X-ray attenuation coefficient measurements for photon energies 4.508-13.375 keV in Cu, Cr and their compounds and the validity of the mixture rule

To investigate the validity of the mixture rule which is used to compute the mass attenuation coefficients in compounds, the total mass attenuation coefficients for Cu, Cr elements and Cu₂O, CuC₂O₄, CuCl₂·2H₂O, Cu(C₂H₃O₂)₂·H₂O, Cr₂O₃, Cr(NO₃)₃, Cr₂(SO₄)₃·H₂O, Cr₃(CH₃CO₇)(OH)₂ compounds were measured at photon energies between 4.508 and 13.375 keV by using the secondary excitation method. Ti, Mn, Fe, Ni, Zn, Ge, As, Rb elements were used as secondary exciters. 59.5 keV gamma rays emitted from an annular source were used to excite the secondary exciters and Kα (K-L₃, L₂) rays emitted from the secondary exciter were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. Our measurements indicate that the mixture rule is not a suitable method for the computation of mass attenuation coefficients of compounds especially at an energy that is near the absorption edge. Obtained values were compared with theoretical values.     

KBaR(BO<Subscript>3</Subscript>)<Subscript>2</Subscript> orthoborates (R = REE): Synthesis and study

The search for compounds with the formula composition KBaR(BO₃)₂ has been performed by solid-phase synthesis and differential thermal analysis. The compounds synthesized in this series are KBaPr(BO₃)₂ and KBaNd(BO₃)₂, which are isostructural to KBaY(BO₃)₂, are isotypical to butschliite K₂Ca(CO₃)₂, and crystallize in a trigonal system with space group R3m. The structural characteristics of compounds calculated for the entire series of REEs are given.     

The kinetic deuterium isotope effect in the thermal dehydration of boric acid

The kinetic deuterium isotope effect in the thermal dehydration process from H₃BO₃ to HBO₂(III) was determined using simultaneous TG and DSC. The rate constant ratio of H₃BO₃ to D₃BO₃ obtained by the analysis of isothermal TG and DSC curves was found to be smaller than unity. Both activation energy, E, and frequency factor, A, for the dehydration of H₃BO₃ proved to be larger than those of D₃BO₃, using non-isothermal TG and DSC. The origin of the deuterium kinetic isotope effect in the thermal dehydration of boric acid is also briefly discussed.     

Concentration quenching of the Nd3+ emission in alkali rare earth borates

Four new ternary compounds with compositions Li₆Nd(BO₃)₃, Na₃Nd(BO₃)₂, and Na₁₈Nd(BO₃)₇ have been found in the M₂ONd₂O₃B₂O₃ systems, where M is either Li or Na. Concentration quenching of the neodymium emission in homologous lanthanum or gadolinium borates has been investigated. While in the Li₆Gd(BO₃)₃, Na₃La₂(BO₃)₃, and Na₃La(BO₃)₂ host lattices the quenching rate shows a quadratic dependence on Nd³⁺ concentration, as expected since the coordination polyhedra are connected by common faces or edges, in Na₁₈La(BO₃)₇ the luminescent lifetime is not influenced by neodymium concentration. Lifetimes and crystal field splitting of the J levels are compared to those of other oxide host lattices.     

Direct Potentiometric Measurement of NH4H2BO3 Following a Kjeldahl Distillation

Abstract

A method is described for the direct potentiometric measurement of NH₄H₂BO₃, following a Kjeldahl distillation. The NH₃ is distilled into a H₃BO₃ solution, and the activity of the NH₄H₂BO₃ is measured using a cation electrode sensitive to NH₄ ⁺ and an anion electrode sensitive to H₂BO₃. The method has been used to determine nitrogen in dried blood samples with assigned N values, and the potentiometric values agreed with the titrimetric results.     

Syntheses and crystal structures of two new hydrated borates, Zn8[(BO3)3O2(OH)3] and Pb[B5O8(OH)]·1.5H2O

Two new hydrated borates, Zn₈[(BO₃)₃O₂(OH)₃] and Pb[B₅O₈(OH)]·1.5H₂O, have been prepared by hydrothermal reactions at 170 °C. Single-crystal X-ray structural analyses showed that Zn₈[(BO₃)₃O₂(OH)₃] crystallizes in a non-centrosymmetric space group R32 with a=8.006(2) Å, c=17.751(2) Å, Z=3 and Pb[B₅O₈(OH)]·1.5H₂O in a triclinic space group P1¯ with a=6.656(2) Å, b=6.714(2) Å, c=10.701(2) Å, α=99.07(2)°, β=93.67(2)°, γ=118.87(1)°, Z=2. Zn₈[(BO₃)₃O₂(OH)₃] represents a new structure type in which Zn-centered tetrahedra are connected via common vertices leading to helical ribbons _∞¹[Zn₈O₁₅(OH)₃]¹⁷⁻ that pack side by side and are further condensed through sharing oxygen atoms to form a three-dimensional _∞³[Zn₈O₁₁(OH)₃]⁹⁻ framework. The boron atoms are incorporated into the channels in the framework to complete the final structure. Pb[B₅O₈(OH)]·1.5H₂O is a layered compound containing double ring [B₅O₈(OH)]²⁻ building units that share exocyclic oxygen atoms to form a two-dimensional layer. Symmetry-center-related layers are stacked along the c-axis and held together by interlayer Pb²⁺ ions and water molecules via electrostatic and hydrogen bonding interactions. The IR spectra further confirmed the existence of both triangular BO₃ and OH groups in Zn₈[(BO₃)₃O₂(OH)₃], and BO₃, BO₄, OH groups as well as guest water molecules in Pb[B₅O₈(OH)]·1.5H₂O.     

ChemInform Abstract: Synthesis and Characterizations of Two Anhydrous Metal Borophosphates: M2IIIBP3O12 (M: Fe,In).

The title compounds are obtained quantitatively by reacting mixtures of M₂O₃ (M: Fe, In), H₃BO₃, and NH₄H₂PO₄ in a molar ratio of 1:1:3 at 1153 K.     

A 45Sc-NMR and DFT calculation study of crystalline scandium compounds

A series of scandium compounds, namely ScPO₄, ScOF, Li₃Sc(BO₃)₂, and CaSc₂O₄, were prepared according to procedures described in the literature, and then characterised by powder X-ray diffraction and solid-state ⁴⁵Sc-NMR spectroscopy. By computer fitting, the quadrupolar interaction parameters χ and η, as well as the isotropic chemical shifts δ_iso were extracted from the NMR spectra. For comparison and site assignment of ⁴⁵Sc, density functional theory (DFT) calculations of the EFG tensor were carried out with the Castep code. For the compounds with a well-defined formal coordination number (CN), a convincing linear correlation between CN and isotropic chemical shift could be established.     

Study of γ‐Fast Neutron Attenuation and Mechanical Characteristics of Modified Concretes for Shielding and Sheltering Purposes

The study of γ‐neutrons attenuation and mechanical characteristics of modified concrete are vital and crucial parameters for the construction of civilian radiological, nuclear shielding, and/or shelters. In this work, fifteen samples of ordinary concretes with five different additives; steel fibers, polypropylene, silica fume, and fly ash, with variation of cement percentages, were prepared and used for performing the mechanical and radiation attenuation investigations. The compressive strength, tensile strength, slump test, bulk density, and water permeability were also carried out for the prepared concrete mixes. Collimated coherent beams from ⁶⁰Co and Pu‐Be fast neutron sources were used to check the radiation penetrability through the syntheized mixed concrete‐additives. Very sensitive and well calibrated gamma‐neutron pulse shape discriminating spectrometer with its electronic componenets and stilbene organic detector and 3′′ × 3′′ NaI scintillation crystal was used to measure the radiation before and after attenuation and transmission. The integrated fast neutron removal macroscopic cross section (Σ_r) and linear attenuation coefficient of total gamma rays (μ) were calculated for all the analysed concrete mixes. The results of measurements, tests, analyses and calculations are given and explained. The investigated modified concrete mixes show good workability and properties from the view point of mechanical loads and γ‐fast neutrons penetrability and resistance. These results can be used for shielding and sheltering design.     

ChemInform Abstract: Three Alkali Metal Lead Orthophosphates - Syntheses,Crystal Structures and Properties of APbPO4(A:K,Rb, Cs).

Single crystals of the title compounds are prepared by solid state reactions of M₂CO₃ (M: K, Rb, Cs), PbO, PbF₂, H₃BO₃, and (NH₄)H₂PO₄ in a molar ratio of 2:5:5:4:3 (Pt crucible, 700 °C, 10 h).     

Tetrametallomethanes containing one,two, or three group IV metal atoms and boron

The propanediol methanetetraboronic ester, C(BO₂C₃H₆)₄, provides much better properties than the previously used methyl ester, C[B(OMe)₂]₄, for the synthesis of new tetrametallomethanes. Treatment with butyllithium yields the lithium salt LiC(BO₂C₃H₆)₃, which reacts with Ph₃MCl to form Ph₃MC(BO₂C₃H₆)₃, where M is Ge, Sn, or Pb. Repetition of these processes leads to (Ph₃M)₂C(BO₂C₃H₆)₂, where the Group IV metals M may be the same of different. The series was extended to (Ph₃Sn)₃CBO₂C₃H₆, but the last boron atom resisted removal. Iodination of the appropriate lithium salt intermediates yielded Ph₃SnCl(BO₂C₃H₆)₂ and (Ph₃Sn)₂CIBO₂C₃H₆.     

Two new barium borate bromides: Ba2BO3Br and Ba3BO3Br3

Two new barium borate bromide crystals, Ba₂BO₃Br and Ba₃BO₃Br₃, have been obtained by spontaneous crystallization. Ba₂BO₃Br crystallizes in P−3m1 space group, with cell parameters of a = 5.5157(10) Å, c = 11.019(4) Å, and Z = 2, its structure is build up by alternately stacking along c-axis of [Ba₂(BO₃)₂]²⁻ layers and bromide [Ba₂Br₂]²⁺ layers. The solved structure is analog to Ba₂(BO₃)_1−x(CO₃)_xCl_1+x except the interstitial halogen atoms at (0, 0, 1/2) is missing and accordingly the partly CO₃ substitution for BO₃ has not been observed. Ba₃BO₃Br₃ crystallizes in a new structure type with P−1 space group and cell parameters of a = 9.280(4) Å, b = 9.349(7) Å, c = 13.025(9) Å, α = 92.71(3)°, β = 98.29(3)°, γ = 116.200(18)° and Z = 4. The basic structural unit in Ba₃BO₃Br₃ is the clusters composed of 4 BO₃ groups and 12 Ba atoms, which in turn are linked by eight Ba–O bonds with other four clusters to form sheets extend in the (001) plane.     

Synthesis and crystal structure of new layered BaNaSc(BO3)2 and BaNaY(BO3)2 orthoborates

Crystals of two new layered BaNaSc(BO₃)₂ (I) and BaNaY(BO₃)₂ (II) orthoborates are grown from the melt-solution by the spontaneous crystallization onto the platinum loop. Single crystal X-ray analysis showed that the compounds are isostructural with the space group R3¯, a=5.23944(12) and 5.3338(2) Å, and c=34.5919(11) and 35.8303(19) Å for I and II, respectively, Z=6. The distinctive feature of the structure is the close-packed composite anion-cation (Ba,Na)(BO₃) layers. The layers are combined into the base building packages of two types: {M³⁺[Ba²⁺(BO₃)³⁻]₂}⁺ and {M³⁺[Na⁺(BO₃)³⁻]₂}⁻, where M is Sc or Y. Neutral-charge two-package (four-layer) blocks are stacked by the rhombohedral principle into twelve layers of the cubic packing.     

Mixed ligand complex formation of FeIII with boric acid and typical N-donor multidentate ligands

Equilibrium study of the mixed ligand complex formation of Fe^III with boric acid in the absence and in the presence of 2,2′-bipyridine, 1,10-phenanthroline, diethylenetriamine and triethylenetetramine (L) in different molar ratios provides evidence of formation of Fe(OH)²⁺, Fe(OH) ₂ ⁺ , Fe(L)³⁺, Fe(H₂BO₄),Fe(OH)(H₂BO₄), Fe(OH)₂(H₂BO₄)^2-, Fe(L)(H₂BO₄) and Fe₂(L)₂(BO₄)⁺ complexes. Fe(L) ₂ ³⁺ , Fe(L)₂(H₂BO₄) and Fe₂(L)₄(BO₄)⁺ complexes are also indicated with 2,2′-bipyridine and 1,10-phenanthroline. Complex formation equilibria and stability constants of the complexes at 25 ± 0.l°C in aqueous solution at a fixed ionic strength,I = 0.1 mol dm^-3 (NaNO₃) have been determined by potentiometric method.     

Luminescence properties of efficient X-ray phosphors of YBa3B9O18, LuBa3(BO3)3, α-YBa3(BO3)3 and LuBO3

The samples of YBa₃B₉O₁₈, LuBa₃(BO₃)₃, α-YBa₃(BO₃)₃ and LuBO₃ powders have been synthesized by the solid-state reaction methods at high temperature and their X-ray excited luminescent properties were investigated. All the studied materials show a broad emission band in the wavelength range of 300-550 nm with the peak centers at about 385 nm for YBa₃B₉O₁₈ and LuBa₃(BO₃)₃, 415 nm for α-YBa₃(BO₃)₃ and 360 nm for LuBO₃ powders, respectively. Even though those compounds have the different atomic structures, they have the common structural feature of each yttrium or lutetium ion bonded to six separate BO₃ groups, i.e., octahedral RE(BO₃)₆ (RE=Lu or Y) moiety. This octahedral RE(BO₃)₆(RE=Lu or Y) moiety seems to be an important structural element for efficient X-ray excited luminescence of those compounds, as are the edge-sharing octahedral TaO₆ chains for tantalate emission.     

Studies on some ternary oxyborates of the Na2O-Me2O3-B2O3 (Me=rare earth or aluminum) systems: Synthesis, structure and crystal growth

Sodium rare-earth oxyborates Na₂RE₂O(BO₃)₂ (RE=Y, Nd, Er) were prepared for the first time in the present study. They were found to be isostructural with phases of the same composition containing Sm, Eu or Gd and reported by Corbel et al. [J. Solid State Chem.144 (1999) 35-44]. It was shown that the yttrium and erbium compounds could be synthesized at 900-1000 °C by a solid-state reaction between oxides in an equimolecular ratio. With both oxyborates melting led to decomposition into a mixture of Y(Er)BO₃, Y₂(Er₂)O₃ and Na₂B₄O₇. Just the opposite was observed during thermal treatment of the oxide mixture containing Nd₂O₃, from which a practically pure phase of Na₂Nd₂O(BO₃)₂ was only obtained after melting. The attempts to synthesize the oxyborate Na₂La₂O(BO₃)₂ showed it to be unstable, this leading to the formation of a mixture containing, in addition to Na₂La₂O(BO₃)₂, also other already known stable phases of the system Na₂O-La₂O₃-B₂O₃ along with an unknown ternary oxide phase. This phase was found to represent a new oxyborate of sodium and lanthanum with the formula Na₃La₉O₃(BO₃)₈, whose single crystals were obtained by flux growth. It was established that synthesis of a polycrystalline material with the same composition was also possible using solid-state interaction between Na₂CO₃, La₂O₃ and H₃BO₃ at 1000-1100 °C. X-ray diffraction experiments on single crystals were used to solve the structure of Na₃La₉O₃(BO₃)₈. The unit cell was found to be hexagonal, space group P62m (No. 189) with Z=1. The compound can be regarded as the forefather of a second group of oxyborates representing a new family of isostructural compounds, Na₃RE₉O₃(BO₃)₈. Such phases were obtained with RE=Nd, Sm and Eu whereas with RE=Y and Gd, the synthesis experiments failed.The concentration and temperature regions of crystallization of the double-oxyborate Na₂Al₂O(BO₃)₂ in the ternary system Na₂O-Al₂O₃-B₂O₃ were determined. This compound was shown to melt incongruently at 970±3 °C, which made high-temperature solution growth most appropriate for obtaining its single crystals with NaBO₂ as the best solvent. On the basis of the data obtained, a composition of the initial solution was proposed, the validity of the choice being demonstrated by the growth of Na₂Al₂O(BO₃)₂ single crystals on a seed using the top-seeded solution growth (TSSG) technique and slow cooling of the solution.     

Refinement of α-CsB9O14 crystal structure

The structure of α-CsB₉O₁₄ was re-examined because the first determination corresponded to a poor reliability factor (12.9%). Single crystals were obtained by heating, melting and slow cooling a stoichiometric mixture (1:4) of β-Cs[B₅O₆(OH)₄]·2H₂O and H₃BO₃. This compound crystallizes in the non-centrosymmetric orthorhombic space group P222₁ (and not P4₁22) with the following parameters: a=8.732(2)Å, b=8.767(3)Å, c=15.736(4)Å, V=1204.6(6)ų, Z=4; after taking into consideration twinning, the structure was refined from 3188 reflections until R₁=0.0304. It consists of two infinite, interleaved three-dimensional boron-oxygen frameworks of the Fundamental Building Blocks formed by two B₃O₆ and one B₃O₇ groups; its shorthand notation is 9:∞³[(3:2Δ+T)+2(3:3Δ)] (Δ, triangle BO₃ and T, tetrahedron BO₄). Knowledge of the correct space group and the structure of α-CsB₉O₁₄ may help in the study of its physical properties, especially the non-linear optical ones.     

Effects of boric acid on structural and luminescent properties of BaAl<Subscript>2</Subscript>O<Subscript>4</Subscript>:(Eu<Superscript>2+</Superscript>, Dy<Superscript>3+</Superscript>) phosphors

Eu²⁺/Dy³⁺-codoped BaAl₂O₄ phosphors were prepared by conventional solid-state reaction with boric acid flux. The effects of boric acid on structural and luminescent properties of BaAl₂O₄:(Eu²⁺, Dy³⁺) were investigated. The crystallinity of BaAl₂O₄ improved with increasing amount of H₃BO₃. Incorporation of Eu²⁺ and Dy³⁺ ions into effective lattice sites was promoted by H₃BO₃ addition. As a result, Eu²⁺ emission in BaAl₂O₄ was greatly enhanced by H₃BO₃, and the duration of persistent luminescence increased with the amount of H₃BO₃. However, the decay lifetime of persistent luminescence was not strongly influenced by the amount of H₃BO₃.     

Elastic and inelastic neutron studies of hydrogen molybdenum bronzes

Hydrogen molybdenum bronzes H_xMoO₃ (～0.3 < x < 2.0) have been investigated with elastic and inelastic neutron scattering. Neutron diffraction studies of orthorhombic D_0.36MoO₃ show that deuterium is incorporated as -OD without any major structural change to the MoO₃ layer lattice. The inelastic neutron scattering spectra of H_xMoO₃ phases confirm that, for H_0.34MoO₃, H is present as -OH, but, for the monoclinic phases H_0.93MoO₃, H_1.68MoO₃ and H_2.0MoO₃, only peaks associated with -OH₂ groups are found.     

On tertiary BOx± ions in HF-plasma SNMS

The effect of plasma electron impact on negative secondary ions is investigated by example of a sputtered H₃BO₃/Cu powder pellet. O^–, BO^–, BO⁺, and B⁺ tertiary ions, fractured from strongly forward focussed secondary BO₂ ^– ions, are identified by their kinetic energies. Since most of them are accepted by the ion optics, this process may affect quantification in HF-plasma SNMS.