Synthesis of thorn-like Ca<Subscript>2</Subscript>B<Subscript>2</Subscript>O<Subscript>5</Subscript>·H<Subscript>2</Subscript>O by hydrothermal method

Thorn-like polycrystalline Ca₂B₂O₅·H₂O microspheres with nano-sized slices were synthesized using boric acid and calcium hydroxide as reactants by a facile catalyst-free hydrothermal method at low temperature. The products were characterized by means of X-ray powder diffraction (XRD) and scanning electron microscopy (SEM). The XRD pattern reveals that the Ca₂B₂O₅·H₂O is a monoclinic phase polycrystalline with cell parameters a = 0·6702, b = 0·5419 and c = 0·3558 nm. SEM also reveals that the monoclinic phase polycrystalline are thorn-like microspheres composed of many flakes with an average thickness of <100 nm. Possible reaction and growth mechanism were also discussed.     

Mechanism of UO<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>·6H<Subscript>2</Subscript>O decomposition under the action of microwave radiation

The effect of microwave radiation (MWR) on the decomposition of UO₂(NO₃)₂·6H₂O was studied. Determination of [UO ₂ ²⁺ ] and [NO ₃ ^? ], and also of the molar ratio NO ₃ ^? : UO ₂ ²⁺ in various fractions of the decomposition product showed that the mechanism of the UO₂(NO₃)₂·6H₂O decomposition under the action of MWR differs from the mechanism of its decomposition under common convection heating. The main precursor of UO₃ as product of UO₂(NO₃)₂·6H₂O decomposition under the action of MWR is uranyl hydroxonitrate UO₂(OH)NO₃ formed already in the first minutes of the irradiation. In contrast to the thermolysis under convection heating, UO₂(NO₃)₂ or its hydrates were not detected as intermediates. The mechanism of the UO₂(NO₃)₂·6H₂O decomposition under the action of MWR can be presented by the reactions UO₂(NO₃)₂·6H₂O → UO₂(OH)NO₃ + 5H₂O + HNO₃ and UO₂(OH)NO₃ → UO₃ + HNO₃. The solubility of UO₂(OH)NO₃ in H₂O at 20°C was estimated experimentally at 6.83 × 10^?2 M.     

Morphologies and properties of NiO particles prepared from NiSO<Subscript>4</Subscript>·6H<Subscript>2</Subscript>O and Ni(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>·6H<Subscript>2</Subscript>O by spray pyrolysis

Nickel oxide particles were prepared by spray pyrolysis of aqueous solutions of NiSO₄·6H₂O and Ni(NO₃)₂·6H₂O. In spray pyrolysis reactor hollow salt particles initially formed were collapsed by decomposition to reduce their size. For NiSO₄·6H₂O less hollowness of the primitive particles and its higher decomposition temperature made the oxide particles highly spherical with very smooth surface. On the other hand the particles prepared from Ni(NO₃)₂·6H₂O were so hollow and fragile with rough surface since they were formed on the liquid pool of the salt melt. The particle size decreased with the furnace set temperature while increased with the initial salt concentration. Single oxide particle was composed of many small nuclei without sintering whose size varied with the rate of decomposition. The crystallinity of the particles increased with both temperature and the initial salt concentration. Preliminary drying in diffusion dryer fixed the size of the oxide particles from NiSO₄·6H₂O at that of the primitive particles, independent of the temperature. However, by the preliminary drying the particles from Ni(NO₃)₂·6H₂O became more hollow and fragile, whose sizes decreased with the temperature.     

Synthesis and characterization of the M<Superscript>II</Superscript>U<Subscript>3</Subscript>O<Subscript>10</Subscript> · 6H<Subscript>2</Subscript>O (M<Superscript>II</Superscript> = Ni,Zn) triuranates

We have developed a process for the synthesis of Ni(II) and Zn(II) triuranates with the general formula M^IIU₃O₁₀ · 6H₂O through reaction of schoepite, UO₃ · 2.25H₂O, with aqueous solutions of nickel and zinc nitrates under hydrothermal conditions. Using chemical analysis, X-ray diffraction, IR spectroscopy, and thermal analysis, we have determined the composition and structure of the triuranates and investigated their dehydration and thermal decomposition.     

Mechanism of UO<Subscript>2</Subscript>(NO<Subscript>3</Subscript>)<Subscript>2</Subscript>·6H<Subscript>2</Subscript>O decomposition under the action of microwave radiation: Part 2

Products of UO₂(NO₃)₂·6H₂O decomposition under the action of microwave radiation (MWR) were studied by thermal gravimetric analysis, X-ray phase analysis, IR spectroscopy, and electron microscopy. The results of physicochemical studies of these decomposition products were compared to the published data for various uranium compounds, including UO₂(NO₃)₂·6H₂O. Apart from gaseous products, the final products of decomposition of 2–10 g of UO₂(NO₃)₂·6H₂O under the action of MWR for 35 min (the maximal process temperature, 170–320°C, is attained in the first 2–5 min of irradiation) are uranyl hydroxonitrate UO₂(OH)NO₃ and uranium trioxide UO₃ or their hydrates. The results obtained are consistent with the mechanism suggested in our previous paper and involving the reactions (1) UO₂(NO₃)₂·6H₂O → UO₂(OH)NO₃ + 5H₂O + HNO₃ and (2) UO₂(OH)NO₃ → UO₃ + HNO_3. The physicochemical study confirms the conclusions on the composition of products of UO₂(NO₃)₂·6H₂O decomposition under the action of MWR, made previously on the basis of chemical studies. The only precursor of UO₃ in microwave treatment of UO₂(NO₃)₂·6H₂O is UO₂(OH)NO₃ (or its hydrates). This is the main difference between the courses of uranyl nitrate decomposition under the conditions of microwave and convection heating. In the latter case, uranyl nitrate and its hydrates also participate in the formation of UO₃.     

Crystal Structure of Uranyl Malonate Trihydrate [UO<Subscript>2</Subscript>(OOC)<Subscript>2</Subscript>CH<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)]·2H<Subscript>2</Subscript>O

Single crystals of [UO₂(OOC)₂CH₂(H₂O)]·2H₂O (I) were prepared by recrystallization of finely crystalline uranyl malonate trihydrate under hydrothermal conditions. The crystal structure of I consists of electroneutral [UO₂(OOC)₂CH₂(H₂O)]_n layers and water molecules located between them. The uranium coordination number is 7. The uranium coordination polyhedron is a distorted pentagonal bipyramid with the oxygen atoms of the uranyl group in the apices. The equatorial plane is occupied by four O atoms of three malonate ligands and the water molecule. The malonate anion is coordinated in the bidentate fashion to one uranyl ion to form a six-membered ring and in the monodentate fashion to two other uranyl ions.     

Investigation of solid solution of ZrP<Subscript>2</Subscript>O<Subscript>7</Subscript>–Sr<Subscript>2</Subscript>P<Subscript>2</Subscript>O<Subscript>7</Subscript>

In this study, ZrP₂O₇ was synthesized by the solid state reaction of ZrO₂ and NH₄H₂PO₄ at 900 °C. Then, in set 1; 10, 5, 1, 0.5, 0.1, 0.05, 0.03% previously prepared Sr₂P₂O₇ were doped into ZrP₂O₇, and Sr₂P₂O₇ slightly affect the unit cell parameter of cubic ZrP₂O₇ (a = 8.248(6)–8.233(8) Å). The reverse of this process was also applied to Sr₂P₂O₇ system (set 2). ZrP₂O₇ changes the unit cell parameters of orthorhombic Sr₂P₂O₇ in between a = 8.909(5)–8.877(5) Å, b = 13.163(3)–13.12(1) Å, and c = 5.403(2)–5.386(4) Å. Analysis of the vibrations of the P₂O ₇ ^4? ion and approximate band assignments for IR and Raman spectra are also reported in this work. Some coincidences in infrared and Raman spectra both sets were found and strong P–O–P bands were observed. Surface morphology, EDX analysis, and thermoluminescence properties of both sets were given the first time in this paper.     

Crystal structure of a Np(V) sesquioxalate,Na<Subscript>4</Subscript>(NpO<Subscript>2</Subscript>)<Subscript>2</Subscript>(C<Subscript>2</Subscript>O<Subscript>4</Subscript>)<Subscript>3</Subscript>·2H<Subscript>2</Subscript>O

The crystal structure of a previously unknown Np(V) sesquioxalate, Na₄(NpO₂)₂(C₂O₄)₃·2H₂O was studied. The crystal structure consists of neptunyl(V) cations, sodium cations, oxalate anions, and water molecules of crystallization. Neptunyl(V) cations and oxalate ions form anionic chains [(NpO₂)₂(C₂O₄)₃] _n ^4n? . The coordination polyhedron (CP) of Np (pentagonal bipyramid) contains two apical “yl” oxygen atoms and five equatorial O atoms of three oxalate ions. The CP of Na(1) and Na(2) cations are combined through the common edges into zigzag chains in the [010] direction. Two independent oxalate ions are tridentate and tetradentate ligands.     

Crystal structure of U(VI) phthalate dihydrate [UO<Subscript>2</Subscript>(OOC)<Subscript>2</Subscript>C<Subscript>6</Subscript>H<Subscript>4</Subscript>•H<Subscript>2</Subscript>O]•H<Subscript>2</Subscript>O

Crystalline uranyl phthalate dihydrate was prepared by hydrothermal method, and its crystal structure was determined. The crystal structure consists of infinite chains [UO₂LH₂O]_n coupled in bands [(UO₂)₂L₂(H₂O)₂]_n [L = C₆H₄(COO)₂], between which water molecules of crystallization are located. The coordination polyhedron of uranium atoms is a pentagonal bipyramid with the equatorial plane formed by oxygen atoms of three phthalate ions and coordinated water molecule. The U-O bond length in the UO ₂ ²⁺ cations is 1.766 . The coordination capacity of the ligands is 4. Anions are bidentately coordinated to uranium atoms to form seven-membered rings. Being bridging ligands, phthalate ions combine the neighboring uranium atoms into chains through one carboxy group, and the chains into bands, through the other carboxy group.Translated from Radiokhimiya, Vol. 46, No. 6, 2004, pp. 513–515.Original Russian Text Copyright © 2004 by Charushnikova, Krot, Starikova.     

Evaluation of CaO–SiO<Subscript>2</Subscript>–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–Na<Subscript>2</Subscript>O–Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> bioglass-ceramics for hyperthermia application

Magnetic bioglass ceramics (MBC) are being considered for use as thermoseeds in hyperthermia treatment of cancer. While the bioactivity in MBCs is attributed to the formation of the bone minerals such as crystalline apatite, wollastonite, etc. in a physiological environment, the magnetic property arises from the magnetite [Fe₃O₄] present in these implant materials. A new set of bioglasses with compositions 41CaO · (52 ? x)SiO₂ · 4P₂O₅  · xFe₂O₃ · 3Na₂O (2 ≤ x ≤ 10 mol% Fe₂O₃) have been prepared by melt quenching method. The as-quenched glasses were then heat treated at 1050°C for 3 h to obtain the glass-ceramics. The structure and microstructure of the samples were characterized using X-ray diffraction and microscopy techniques. X-ray diffraction data revealed the presence of magnetite in the heat treated samples with x ≥ 2 mol% Fe₂O₃. Room temperature magnetic property of the heat treated samples was investigated using a Vibrating Sample Magnetometer. Field scans up to 20 kOe revealed that the glass ceramic samples had a high saturation magnetization and low coercivity. Room temperature hysteresis cycles were also recorded at 500 Oe to ascertain the magnetic properties at clinically amenable field strengths. The area under the magnetic hysteresis loop is a measure of the heat generated by the MBC. The coercivity of the samples is another important factor for hyperthermia applications. The area under the loop increases with an increase in Fe₂O₃ molar concentration and the. coercivity decreases with an increase in Fe₂O₃ molar concentration The evolution of magnetic properties in these MBCs as a function of Fe₂O₃ molar concentration is discussed and correlated with the amount of magnetite present in them.     

Influence of cryochemical and ultrasonic processing on the texture and thermal decomposition of xerogels and properties of nanoceramics in the ZrO<Subscript>2</Subscript>〈Y<Subscript>2</Subscript>O<Subscript>3</Subscript>〉–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> system

We have studied the influence of cryochemical and ultrasonic processing on the formation, structure, particle size, and thermal decomposition of xerogels in the ZrO₂〈Y₂O₃〉–Al₂O₃ (20 wt %) system. Nanopowders of tetragonal-zirconia-based solid solutions with a high degree of tetragonality (c/a = 1.4366) have been synthesized. Al₂O₃ has been shown to slow down t-ZrO₂ crystallite growth in the temperature range 600–1400°C. We have optimized nanopowder consolidation conditions, obtained nanoceramics stable to low-temperature “aging” in a humid medium, and investigated their physicochemical and mechanical properties.     

Synthesis and characterization of hydroxyapatite by microwave heating using CaSO<Subscript>4</Subscript>·2H<Subscript>2</Subscript>O and Ca(OH)<Subscript>2</Subscript> as calcium source

In this paper, synthesis of hydroxyapatite (HAp) in the absence or presence of 1.05 wt% magnesium oxide, as sintering additive, by heating in a microwave oven was studied. For this purpose, CaSO₄·2H₂O, Ca(OH)₂, Mg(OH)₂ and (NH₄)₂HPO₄ were used as raw materials. The total chemical reactions for all the studied compositions were observed after a 3 h microwave treatment. In case of pure hydroxyapatite, a powder with needle-like grains results. In the presence of Mg(OH)₂, the (Mg, Ca₂)·O·(HPO₄)₂·H₂O hydrated phosphate is formed besides hydroxyapatite. Pure hydroxyapatite, thermally treated at 1,200 °C, mostly transforms in β-Ca₃P₂O₈. By adding MgO into the precursor mixture, hydroxyapatite was stabilised, and found in a much greater proportion at 1,200 °C. After the thermal treatment, the hydroxyapatite, analysed by electronic microscopy, shows a prismatic morphology originating in its initial state.     

Chemical interaction of InAs,InSb, GaAs,and GaSb with (NH<Subscript>4</Subscript>)<Subscript>2</Subscript>Cr<Subscript>2</Subscript>O<Subscript>7</Subscript>–HBr–C<Subscript>4</Subscript>H<Subscript>6</Subscript>O<Subscript>6</Subscript> etching solutions

This paper presents results on the kinetics and mechanism of the physicochemical interaction of InAs, InSb, GaAs, and GaSb semiconductor surfaces with (NH₄)₂Cr₂O₇–HBr–C₄H₆O₆ etching solutions under reproducible hydrodynamic conditions in the case of laminar etchant flow over a substrate. We have identified regions of polishing and nonpolishing solutions and evaluated the apparent activation energy of the process. The surface morphology of the crystals has been examined by microstructural analysis after chemical etching. The results demonstrate that the presence of C₄H₆O₆ in etchants helps to reduce the overall reaction rate and extend the region of polishing solutions.     

Crystal structures of zeolites with the general formula CaAl<Subscript>2</Subscript>Si<Subscript>6</Subscript>O<Subscript>16</Subscript>·<Emphasis Type="Italic">n</Emphasis>H<Subscript>2</Subscript>O

Analysis of the structures of goosecreekite and yugawaralite indicates that, like in the zeolites with the general formula CaAl₂Si₄O₁₂ · nH₂O (chabazite, laumontite, and wairakite), the structural framework of goosecreekite is made up of alternating six-and four-membered rings. In the structural frameworks of goosecreekite, chabazite, and wairakite, such chains are linked so as to form eight-membered rings. In contrast, the structural framework of yugawaralite is made up of chains of two five-membered rings and one four-membered ring. The salient features of the zeolites with the general formula CaAl₂Si₆O₁₆ · nH₂O are the presence of calcium-water chains in the structure of goosecreekite and a calcium-water network in the structure of yugawaralite. Analysis of calcium-oxygen, calcium-water, and oxygen-hydrogen bonds has made it possible to reveal features common to the structures of yugawaralite and wairakite.     

Ion-selective properties of metastable (VO)<Subscript>0.09</Subscript>V<Subscript>0.18</Subscript>Mo<Subscript>0.82</Subscript>O<Subscript>3</Subscript> · 0.54H<Subscript>2</Subscript>O

This paper describes a thin-film solid electrode with an ion-sensitive membrane based on the mixed oxide (VO)_0.09V_0.18Mo_0.82O₃ · 0.54H₂O. The electrode is selective for tetravalent vanadium in the concentration range 3 ≤ pC _V ⁴⁺ ≤ 5 and acidity range 4.5 ≤ pH ≤ 6, with a slope close to the theoretical value. In the range 1 ≤ pH < 5, the electrode responds to changes in hydrogen ion concentration, with a slope of 50 ± 2 mV/pH. Its alkali-metal-ion response shows up in the range 1 ≤ pC _M ⁺ ≤ 4 for pH ≥ 6. We examine the effect of the Li⁺, K⁺, Na⁺, Cs⁺, Rb⁺, Mg²⁺, Ca²⁺, Sr²⁺, Ba²⁺, Co²⁺, Ni²⁺, Mn²⁺, Al³⁺, Cr³⁺, and VO₂⁺ ions on the potential of the electrode and determine its selectivity coefficients for these cations.     

Synthesis and study of structural,dielectric, magnetic and magnetoelectric properties of K<Subscript>0.5</Subscript>Na<Subscript>0.5</Subscript>NbO<Subscript>3</Subscript>–CoMn<Subscript>0.2</Subscript>Fe<Subscript>1.8</Subscript>O<Subscript>4</Subscript> composites

Magnetoelectric (ME) composites consisting of K_0.5Na_0.5NbO₃ (KNN) as ferroelectric phase and CoMn_0.2Fe_1.8O₄ (CMFO) as ferrite phase with general formula (x) CoMn_0.2Fe_1.8O₄–(1???x) K_0.5Na_0.5NbO₃ (x?=?10, 20, 30, 40 and 50 wt%) were synthesized using solid state reaction method. X-ray diffraction analysis asserts the existence of component phases including spinel phase of CMFO and orthorhombic phase of KNN. Field emission scanning electron microscopy has been used for studying the morphology and calculation of average grain size. The temperature dependent dielectric properties including dielectric constant (\(\varepsilon ^{\prime}\)) and dielectric loss (tan δ) at different frequencies has been studied and both are found to increase with incorporation of CMFO. Magnetic hysteresis loops have been measured at temperatures of 300 and 5 K. Variation of magnetization versus temperature has been studied in field cooled and zero field cooled modes. Polarization versus electric field (P–E) hysteresis loops are obtained at room temperature indicating presence of ferroelectric ordering in the composites at room temperature. The remnant polarization (2P_r) and coercive field (2E_c) are found to decrease linearly with incorporation of CMFO. ME voltage coefficient (α_ME) has been measured. The maximum value of α_ME is found to be 5.941 mV/cm-Oe for 10% CMFO–90% KNN bulk composite.     

Synthesis,bioactivity and preliminary biocompatibility studies of glasses in the system CaO–MgO–SiO<Subscript>2</Subscript>–Na<Subscript>2</Subscript>O–P<Subscript>2</Subscript>O<Subscript>5</Subscript>–CaF<Subscript>2</Subscript>

New compositions of bioactive glasses are proposed in the CaO–MgO–SiO₂–Na₂O–P₂O₅–CaF₂ system. Mineralization tests with immersion of the investigated glasses in simulated body fluid (SBF) at 37°C showed that the glasses favour the surface formation of hydroxyapatite (HA) from the early stages of the experiments. In the case of daily renewable SBF, monetite (CaHPO₄) formation competed with the formation of HA. The influence of structural features of the glasses on their mineralization (bioactivity) performance is discussed. Preliminary in vitro experiments with osteoblasts’ cell-cultures showed that the glasses are biocompatible and there is no evidence of toxicity. Sintering and devitrification studies of glass powder compacts were also performed. Glass-ceramics with attractive properties were obtained after heat treatment of the glasses at relatively low temperatures (up to 850°C).     

Thermodynamic properties of Dy<Subscript>2</Subscript>O<Subscript>3</Subscript> · 2ZrO<Subscript>2</Subscript> and Ho<Subscript>2</Subscript>O<Subscript>3</Subscript> · 2ZrO<Subscript>2</Subscript> in the range 10–340 K

The low-temperature heat capacity of Dy₂O₃ · 2ZrO₂ and Ho₂O₃ · 2ZrO₂ has been determined by adiabatic calorimetry in the temperature range 10–340 K. The results have been used to calculate the entropy, enthalpy increment, and reduced Gibbs energy of the zirconates without taking into account their low-temperature magnetic transformations.     

Thermal analysis,AC conductivity and dielectric relaxation in Bis(2-methoxyanilinium) hexabromidostannate(IV) dihydrate: (C<Subscript>7</Subscript>H<Subscript>10</Subscript>NO)<Subscript>2</Subscript>SnBr<Subscript>6</Subscript>·2H<Subscript>2</Subscript>O

The (C₇H₁₀NO)₂SnBr₆·2H₂O compound is characterized by using the X-ray powder analysis, thermogravimetric analyses, differential scanning calorimetry (DSC) and complex impedance spectroscopic data. This compound exhibits a phase transition at 300 K which is characterized by differential scanning calorimetry, AC conductivity and dielectric measurements. The measurements of impedance spectroscopic are carried out in the frequency range from 100 Hz to 1 MHz with temperatures varying between 275 and 330 K. The impedance measurements indicate that the electrical properties are strongly temperature dependent. Nyquist plots (?Z′′ versus Z′) show that the conductivity behavior is accurately represented by an Rp//CPE equivalent electrical circuit model. Besides, the frequency dependence of conductivity follows Jonscher’s dynamical law with the relation: \(\sigma (\omega ,T)={\sigma _{DC}}+A(T){\omega ^{S(T)}}\). The relaxation mechanism can be observed in the complex modulus analysis M^* and the complex polarizability α^*.