Metal Borate Research Articles

Structural Modification-Induced Valence Change of the Europium Ion Doped in Barium Octaborate

Valence states of the europium ion doped in barium octaborate, , were alternately changed between the trivalent and divalent ones by performing the crystallization or vitrification treatment for the host material in air at , and such valence change characteristics were discussed on the basis of the mutual transformation between and units and their connection manners via bridged oxygens in the networks of crystalline and vitreous forms, so that the redox mechanism proposed was applied to other metal borate host materials to predict and control the valence state of ions. ©1999 The Electrochemical Society

Organophosphorus Compounds, 118. Reactions of 1‐Chloro‐1H‐phosphirenes with Nucleophiles

AbstractThe halogen atoms in the 1‐chloro‐1H‐phosphirenes, 5a–c, are easily substituted on reaction with organolithium and Grignard reagents, 14a–p, with formation of the corresponding O‐, N‐, C‐, Si‐, and Ge‐substituted 1H‐phosphirenes, 15a–t. C1/H exchange reactions also occur on reaction with lithium metal hydrides (5a → 17). Furthermore, substitution reactions are also realized with the alkali metal borates, 18a–g (→19a–g); the same is true for reactions with trimethylsilyl cyanide and azide (→22a–d). Some of the substitution products have been characterized in the form of their metal complexes, 16, 23, 24, and 25.

Chemical modification of polymers to improve flame retardance—I. The influence of boron-containing groups

Samples of a linear polystyrene have been boronated, predominantly in the para-positions on the phenyl rings, by reaction first with mercuric tri-fluoroacetate and then with catechol borane, and the products then hydrolysed to give the polymeric boronic acids. Flame-retardant effects of these modifications have been assessed by measurements of limiting oxygen indices (LOI), and of weight losses and char yields on heating in air. The boron modified polymers have increased LOI values and give greater yields of char in comparison with those of the unmodified polystyrene. The surface modification of films of poly(vinyl alcohol) and of poly(ethylene-co-vinyl alcohol) with alkali metal borates has also given some encouraging results. Increases in LOI values and char yields can be optimised by adjusting the concentrations of the aqueous solutions of boric acid and sodium hydroxide used to effect the modifications.

Impedance of Interface between Pt Metal and Sodium Borate Melts Containing Fe<SUB>2</SUB>O<SUB>3</SUB>, CuO or Cr<SUB>2</SUB>O<SUB>3</SUB>

The impedance of the interface between Pt metal and sodium borate melts containing Fe2O3, CuO or Cr2O3 as solutes was measured. The O2/O2− redox of the solvent melts was found to be irreversible. The contribution of the peripheral portion, where gas-metal-melt coexist, was evaluated. The effect of a direct potential on the impedance was measured, from which the redox reactions of the solute oxides were found to be reversible.

Refractory products for the production units of amorphous metals and alloys

In order to obtain amorphous metals and alloys, we worked out the optimum composition and the production technology of the components having long-term mechanical strength, thermal shock resistance, and corrosion resistance. The structure—property relationship was established. The products of the developed systems can also be used under the conditions involving the action of aggressive chemical media (in particular, in the melts of the borates of alkali-earth metals).

Borohydride reductions of metal ions. A new understanding of the chemistry leading to nanoscale particles of metals, borides, and metal borates

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTBorohydride reductions of metal ions. A new understanding of the chemistry leading to nanoscale particles of metals, borides, and metal boratesGeorge N. Glavee, Kenneth J. Klabunde, Christopher M. Sorensen, and George C. HadjapanayisCite this: Langmuir 1992, 8, 3, 771–773Publication Date (Print):March 1, 1992Publication History Published online1 May 2002Published inissue 1 March 1992https://doi.org/10.1021/la00039a008RIGHTS & PERMISSIONSArticle Views2040Altmetric-Citations163LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (301 KB) Get e-Alerts Get e-Alerts

Thermal stability of alkali metal borates and alkaline earth metal borates

The correlation between the enthalpies of formation of alkali metal and alkaline earth metal borates and the composition of the vapor in equilibrium with their melts is considered. The thermal stabilities of the studied borates have been estimated. A method is suggested for determination of the relative composition of the vapor over borate melts on the basis of their enthalpies of formation.

The effect of pressure on the formation of alkali metal borate ion pairs at 25�C

Pressure dependent UV-visible spectrophotometric measurements were used to determine\(\Delta \bar V^ * \) and\(\Delta \bar \kappa ^ * \) for the formation of alkali metal borate ion pairs. The association constant for each ion pair was measured at 25°C and at ionic strengths of 0.1 and 1.0m over a pressure range of 1 to 2000 atm. The pressure dependence of the apparent association constants, KA(P)/KA(1), have been fitted to $$[RT/(P - 1)]ln[K_A (P)]/[K_A (1)] = - \Delta \bar V^0 + \Delta \bar \kappa ^0 [(P - 1)/2]$$ to determine\(\Delta \bar V^0 and \Delta \bar \kappa ^0 \). The\(\Delta \bar V^0 \) for the alkali metal borate ion pairs range from 5–9 cm3-mol−1. The association constants were also measured as a function of ionic strength at 1 atm. Extrapolation to I=0 yielded KA of 2.12, 0.66, 0.76 and 1.12 for [LiB(OH)4], [KB(OH)4], [RbB(OH)4] and [CsB(OH)4], respectively. The trend generally indicates less ion pairing and a smaller volume change for the ion pair formation as the size of the cation increases. The concept of localized hydrolysis is used to explain the trend observed in the equilibrium constant of the ion pair as the cation size is changed.

Synthesis, characterization and magnetic properties of LnBO 3 (Ln ≡ Nd, Gd, Tb, Dy, Ho and Er)

A new method for the synthesis of some lanthanide orthoborates LnBO 3 (Ln ≡ Nd, Gd, Tb, Dy, Ho and Er) has been successfully used. The different orthoborates LnBO 3 were obtained by mixing metal hydroxides Ln(OH) 3 and orthoboric acid B(OH) 3 in stoichiometric amounts at low temperatures between 873 and 973 K and at pressures of between 10 −4 and 10 −5 mm Hg. The results seem to indicate that this method of synthesis can be applied to the isolation of metal borates at temperatures that are several hundreds of degrees below those reported in the literature. The characterization of these materials has been carried out by X-ray powder diffraction and IR spectrometry. The magnetic susceptibilities of these orthoborates have also been measured in the temperature range 4.2–300 K. From 50 to 300 K the data fit a Curie-Weiss behaviour and the Weiss constants are negative for all the compounds. Magnetic susceptibility shows a quasi-Curie-like behaviour for GdBO 3.

Synthesis and structural characterization of solid solutions Cd xHg 1− xB 4O 7 ( x = 1, 0.75, 0.5, 0.25, 0)

Solid solutions, Cd x Hg 1− x ,B 4O 7, were obtained from Cd(OH) 2,HgO and B(OH) 3 in appropriate stoichiometric amounts, at low temperatures ranging between 523 and 623 K and 10 −4–10 −5 Hg mm. These materials were characterized by X-ray powder diffraction, giving orthorhombic symmetry (space group Pbca, No. 61) and the lattice parameters (in Å) are: a = 8.704, b = 14.176, c = 8.229 (for x = 1), a = 8.729, b = 14.168, c = 8.242 (for x = 0.75), a = 8.758, b = 14.162, c = 8.303 (for x = 0.5), a = 8.769, b = 14.147, c = 8.348 (for x = 0.25) and a = 8.792, b = 14.107, c = 8.382 (for x = 0). IR spectra and TG are discussed on the basis of the stereochemistry of the boron atoms in these structures. The results seem to indicate that this method of synthesis can be applied to the isolation of related metal borates at temperatures that are several hundred degrees below those cited in the literature.

Calorimetric study of vitreous and crystalline alkali metal borates

The enthalpies of solution in 2 N nitric acid at 298 K were measured for alkali metal borate glasses and crystals. From the data obtained, their enthalpies of formation from the oxides and the heats of crystallization of the glasses were calculated. The negative deviation from ideality observed in alkali metal borate systems is interpreted in terms of the acid-base interaction of their components. The heats of crystallization of the glasses appeared to be mainly determined by the ordering effect of the boron-oxygen network. The contents of different borate groupings in the glasses studied were estimated. The structures of the borate glasses are discussed.

Dissociation of alkali metal borates and acid-base interactions in oxide systems

The stability relative to decomposition to oxides has been estimated for alkali metal borates M2O·nB2O3(M=Li, Na, K, Rb and Cs), wheren=1,2,3 and 4. The correlation between the degrees of dissociation and the enthalpies of formation is discussed.

Cation-network interactions in binary alkali metal borate glasses. A far-infrared study

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCation-network interactions in binary alkali metal borate glasses. A far-infrared studyE. I. Kamitsos, M. A. Karakassides, and G. D. ChryssikosCite this: J. Phys. Chem. 1987, 91, 22, 5807–5813Publication Date (Print):October 1, 1987Publication History Published online1 May 2002Published inissue 1 October 1987https://doi.org/10.1021/j100306a058RIGHTS & PERMISSIONSArticle Views344Altmetric-Citations75LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (828 KB) Get e-Alerts

Acid-base concept in oxide glasses

The relationship between the acid-base properties of oxide glasses and the atomic characteristics of their components was studied. It has been found that the increase in the basicity of oxides in the order Li2O < Na2O < K2O < Rb2O < Cs2O is due to an increase in the ionic character of metaloxygen bonds during the formation of alkali metal borate glasses from oxides.

Glucose Isomerase and Its Behaviour under Hydrogenation Conditions

AbstractA survey is given of glucose isomerase, its sources, its mechanism of isomerization and its data and properties in three different immobilized forms. In addition, the effect of a number of parameters on the activity of immobilized glucose isomerase has been investigated, e. g. hydrogen pressure, Mg(II) and Ca(II), transition metal ions, borate and sugar alcohols. Immobilized glucose isomerase remains sufficiently active under hydrogenation conditions to maintain D‐glucose and D‐fructose in equilibrium. D‐Glucitol, in contrast to D‐mannitol, has some inhibiting effect on the enzyme action. The D‐glucose/D‐fructose equilibrium constant is independent of the total sugar concentration (between 0.2 – 2.2‐M).

The mechanism of evaporation of boron compounds when E-type glass is melted

During the melting of E-type glasses, the loss of boron compounds reaches 10-25%. Measurements of the concentration of B/sub 2/O/sub 3/ in the glassmelting furnace showed that it evaporates predominantly in the first stage when the batch is converted to the molten glass. A more detailed study of this question over the temperature ranges in which the batch is transformed into molten glass made by studying the volatility of boron by determining the spectral analysis of the products deposited from it while the material was being heated, made it possible to establish that when E-type glass is melted, evaporation of boron compounds occurs over two temperature intervals and is not associated with the evaporation of borates. The main loss of boron occurs in the low-temperature interval. The loss of B/sub 2/O/sub 3/ during the melting of E-type glass is mainly determined by the form of boron-containing raw material and occurs at a temperature of 200-500/sup 0/C. The most effective method of reducing boron loss is to use nonaqueous compounds of boron in the batch, particularly borates of alkaline earth metals, to use finely milled batch components, and particularly to granulate the batch.

Applications of Xanthan gum

AbstractXanthan gum, the extracellular polysaccharide from Xanthomonas comperstris, provides aqueous solutions with properties that are extremely useful in a large number of industrial applications, both food and non‐food. These properties, a consequence of xanthan gum's particular molecular shape, are: high at‐rest or low‐shear viscosity even at low gum concentrations, yield value, high pseudoplasticity, increased viscosity in the presence of added salt depending on gum concentration, stable viscosity over a wide range of temperature and pH in the presence of added salt, synergistic increase in viscosity in the presence of guar gum and locust bean gum, thermoreversible gelation with locust bean gum at appropriate gum concentratins, and gelation with di‐and trivalent metal ions and borates under specific conditions. Xanthan gum is thus an excellent stabiliser for a wide variety of suspensions, emulsions, and foams and is highly effective over a range of temperature, pH and ionic strength. In addition, its pseudoplasticity allows the formulation of products which require not only high at‐rest viscosity but also low viscosity under highshear application conditions.

Preparation and mechanistic studies of halogen boracites

A new synthesis for the preparation of multigram amounts of high purity halogen boracites is presented. The boracites NiBr, MgCl, ZnCl, CoBr and MnI among others are prepared in essentially 100% yields and at temperatures as low as 200°C in less than six hours. Mechanistic studies prove that the metal oxide is not necessary for boracite formation, but demonstrates its utility in previous boracite syntheses. Water is found to be essential for the formation of boracite presumably in the form of HBO 2. An oxidizing atmosphere is shown to inhibit boracite formation by preferentially forming metal borates.

Reduction by polymetallic complex hydrides. Part 1. Dihydrobis(pyrazol-1-yl)borates of transition metals with cyclohexanone and cyclohex-3-enone

The reactivity of CoII, NiII, CdII, CuII, and ZnII dihydrobis(pyrazol-1 -yl)borates have been tested towards the ketonic function of cyclohexanone and cyclohex-3-enone under various experimental conditions. Reduction rate and selectivity vary with the nature of the transition metal, independently of both the molar ratio of hydride to ketone and the temperature.

Industrial applications of boron compounds

Abstract