3n−6 to the longer-chain 22∶6n−3 and 22∶5n−6 was enhanced by RO feeding in Atlantic salmon hepatocytes. The increased capacity of RO hepatocytes to produce 22∶6n−3 was, however, not enought to achieve the levels found in FO hepatocytes. Our data further showed that there were no differences in the hepatocyte FA oxidation capacity and the lipid deposition of carcass and liver between the two groups.     

Dioxirane oxidation of 3β-substituted Δ<Superscript>5</Superscript>-steroids

This article reviews the utility of dioxiranes in the oxidation of 3beta-substituted delta5-sterols. Dioxiranes are the smallest cyclic peroxides that contain a carbon atom. They can be generated in situ from Oxone (2KHSO5.KHSO4.K2SO4) and a ketone. Dioxiranes are versatile oxidizing agents. The most common reaction of dioxiranes is epoxidation, with nearly 1:1 ratios of alpha/beta isomer products in all cases. delta5-Steroids with different side chains were epoxidized by dioxiranes generated in situ from several commercially available ketones. Although ketones function as catalyst, they were used in about an equivalent amount or large excess to accelerate the reaction.     

Electrochemical promotion in O<Superscript>2−</Superscript> cells during propane oxidation

The catalytic oxidation of propane was studied in an oxygen ion conducting solid electrolyte cell at 623–773 K and atmospheric total pressure. Three catalyst-electrodes were tested, Pt, Pd and Ag. Under open circuit, the technique of Solid Electrolyte Potentiometry (SEP) was used to monitor the thermodynamic activity of oxygen adsorbed on the catalyst surface during reaction. Under closed circuit, the effect of electrochemical promotion was investigated. On Pt and Pd, the promoting effect was of the “inverted volcano” type. On Pt, the reaction exhibited a strong NEMCA effect; the closed circuit rate exceeded the open circuit rate by more than three orders of magnitude. On Pd, on the other hand, the effect was hardly Faradaic. On Ag, a moderate NEMCA behavior was observed and the promoting effect was purely electrophobic. Both open and closed circuit results obtained with these three catalyst-electrodes, are evaluated and compared to each other.     

Core–Shell Heterostructured BiVO<Subscript>4</Subscript>/BiVO<Subscript>4</Subscript>:Eu<Superscript>3+</Superscript> with Improved Photocatalytic Activity

To enhance the photocatalytic activity of monoclinic scheelite (ms) BiVO₄ for dye degradation, the heterostructured core (BiVO₄)/shell (BiVO₄:Eu³⁺) samples were synthesized by sol–gel method. The samples were characterized by UV–Vis diffuse reflectance spectroscopy, X-ray diffraction (XRD) and X-ray photoelectron spectra (XPS). The results reveal that as-synthesized photocatalysts are characteristic of ms core/shell structure, responsive to visible light. The XPS spectra confirm that the doped Eu³⁺ mainly distributed in the outside layer of BiVO₄ particle. The valence band (VB) spectra indicate the shell (BiVO₄:Eu³⁺) exhibits a high carrier mobility. The core/shell photocatalysts showed higher photocatalytic activity than pure BiVO₄ through degrading Rhodamine B and Methylene blue. The better performance of core/shell heterojunction mainly results from that the Eu³⁺ ions selectively present on shell layer, increasing the VB value of shell layer (forming a interface electric field with core) and carrier mobility. It is considered that the half-filled 7f–electron configuration of Eu³⁺ can improve the electron trapping and transfer. Besides, the low PL intensity and high S_BET of BiVO₄/BiVO₄:Eu³⁺ contribute to enhanced photocatalytic performances.     

Synthesis and Properties of PPV–Based (η<Superscript>6</Superscript>–Arene)Cr(CO)3–Containing Polymers Having Alkyldiphenylamine or Triarylamine in the Main Chain

Summary Novel poly(p–phenylenevinylene)–based (⁶–arene)Cr(CO)3–containing polymers including the alkyldiphenylamine or triarylamine units in the main chain were synthesized by the Homer–Wadsworth–Emmons coupling reaction. The structures of the polymers were confirmed by NMR and FT–IR spectra. The polymers were soluble in common organic solvents such as THF, CHCl₃, and CH₂Cl₂. The polymer showed interaction between the electron–withdrawing (⁶–arene)Cr(CO)³ unit and the unshared electron pair on the nitrogen atom along the polymer backbone.     

Crystallographic studies of fully dehydrated partially Zn<Superscript>2+</Superscript>-exchanged zeolite Y (FAU,Si/Al = 1.56) depending on Zn<Superscript>2+</Superscript> concentration of aqueous solution during exchange

Four single crystals of fully dehydrated and partially Zn²⁺-exchanged zeolites Y (Si/Al?=?1.56) were prepared by the static ion-exchange method using a mixed ion-exchange solution in which Zn(NO₃)₂:NaCl mole ratios were 1:1 (crystal 1), 1:25 (crystal 2), 1:50 (crystal 3), and 1:100 (crystal 4), respectively, with a total concentration of 0.05 M, and followed by vacuum dehydration at 673 K. Their single-crystal structures were determined by single-crystal synchrotron X-ray diffraction techniques in the cubic space group Fd\(\bar {3}\)m and refined to the final error indices R₁/wR₂?=?0.0459/0.1454, 0.0449/0.1283, 0.0427/0.1284, and 0.0486/0.1680, respectively. Their unit-cell formulas are |Zn₂₅Na₂₅|[Si₁₁₇Al₇₅O₃₈₄]-FAU (crystal 1), |Zn_19.5Na₃₆|[Si₁₁₇Al₇₅O₃₈₄]-FAU (crystal 2), |Zn_19.5Na₃₆|[Si₁₁₇Al₇₅O₃₈₄]-FAU (crystal 3), and |Zn₇Na₆₁|[Si₁₁₇Al₇₅O₃₈₄]-FAU (crystal 4), respectively. The degree of Zn²⁺ exchange decreases from 67 to 19% as the initial concentration of Zn²⁺ decrease and the initial concentration of Na⁺ increases in given ion-exchange solutions.     

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.