Discovery of a new bimetallic borate with strong optical anisotropy activated by π-conjugated [B2O5] units.

Birefringent materials with high optical anisotropy have been identified as a research hotspot owing to their significant scientific and technological significance in modern optoelectronics for manipulating light polarization. Researchers studying borate systems have discovered that adding π-conjugated units placed in parallel can significantly increase the birefringence of crystalline solids; some examples include [BO3] units, [B2O5] units, and [B3O6] units. However, there are not many borates with strictly parallel configurations of π-conjugated [B2O5] units. In this study, a new bimetallic borate Sr2Cd4(B2O5)3 with near-parallel arrangement of π-conjugated [B2O5] units was discovered. Sr2Cd4(B2O5)3 possesses the maximum number density of [B2O5] units, shortest dihedral angle of [B2O5] units (between the two [BO3]), and largest degree of [CdO6] octahedral distortion among all the currently known Sr-Cd-B-O tetragonal system borates, making it demonstrate a large birefringence of 0.102 at 532 nm. Theoretical analysis proves that π-conjugated [B2O5] anions are the primary source of the large birefringence of Sr2Cd4(B2O5)3.

Rb3MgB5O10 and LiBaAl(BO3)2: covalent tetrahedra MO4-containing borates with deep-ultraviolet cutoff edges.

Borates are favored by materials scientists and chemists because of the significant electronegativity difference between B and O atoms and their flexible assembly modes resulting in abundant structures and excellent properties. For the design of deep-ultraviolet (DUV) optical crystals with excellent macroscopic performance, it is crucial to choose appropriate cations and anionic groups and microscopically reasonable assembly patterns. Herein, by introducing covalent tetrahedra ([MO4], M = Mg, Al), two new mixed alkali metal and alkaline earth metal borates, Rb3MgB5O10 and LiBaAl(BO3)2, were synthesized using the melt method and high-temperature solution method. They contain M-B-O two-dimensional (2D) layers (2∞[MgB5O10] and 2∞[Al(BO3)2], respectively) composed of isolated B-O groups ([B5O10]5- and [BO3]3-, respectively) and metal-centered tetrahedral connectors ([MgO4]6- and [AlO4]5-, respectively). Combining experiments and theoretical calculations shows that the two compounds have short cutoff edges (<200 nm) and moderate birefringences. Further analysis manifests that the isolated [MO4] covalent tetrahedra can optimize the arrangement of anion groups, guarantee the balanced optical properties of materials, and point out the direction for further exploration of novel borate structures.

Investigation on mercury removal and recovery based on enhanced adsorption by activated coke.

This work is to systematically study the mercury-removal behavior of activated coke (AC), regeneration of spent AC by microwave treatment and subsequent recycling of Hg0. The powdery (AC) was obtained under coal-fired hot gas conditions in a drop-tube reactor. The adsorption mechanism and capacity of the AC for Hg0 removal in a H2O + SO2 + O2 atmosphere were investigated. The regeneration of the AC by microwave heating and recovery of Hg0 were studied. The results showed that this AC preparation method can greatly simplify the process, and the AC's large surface area, developed pore structure, and abundant functional groups played a key role in the adsorption of Hg0. The adsorption mechanism and the optimum reaction conditions were determined, with a highest average Hg0-adsorption efficiency of 91% obtained at 70 °C in 3 h. Desorption of Hg0 was also studied, in which the alkaline-functional-group content and pore structure were enhanced, and S was detected by X-ray photoelectron spectroscopy in microwave-regenerated AC, which could improve the Hg0 removal efficiency increased to 96% after five adsorption/desorption cycles. The Hg0 could subsequently be recovered from the desorbed gas by condensation with an efficiency of 87.4% using ice-water.

Rational Design via Synergistic Combination Leads to an Outstanding Deep-Ultraviolet Birefringent Li2Na2B2O5 Material with an Unvalued B2O5 Functional Gene.

Birefringent materials, the key components in modulating the polarization of light, are of great importance in optical communication and the laser industry. Limited by their transparency range, few birefringent materials can be practically used in the deep ultraviolet (DUV, λ < 200 nm) region. Different from the traditional BO3- or B3O6-based DUV birefringent crystals, we propose a new functional gene, the B2O5 unit, for designing birefringent materials. Excitingly, the synergistic combination of Li4B2O5 and Na4B2O5 generates a new compound, Li2Na2B2O5, with enhanced optical properties. The Li2Na2B2O5 crystal with a size of up to 35 × 15 × 5 mm3 was grown by the top-seeded solution growth (TSSG) method, and its physicochemical properties were systematically characterized. Li2Na2B2O5 features a large amount of birefringence (0.095@532 nm), a short DUV cutoff edge (181 nm) with a high laser-induced damage threshold (LDT, 7.5 GW/cm2 @1064 nm, 10 ns), favorable anisotropic thermal expansion (αa/αb = 5.6), and the lowest crystal growth temperature (<609 °C) among the commercial birefringent crystals. Moreover, the influences of the B2O5 structural configurations on the optical anisotropy were explored. The fascinating experimental results will provide a prominent DUV birefringent crystal and an effective synthesis strategy, which can facilitate the design of DUV birefringent materials.

Versatile Coordination Mode of LiNaB8O13 and α- and ß-LiKB8O13 via the Flexible Assembly of Four-Connected B5O10 and B3O7 Groups.

Three new alkali-metal mixed borates, LiNaB8O13, α-LiKB8O13, and ß-LiKB8O13, containing a (3)∞[B8O13] three-dimensional network have been successfully synthesized. Their fundamental building block is [B8O16](8-) formed by the vertex-sharing [B5O10](5-) and [B3O7](5-) groups, which are topologically identical when they are considered as four-connected nodes. The viewpoints give us a feasible way to investigate the versatile structure assembly of borates with a complex network.