Preparation and characterization of the AP/Al/Fe2O3 ternary nano-thermites

A novel ammonium perchlorate (AP)/aluminum (Al)/iron oxide (Fe₂O₃) nano-thermites was prepared by orderly using sol–gel, wet impregnation, and solvent-anti-solvent processes. Samples prepared in this work were characterized by scanning electron microscope (SEM), nitrogen adsorption–desorption tests, X-ray diffraction (XRD), and differential scanning calorimetric (DSC) measurements. The results showed that AP and nano-aluminum were dispersed in the pores of the iron oxide gel, resulting in a large specific surface area (84.7 m² g^?1). The XRD results showed that AP dispersed homogeneously in the energetic composites at nano-scale. DSC analyses indicate that the Al/Fe₂O₃ nano-thermites played a catalytic role in the thermal decomposition of AP, thus the interaction of thermite reaction was greatly enhanced by accelerated decomposition of AP. The experimental results showed that the as-prepared AP/Al/Fe₂O₃ nano-thermites were of high energy, making it a competitive candidate material in the field of micro-propellants.     

Hierarchical Hollow-Nanocube Ni−Co Skeleton@MoO3/MoS2 Hybrids for Improved-Performance Lithium-Ion Batteries

Improving the performance of anode materials for lithium-ion batteries (LIBs) is a hotly debated topic. Herein, hollow Ni−Co skeleton@MoS₂/MoO₃ nanocubes (NCM-NCs), with an average size of about 193 nm, have been synthesized through a facile hydrothermal reaction. Specifically, MoO₃/MoS₂ composites are grown on Ni−Co skeletons derived from nickel–cobalt Prussian blue analogue nanocubes (Ni−Co PBAs). The Ni−Co PBAs were synthesized through a precipitation method and utilized as self-templates that provided a larger specific surface area for the adhesion of MoO₃/MoS₂ composites. According to Raman spectroscopy results, as-obtained defect-rich MoS₂ is confirmed to be a metallic 1T-phase MoS₂. Furthermore, the average particle size of Ni−Co PBAs (≈43 nm) is only about one-tenth of the previously reported particle size (≈400 nm). If assessed as anodes of LIBs, the hollow NCM-NC hybrids deliver an excellent rate performance and superior cycling performance (with an initial discharge capacity of 1526.3 mAh g⁻¹ and up to 1720.6 mAh g⁻¹ after 317 cycles under a current density of 0.2 A g⁻¹). Meanwhile, ultralong cycling life is retained, even at high current densities (776.6 mAh g⁻¹ at 2 A g⁻¹ after 700 cycles and 584.8 mAh g⁻¹ at 5 A g⁻¹ after 800 cycles). Moreover, at a rate of 1 A g⁻¹, the average specific capacity is maintained at 661 mAh g⁻¹. Thus, the hierarchical hollow NCM-NC hybrids with excellent electrochemical performance are a promising anode material for LIBs.     

Bi7−xAs1+xMo3O21 (0⩽x⩽1) a new pillar structure type: synthesis,crystal structure and conductivity

An original structure of chemical formula Bi₁₃As₃Mo₆O₄₂ has been obtained in the system Bi₂O₃:MoO₃:As₂O₃ by chemical transport reaction in presence of As₂O₃. It crystallizes in the monoclinic system, space group P2₁/n with a=12.7770(11) Å, b=5.5890(4) Å, c=27.971(2) Å and β=101.009(7)°. The structure exhibits infinite [Bi₁₃As₃Mo₆O₄₂]_n complex pillars with a quite different organization compared with original [Bi₁₂O₁₄]_n⁸ⁿ⁺ columns surrounded by (MoO₄) tetrahedra in the Bi_2/3[Bi₁₂O₁₄](MoO₄)₅ prototype structure. Nevertheless, the heavy atoms design almost perfect fluorite subnetwork—a common structural feature of these pillar structures. The conditions of synthesis via solid-state chemistry using basic oxides Bi₂O₃, As₂O₃ and MoO₃ have been established and the phase identified by X-ray powder pattern. The indexing fits single crystal data as well as the values of volumic mass, ρ_exp=7.04(4) g cm⁻³ for ρ_X=7.096 g cm⁻³ for Z=4. This Bi₁₃As₃Mo₆O₄₂ phase shows also an interesting anionic conductivity around σ=7.98×10⁻⁴ S cm⁻¹ at 980 K and is compared with related phases.     

Preparation and characterization of optical spectroscopy of Lu2O3:Eu nanocrystals

Nanoscale Lu₂O₃:Eu powders were prepared by solution combustion synthesis. X-ray diffraction (XRD), high-resolution electronic microscope (HREM), Fourier transform infrared spectroscopy (FT-IR), excitation and emission spectra, as well as fluorescent decay curves were measured to characterize the structure and luminescent properties of the samples. The results show that the compound of composition Lu₂O₃ crystallizes in pure cubic structure. By changing the ratio of glycine to nitrate in the combustion process, the particle size varies from 40 nm to less than 5 nm. The emission and excitation spectra strongly depend on the particle size of the samples. Novel emission band, red-shift of charge transfer band (CTB) and shortening of lifetime were observed in nanoscale samples.     

One-step hydrothermal synthesis of LiMn2O4 cathode materials for rechargeable lithium batteries

LiMn₂O₄ cathode materials with high discharge capacity and good cyclic stability were prepared by a simple one-step hydrothermal treatment of KMnO₄, aniline and LiOH solutions at 120–180 °C for 24 h. The aniline/KMnO₄ molar ratio (R) and hydrothermal temperature exhibited an obvious influence on the component and phase structures of the resulting product. The precursor KMnO₄ was firstly reduced to birnessite when R was less than 0.2:1 at 120–150 °C. Pure-phased LiMn₂O₄ was formed when R was 0.2:1, and the LiMn₂O₄ was further reduced to Mn₃O₄ when R was kept in the range of 0.2–0.3 at 120–150 °C. Moreover, LiMn₂O₄ was fabricated when R was 0.15:1 at 180 °C. Octahedron-like LiMn₂O₄ about 300 nm was prepared at 120 °C, and particle size decreased with an increase in hydrothermal temperature. Especially, LiMn₂O₄ synthesized at 150 °C exhibited the best electrochemical performance with the highest initial discharge capacity of 127.4 mAh g⁻¹ and cycling capacity of 106.1 mAh g⁻¹ after 100 cycles. The high discharge capacity and cycling stability of the as-prepared LiMn₂O₄ cathode for rechargeable lithium batteries were ascribed to the appropriate particle size and larger cell volume.     

Advanced Li-Ion Batteries with High Rate,Stability, and Mass Loading Based on Graphene Ribbon Hybrid Networks

To optimize the cycle life and rate performance of lithium-ion batteries (LIBs), ultra-fine Fe₂O₃ nanowires with a diameter of approximately 2 nm uniformly anchored on a cross-linked graphene ribbon network are fabricated. The unique three-dimensional structure can effectively improve the electrical conductivity and facilitate ion diffusion, especially cross-plane diffusion. Moreover, Fe₂O₃ nanowires on graphene ribbons (Fe₂O₃/GR) are easily accessible for lithium ions compared with the traditional graphene sheets (Fe₂O₃/GS). In addition, the well-developed elastic network can not only undergo the drastic volume expansion during repetitive cycling, but also protect the bulk electrode from further pulverization. As a result, the Fe₂O₃/GR hybrid exhibits high rate and long cycle life Li storage performance (632 mAh g⁻¹ at 5 A g⁻¹, and 471 mAh g⁻¹ capacity maintained even after 3000 cycles). Especially at high mass loading (≈4 mg cm⁻²), the Fe₂O₃/GR can still deliver higher reversible capacity (223 mAh g⁻¹ even at 2 A g⁻¹) compared with the Fe₂O₃/GS (37 mAh g⁻¹) for LIBs.     

Scalable one-pot synthesis of bismuth sulfide nanorods as an electrode active material for energy storage applications

The quest for developing the scalable methods of synthesis of materials with potential electrochemical energy storage applications remains a great challenge. Herein, we propose a facile, one-step chemical precipitation method for the synthesis of Bi₂S₃ with the nanorods morphology. Influence of different synthesis temperatures on the physical, chemical, and electrochemical performance was investigated. Relatively low BET surface area and mesopore volume of Bi₂S₃ increased with the higher reaction temperature. Bismuth sulfides synthesized at various temperatures were used as an electrode active material in supercapacitor. The semiconductive properties of Bi₂S₃ resulted in exceptional capacitive behavior. Bismuth sulfide synthesized at 75 °C exhibited a specific capacitance of 457 F g⁻¹ at 1 A g⁻¹ in 6 mol L⁻¹ KOH solution as an electrolyte. Moreover, material prepared at 75 °C maintained the best capacitance value at a large current density of 20 A g⁻¹, compared with bismuth sulfides synthesized at the temperatures of 0 °C and 25 °C.

     

Preparation and characterization of bismuth silicate nanopowders

Bismuth silicate (Bi₄Si₃O₁₂) nanopowders were prepared by the sol-gel method. Tetraethyl orthosilicate (TEOS) and Bi₂O₃ were used as the starting materials. The precursors were heat-treated at 750°C for 2 h. The size distribution of Bi₄Si₃O₁₂ nanopowders is 40–100 nm. The thermogravimetry and differential thermal analysis (TG-DTA) curves, the X-ray diffraction (XRD) patterns and the transmission electron microscopy (TEM) microphotograph of Bi₄Si₃O₁₂ were discussed. Compared with crystal materials, the excitation and emission spectra of Bi₄Si₃O₁₂ nanopowders indicated a blue shift. Translated from Chinese Journal of Inorganic Chemistry, 2006, 22(7): 1327–1329 (in Chinese)     

Dynamic Hydrogen-Bond Network as a Modulator of Bismuth–Antimony Complex Anodes for Self-Healable and Wider Temperature Adaptive Potassium Ion Batteries

Antimony (Sb)-based anodes are attractive candidates in potassium-ion batteries (PIBs) due to their superior capacities and rational potassium inserting voltages. However, the sluggish kinetics and poor interface compatibility severely hinder practical application. Herein, Bi_0.67Sb_1.33S₃ nanospheres embedded into in situ formed poly(3,4-ethylenedioxythiophene) crosslinked with polythioctic acid (PET@PTA) (Bi_0.67Sb_1.33S₃/PET@PTA) were elaborately conceptualized with hydrogen bonds exchangeable binding (HBEB) sites. Bi_0.67Sb_1.33S₃/PET@PTA exhibits notable self-healing ability and wider temperature adaptability. Bi_0.67Sb_1.33S₃/PET@PTA displays an impressive capacity of 819 mAh g⁻¹ at 0.05 A g⁻¹, prominent cycle ability with a 73 % capacity conservation after 500 cycles at 2 A g⁻¹, and high capacity retention of 66 % and 84 % at −40 and 70 °C to that case at room temperature, respectively, for potassium storage. This work provides a new perspective for HBEB sites in maximizing the desirable K⁺ storage performance.     

Structures and ionic conductivities in two fluorite type families: Pb5Bi17X5O43 and Pb5Bi18X4O42 (X=P,V and As)

The phases Pb₅Bi₁₇P₅O₄₃ and Pb₅Bi₁₈P₄O₄₂ are among many recent new oxyphosphates discovered in the ternary system PbO–Bi₂O₃–P₂O₅. The syntheses of the vanadates and arsenates led to isostructural compounds. Both series display a distorted 3×3×3 superstructure of the tetragonal δ-Bi₂O₃ polymorph. These types of phases display interesting anion conductivities and measurements were performed from 300 °C to 800 °C on the phosphates, arsenates and vanadates of the two families. The Pb₅Bi₁₈X₄O₄₂ phases have higher conductivity values than those of Pb₅Bi₁₇X₅O₄₃. Of the three homologues the vanadates always have the highest conductivities, i.e., at 800 °C: 1.6×10⁻² Siemens·cm⁻¹ for Pb₅Bi₁₈V₄O₄₂ and 1.6×10⁻³ Siemens·cm⁻¹ for Pb₅Bi₁₇V₅O₄₃. An increase of the volume of the unit cell due to the increasing radius of the pentavalent cations from P, As to V, 0.34 Å, 0.47 Å, 0.59 Å respectively, helps the anion migration through the structure.     

Gasphasengleichgewichte quaternärer Bismut‐Selen‐Oxidchloride

Gas‐Phase Equilibria of Quaternary Bismuth Selenium Oxidechlorides The existence of new compounds Bi₄O₄SeCl₂, Bi₁₀O₁₂SeCl₄, and Bi₂₂O₂₈SeCl₈ in the pseudoternary area Bi₂O₃/Bi₂Se₃/BiCl₃ has been established by solid state and chemical vapour transport reactions. Furthermore, heterogeneous equilibria between solid state and vapour phase have been studied by mass‐spectrometric measurements. The novel gas‐molecule BiSeCl has been detected. The results of ab initio calculations for structure and refining of thermochemistry of this molecule are given: (Bi–Se) = 2,44 Å; (Bi–Cl) = 2,49 Å; (Se–Bi–Cl) = 106,0°; Thermodynamics: δH°_B,298 (BiSeCl_g) = 6,0 kcal/mol; S°₂₉₈ (BiSeCl_g) = 75,8 cal/mol K; Cp (BiSeCl_g) = 13,583 + 0,64 · 10^–3 · T – 0,41 · 10⁵ · T^–2 – 0,35 · 10^–6 · T² cal/mol K. Finally, the composition of the gaseous phase has been calculated and estimations about chemical vapour transport were carried out by thermodynamic modelling.     

Pseudocapacitive Lithium Storage of Cauliflower-Like CoFe2O4 for Low-Temperature Battery Operation

Binary transition-metal oxides (BTMOs) with hierarchical micro–nano-structures have attracted great interest as potential anode materials for lithium-ion batteries (LIBs). Herein, we report the fabrication of hierarchical cauliflower-like CoFe₂O₄ (cl-CoFe₂O₄) via a facile room-temperature co-precipitation method followed by post-synthetic annealing. The obtained cauliflower structure is constructed by the assembly of microrods, which themselves are composed of small nanoparticles. Such hierarchical micro–nano-structure can promote fast ion transport and stable electrode–electrolyte interfaces. As a result, the cl-CoFe₂O₄ can deliver a high specific capacity (1019.9 mAh g⁻¹ at 0.1 A g⁻¹), excellent rate capability (626.0 mAh g⁻¹ at 5 A g⁻¹), and good cyclability (675.4 mAh g⁻¹ at 4 A g⁻¹ for over 400 cycles) as an anode material for LIBs. Even at low temperatures of 0 °C and −25 °C, the cl-CoFe₂O₄ anode can deliver high capacities of 907.5 and 664.5 mAh g⁻¹ at 100 mA g⁻¹, respectively, indicating its wide operating temperature. More importantly, the full-cell assembled with a commercial LiFePO₄ cathode exhibits a high rate performance (214.2 mAh g⁻¹ at 5000 mA g⁻¹) and an impressive cycling performance (612.7 mAh g⁻¹ over 140 cycles at 300 mA g⁻¹) in the voltage range of 0.5–3.6 V. Kinetic analysis reveals that the electrochemical performance of cl-CoFe₂O₄ is dominated by pseudocapacitive behavior, leading to fast Li⁺ insertion/extraction and good cycling life.     

The effect of slow heating rates on the reaction mechanisms of nano and micron composite thermite reactions

Thermal analyses were performed on Al+MoO₃ thermite reactions as a function of Al particle size (ranging from 50 to 20 μm) and heating rate (from 2.5 to 15 K min^–1 ). Results include ignition (onset) temperatures and heats of reaction. The nano-thermites initiate prior to reactant phase changes and at least 300°C below micron-thermites. The differences in ignition temperatures are suggestive of different ignition mechanisms. Nano-thermites display higher heats of reaction that are dependent on experimental conditions.     

Synergy of Bi2O3 and RuO2 Nanocatalysts for Low-Overpotential and Wide pH-Window Electrochemical Ammonia Synthesis

Electrocatalytic nitrogen reduction reaction (NRR) under ambient conditions is still seriously impeded by the inferior NH₃ yield and low Faradaic efficiency, especially at low overpotentials. Herein, we report the synthesis of nano-sized RuO₂ and Bi₂O₃ particles grown on functionalized exfoliated graphene (FEG) through in situ electrodeposition, denoted as RuO₂−Bi₂O₃/FEG. The prepared self-supporting RuO₂−Bi₂O₃/FEG hybrid with a Bi mass loading of 0.70 wt% and Ru mass loading of 0.04 wt% shows excellent NRR performance at low overpotentials in acidic, neutral and alkaline electrolytes. It achieves a large NH₃ yield of 4.58±0.16 μg_NH3 h⁻¹ cm⁻² with a high Faradaic efficiency of 14.6 % at −0.2 V versus reversible hydrogen electrode in 0.1 M Na₂SO₄ electrolyte. This performance benefits from the synergistic effect between Bi₂O₃ and RuO₂ which respectively have a fairly strong interaction of Bi 6p orbitals with the N 2p band and abundant supply of *H, as well as the binder-free characteristic and the convenient electron transfer via graphene nanosheets. This work highlights a new electrocatalyst design strategy that combines transition and main-group metal elements, which may provide some inspirations for designing low-cost and high-performance NRR electrocatalysts in the future.     

Vacuum Ultraviolet Excited Photoluminescence Properties of Y2O2S：Eu^3＋,Bi^3＋ Phosphor

As an Hg-free lamp using phosphor, the Bi^3＋ and EH^3＋ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet（VUV） excitation were investigated. The VUV photoluminescent intensity of Y2O2S：Eu^3＋ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S：Eu^3＋,Bi^3＋ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S：Eu^3＋,Bi^3＋ at 147 nm is mainly because the Bi^3＋ acts as a medium and effectively performs the energy transfer process： Y^3＋-O^2-→Bi^3＋→Eu^3＋, while the intense emission band at 172 nm is attributed to the absorption of the characteristic ^1So-^1P1 transition of Bi^3＋ and the direct energy transfer from Bi^3＋ to Eu^3＋. The Y2O2S：Eu^3＋,Bi^3＋ shows excellent VUV optical properties compared with the commercial （Y,Gd）BO3：Eu^3＋. Thus, the Y2O2S：Eu^3＋,Bi^3＋ can be a potential red VUV-excited candidate applied in Hg-free lamps for backlight of liquid crystal display.     

溶液燃烧法制备的Ni基催化剂及其浆态床甲烷化催化性能

分别以硝酸铝、硝酸氧锆、硝酸镧和硝酸铈为载体前驱体,与硝酸镍和尿素配制水溶液,采用溶液燃烧法制备了Ni-Al₂O₃、Ni-ZrO₂、Ni-La₂O₃和Ni-CeO₂催化剂,研究了浆态床CO甲烷化催化性能,并进行了低温N₂吸附-脱附、XRD、SEM、TEM、H₂-TPR和H2化学吸附等表征分析.结果表明,以硝酸铝为前驱体制备Ni-Al₂O₃催化剂时燃烧火焰稳定且持续时间长,达23 s,样品比表面积(468 m²·g^-1)和金属Ni表面积(10 m²·g^-1)均较大、Ni粒径小(3~5 nm)且分散度高,CO甲烷化催化活性和稳定性好,CO转化率和CH₄选择性分别达到94%和95%,在100 h的甲烷化反应中未出现明显失活;以硝酸氧锆和硝酸镧为前驱体制备样品时未出现明显的燃烧火焰,持续时间仅为12 s和5 s,催化剂比表面积、金属表面积及催化活性均较低;以硝酸铈为前驱体制备样品时燃烧过程迅速而剧烈,样品比表面积(22 m²·g^-1)和金属Ni表面积(5 m²·g^-1)小、Ni粒径大且分散性差,甲烷化催化性能最差,CO转化率仅为41%,CH₄选择性仅为89%.     

溶液燃烧法制备的Ni基催化剂及其浆态床甲烷化催化性能

分别以硝酸铝、硝酸氧锆、硝酸镧和硝酸铈为载体前驱体,与硝酸镍和尿素配制水溶液,采用溶液燃烧法制备了Ni-Al2O3、Ni-Zr O2、Ni-La2O3和Ni-Ce O2催化剂,研究了浆态床CO甲烷化催化性能,并进行了低温N2吸附-脱附、XRD、SEM、TEM、H2-TPR和H2化学吸附等表征分析。结果表明,以硝酸铝为前驱体制备Ni-Al2O3催化剂时燃烧火焰稳定且持续时间长,达23 s,样品比表面积(468 m2·g-1)和金属Ni表面积(10 m2·g-1)均较大、Ni粒径小(3~5 nm)且分散度高,CO甲烷化催化活性和稳定性好,CO转化率和CH4选择性分别达到94%和95%,在100 h的甲烷化反应中未出现明显失活;以硝酸氧锆和硝酸镧为前驱体制备样品时未出现明显的燃烧火焰,持续时间仅为12 s和5 s,催化剂比表面积、金属表面积及催化活性均较低;以硝酸铈为前驱体制备样品时燃烧过程迅速而剧烈,样品比表面积(22 m2·g-1)和金属Ni表面积(5 m2·g-1)小、Ni粒径大且分散性差,甲烷化催化性能最差,CO转化率仅为41%,CH4选择性仅为89%。     

Improved pressure discharge property of surface modified Al/Bi2O3 composites

Al/Bi₂O₃ nanothermites were prepared via a self-assembly method using poly-4-vinylpyridine and surface modification of particles by a kind of binder oleic acid respectively. The structures, morphology, and energetic properties were characterized. The pressure discharge properties were studied by a closed bomb. The peak pressures and pressurization rates of Al/Bi₂O₃/P4VP and Al/Bi₂O₃/OA were 5590 kPa, 13.976 GPa s^–1 and 4858 kPa, 12.146 GPa s^–1, respectively, better than those of Al/Bi₂O₃ prepared by normal ultrasonic method (4559 kPa, 11.397 GPa s^–1 ). However, the decreased ignition delay time for self-assembled method and the increased one for modifying with oleic acid suggested different mechanism in accelerating the reaction of Al/Bi₂O₃. Moreover, the effect of mass fraction of oleic acid on nanothermite reaction was demonstrated.

     

The metallic 1T-WS2 as cocatalysts for promoting photocatalytic N2 fixation performance of Bi5O7Br nanosheets

Recently, widespread attention has been devoted to the typical layered BiOCl or BiOBr because of the suitable nanostructure and band structure. However, owing to the fast carrier recombination, the photocatalytic performance of BiOX materials is not so satisfactory. Loading 1T phase WS₂ nanosheets (NSs) onto Bi₅O₇Br NSs can improve the photocatalytic N₂ fixation activity. Among these, the obtained 1T-WS₂@Bi₅O₇Br composites with optimum 5% 1T-WS₂ NSs display a significantly improved photocatalytic N₂ fixation rate (8.43 mmol L⁻¹ h⁻¹ g⁻¹), 2.51 times higher than pure Bi₅O₇Br (3.36 mmol L⁻¹ h⁻¹ g⁻¹). And the outstanding stability of 1T-WS₂@Bi₅O₇Br-5 composites is also achieved. Exactly, the photoexcited electrons from Bi₅O₇Br NSs are quickly transferred to conductive 1T phase WS₂ as electron acceptors, which can promote the separation of carriers. In addition, 1T-WS₂ NSs can provide abundant active sites on the basal and edge planes, which can promote the efficiency of photocatalytic N₂ fixation. This work offers a novel solution to improve the photocatalytic performance of Bi₅O₇Br NSs.     

Bismuth oxide coated amorphous manganese dioxide for electrochemical capacitors

With MnSO₄, NaOH and K₂S₂O₈ as the raw materials, the amorphous and δ-type manganese dioxide (MnO₂) is separately prepared by using different chemical precipitation-oxidation methods. The results of charge–discharge and electrochemical impedance spectroscopy (EIS) tests show that (i) the specific capacitance of the amorphous MnO₂ reaches to 301.2 F g⁻¹ at a current density of 200 mA g⁻¹ and its capacitance retention rate after 2000 cycles is 97%, which is obviously higher than 250.8 F g⁻¹ and 71% of the δ-type one, respectively; (ii) good electrochemical capacitance properties of the amorphous MnO₂ should be contributed to easy insertion/extraction of ions within the material; (iii) when 5 wt% Bi₂O₃ is coated on the amorphous MnO₂, its specific capacitance increases to 352.8 F g⁻¹ and the capacitance retention rate is 90% after 2000 cycles.