Pentaborate Salts Research Articles

Small molecule additives in multilayer polymer-clay thin films for improved heat shielding of steel

In an effort to improve the heat shielding ability of multilayer polymer-clay films, the influence of various small molecule additives was studied. Tris(hydroxymethyl)aminomethane (THAM), pentaerythritol (PER), and ammonium pentaborate (PB) are each utilized in flame retardant applications for the benefits they provide in reducing the propagation of fire. In the present study, these additives combined with polyethylenimine (PEI) and vermiculite (VMT) clay and the resulting growth of the coatings and the thermal resistivity were measured. THAM and PB salts contribute most to the overall growth of the layer-by-layer assembled films, generating an increase in film thickness of 50% or more, while PER has a greater impact on heat shielding. A 14-bilayer (THAM + PER + PEI)/VMT coating (~25 µm thick) on steel can achieve a temperature differential of over 125 °C due to a layering effect that occurs within the architecture of the macroscopic insulation bubble and disordered char. This improved thermal resistivity across a relatively thin film generates a heat shield that can be applied in novel applications such as a single-use protective barrier for aerospace components.

Zwitterionic amino acids as precursors for nonmetal cation pentaborate salts

AbstractNonmetal cation (NMC) pentaborate structures were synthesized using the amino acid molecules as cations precursors. Chemical composition analysis, infrared spectroscopy, mass analysis, boron nuclear magnetic resonance, and thermal gravimetric analysis (TGA/DTA) methods were used for structural characterization. The hydrogen storage efficiency of molecules was also determined experimentally. The recorded infrared spectra support the structural similarities of the molecules. Stretchings of pentaborate rings and characteristic peaks of amino acids were detected in infrared spectra. When the thermal analysis curves were recorded, it was found that the structures showed similar decomposition steps. Due to the result of thermal decay, glassy boron oxide (B2O3) formation was observed as the final decomposition products of all molecules. Peaks associated with boric acid, triborate, and pentaborate were observed in the 11B spectra of these salts. Powder X‐ray diffraction spectroscopy supports the presence of BO3 and BO4− groups regarding the presence of pentaborate rings. It also indicates the high crystallinity of the structures. The molecular cavities detected by brunauer–emmett–teller analysis were found to be 3.586, 1.922, 1.673, and 1.923 g/cm3. Low‐molecular cavities can be attributed to the high hydrogen‐bonding capacity of the structures. The hydrogen capture efficiency of the pentaborate salts was found to be in the range of 0.039‐0.

Novel Non-Metal Cation (NMC) Pentaborate Salts of Some Amino Acids.

Non-metal cation (NMC) pentaborate structures, in which some amino acids (valine, leucine, isoleucine, and threonine) were used as cations, were synthesized. The structural characterization of molecules was carried out by elemental analysis, FT-IR, mass, 11B-NMR, and thermal analysis (TGA/DTA) methods. The hydrogen storage capacity of molecules was also calculated by taking experimental results into consideration. The FT-IR spectra support the similarity of structures. The characteristic peaks attributable to pentaborate rings and amino acids were observed. When thermal analysis data were examined, it was observed that pentaborate salts gave similar degradation steps and degradation products. As a final degradation product of all thermal analysis experiments, a glassy form of B2O3 was observed. The valine pentaborate is the most thermally stable. Also, the amounts of hydrate water outside the coordination sphere of the compounds were determined by thermal analysis curves. The peaks of boric acid, triborate, and pentaborate structures were obtained in ppm with the 11B-NMR results of synthesized pentaborate compounds. With powder X-ray spectroscopy, all structures were found to be crystalline but not suitable for single-crystal X-ray analysis. The molecular cavities of the compounds detected by BET were found to be 3.286, 1.873, 2.309, and 1.860 g/cm3, respectively. A low number of molecular cavities can be interpreted in several existing hydrogen bonds in structures. The hydrogen storage capacities of the molecules were found to be in the range of 0.04 to 0.07% by mass.

Phase Equilibria and Phase Diagrams for the Ternary Aqueous System Containing Lithium, Sodium, and Pentaborate Ions at 298.15 and 323.15 K and 101.325 kPa

Phase equilibria and phase diagrams for the ternary aqueous system containing lithium, sodium, and pentaborate ions at 298.15 and 323.15 K and 101.325 kPa were investigated by the methods of isothermal dissolution equilibrium. From the experimental data, the phase diagrams and the diagrams of physicochemical properties versus composition of lithium pentaborate in the equilibrium systems were plotted, respectively. The phase diagrams of the ternary system LiB5O8 + NaB5O8 + H2O at two temperatures contain one invariant point, two univariant curves, and two crystallization regions corresponding to sodium pentaborate pentahydrate (NaB5O8·5H2O) and lithium pentaborate pentahydrate (LiB5O8·5H2O). Due to the different dissolution behaviors of pentaborate salts in the aqueous systems, the component of LiB5O8 has a relatively strong effect on the solubility of NaB5O8. It was found that this system belongs to a simple eutectic type at two temperatures, and neither double salts nor solid solutions were formed. The densities and refractive indices in the ternary system at 298.15 and 323.15 K are as similar as changing regularly with the increase of LiB5O8 concentration. On the basis of empirical equations of the density and refractive index in electrolytes, the calculated values of density and refractive index agreed well with the experimental values at two temperatures.

Synthesis, XRD Studies and NLO Properties of [p-H2NC6H4CH2NH3][B5O6(OH)4]\xb71/2H2O and NLO Properties of Some Related Pentaborate(1\u2212) Salts

The non-metal cation pentaborate(1−) salt [p-H2NC6H4CH2NH3][B5O6(OH)4]·1/2H2O (1) was synthesised from B(OH)3 and p-H2NC6H4CH2NH2 and crystallized from aqueous solution. Compound 1 was characterized by thermal (TGA/DSC), spectroscopic (IR, NMR) and single-crystal X-ray diffraction methods and it was found to crystallize in the non-centrosymmetric point group P21. Powder SHG measurements on 1 and some related alkylammonium pentaborate salts, [NH3CMe2(CH2OH)][B5O6(OH)4], [NH3CMe(CH2OH)2][B5O6(OH)4] and [NH3CHMeCH2OH][B5O6(OH)4], a substituted imidazolium salt, [1,2,3-Me3C3H2N2][B5O6(OH)4], a substituted piperidinium salt, [(CH2)5NH(CH2CH2OH)][B5O6(OH)4], and a substituted pyrrolidinium salt, [S-(+)-2-(HOCH2)C4H7NH2][B5O6(OH)4], were determined. Compound 1 and all compounds, except [1,2,3-Me3C3H2N2][B5O6(OH)4], showed some weak SHG activity with SHG efficiencies of 0.1–0.2 relative to that of KH2PO4 (KDP).

Triborate and pentaborate salts of non-metal cations derived from N-substituted piperazines: synthesis, structural (XRD) and thermal properties

The synthesis and characterization of a triborate salt, [H2N(CH2CH2)2NH2][B3O3(OH)4]2 (1), and four pentaborate salts, [H2N(CH2CH2)2NH][B5O6(OH)4] (2a), [MeHN(CH2CH2)2NH][B5O6(OH)4] (2b), [MeHN(CH2CH2)2NMe][B5O6(OH)4] (2c) and [Me2N(CH2CH2)2NMe2][B5O6(OH)4]2 (2d) are described. TGA and DSC analysis (in air, 25–1000 °C) indicate that triborate 1 decomposes to B2O3via a multistage process, with the first stage (<250 °C) being dehydration to condensed polymeric hexaborate of approximate composition: [H2N(CH2CH2)2NH2][B6O10]. The pentaborates (2a–2d) are thermally decomposed to B2O3via a 2 stage process involving polymeric [NMC][B5O8]. The anhydrous polyborates were amorphous. BET analysis of materials derived from the thermolysis of 1 at 250, 400, 600, and 1000 °C, were all non-porous (surface area <1.8 m2 g−1). A single-crystal X-ray diffraction study of 1 showed that it contains isolated triborate(1−) anions in a structure comprised of alternating cationic and anionic layers held together via extensive H-bonds. Single-crystal XRD structural studies on pentaborate salts 2c and 2d are also reported.

2,2′-(Piperazine-1,4-diyl)diethanaminium bis(2-hydroxybenzoate)

The asymmetric unit of the title salt, C8H22N4 2+·2C7H5O3 −, comprises half a 2,2′-(piperazine-1,4-di­yl)diethan­aminium dication plus a 2-hy­droxy­benzoate anion. In the crystal, the anions and cations are linked by N—H⋯O and O—H⋯O hydrogen bonds to form infinite two-dimensional networks parallel with the a unit-cell face. The conformation adopted by the cation in the crystal is very similar to that adopted by the same cation in the structures of the nitrate and tetra­hydrogen penta­borate salts.

2,2′-(Piperazine-1,4-diyl)diethanaminium dibenzoate

The asymmetric unit of the title salt C8H22N4 2+·2C7H5O2 −, comprises two independent pairs of half a 2,2′-(piperazine-1,4-di­yl)diethanaminium dication plus a benzoate anion. The dications are symmetrical and lie across crystallographic centres of inversion. The crystal structure was refined as a two-component pseudo-merohedral twin using the twin law 001 0-10 100 [he domain fractions are 0.8645 (8) and 0.1355 (8)]. The anions and cations are linked by N—H⋯O hydrogen bonds and weak N—H⋯O inter­molecular inter­actions to form infinite two-dimensional networks parallel to [101]. The conformation adopted by the cation in the crystal structure is very similar to that adopted by the same cation in the structures of the 2-hy­droxy­benzoate [Cukrowski et al. (2012 ▶). Acta Cryst, E68, o2387], the nitrate and the tetra­hydrogen penta­borate salts.

Structural and thermal studies of non-metal cation pentaborate salts with cations derived from 1,5-diazobicyclo[4.3.0]non-5-ene, 1,8-diazobicyclo[5.4.0]undec-7-ene and 1,8-bis(dimethylamino)naphthalene

The reaction of the cyclic amines 1,5-diazobicyclo[4.3.0]non-5-ene (DBN), 1,8-diazobicyclo[5.4.0]undec-7-ene (DBU) and 1,8-bis(dimethylamino)naphthalene (PS) with B(OH)3 in a 1:5 ratio affords in high yields the non-metal cation pentaborate salts [HDBN][B5O6(OH)4] (1), [HDBU][B5O6(OH)4] (2) and [HPS][B5O6(OH)4]·B(OH)3 (3). Compounds 1–3 were characterized by spectroscopic studies (NMR, IR) and compounds 1 and 3 were further characterized by single-crystal XRD studies. The pentaborate salts compounds show extensively H-bonded supramolecular anionic lattices which are templated by the cations. Thermal analysis (TGA) of 1–3 showed that thermally decomposed in air at 1000° to B2O3 in a two step process involving dehydration (<250°C) and oxidation (250–600°C). BET analysis of materials derived from thermolysis of 1–3 had internal porosities of <1m2/g.

Templated heptaborate and pentaborate salts of cyclo-alkylammonium cations: structural and thermal properties

The synthesis and characterization of a series of cyclo-alkylammonium pentaborate salts {[cyclo-C(n)H(2n-1)NR(3)][B(5)O(6)(OH)(4)] (R = H, n = 3, 5-7 (1-4); R = Me, n = 6 (5))} are reported. Compounds 1, 2 and 5 have been further characterized by single-crystal XRD studies. Attempted recrystallization of 3 and 4 yielded small crops of the unexpected heptaborate salts, [cyclo-C(6)H(11)NH(3)](2)[B(7)O(9)(OH)(5)]·3H(2)O·B(OH)(3) (6) and [cyclo-C(7)H(13)NH(3)](2)[B(7)O(9)(OH)(5)]·2H(2)O·2B(OH)(3) (7) which were also characterized crystallographically. All compounds show extensive supramolecular H-bonded anionic lattices templated by the cations. H-bond interactions are described in detail. TGA-DSC analysis of the pentaborates 1-5 showed that they thermally decomposed in air at 800 °C to 2.5B(2)O(3), in a 2 step process involving dehydration (<250 °C) and oxidative decomposition (250-600 °C). BET analysis of materials derived from the pentaborates had internal porosities of <1 m(2) g(-1).

Structural (XRD) and thermal (DSC, TGA) and BET analysis of materials derived from non-metal cation pentaborate salts

The synthesis, structural characterization (XRD), and thermal properties of nine non-metal cation (NMC) pentaborate anion salts, [NMC][B(5)O(6)(OH)(4)] (1a-1i) is described (NMC = [NH(3)CMe(2)(CH(2)OH)](+) (a), [O(CH(2)CH(2))(2)NH(2)](+) (b), [NH(3)CMe(CH(2)OH)(2)](+) (c), [2-(2-CH(2)CH(2)OH)PyH](+) (d), [(CH(2))(4)NH(CH(2)CH(2)OH)](+) (e), [(CH(2))(5)NH(CH(2)CH(2)OH)](+) (f), [2-MeImid](+) (g), [Me(3)NCMe(2)(CH(2)OH)](+) (h), [O(CH(2)CH(2))(2)NMe(2)](+) (i). Single-crystal X-ray diffraction studies on all compounds show that they contain isolated pentaborate anions, H-bonded together in a supramolecular array, with the cations occupying the cavities within the network. Compound 1c was obtained as a partial hydrate (0.16H(2)O). TGA and DSC analysis (in air, 25-1000 degrees C) indicate that compounds 1a-1i thermally decompose via a 2 stage process to B(2)O(3). The first stage (<250 degrees C) is dehydration to condensed polymeric pentaborates {approximate composition: [NMC][B(5)O(8)] (2a-2i)}. Five condensed pentaborates (2a-c, 2e, 2g) were synthesised and characterized by powder XRD and BET analysis. These condensed pentaborates were amorphous. The isolated pentaborates intumesced at approximately 600 degrees C (occupying approximately 10 times their original volume), and then contracted back to black glassy B(2)O(3) solids at 1000 degrees C. The intumescent materials (3a), (3b), (3e), (3g), and a final B(2)O(3) sample (4b) were synthesised and isolated and their porosities determined. BET surface area analysis on the isolated pentaborates (1a-c, 1e, 1g), the condensed pentaborates (2a-c, 2e, 2g), intumesced materials (3a, 3b, 3e, 3g), and B(2)O(3) (4b) showed that they were all 'non-porous' (<1.59 m(2) g(-1)).

Novel hydrogen-bonded host lattices in inclusion compounds of urea and peralkylated ammonium pentaborate salts

Novel hydrogen-bonded host lattices in inclusion compounds of urea and peralkylated ammonium pentaborate salts