11B MAS NMR Spectra Research Articles

Low-Temperature Thermal Treatment and Boron Speciation Analysis from Coals

Despite urgent calls for decarbonization, the continued increasing demand for electricity, primarily from coals, has presented challenges in managing coal-derived wastes such as coal fly ash (CFA), which are enriched with environmentally hazardous substances like boron. This study explores a low-temperature heating process to remove boron from coal, aimed at preventing its condensation and enrichment into CFA during combustion. Initial boron concentrations in coals varied widely from 50 to 500 ppm by weight and were found to correlate with fixed carbon content (FC) through the following polynomial equation: [B]o = 0.0929(FC)2 − 14.388(FC) + 601.85; R2 = 0.9173. This relationship suggests that as coal undergoes coalification, boron-containing compounds are decomposed and released, resulting in a decline in boron levels as the coal matures. Boron-removal efficiency was investigated by drying coal samples at 110 °C, 160 °C, and 210 °C under natural air convection, and nuclear magnetic resonance (NMR) spectroscopy was used to assess changes in boron speciation during heating. Our results demonstrate that boron removal ranged from 5% to 82%, with minimal improvements observed beyond 110 °C. In addition, the 11B MAS-NMR spectra of the coal samples showed four peaks at isotropic chemical shift values of −1.0, 2.0, 8.0, and 14.0 ppm and suggested that the species of boron volatilized at low temperatures is the inorganic BO4 assigned to peak no. 0 at −1.0 ppm. The association of boron with inorganic components in coal suggests potential for efficient removal, particularly in coals with higher fixed carbon content. These findings highlight the viability of low-temperature thermal treatment as a cost-effective method for boron removal, which is crucial in mitigating the risks associated with coal combustion by-products.

Experiments on the thermal activation of hydrogen release of NaBH4-sodalites characterized by IR- and MAS-NMR spectroscopy

New results on the reactions of the (BH4)-anion enclathrated in the cages of sodalites are reported. Hydrothermally synthesized NaBH4-sodalites (ǀNa8(BH4)2ǀ[SiAlO4]6) always contain hydro-sodalite type cages (ǀNa3(H2O)4ǀ[SiAlO4]3). With increasing temperature dehydration occurs. Above 250 °C a limited reaction of the residual water is going on with (BH4)-cage fillings releasing hydrogen and the appearance of certain borate specifications enclosed in the sodalite cages. The effect of a reaction of oxygen with the (BH4)-anions in the sodalite-cages at temperatures above 400 °C is also shown. The degree of (BH4)-conversion using wet and dry N2 stream is further followed by IR and MAS NMR investigations. External supply of water largely enhances the degree of reaction, e.g. at 400 °C from 16% to 44% loss of (BH4)-absorption intensity. However, 11B MAS NMR shows 8% and 22% of a conversion of (BH4)-cage fillings into new borate species in dry and wet N2 stream, respectively. These lower values are explained by a loss of B-ions via formation and evaporation of BH3 from the sodalite. Further evaluation of the 11B MAS NMR spectra could resolve the formation of (B(OH)3)-, (BO(OH)2)-, (B(OH)4)- along with unreacted (BH4)-species in the cages. 1H-MAS NMR shows a −3.8 ppm signal related to cage isolated (OH)-, which suggests an initial reaction step via (H+ + BH4−) to (BH3 + H2). The formation of (B(OH)3), however, also indicated sufficient water for a reaction of BH3 releasing further hydrogen. The formation of (BH3) could be observed in temperature dependent IR investigations at temperatures above 400 °C.

11B Nuclear Spin–Electron Spin Interactions in 11B MAS NMR Spectra of Paramagnetic Metal Borohydrides

Isotropic and anisotropic couplings between the 11B nuclear spin and the electron spin of paramagnetic electrons are observed in 11B MAS NMR spectra of α-Pr(BH4)3 and LiCe(BH4)3Cl. The 11B NMR spec...

Characterization of crystalline borates prepared from solution and derived glasses

An aqueous solution route has been developed to prepare calcium sodium borate compositions of the formula xB2O3·(100–x)(0.5CaO·0.45Na2O·0.05P2O5) (36.2 ≤ x ≤ 61.3 mol%). The effect of heat-treatment and melt-quenching on the structure and physical properties was investigated using differential thermal analysis, X-ray diffraction, FTIR spectroscopy, 11B MAS NMR and density. Dried powders were heat treated at temperatures 400–800 °C for 3h. XRD revealed formation of crystalline Na2B4O7·5H2O, Ca5(PO4)3OH, Na3B5O9H2O and CaB3O5(OH) in the samples treated up to 500 °C. Samples treated at higher temperature show the presence of CaNaB5O9, CaNa3B5O10 and CaNaPO4. Quenched solids obtained by melting powders are amorphous. It is deduced from FTIR spectra that CaO and Na2O modify the borate network forming BO4 and BO3 with non-bridging units, which depend on the molar ratio R =(Na2O+CaO)/B2O3 and temperature. The fraction N4 of four coordinated boron atoms changes with R and can be predicted by treating the compositions as if they are mixtures of Na2O–B2O3 and CaO–B2O3 matrices. N4 values have been used to calculate the fraction of all units in the glass structure. The results are confirmed by 11B MAS NMR spectra that show the presence of symmetric and asymmetric trigonal BO3 groups and splitting line shape of [4]B. The latter is assumed being related to different four-coordinated boron environments. Density and molar volume obtained by using mixed matrices concept agree well with the experimental data.

The influence of H2O and SiO2 on the structure of silicoborate glasses

To understand the impact of dissolved water on structure and properties, four boron-rich glasses of molar compositions 15-x Na2O x CaO 15 SiO2 70 B2O3 (with x = 0, 7.5, 10) and 10 Na2O 15 SiO2 75 B2O3 were prepared and subsequently hydrated (up to 8 wt% H2O). Density measurements show a non-linear trend upon hydration implying large structural changes in particular at water contents <2 wt%. Near-infrared spectroscopy shows hydroxyl groups are the dominant species in all glasses upon the entire range of water content. Molecular H2O is detectable only at total water contents >2 wt%. 11B MAS NMR spectra show that the abundance of BO4 species is mainly controlled by ratio of (Na2O + CaO)/B2O3 while incorporation of water plays a minor role. Compared to borate glasses, the efficiency of formation of BO4 tetrahedra is favored by crosslinking of the network by SiO4-units. The glass transition temperatures, determined by differential thermal analysis, decreases continuously with water content due to breakage of B-O-B bonds by hydrolysis. However, compared to silicates and aluminosilicates, the effect of dissolved water is less pronounced which can be explained by weaker B-O-B bonds in comparison to Si-O-Si bonds.

The effect of magnesium on the local structure and initial dissolution rate of simplified UK Magnox waste glasses

A series of simplified glasses were prepared to mimic the United Kingdom's Magnox radioactive waste glasses and determine the separate effect of the presence of Mg on the glass structure and the initial dissolution rate. These glasses had an alkaline earth (Ca/Mg) content of 6.5 mol% and relative ratios of Si, B and Na similar to 25 wt% waste loaded Magnox waste glass simulant. Each simplified glass had similar macroscopic properties, differing only in Ca/Mg ratio. 25Mg magic angle spinning nuclear magnetic resonance (MAS NMR) spectra of the simplified Mg endmember (MgEM) glass (with no Ca) and the full-component simulant glass were similar, consistent with the similar Mg local environments in both glasses. 11B MAS NMR spectra of the series of simplified glasses showed a systematic increase in the amount of three-coordinated boron ([3]B) with increasing amounts of Mg. A clear change in the charge balancing of four-coordinated boron ([4]B) by Mg compared with Ca is observed. However, 11B NMR measurements of the leached material showed that the additional [3]B was not preferentially leached from the Mg containing samples. Despite the structural changes in the glass induced by Ca/Mg substitution, initial dissolution rates (r0) remained invariant, within error, with Ca/Mg ratio. This indicates that the poorer aqueous durability of Mg-containing Magnox waste glass measured experimentally in long-term leaching experiments, compared with SON68 glass containing Ca, is not caused by a primary structural effect in the glass.

11B-MAS NMR approach to the boron adsorption mechanism on a glucose-functionalised mesoporous silica matrix

Boron chemistry has raised much interest because, despite the difference between necessities and toxicity being very narrow, it is still widely used in industrial processes. In a previous work we reported an adsorbent for boron extraction from water by the functionalisation of a UVM-7 mesoporous silica matrix with gluconamide moieties. The ability of this material to adsorb boron is based on its well-known affinity for coordinating the cis-diols present in attached saccharide. Although much research on the formation of boron esters with sugars and sugar derivatives in solution has been done, very few reports have dealt with the adsorption mechanism of boron onto functionalised materials in the solid state. Hence an in-depth study of the adsorption process was conducted in this paper. For this purpose, several solids with increasing boron contents were prepared from the gluconamide-functionalised UVM-7 material and an isothermal boron adsorption curve was obtained. The 11B and 13C MAS NMR techniques were used to characterise the obtained solids, and the simulation of the boron NMR and isothermal adsorption combined data was accomplished to enlighten the boron adsorption process. A model with three different coordination environments, two possible adsorption sites and the presence of oligomeric boron species allowed us to reproduce not only the isothermal boron adsorption curve, but also the evolution of the integrated areas for the signals in the 11B MAS NMR spectra obtained for the different boron-containing gluconamide-functionalised UVM-7 materials.

Structural studies on new xCeO2·(50 − x)PbO·50B2O3 glasses and glass ceramics

Influence of CeO2 substitution for PbO on network structure of the glasses in the system xCeO2−(50−x)PbO·50B2O3 (0≤x≤50mol%) has been studied. Stretching and bending vibrations due to CeO, PbO and BO bonds were assigned on the bases of their FTIR absorbance spectra. The quantitative values represent CeO4, PbO4 and BO4 species have been determined. The results were correlated with data based on X-Ray diffraction (XRD), Transmission Electron Microscopy (TEM) and Electron Diffraction Pattern (EDP) spectroscopies. The fraction of different tetrahedral structural units (B4) is a significant variable parameter in altering the structure changes. The determined values of fraction of tetrahedral boron (N4) obtained from FTIR spectra agree well with that obtained from 11B MAS NMR spectra of the same glasses having ≤7.5mol% CeO2. The lowest value of fraction of tetrahedral groups (B4) is found at 50mol% CeO2 (lead free glass). In this regard, 50CeO2-50B2O3 composition showed lower value of B4 than that found in 50PbO-50B2O3 glass.

Structural investigation of BaO[sbnd]B2O3[sbnd]P2O5 glasses by NMR and Raman spectroscopy

Glasses of the ternary system BaOB2O3P2O5 were prepared and studied in broad concentration limits covering the whole vitrification domain: 20–50 mol% BaO, 0–40 mol% B2O3 and 20–60 mol% P2O5. Their structure was studied with combinations of Raman spectroscopy, 31P MAS NMR spectroscopy and 11B MAS NMR spectroscopy. The obtained results are discussed in several compositional lines A: (100-x)Ba(PO3)2xB2O3, B: 40BaOyB2O3(60-y)P2O5, C: (50-z)BaOzB2O350P2O5, D: (60-w)BaOwB2O340P2O5 and E: uBaO40B2O3(60-u)P2O5. Boron oxide incorporates into the phosphate network in the form of BO4 and BO3 groups and increases their glass transition temperature. Nevertheless, the increase in Tg is only steep within the region of 0–20 mol% B2O3 reaching a maximum at the glasses with ∼30 mol% B2O3. In the lines A, B and E a decrease in the P2O5 and an increase of B2O3 content results in the shortening of phosphate chains with decreasing P2O5 content; these changes are most pronounced in line B with a constant BaO content. In lines C and D with a constant P2O5 content a decrease in the BaO content results, in contrast, in the reverse transformation of phosphate structural units in the direction Q1 → Q2 → Q3 as detected from Raman spectra and 31P MAS NMR spectra. 11B MAS NMR spectra revealed that only BO4 units are present in the glasses with 0–20 mol% B2O3. In the glasses of the E series the fraction of BO3 units increases with a decreasing P2O5 content. By the decomposition of the 11B MAS NMR spectra it is possible to estimate the fractions of basic structural units formed by boron - B(OP)3O, B(OP)2O2 and BO3 in all the glasses of the glass forming region.

Structure–property relationships in barium borophosphate glasses modified with niobium oxide

Phosphate glasses containing a high amount of niobium oxide exhibit non-linear optical properties which make them attractive for various optical devices. This contribution is devoted to the investigation of glasses of the series (100−x)[0.5BaO–0.1B2O3–0.4P2O5]–xNb2O5 with x=0–45 and 80[0.5BaO–yB2O3–(0.5−y)P2O5]–20Nb2O5 with y=0–0.25. The basic characteristic parameters of the prepared glasses were determined. The index of refraction of these glasses increases substantially with increasing Nb2O5 content from 1.620 to 2.007 and the glass transition temperature increases within the range of 551–704°C. The glass structure was investigated by 31P, 11B and 93Nb NMR, and Raman spectroscopies. Raman spectra revealed that at low Nb2O5 content a strong vibrational band of isolated NbO6 octahedra dominates the spectra. New bands appear in the Raman spectra in the glasses with 30mol% of Nb2O5 that were assigned to vibrations of Nb–O–Nb bonds interconnecting NbO6 octahedra. 11B MAS NMR spectra reveal the dominant role of BO4 units in the glass structure. 11B MAS NMR spectra revealed that with increasing Nb2O5 content new resonances of BO4 units appear in the spectra due to the replacement of B–O–P bonds by B–O–Nb and B–O–B bonds. With an increasing Nb2O5 content, part of the BO4 units is also converted to BO3 units. 93Nb MAS NMR spectra primarily reflect changes in the length of Nb–O bonds in the NbO6 octahedra manifested in a decreasing asymmetry of the octahedra with increasing Nb2O5 content and the formation of niobate clusters. Niobo-borophosphate glasses reveal very high chemical durability as well as high glass transition temperatures due to the replacement of weaker P–O bonds with stronger Nb–O bonds.

Quantification of the boron speciation in alkali borosilicate glasses by electron energy loss spectroscopy.

Transmission electron microscopy and related analytical techniques have been widely used to study the microstructure of different materials. However, few research works have been performed in the field of glasses, possibly due to the electron-beam irradiation damage. In this paper, we have developed a method based on electron energy loss spectroscopy (EELS) data acquisition and analyses, which enables determination of the boron speciation in a series of ternary alkali borosilicate glasses with constant molar ratios. A script for the fast acquisition of EELS has been designed, from which the fraction of BO4 tetrahedra can be obtained by fitting the experimental data with linear combinations of the reference spectra. The BO4 fractions (N4) obtained by EELS are consistent with those from 11B MAS NMR spectra, suggesting that EELS can be an alternative and convenient way to determine the N4 fraction in glasses. In addition, the boron speciation of a CeO2 doped potassium borosilicate glass has been analyzed by using the time-resolved EELS spectra. The results clearly demonstrate that the BO4 to BO3 transformation induced by the electron beam irradiation can be efficiently suppressed by doping CeO2 to the borosilicate glasses.

Enhanced ionic conductivity of Li3.5Si0.5P0.5O4 with addition of lithium borate

A series of lithium borate added electrolyte compounds, xLi3BO3-(1−x)Li3.5Si0.5P0.5O4 (0≤x≤0.2), are synthesized and characterized. This so-called LISICON electrolyte system is analyzed by using X-ray diffraction (XRD), scanning electron microscopy (SEM), solid state nuclear magnetic resonance (ss-NMR), electrochemical impedance spectra (EIS), and direct current (DC) polarization methods. From 11B MAS NMR spectra, it is demonstrated that a small fraction of boron exists in the form of BO4, while its majority settles at grain boundaries in the form of BO3, indicating that lithium borate glasses play a role as sintering assistant. This prominently increases the relative density of samples, and is beneficial to the ionic conductivity. Further results show that the electrical conduction of lithium borate added LISICONs is dominated by Li+ ions, with a transference number of tLi+≥0.996 and a corresponding ionic conductivity of about 6.5×10−6Scm−1 at room temperature, almost two times that of pristine Li3.5Si0.5P0.5O4.

Behavior of indium oxide in zinc phosphate and borophosphate glasses

The effect of indium oxide on the structure and properties of zinc phosphate and zinc borophosphate glasses has been investigated in the series (50−x)ZnO–xIn2O3–50P2O5 and 30ZnO–(20−x)B2O3–xIn2O3–50P2O5 with x = 0–20 mol% In2O3 in both series. Their physical properties were measured, and their structure was studied by Raman and NMR spectroscopy. Glass transition temperature in the phosphate glass series increases with increasing In2O3 content as well as their chemical durability. The observed changes in the 31P MAS NMR spectra with increasing In2O3 content revealed the depolymerization of phosphate chains due to the replacement of ZnO by In2O3 resulting in an increase in the O/P ratio in the glass structure. 11B MAS NMR spectra revealed the presence of BO4 units in the glass structure in the borophosphate glass series; these spectra give no evidence for the formation of B–O–In bonds. Their glass transition temperature slightly decreases with increasing In2O3 content. The values of the molar volume in these glasses do not change substantially when B2O3 is replaced by In2O3. This can be ascribed not only to differences in boron (BO4) and indium (InO6) coordination, but also to a higher ionicity of In···O bonds in comparison with B–O bonds. The obtained data resulted in the conclusion that indium oxide behaves as a modifying oxide in both glasses.

Synthesis, Crystal Structure, Thermal Decomposition, and 11B MAS NMR Characterization of Mg(BH4)2(NH3BH3)2

A metal borohydride–ammonia borane complex, Mg(BH4)2(NH3BH3)2 was synthesized via a solid-state reaction between Mg(BH4)2 and NH3BH3. Different mechanochemical reaction mechanisms are observed, since Mg(BH4)2(NH3BH3)2 is obtained from α-Mg(BH4)2, whereas a mixture of Mg(BH4)2(NH3BH3)2, NH3BH3, and amorphous Mg(BH4)2 is obtained from γ-Mg(BH4)2. The crystal structure of Mg(BH4)2(NH3BH3)2 has been determined by powder X-ray diffraction and optimized by first-principles calculations. The borohydride groups act as terminal ligands, and molecular complexes are linked via strong dihydrogen bonds (<2.0 A), which may contribute to the high melting point of Mg(BH4)2(NH3BH3)2 found to be ∼48 °C in contrast to those for other molecular metal borohydrides. Precise values for the 11B quadrupole coupling parameters and isotropic chemical shifts are reported for the two NH3BH3 sites and two BH4– sites in Mg(BH4)2(NH3BH3)2 from 11B MAS NMR spectra of the central and satellite transitions and MQMAS NMR. The 11B quadrupole...

Exploring the Origin of Enhanced Activity and Reaction Pathway for Photocatalytic H2 Production on Au/B-TiO2 Catalysts

Gold-embedded boron-doped TiO2 (Au/B-TiO2) photocatalysts were synthesized by a sol–gel hydrothermal method. The TEM images display that the gold nanoparticles were embedded into the B-TiO2 framework. Hydrogen evolution under light irradiation showed that doping of boron into TiO2 enhanced the photocatalytic activity. A further remarkable improvement of the activity was observed over the Au/B-TiO2. Evidenced by B 1s XPS and 11B MAS NMR spectra, the embedment of Au nanoparticles contributes to the formation of more interstitial boron species in B-TiO2. In turn, it gives rise to surface or near-surface states facilitating the embedment of Au nanoparticles, as demonstrated by the Au 4f XPS spectra, which indicates the strong interaction between gold and the B-TiO2 framework. This specific synergy significantly contributes to the enhancement of photocatalytic activity. For the first time, the isotopic tracer studies using a gas chromatograph isotope ratio mass spectrometer along with a series of control experiments reveal that the produced hydrogen originated mainly from water rather than methanol, whereas the direct oxidation of methanol did not lead to hydrogen generation. Acting as a sacrificial reagent, methanol could be oxidized to formaldehyde by protons/water under oxygen-free conditions.

Effect of boron on ZSM-5 catalyst for methanol to propylene conversion

Abstract B-ZSM-5 catalysts were prepared by various modification methods with boric acid, including ion-exchange, impregnation and direct synthesis. The catalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), NH3-Temperature Programmed Desorption (NH3-TPD), N2 adsorption-desorption, Fourier Transform Infrared spectrometry (FT-IR), 27Al and 11B MAS NMR spectra. The results revealed that the weak acidity of catalysts was significantly increased by modification. The catalytic activity was measured in a fixed bed at 460°C for methanol to propylene (MTP) reaction. The results of MTP reaction showed a great increment of the propylene selectivity for the boron modified samples, especially for the directly synthesized B-ZSM-5 which also displayed high activity and selectivity towards C2 =-C4 = olefins. It was found that the remarkable selectivity strongly depended on the intensity of weak acidity.

Structure of an Amorphous Boron Carbide Film: An Experimental and Computational Approach

An amorphous boron carbide ceramic is prepared via hot wall chemical vapor deposition at 1000 °C using a BCl3/CH4/H2 mixture. Its elemental composition is assessed by electron probe microanalysis (EPMA) and its structure studied by Raman spectroscopy, transmission electron microscopy (TEM), both X-ray diffraction (XRD) and neutron diffraction, 11B magic angle spinning nuclear magnetic resonance (MAS NMR), X-ray absorption spectroscopy (XAS), and ab initio modeling. The atomic structure factor and pair distribution function derived from neutron diffraction data are compared to those deduced from an atomistic model obtained by a liquid quench ab initio molecular dynamics simulation. The good agreement between experimental data and simulation shows that the as-prepared material is essentially made of a random arrangement of icosahedra (B12, B11C, and B10C2) embedded in an amorphous matrix rich in trigonal (BC3 or BC2B) and tetrahedral (CB4) sites. The existence of trigonal boron environments is clearly confirmed by a peak at 50 ppm in both the experimental and simulated 11B MAS NMR spectra, as well as a 190.0 eV component in the XANES-B(1s) spectrum. The intericosahedral linear C–B–C chains observed in crystalline B4C are absent in the as-processed material. Free hexagonal carbon and B4C crystallites appear in the ceramic when heat-treated at 1300 °C/2 h/Ar, as evidenced by high-resolution TEM and Raman spectroscopy. Comparing the pair distribution functions of the heat-treated material with the crystalline B4C model allows confirming the apparition of C–B–C chains in the material. Indeed, two new peaks located at 1.42 and 2.35 Å can only be attributed to a first-neighbor distance between the B and C atoms in the chain and a second-neighbor distance between a chain-boron atom and an icosahedron-boron atom, respectively.

Effect of germanium oxide on the structure and properties of lithium borophosphate glasses

Lithium borophosphate glasses with addition of germanium oxide were studied along the compositional series (100−x)[0.5Li2O–0.1B2O3–0.4P2O5]–xGeO2, with x=0–25mol.%. Their properties (density, glass transition temperature, coefficient of thermal expansion, chemical durability) were measured and their structure was studied by 31P and 11B MAS NMR spectroscopy and Raman spectroscopy. The addition of GeO2 to the parent borophosphate glass results in an increase of their glass transition temperature, while their chemical durability only slightly decreases. 31P MAS NMR and Raman spectra reflect the depolymerization of phosphate chains by the incorporation of GeOn polyhedra. 11B MAS NMR spectra reveal the formation of mixed structural units B(OP)3(OGe) in the borophosphate glasses and the decomposition of 11B MAS NMR spectra brings quantitative data on the number of BO3 and B(OP)3(OGe) structural units. A small amount of BO3 trigonal units is formed in the glasses as well.

LiCe(BH4)3Cl, a New Lithium-Ion Conductor and Hydrogen Storage Material with Isolated Tetranuclear Anionic Clusters

Mechanochemical synthesis using CeCl3-MBH4 (M = Li, Na or K) mixtures are investigated and produced a new compound, LiCe(BH4)3Cl, which crystallizes in a cubic space group I4̅3m, a = 11.7204(2) Å. The structure contains isolated tetranuclear anionic clusters [Ce4Cl4(BH4)12]4– with a distorted cubane Ce4Cl4 core, charge-balanced by Li+ cations. Each Ce atom coordinates three chloride ions and three borohydride groups via the η3–BH3 faces, thus completing the coordination environment to an octahedron. Combination of synchrotron radiation powder X-ray diffraction (SR-PXD), powder neutron diffraction and density functional theory (DFT) optimization show that Li cations are disordered, occupying 2/3 of the 12d Wyckoff site. DFT calculation indicates that LiCe(BH4)3Cl is stabilized by higher entropy rather than lower enthalpy, in accord with the disorder in Li positions. The structural model also agrees well with the very high lithium ion conductivity measured for LiCe(BH4)3Cl of 1 × 10–4 Scm–1 at T = 20 °C. In situ SR-PXD reveals that the decomposition products consist of LiCl, CeB6 and CeH2. The Sieverts measurements show that 4.7 wt % H2 is released during heating to 500 °C. After rehydrogenation at 400 °C and p(H2) = 100 bar for 24 h an amount of 1.8 wt % H2 is released in the second dehydrogenation. The 11B MAS NMR spectra of the central and satellite transitions for LiCe(B(D/H)4)3Cl reveal highly asymmetric manifolds of spinning sidebands from a single 11B site, reflecting dipolar couplings of the 11B nuclear spin with the paramagnetic electron spin of the Ce3+ ions.

Novel LaBO3 hollow nanospheres of size 34 ± 2 nm templated by polymeric micelles

Novel lanthanum borate (LaBO3) hollow nanospheres of size 34±2nm have been reported for the first time by soft-template self-assembly process. Poly(styrene-b-acrylic acid-b-ethylene oxide) (PS-PAA-PEO) micelle with core–shell–corona architecture serves as an efficient soft template for fabrication of LaBO3 hollow particles using sodium borohydride (NaBH4) and LaCl3⋅7H2O as the precursors. In this template, the PS block (core) acts as a template of the void space of hollow particle, the anionic PAA block (shell) serves as reaction field for metal ion interactions, and the PEO block (corona) stabilizes the polymer/lanthana composite particles. The PS-PAA-PEO micelles and the resulting LaBO3 hollow nanospheres were thoroughly characterized by dynamic light scattering (DLS), transmission electron microscope (TEM), X-ray diffraction, magic angle spinning-nuclear magnetic resonance (11B MAS NMR), energy dispersive X-ray analysis, thermal analyses, Fourier transform infra red spectroscopy, and nitrogen adsorption/desorption analyses. The nitrogen adsorption/desorption analyses and TEM observation of the hollow particles confirmed the presence of disordered mesopores in the LaBO3 shell domain. The solid state 11B MAS NMR spectra of LaBO3 hollow nanospheres revealed that the shell part contains both trigonal and tetrahedral boron species. The LaBO3 hollow particles were applied to anode materials in lithium-ion rechargeable batteries (LIBs). The hollow particles exhibited high coulombic efficiency and charge–discharge cycling capacities of up to 100 cycles in the LIBs.