Spectrophotometric Determination of Traces of Boron in High Purity Silicon

Abstract

A reddish brown complex is formed between boron and curcumin in concentrated sulphuric acid and glacial acetic acid mixture (1:1). the coloured complex is highly selective and stable for about 3 hours and has the maximum absorbance at 545 nm. the sensitivity of the method is extremely high and the detection limit is 3 parts per billion based on 0.004 absorbance value. the interference of some of the important cations and anions relevant to silicon were studied and it is found that 100 fold excess of most of these cations and anions do not interfere in the determination of boron. the method is successfully employed for the determination of boron in silicon used in semiconductor devices. the results have been verified by standard addition method.     

Li- and Mg-doping into icosahedral boron crystals, α- and β-rhombohedral boron, targeting high-temperature superconductivity: structure and electronic states

The possibility of high T_C superconductivity is suggested for lithium- and magnesium-doped icosahedral boron crystals, α- and β-rhombohedral boron. The doping of these elements was attempted by a vapor diffusion processing. Both lithium and magnesium are hardly doped into the α-rhombohedral boron, although small amounts of metallic parts are found in the sample. In only one Li-doped sample, the metallic part contained 0.02 vol% of the superconductive phase (T_C∼36 K). Magnesium was successfully doped into β-rhombohedral boron homogeneously up to 4 at% (Mg_4.1B₁₀₅), although considerable amount of impurity silicon was introduced together with magnesium. The structures of the doped samples were analyzed assuming co-doping of magnesium and silicon. The relation between the site occupancies of the dopants and the lattice expansion is discussed. The estimation of the density of states near the Fermi energy by EELS and magnetic susceptibility measurements suggested a metal transition of the β-rhombohedral boron by the doping of magnesium and silicon. The relation between the metal transition and the intrinsic acceptor level is also discussed.     

Boron: Elementary Challenge for Experimenters and Theoreticians

Many of the fundamental questions regarding the solid‐state chemistry of boron are still unsolved, more than 200 years after its discovery. Recently, theoretical work on the existence and stability of known and new modifications of the element combined with high‐pressure and high‐temperature experiments have revealed new aspects. A lot has also happened over the last few years in the field of reactions between boron and main group elements. Binary compounds such as B₆O, MgB₂, LiB_1?x, Na₃B₂₀, and CaB₆ have caused much excitement, but the electron‐precise, colorless boride carbides Li₂B₁₂C₂, LiB₁₃C₂, and MgB₁₂C₂ as well as the graphite analogue BeB₂C₂ also deserve special attention. Physical properties such as hardness, superconductivity, neutron scattering length, and thermoelectricity have also made boron‐rich compounds attractive to materials research and for applications. The greatest challenges to boron chemistry, however, are still the synthesis of monophasic products in macroscopic quantities and in the form of single crystals, the unequivocal identification and determination of crystal structures, and a thorough understanding of their electronic situation. Linked polyhedra are the dominating structural elements of the boron‐rich compounds of the main group elements. In many cases, their structures can be derived from those that have been assigned to modifications of the element. Again, even these require a critical revision and discussion.     

MACROCYCLES [Agrave] ATOMES DE PHOSPHORE ET DE BORE HYPERVALENTS DÉTERMINATION DE LEUR TAILLE PAR SPECTROMÉTRIEDE MASSE

Abstract

Macrorings bearing hexacoordinated phosphorus atoms or (and) tetracoordinated boron atoms, have been prepared from condensation of phenyldichlorophosphane in presence of diethylamine, or (and) boric or phenylboronic acids with some polyphenols. Their structures-have been established by NMR, microanalysis and mass spectrometry. These compounds are constituted according to (1 + 1), (2 + 2) and (3 + 3) stoichiometry.     

A New Class of Boron Nanotube

The configurations, stability and electronic structures of a new class of boron sheet and related boron nanotubes are predicted within the framework of density functional theory. This boron sheet is sparser than those of recent proposals. Our theoretic results show that the stable boron sheet remains flat and is metallic. There are bands similar to the π‐bands in graphite near the Fermi level. Stable nanotubes with various diameters and chiral vectors can be rolled from the sheet. Within our study, only the thin (8, 0) nanotube with a band gap of 0.44 eV is semiconducting, while all the other thicker boron nanotubes are metallic, independent of their chirality. It indicates the possibility, in the design of nanodevices, to control the electronic transport properties of the boron nanotube through the diameter.     

Extensive Structural Rearrangements upon Reduction of 9H‐9‐Borafluorene

Common wisdom has it that organoboranes are readily oxidized. Described herein is that also their reduction can result in remarkable chemistry. Treatment of dimeric 9H‐9‐borafluorene with Li metal in toluene yields two strikingly different classes of compounds. One part of the sample reacts in a way similar to B₂H₆, thus affording an aryl(hydro)borane cluster reminiscent of the [B₃H₈]^? anion. The other part furnishes a dianionic boron‐doped graphene flake devoid of hydrogen substituents at the boron centers and featuring a central B?B bond. A change in the solvent to THF allows an isolation of this dibenzo[g,p]chrysene analogue in good yields.     

Boron‐Double‐Ring Sheet,Fullerene, and Nanotubes: Potential Hydrogen Storage Materials

Similar to carbon‐based graphene, fullerenes and carbon nanotubes, boron atoms can form sheets, fullerenes, and nanotubes. Here we investigate several of these novel boron structures all based on the boron double ring within the framework of density functional theory. The boron sheet is found to be metallic and flat in its ground state. The spherical boron cage containing 180 atoms is also stable and has I symmetry. Stable nanotubes are obtained by rolling up the boron sheet, and all are metallic. The hydrogen storage capacity of boron nanostructures is also explored, and it is found that Li‐decorated boron sheets and nanotubes are potential candidates for hydrogen storage. For Li‐decorated boron sheets, each Li atom can adsorb a maximum of 4 H₂ molecules with g_d=7.892 wt %. The hydrogen gravimetric density increases to g_d=12.309 wt % for the Li‐decorated (0,6) boron nanotube.     

A road map to assess critical materials content in boron industrial wastes using sustainable micro-X-ray fluorescence and total reflection X-ray fluorescence instrumentation

Turkey is the leading country in the world in terms of boron production and sale. Increasing boron production goes along with an increasing generation of boron wastes. The pollution of the soil and the air around the waste piles, as well as the occupation of several square kilometers of ground, are major environmental problems. It is, therefore, very important to make use of the wastes to both protect the environment and create revenue. This work presenteda road map for fast screening of boron waste for critical elements followed by determination of the elements using small footprint low power instrumentation. The sample preparation was kept to a minimum. A procedure that allowed an assessment of critical materials in industrial production waste with minimal consumption of hazardous acids, energy, and time was presented. The samples were first screened for valuable and hazardous elements by micro-X-ray fluorescence (XRF). Samples with considerable contents of Cs, Rb, and Aswere then prepared as slurries for the total reflection XRF (TXRF) measurement. To evaluate the TXRF procedure, a standard reference material was analyzed. As a result, Rb and Cs in concentrations up to 420 ± 70 and 1500 ± 200 mg/kg were detected in some of the waste forms. The time savings were in order of a factor of 3 when comparing the prescreening combined micro-XRF and TXRF approach to an all TXRFanalysis approach.     

SYNTHESIS AND CHARACTERIZATION OF THE FIRST BORANE ADDUCTS AND BORON CATIONS OF SOME N-ALKYL AND N-AMINOTRIPHENYLPHOSPHORANIMINES

Abstract

The first borane adducts of N-alkyl and N-aminotriphenylphosphoranimines, Ph₃P[dbnd]N—R, were prepared by two different general synthetic methods. The first method involved displacement of THF (tetrahydofuran) from THF-borane by the free imines, and the second employed the reaction of LiBH₄ with iminium bromides, Ph₃P[dbnd]N(R)HBr, in diethyl ether. Imine boranes, Ph₃P[dbnd]N(R)BH₃, were synthesized where R [dbnd] methyl, ethyl, n-propyl, isopropyl, isobutyl, t-butyl. dimethylamino, phenylamino, and methyl, phenylamino as the nitrogen attached groups. Symmetrical boron cations, (Ph₃P[dbnd]NR)₂, BH₂ ⁺, where R = methyl, ethyl, and n-propyl, were synthesized by displacement of iodide from in-situ generated iodoborane adducts, Ph₃P[dbnd]N(R)BH₂I, by the free imines. An attempt to form an unsymmetrical boron cation from (CH₃)₃ NBH₂I and Ph, P[dbnd]N(n-C₃H₇) resulted only in a mixture of the corresponding symmetrical boron cations. Physical, chemical and spectral properties of the borane adducts and boron cations, namely thermal and hydrolytic stabilities, infrared and NMR data are presented. Oxidative and reductive stabilities of the boron cations were studied. The borane adducts can be chlorinated with either HCI or Ph₃CCI. Relative base strengths of some imines were determined by following the exchange of BH₃ between borane adducts of (CH₃)₃ N or 4- (CH₃)C₅H₄ N and the imines via NMR.     

Developments in transfer hydrogenations of aromatic ketones catalyzed by boron compounds

Boron complexes BL1 and BL2 were prepared from O-donor ligands, 2,2′-(1E,1′E)-(ethane-1,2-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L1) and 2,2′-(propane-1,3-diylbis(azan-1-yl-1-ylidene))bis(methane-1-yl-1-ylidene)diphenol (L2). The complexes were fully characterized by ¹H and ¹³C NMR, LC-MS/MS, TGA/DTA, UV-Vis, elemental analysis, SEM, and FTIR. The transfer hydrogenation of acetophenone derivatives was investigated by the boron complexes in the presence of isoPrOH, as the hydrogen source, under basic condition with NaOH. The results showed that the boron complexes were promising catalytic precursors for transfer hydrogenation of aromatic ketones in 0.1 M isoPrOH solution (up to 99%). Both steric and electronic factors of this class of molecules had a significant impact on the catalytic properties.     

Ion Exchange Extraction of Boron from Aqueous Fluids by Amberlite IRA 743 Resin

The ion exchange characteristics d Amherlite IRA 743 resin for extracting boron from aqueous fluids have been investigated in detail. The results show that AmherHte IRA 743 resin, a boron specific ion exchange resin, can quantitatively extract boron as the B (OH)4- spedes from weakly basle solution. Some exchangeable anions such as CI- and SO4^2- are present, resulting in an increase in pH value of the loeded solution within the nan, and the boron in natural aqueous fluids with low nH is also extracted by Amberlite IRA 743 resin. However, the voiume of loaded solution must be restricted. The maximum voiume of loaded solution giving quantitative extraction of boron decreases for sample soh.,tiom of lower pH value. Warm HCI solution is more effective than room temperature HCI solution for eluting boron from Amberllte IRA 743 resin.     

Chelate synthesis of 8-diaminomethylene-5,6,7,8-tetrahydroquinazoline-7-one derivatives

A scheme for synthesizing 5,6,7,8-tetrahydroquinazoline systems from ketene aminal1 via its diphenylboron chelate2 has been suggested. The interaction ofp-toluamidine with the condensation product of the chelate with dimethylformamide dimethylacetal results in the formation of 8-(N-benzoyldiaminomethylene)-2-p-tolyl-5,6,7,8-tetrahydroquinazoline-7-one, which is easily debenzoylated by sodium ethoxide. 8-Diaminomethylene-5,6,7,8-tetrahydroquinazolinone derivatives can be used for the preparation of boron chelate complexes.Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 5, pp. 888–890, May, 1994.     

1, 1‐Dianthrimide as a Reagent for the Spectrophotometric Determination of Boron

Abstract

The optimum conditions for the formation of the blue 1:1 complex by the reaction of 1, 1‐dianthrimide and boric acid in 95% by weight sulfuric acid have been determined. The effect of certain diverse ions are reported. The procedure is applicable to the determination of 1 to 10 μ of boron.     

First-principles study of the crystal and electronic structures of α-tetragonal boron

The crystal and electronic structures of α-tetragonal (α-t) boron were investigated by first-principles calculation. Application of a simple model assuming 50 atoms in the unit cell indicated that α-t boron had a metallic density of state, thus contradicting the experimental fact that it is a p-type semiconductor. The presence of an additional two interstitial boron atoms at the 4c site made α-t boron semiconductive and the most stable. The cohesive energy per atom was as high as those of α- and β-rhombohedral boron, suggesting that α-t boron is produced more easily than was previously thought. The experimentally obtained α-t boron in nanobelt form had about two interstitial atoms at the 8i sites. We consider that the shallow potential at 8i sites generates low-energy phonon modes, which increase the entropy and consequently decrease the free energy at high temperatures. Calculation of the electronic band structure showed that the highest valence band had a larger dispersion from Γ to Z than from Γ to X; this indicated a strong anisotropy in hole conduction.     

Microprecipitation in boron-containing high-carbon steels

The dissolution and precipitation of boron have been studied in a high-carbon steel. Boron was found in different states: boron oxides, boron carbonitrides and iron-borocarbides Fe₂₃(B,C)₆. The dissolution of iron-borocarbides in austenite is complete at 1100 °C and precipitation along grain boundaries of this boron-bearing phase was observed after water-quenching from high austenitizing temperature. Therefore, boron precipitates along grain boundaries before pearlite nucleation.     

Polyhedral boron nitride molecules

The geometrical and electronic structures of two isomers (1 and2) of the polyhedral boron nitride molecule, B₁₂N₁₂, have been calculated using the MNDO method. Structure1 having the form of a truncated octahedron is more energetically preferable (ΔH _f ⁰=−128 kcal mol⁻¹) than isomer2, which hasC _6v symmetry. The equilibrium geometries of the N₆B₆(CH₂)₆ isomers (3 and4), which simulate fragments of structure2, have been calculated. The stabilization mechanism of the N₆ nitrogen cluster (hexaazabenzene) in polyhedral structures is discussed. The parameters calculated for molecules1 and2 have been correlated with the corresponding characteristics of their carbon analogs. Translated fromIzvestiya Akademii Nauk. Seriya Khimicheskaya, No. 10, pp. 1712–1714, October, 1993.     

Synergistic flame‐retardant effect and mechanisms of boron/phosphorus compounds on epoxy resins

To explore the component synergistic effect of boron/phosphorus compounds in epoxy resin (EP), 3 typical boron compounds, zinc borate (ZB), boron phosphate (BPO₄), and boron oxide (B₂O₃), blended with phosphaphenanthrene compound TAD were incorporated into EP, respectively. All 3 boron/phosphorus compound systems inhibited heat release and increased residue yields and exerted smoke suppression effect. Among 3 boron/phosphorus compound systems, B₂O₃/TAD system brought best flame‐retardant effect to epoxy thermosets in improving the UL94 classification of EP composites and also reducing heat release most efficiently during combustion. B₂O₃ can interact with epoxy matrix and enhance the charring quantity and quality, resulting in obvious condensed‐phase flame‐retardant effect. The combination of condensed‐phase flame‐retardant effect from B₂O₃ and the gaseous‐phase flame‐retardant effect from TAD effectively optimized the action distribution between gaseous and condensed phases. Therefore, B₂O₃/TAD system generated component synergistic flame‐retardant effect in epoxy thermosets.     

DITHIOPHOSPHORIC ACIDS AND TETRAPHOSPHORUS DECASULFIDE IN THE SYNTHESIS OF BORON DITHIOPHOSPHATES

Abstract

The reactions of O,O-dialkyl dithiophosphoric acids with triisobutyl borate, ammonium O,O-diisobutyl dithiophosphate with fluorodiisobutyl borate, and tetraphosphorus decasulfide with triisobutyl borate were studied. On the basis of these studies, new boron derivatives of dithiophosphoric acids were obtained. Low frequency ultrasonic irradiation (22 kHz, power 130 W) leads to reduction in reaction temperature and time in the reactions studied.     

Prediction of Boron–Boron Triple‐Bond Polymers Stabilized by Janus‐Type Bis(N‐heterocyclic) Carbenes

A class of polymeric compounds containing boron–boron triple bonds stabilized by N‐heterocyclic biscarbenes is proposed. Since a triply bonded B₂ is related to its third excited state, the predicted macromolecule would be composed by several units of an electronically excited first‐row homonuclear dimer. Moreover, it is shown that the replacement of biscarbene with N₂ or CO as spacers could change the bonding profile of the boron–boron units to a cumulene‐like structure. Based on these results, different types of diboryne polymers are proposed, which could lead to an unprecedented set of boron materials with distinct physical properties. The novel diboryne macromolecules could be synthesized by the reaction of Janus‐type biscarbenes with tetrabromodiborane, B₂Br₄, and sodium naphthalenide, [Na(C₁₀H₈)], similarly to Braunschweig’s work on the room temperature stable boron–boron triple bond compounds (Science, 2012 , 336, 1420).