Bismuth-containing Materials Research Articles

Metallic bismuth morphology and microstructure control during the membrane electro-deposition in methane-sulfonic acid system

As the mainstream process for bismuth hydrometallurgical extraction, the “chloride leaching – membrane electro-deposition” technology faces disadvantages such as strong volatility of reaction solution, serious occupational health harms, and unsatisfactory morphology of metallic bismuth. In this paper, the green methane-sulfonic acid (MSA) is proposed as hydrometallurgical medium to replace conventional chloride solution. During the bismuth membrane electro-deposition, the effects of additive type and its concentration, temperature, cathode current density, and electrolyte composition on the morphology and microstructure of cathodic bismuth are systematically investigated. Compared to sodium dodecyl sulfate, Trilon M, Lugalvan BNO 12, the addition of calcium lignosulfonate (CL) significantly suppressed the formation of “triangular cone” shaped bismuth grains, and therefore the surface smoothness of cathodic bismuth was greatly improved. Potentiodynamic polarization reveals that CL concentration increasing induced the negative shift of deposition potential (φdep), and this contributed to obtain fine-grained bismuth deposits. The current density and bismuth concentration significantly affected the surface morphology of bismuth deposits. At a current density of 180 A/m2, flat and dense bismuth deposit (99.97% purity) could be produced from 0.5 g/L CL-assisted electrolyte at 35 °C for 8 h. In contrast to the electro-deposition method in chloride solution, the proposed process has green (less volatility and biodegradability), efficient (current efficiency 98.80 %) and energy-saving (electric energy consumption 712.53 kWh/t Bi) features, and has important application in the hydrometallurgical treatment of bismuth-containing materials.

Electrokinetic Characteristics of Bismuth-Containing Materials Based on Porous Glasses

Bismuth-containing composite materials based on high-silica porous glasses (PGs) of various types are prepared. Their structural parameters and electrokinetic potential in 10–2 М KNO3 solutions in the pH range 1.5–8.5 are studied. The results are compared with the analogous properties of matrices not modified with bismuth oxide, as well as the pH dependence of the zeta-potential for SiO2 particles and the sols of synthesized and industrial bismuth(III) oxide. It is determined that modification of larger-pore particles not containing secondary silica with bismuth(III) oxide results in the deviation of the form of the ζ–рН dependences from those intrinsic for high-silica PG and SiO2 particles.

Adsorption of CO2 on Heterostructures of Bi2O3 Nanocluster-Modified TiO2 and the Role of Reduction in Promoting CO2 Activation.

The capture and conversion of CO2 are of significant importance in enabling the production of sustainable fuels, contributing to alleviating greenhouse gas emissions. While there are a number of key steps required to convert CO2, the initial step of adsorption and activation by the catalyst is critical. Well-known metal oxides such as oxidized TiO2 or CeO2 are unable to promote this step. In addressing this difficult problem, a recent experimental work shows the potential for bismuth-containing materials to adsorb and convert CO2, the origin of which is attributed to the role of the bismuth lone pair. In this paper, we present density functional theory (DFT) simulations of enhanced CO2 adsorption on heterostructures composed of extended TiO2 rutile (110) and anatase (101) surfaces modified with Bi2O3 nanoclusters, highlighting in particular the role of heterostructure reduction in activating CO2. These heterostructures show low coordinated Bi sites in the nanoclusters and a valence band edge that is dominated by Bi–O states, typical of the Bi3+ lone pair. The reduction of Bi2O3–TiO2 heterostructures can be facile and produces reduced Bi2+ and Ti3+ species. The interaction of CO2 with this electron-rich, reduced system can produce CO directly, reoxidizing the heterostructure, or form an activated carboxyl species (CO2–) through electron transfer from the reduced heterostructure to CO2. The oxidized Bi2O3–TiO2 heterostructures can adsorb CO2 in carbonate-like adsorption modes, with moderately strong adsorption energies. The hydrogenation of the nanocluster and migration to adsorbed CO2 is feasible with H-migration barriers less than 0.7 eV, but this forms a stable COOH intermediate rather than breaking C–O bonds or producing formate. These results highlight that a reducible metal oxide heterostructure composed of a semiconducting metal oxide modified with suitable metal oxide nanoclusters can activate CO2, potentially overcoming the difficulties associated with the difficult first step in CO2 conversion.

Structural, electronic, vibrational and optical properties of Bin clusters

The neutral, anionic and cationic bismuth clusters with the size n up to 14 are investigated by using B3LYP functional within the regime of density functional theory and the LAN2DZ basis set. By analysis of the geometries of the Bi[Formula: see text] (n = 2–14) clusters, where cationic and anionic bismuth clusters are largely similar to those of neutral ones, a periodic effect by adding units with one to four atoms into smaller cluster to form larger cluster is drawn for the stable structures of bismuth clusters. An even–odd alteration is shown for the properties of the clusters, such as the calculated binding energies and dissociation energies, as well as frontier orbital energies, electron affinities, ionization energies. All the properties indicate that the Bi4 cluster is the most possible existence in bismuth-containing materials, which supports the most recent experiment. The orbital compositions, infrared and Raman activities and the ultraviolet absorption of the most possible tetramer bismuth cluster are given in detail to reveal the periodic tendency of adding bismuth atoms and the stability of tetramer bismuth cluster.

Color Stability of White Mineral Trioxide Aggregate in Contact with Hypochlorite Solution

IntroductionOne of the uses of white mineral trioxide aggregate (MTA) is as an apical barrier in immature teeth. Although this treatment has been reported to have high success rates, a number of cases of discoloration have been noted. The aim of this research was to investigate the color stability of white MTA in contact with various solutions used in endodontics. MethodsThe change in color of white MTA after immersion in water, sodium hypochlorite, or hydrogen peroxide was assessed by viewing the color change on digital photographs and also by using a spectrophotometer. White MTA, white Portland cement, and bismuth oxide were assessed. The changes in the material after immersion in the different solutions were assessed by x-ray diffraction analysis and Fourier transform infrared spectroscopy. ResultsImmersion of white MTA and bismuth oxide in sodium hypochlorite resulted in the formation of a dark brown discoloration. This change was not observed in Portland cement. X-ray diffraction analysis and Fourier transform infrared analysis displayed the reduction of sodium hypochlorite in contact with bismuth oxide and MTA to sodium chloride. ConclusionsContact of white MTA and other bismuth-containing materials with sodium hypochlorite solution should be avoided.

Bismuth nano-droplets for group-V based molecular-beam droplet epitaxy

Self-assembly of bismuth droplets at nanoscale on GaAs(100) surface using molecular beam epitaxy was demonstrated. Fine control of density and size was achieved by varying growth temperature and total bismuth deposition. Droplet density was tuned by roughly 3 orders of magnitude, and the density-temperature dependence was found to be consistent with classical nucleation theory. These results may extend the flexibility of droplet epitaxy by serving as templates for group V based droplet epitaxy, which is in contrast to conventional group III based droplet epitaxy and may encourage nanostructure formation of bismuth-containing materials.

Application of Solid-State 209Bi NMR to the Structural Characterization of Bismuth-Containing Materials

Herein, we report the first detailed study of (209)Bi solid-state NMR (SSNMR) spectroscopy of extremely broad central transition powder patterns. (209)Bi ultrawideline SSNMR spectra of several bismuth-containing materials (bismuth oxyhalides, bismuth nitrate pentahydrate, nonaaquabismuth triflate, and bismuth acetate) were acquired at field strengths of 9.4 and 21.1 T using frequency-stepped techniques. The (209)Bi SSNMR experiments at 9.4 T yield powder patterns with breadths ranging from 0.9 to 14.6 MHz, from which quadrupolar coupling constants, C(Q)((209)Bi), between 78 and 256 MHz, were extracted via analytical simulations. The breadths of the quadrupolar-dominated spectra and overall experimental times are greatly reduced for experiments conducted at 21.1 T, which yield high signal-to-noise spectra in which the smaller effects of bismuth chemical shift anisotropy can be clearly observed. The (209)Bi electric field gradient (EFG) and chemical shift (CS) tensor parameters extracted from these spectra are correlated to the molecular structures at the bismuth sites, via first principles calculations of (209)Bi EFG and CS tensors performed using CASTEP for periodic solids and Gaussian 03 for molecular clusters. The rapidity with which (209)Bi SSNMR spectra can be acquired at ultrahigh fields, the sensitivity of the (209)Bi NMR parameters to the bismuth environment, and the predictive power of theoretically calculated NMR interaction tensors suggest that (209)Bi SSNMR may be useful for the characterization of a variety of Bi-containing materials and compounds.

Thermoelectric Properties of Mixed-Metal Tellurides

AbstractA new series of thallium-containing materials, Tl1-xPbmATem+2 (A= Sb, Bi; m=10, 18; 0≤x≤0.3), has been prepared. Diffraction data reveal that a rocksalt-type structure is adopted at all compositions. Transport property measurements indicate n-type behaviour for the bismuth-containing materials and p-type for the antimony analogues. The reduced power factors for the latter, compared to the bismuth-containing materials, are primarily due to their more resistive nature. The highest power factors occur at a thallium deficiency in the range 0.1≤x≤0.2. Measured thermal conductivities are reduced from that of the binary telluride, suggesting that the materials may have potential as n/p-type components in device applications.