A survey of ABX3 halides for optical second harmonic generation

A group of ABX₃ halides have been searched for nonlinear optical character by testing each for second harmonic generation in powdered samples using the method of Kurtz and Perry. It was found that most simple ternary halides do not produce second harmonic light and apparently have centrosymmetric structures. (CH₃)₄NHgCl₃, (CH₃)₄NHgI₃, (CH₃)₄NHgBr₃, KHgI₃·H₂O, and RbHgI₃·H₂O were found to produce SHG and the first two of these compounds were found to be phase-matchable.     

Preparation of hydroxyapatite ceramics by hydrothermal hot-pressing method at 300 °C

Hydroxyapatite (HA) ceramics were prepared by a hydrothermal hot-pressing (HHP) method at a low temperature (300 °C). DCPD (CaHPO₄·2H₂O) + Ca(OH)₂, OCP (Ca₈H₂(PO₄)₆·5H₂O) + Ca(OH)₂, DCPD + NH₃·H₂O, OCP + NH₃·H₂O or α-TCP (Ca₃(PO₄)₂) + NH₃·H₂O were used as the precursors. The mixture was treated by HHP under a condition of 300 °C/40 MPa. In sample DCPD + Ca(OH)₂ and OCP + Ca(OH)₂, the HA ceramics obtained showed a porous and homogenous microstructure, and the bending strength were 9.9 MPa and 10.9 MPa, respectively. In sample α-TCP+NH₃·H₂O, rod-like HA crystals produced. When the starting materials were DCPD + NH₃·H₂O, OCP + NH₃·H₂O, the HA particles produced exhibited plate-like features. It appeared that the plate-like HA particles stacked into a lamellar structure. The formation of the lamellar structure leads to a noticeable improvement in fracture property of the HA ceramic. The bending strength and the fracture toughness of the sample prepared from OCP and ammonia water reach 90 MPa and 2.3 MPam^1/2, respectively.     

Three-dimensional printing of flash-setting calcium aluminate cement

Three-dimensional indirect printing of flash-setting calcium aluminate cement (CAC) was investigated. Upon water injection into a biphasic mixture of tricalcium aluminate (3CaO·Al₂O₃) and dodecacalcium heptaaluminate (12CaO·7Al₂O₃) (phase ratio 0.56/0.44) initially a gel formed acting as a bonding phase which stabilizes the printed object geometry. Post-exposure in water finally resulted in the formation of 2CaO·Al₂O₃·8H₂O and 4CaO·Al₂O₃·19H₂O reaction phases as confirmed by SEM, X-ray diffraction, and FTIR analyses. Reduction of porosity by volume expansion upon hydrolysis reaction from 50% after printing to 20% after post-treatment gave rise for an increase of compressive strength from 5 to 20 MPa, respectively. A bone regenerating scaffold for a micro-vascular loop model was fabricated by 3D printing and hydraulic reaction bonding to demonstrate the potential of using flash-setting calcium aluminate cement powder for biomedical ceramic applications.     

Sol–gel preparation and characterization of perovskite lanthanum lithium titanate

Lanthanum lithium titanate, belonging to the solid solution La_0.66Li_0.33TiO₃, was prepared by sol–gel method from LiNO₃, La(NO₃)₃·6H₂O and Ti(OC₄H₉)₄ in ideal cation stoichiometry for La_0.66Li_0.33TiO₃. The synthesized product was characterized by X-ray powder diffractometry (XRD) and thermal analyses (DTA-TG). Electron microscopy investigations (SEM and TEM) was used to evaluate the morphology of synthesized La_0.66Li_0.33TiO₃. The bulk quantities of nano-sized particles of layered La_0.66Li_0.33TiO₃ have been obtained at 1,000°C using the modified sol–gel method. The mean diameter of La_0.66Li_0.33TiO₃ nano-crystals was about 123 nm.     

Growth and some properties of barium-cadmium formate single crystals: (I) Crystal growth and morphology

The growth of barium-cadmium formate BaCd(HCO₂)₄·2H₂O single crystals by slow cooling method and their characterization by selective etching are reported. It was found that BaCd(HCO₂)₄·2H₂O crystallizes from aqueous solution in 2/m class of the monoclinic system. Crystals grown during a period of 1 month have dimensions of about 2 × 1.5 × 10 cm³. The typical twinning for these crystals has been observed and investigated by the selective etching. The dislocation density has been estimated to be 3·10² – 2·10³ cm^?2.     

Synthesis of Cu3(PO4)2 · H2O based solid solutions through Co or Ni substitution for Cu

New substitutional solid solutions have been synthesized: (Cu_{1 ? x} Co_x)₃(PO₄)₂ · H₂O (0 < x ≤ 0.20), (Cu_{1 ? x} Ni_x)₃(PO₄)₂ · H₂O (0 < x ≤ 0.12), and (Cu_{1 ? y} Co_y)₃(PO₄)₂ · H₂O (0.55 ≤ y ≤ 0.65). The first two solid solutions are isostructural with Cu₃(PO₄)₂ · H₂O (monoclinic symmetry, sp. gr. C2/c); the third solid solution also has a monoclinic structure, which is a Cu₃(PO₄)₂ · H₂O related superstructure. The lattice parameter b of (Cu_{1 ? y} Co_y)₃(PO₄)₂ · H₂O (0.55 ≤ y ≤ 0.65) is almost twice that of (Cu_{1 ? x} Co_x)₃(PO₄)₂ · H₂O (0 < x ≤ 0.20), while their a and c parameters differ little. The solid solutions have been characterized by chemical analysis, x-ray diffraction, IR spectroscopy, and thermal analysis.     

Fabrication of the monolithic materials via novel monocomponent sol-gel process

SiH(OC₂H₅)₃ was used as a gel accelerant to prepare transparent, noncracking, high-purity silica gel monoliths with a lower volume shrinkage and shorter gel time. The silica gel monoliths prepared via the monocomponent bulk sol-gel process possess a microporous structure and a good transmittance in the UV/Vis region, and consist of 89% silica and 11% small molecules. The text was submitted by the authors in English.     

Mechanism of decomposition of UO2(NO3)2·6H2O + Fe(NO3)3·9H2O mixture under the action of microwave radiation

Products of decomposition of the UO₂(NO₃)₂·6H₂O + Fe(NO₃)₃·9H₂O mixture under the action of microwave radiation (MWR) were studied by thermal gravimetric, X-ray phase, and chemical analyses. The results obtained were compared to the published data for various U and Fe compounds. The final products of decomposition of the UO₂(NO₃)₂·6H₂O + Fe(NO₃)₃·9H₂O mixture under the action of MWR for 3?C5 min (the maximal temperature of the process, equal to 140?C150°, is attained within 2?C3 min of irradiation), apart from gaseous products, are UO₂(OH)NO₃, UO₃, and Fe₂O₃. The action of MWR on the UO₂(NO₃)₂·6H₂O + Fe(NO₃)₃·9H₂O mixture under the examined conditions does not lead to the formation of uranyl ferrite.     

Crystallization behaviour of β-spodumene in the calcination of Li2O-Al2O3-SiO2-ZrO2 gels

This work was carried out in order to prepare precursor powders with a spodumene composition (Li₂O·Al₂O₃·4SiO₂, LAS) and to investigate their crystallization behaviours during calcination. A fine β-spodumene type amorphous powder was obtained through sol-gel techniques using LiOCH₃, Al(OC₂H₅)₃, Si(OC₂H₅)₄ and Zr(OC₂H₅)₄ as the starting metal alkoxides. The process included well controlled hydrolysis polycondensation of the raw alkoxides. Differential thermal analysis (DTA), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and electron diffraction (ED) analyses were utilized to study the crystallization behaviour of the gels. The activation energy of β-spodumene crystallization was 192 kJ mol⁻¹ for LAS gels with 4 wt% ZrO₂, being much smaller than those of LAS gel without ZrO₂, 382 kJmol⁻¹. For calcination at 800–1200°C, the crystallized phases comprised a major phase of β-spodumene and a minor phase of zirconia (ZrO₂).     

Exploration of the structural,spectroscopic and thermal properties of double sulfate monohydrate NaSm(SO4)2·H2O and its thermal decomposition product NaSm(SO4)2

Samarium-sodium double sulfate crystalline hydrate NaSm(SO₄)₂·H₂O was obtained by the crystallization from an aqueous solution containing equimolar amounts of ions. The anhydrous salt of NaSm(SO₄)₂ was formed by a thermally induced release of the equivalent of water from NaSm(SO₄)₂·H₂O. The kinetic parameters of thermal decomposition were determined (E_a = 102 kJ/mol, A = 9·10⁶). The crystal structures of both compounds were refined from the X-ray powder diffraction data. Sulfate hydrate NaSm(SO₄)₂·H₂O crystallizes in the trigonal symmetry, space group P3₁21 (a = 6.91820(3) and c = 12.8100(1) Å, V = 530.963(7) ų). The anhydrous salt crystallizes in the triclinic symmetry, space group P-1 (a = 6.8816(2), b = 6.2968(2) and c = 7.0607(2) Å, α = 96.035(1), β = 99.191(1) and γ = 90.986(1)°, V = 300.17(1) ų). The vibrational properties of compounds are mainly determined by the sulfate group deformations. The luminescence spectra of both sulfates are similar and are governed by the transitions of samarium ions ⁴G_5/2 → ⁶H_J (J = 5/2, 7/2, 9/2 and 11/2). The anhydrous sulfate is stable up to 1100 K and undergoes an almost isotropic expansion when heated. After 1100 K, the compound decomposes into Sm₂(SO₄)₃ and Na₂SO₄.     

Decomposition of uranyl nitrate in the silica gel matrix under the action of microwave radiation

Decomposition of aqueous solutions of uranyl nitrate in a matrix of granulated silica gel of KSKG grade under the action of microwave radiation (MWR) was studied. Microwave irradiation leads not only to formation of solid decomposition products UO₃, UO₂(OH)NO₃, and their hydrates in pores of KSKG granules, but also to accumulation of gaseous NO _x and H₂O. The presence of NO _x in KSKG pores leads to HNO₃ formation in the course of washing of sorbent granules with water. This prevents hydrolysis of uranyl nitrate and formation of UO₂(OH)₂·H₂O in KSKG pores. Washout of uranium with water and HClO₄ solutions from the KSKG fraction containing products of decomposition of 2 and 10 g of the initial UO₂(NO₃)₂·6H₂O under the action of MWR (hereinafter denoted as KSKG-P-I) was studied. Upon ∼7-day contact of the solid and liquid phases at the total ratio S : L = 1 : 20, from 5 to 14% of U passes into the aqueous phase from KSKG-P-I samples obtained in experiments with 10 and 2 g of UO₂(NO₃)₂·6H₂O, respectively. In the course of repeated treatments of KSKG-P-I with water, pH of the wash water increased from 3 to 6, owing to removal of NO _x from KSKG pores. Then an insoluble phase of uranyl hydroxide UO₂(OH)₂·H₂O, which can also be presented as hydroxylated uranium trioxide UO₃·2H₂O, is gradually formed from the solution obtained by treatment of KSKG-P-I with water. On treatment of KSKG-P-I with HClO₄ solutions (pH 1–2), virtually all uranium species formed by MWR treatment of aqueous uranyl nitrate solutions in KSKG matrix dissolve (at a contact time of the solid and liquid phases of ∼21 days, the amount of U that passed into HClO₄ solutions is ∼90%). The amount of the U form that is not extracted with HClO₄ solutions and remains in KSKG granules is ∼12% of its initial amount. X-ray phase analysis suggests that the uranium species remaining in KSKG are silicate compounds formed by sorbent saturation with a uranyl nitrate solution and subsequent MWR treatment.     

Proton conduction in solids—A Raman spectral study

The mechanism of proton conduction in hydrogen-bonded solids and the importance of Raman investigations to understand it are discussed here. The results of Raman investigations on the protonic conductors (NH₄)₃H(SO₄)₂ and Li₂SO₄·H₂O under small d.c. electric fields have been discussed. The enhancement in intensity of the 859, 829 and 330 cm^?1 bands of(NH₄)₃H(SO₄)₂ has been explained on the basis of proton movement along the N-H...O bond. Spectral changes of the bands due to torsional oscillation of the ammonium ion indicate the probability of hindered rotation of this group. The appearance of new bands at 773 and 1680cm^?1 in Li₂SO₄·H₂O indicates the formation of H₃O⁺ electrolysis. The changes in stretching and bending modes of water are explained on the basis of polarizability changes induced by the migration of proton along the 0-H...0 bond and reorientation motion of water molecules.     

Synthesis and luminescent properties of alkali-metal and ammonium fluorosulfatozirconates and fluorosulfatohafnates

We have synthesized a variety of alkali-metal and ammonium fluorosulfatometallates (titanates, zirconates, and hafnates). The alkali fluorosulfatozirconates and fluorosulfatohafnates have been shown to exhibit efficient roentgenoluminescence (RL) in the UV through visible spectral region, with a maximum at 390–440 nm. Their RL spectra depend significantly on their composition (cation, anion, and water content), coordination of KF and K₂SO₄, and relative amounts of fluorine and SO₄ groups. We have examined the effect of heat treatment on the RL of these compounds. The rubidium and cesium fluorosulfatozirconates Rb₃Zr₂F₉SO₄ · 2H₂O, Cs₂ZrF₂(SO₄)₂ · 2H₂O, Cs₈Zr₄F₂(SO₄)₁₁ · 16H₂O, and Cs₂ZrF₄SO₄ offer the most efficient RL.     

Structural,optical, electrical properties of new hybrid organic–inorganic NLO single crystal: bis(1H-benzotriazole) hexaaqua-zinc bis(sulfate) tetrahydrate (BZS)

A new hybrid organic–inorganic nonlinear (NLO) single crystal, Bis(1H-benzotriazole) hexaaqua-zinc bis(sulfate) tetrahydrate (BZS), has been successfully synthesized and the single crystals were grown by slow evaporation solution growth technique (SESG) using Millipore water as a solvent. The structure of the BZS crystal was solved and refined by single-crystal X-ray diffraction and demonstrates that the grown crystals belong to a triclinic system with the space group P-1. The asymmetric part of the titled compound contains isolated organic cation (C₆H₆N₃)₂, metallic cation [Zn(H₂O)₆]²⁺, sulfate anion (SO₄)^2? and free H₂O molecules. The interplay between the wide number of intermolecular interaction such as O–H···O, N–H···O, C–H···O and π–π stacking interactions were discussed. The optical transmittance spectrum shows that the crystal is excellent transmittance in the entire Vis–NIR region with the cutoff wavelength at 345 nm. The presences of expected functional groups were identified by Fourier transform infrared spectroscopy. The dielectric measurements were carried out at different temperature in the frequency range 100 Hz–5MHz. Furthermore, the studies of its third-order NLO properties using a Z-scan technique demonstrate that the BZS crystal possesses a strong reverse saturable absorption (RSA) and the self-focusing (SF) nature with large second order hyperpolarizability (γ?=?6.24?×?10^?34 esu). All the results indicate that BZS crystal might be the potential candidate for the third-order NLO applications.     

Synthesis and characterisation of infinite coordination networks with 1,6-bis(4-pyridyl)hexane and copper nitrate

Crystallisation of 1,6-bis(4-pyridyl)hexane (Py₂C₆H₁₂) with copper nitrate gives two different phases. Phase 1 of composition [Cu(Py₂C₆H₁₂)₃(NO₃)₂]·2[Cu(Py₂C₆H₁₂)₂(H₂O)(NO₃)]·2(NO₃)·EtOH consists of two different infinite chains in a 1:2 ratio that are interlocked. Hydrogen bonds link chains I to II and chains II to II. In contrast phase 2 of composition [Cu₂(Py₂C₆H₁₂)₄(H₂O)₂]·(NO₃)₄·(Py₂C₆H₁₂)·(EtOH)·2(H₂O) is based upon an infinite 3D framework. It consists of four interpenetrating 3D networks that are crystallographically equivalent.     

Synthesis,Spectral Investigations,and Thermal Stability of [60]Fullerene Complexes with TMTSF: 2(C60) · 2(TMTSF) · (C6H6), C60 · TMTSF · 2(CS2), and 2(C60) · 2(TMTSF) · (C6H5Cl)

Abstract

Molecular complexes of [60]fullerene with tetramethyltetraselenafulvalene (TMTSF): C₆₀ · (TMTSF) · 2(CS₂) (1), 2(C₆₀) · (2(TMTSF) · (C₆H₆) (2), and 2(C₆₀) · (2(TMTSF) · (C₆H₅Cl) (3) have been synthesized and their thermal stability and IR spectra vs. light polarization and temperature have been performed.     

Fabrication and characterization of Ag/calcium silicate core-shell nanocomposites

The Ag/calcium silicate nanocomposite with core-shell nanostructure has been successfully synthesized using Ag solution, Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O in ethanol/water mixed solvents at room temperature for 48 h. Ag solution was previously prepared by microwave-assisted method in ethylene glycol (EG) at 150 °C for 10 min. The nanocomposites consisted of Ag core and an amorphous calcium silicate shell. The XRD and EDS results confirmed that the product was the Ag/calcium silicate nanocomposite. The TEM micrographs indicated that the Ag/calcium silicate nanocomposite was core-shell nanoparticles. The effects of Ca(NO₃)₂·4H₂O and Na₂SiO₃·9H₂O concentration on the shells of Ag/calcium silicate nanocomposite were investigated. The products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and energy-dispersive X-ray spectra (EDS). This method is simple, fast and may be extended to the synthesis of the other kinds of core-shell nanocomposites.     

The effect of fillers on chloropolyester blend CPB 4 and inhibition of double-base propellants

A direct bonding inhibition system based on chloropolyester blend CPB 4 has recently been developed for inhibition of double-base rocket propellants. The effect of alumina trihydrate (Al₂O₃ · 3H₂O) and antimony trioxide (Sb₂O₃) on various properties of CPB 4 has been studied, such as effect on gel time, exotherm peak temperature, tensile strength, per cent elongation, water absorption, nitroglycerine absorption, heat resistance, and flame retardant characteristics. The data on flame retardance and other characteristics indicate that CPB 4 with 30% Al₂O₃ · 3H₂O and CPB 4 with 20% Sb₂O₃ are suitable for inhibition of double-base propellants. The double-base propellant sustainers (containing 2-NDPA) have been inhibited with CPB 4 containing 30% Al₂O₃ · 3H₂O and CPB 4 containing 20% Sb₂O₃ separately (without the application of any barrier coating), and statically fired at ambient, sub-zero (after conditioning at ?40°C for 18 h) and high (after conditioning at +50°C for 18 h) temperatures. The pressure—time profiles were found to be smooth and flat in all cases, indicating that the pressure level was the same throughout the combustion duration, inferring the suitability of these systems for inhibition of double-base propellants without the application of any barrier coating.     

Cobalt-mediated synthesis of 2-(4-pyridyl)benzimidazole. x-ray structures of Co[2-(4-pyridyl)benzimidazole]2(H2O)2(NO3)2 and [Co(isonicotinate)(4-pyridiniumcarboxylate)(H2O)(NO3)]∞

We have observed an unusual example of cobalt-mediated cyclization of 4-pyridinecarboxaldehyde and 2-nitroaniline to afford 2-(4-pyridyl)benzimidazole under hydro(solvo)thermal conditions. Reaction of Co(NO₃)₂·6H₂O with 4-pyridinecarboxaldehyde and 2-nitroaniline in ethanol at 120°C gave a cobalt(II) coordination compound, Co[2-(4-pyridyl)benzimidazole]₂(H₂O)₂(NO₃)₂, 1. In contrast, when the hydro(solvo)thermal reaction was carried out between Co(NO₃)₂·6H₂O and isonicotinic acid in the presence of 2-nitroaniline at 110°C, a one-dimensional Co(II) coordination polymer with the formula of [Co(isonicotinate)(4-pyridiniumcarboxylate)(H₂O)(NO₃)]_∞, 2, resulted. The X-ray single crystal structures of both 1 and 2 are described. Interestingly, the isonicotinic acid in 2 exists as a 4-pyridiniumcarboxylate tautomer, and the pyridinium hydrogen atom forms a very strong hydrogen bond to the carboxylate oxygen of the 4-pyridiniumcarboxylate on an adjacent metal center. 1 forms a three-dimensional polymeric network through hydrogen bonding interactions, while 2 exists as a 2-D bilayer polymeric network through hydrogen bonding interactions.     

Synthesis of bipyramidal gold nanoparticle-[C60]fullerene nanowhisker composites and catalytic reduction of 4-nitrophenol

The seed solution was prepared by dissolving hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), trisodium citrate dihydrate (C₆H₅Na₃O₇·2H₂O), and sodium borohydride (NaBH₄) in distilled water. The resulting reddish-purple seed solution was stirred for 3 h at room temperature. The growth solution was prepared by mixing hydrogen tetrachloroaurate(III) trihydrate (HAuCl₄·3H₂O), cetyltrimethylammonium bromide (CTAB, (C₁₆H₃₃)N(CH₃)₃Br), silver nitrate (AgNO₃), hydrochloric acid (HCl), and ascorbic acid (C₆H₈O₆) in distilled water. Subsequently, 100 μL of this seed solution was transferred into 10 mL of the growth solution. The mixed solution was maintained at 30 °C for 3 h to obtain a solution of bipyramidal gold nanoparticles. The bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were synthesized by applying the liquid-liquid interfacial precipitation (LLIP) method to a saturated solution of C₆₀ in toluene, the solution of bipyramidal gold nanoparticles, and isopropyl alcohol. The prepared bipyramidal gold nanoparticle-[C₆₀] fullerene nanowhisker composites were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, and transmission electron microscopy. The catalytic activity of these composites was confirmed in the reduction of 4-nitrophenol by UV-Vis spectroscopy.