河北某地含磷金红石矿综合利用选矿研究

分析了含磷金红石矿的性质并对其作了试验研究,为类似矿山提供了经验。     

Giant permittivity up to 100 MHz in La and Nb co-doped rutile TiO2 ceramics

Dielectric spectroscopy was carried out for reduced and stoichiometric La_0.0025Nb_0.0025Ti_0.995O₂ ceramics synthesized by sintering in different atmospheres. A giant permittivity (~1 × 10⁴) was obtained at a frequency of 100 MHz and temperature range from 170 to 350 K. Three dielectric relaxation mechanisms were observed within the temperature range of 10-300 K via dielectric spectroscopy. A low temperature dipole relaxation peak (in the temperature range of 10-30 K) in the spectra was identified to be associated with the giant permittivity specifically measured at 100 MHz. The origin of such giant permittivity was attributed to dipole orientation polarization. Hopping polaron and interfacial effect contributed to giant permittivity. After annealing treatment, all the relaxation contributions were weakened. Low dielectric loss was attributed to high resistance of grain and grain boundaries. Annealing in ambient conditions led to decreased relaxation times which gives the signature of decreased concentration of oxygen vacancies and Ti³⁺. Dipoles which were related to oxygen vacancies and Ti³⁺, resulted in giant permittivity up to 100 MHz.     

Room temperature flash of single crystal titania: Electronic and optical properties

A single-crystal specimen of rutile (titania) was flashed repetitively, while increasing the electric field after each cycle. As expected, the flash onset temperature continued to drop modestly at higher fields. However, when the field was increased from 400 to 450 V cm^–1, the flashed onset fell dramatically down to room temperature. We have investigated the electrical and optical properties of this room temperature flashed specimen (called SZ). The specimen was electronically conducting. Optical absorption spectroscopy revealed a narrow band of new energy levels that were generated just below the conduction band. The gap between the conduction band and this flash-induced energy level agreed with the peak in the electroluminescence spectrum. Optical second harmonic generation (SHG) is reported. The flash-on condition significantly lowered the SHG, which rebounded when the flash was turned off. This result suggests that the structure becomes more centrosymmetric in the state of flash, which may represent a disordered state of defects. The possibility of studying flash behavior at room temperature, without a furnace (as in SZ type specimens), opens a considerable simplification for in-situ characterization of flash behavior. For example, a possible relationship between memristor physics and the flash phenomenon can be studied.     

Hydrophilic property of titanium oxide aiming for bio-applications

Surface functionalization of titanium metal is very attractive for bio- and environmental applications. This is because titanium metal is very stable and has a good biocompatibility. In this case, surface roughness and crystalline structure are important factors for obtaining effective characteristics. Titanium metal is usually covered with a surface passive film of thermodynamically stable rutile-TiO₂ that grows as the heat treatment temperature in air increases. On the other hand, to obtain an anatase-TiO₂ surface layer on titanium metal, we must employ specific treatments such as our previous method, which uses a silica-coexisting heat-treatment process. In this paper, the relationship between the fine structure formed on the titanium metal and the surface hydrophilic property was clarified, and the potential for the bio-application was discussed. The formed anatase-TiO₂ coexisting with silica exhibited improved biocompatibility with good apatite formation.     

Integrating Energy Band Alignment and Oxygen Vacancies Engineering of TiO2 Anatase/Rutile Homojunction for Kinetics-Enhanced Li–S Batteries

The inferior shuttle effect of intermediate lithium polysulfides and the sluggish kinetics of sulfur redox reaction are two serious puzzles for the application of lithium–sulfur batteries. Herein, energy band alignment is combined with oxygen vacancies engineering to obtain TiO₂ anatase/rutile homojunction (A/R-TiO₂) with effective immobilization and high-efficiency catalytic conversion of polysulfides. Theoretical calculations and experiments reveal that the near perfect energy band alignment in A/R-TiO₂ is conducive to fluent charge transfer and high catalytic activity, while the rich oxygen vacancies are engineered to provide abundant active sites for anchoring and accelerating conversion of soluble polysulfides. As a result, a battery with A/R-TiO₂-modified separator delivers a marked sulfur utilization (1210 mAh g⁻¹ at 0.1 C and 689 mAh g⁻¹ at 1 C, 3.75 mg cm⁻²) and a high capacity retention of 63% over 300 cycles at 0.5 C (3.25 mg cm⁻²). More importantly, the A/R-TiO₂-modified separator endows the pouch cell with a high capacity of 128.5 mAh at 0.05 C with a lean electrolyte/sulfur ratio for practical application (S loading: 4 mg cm⁻²).     

Giant permittivity in (Nb0.5La0.5)xTi1-xO2 ceramics prepared by slip casting in a strong magnetic field

A series of textured (Nb_0.5La_0.5)_xTi_1-xO₂ (x = 0, 0.0025, 0.005, 0.01) ceramics were sintered in a nitrogen environment after magnetic slip casting (12 T). Component x ranges from 0.0025 to 0.01 while the degree of orientation increases from 0.49 to 0.88. (Nb_0.5La_0.5)_0.01Ti_0.99O₂ ceramics in the parallel magnetic field's plane have a high permittivity ɛ_r ≈ 1.6 × 10⁴ and the ultralow dielectric loss tanδ ≈ 0.0038 at 10⁴ Hz. The temperature coefficient value of η ≤ ± 7.1% between 218–473 K, fulfilling the X9R requirements. The giant permittivity properties of textured ceramics are mainly derived from internal barrier layer capacitor impacts, electron hopping, and electron-pinned defect-dipoles polarization. The microstructure evolution of sintered ceramics was modified by texturing in a magnetic field, leading to higher activation energies of dielectric relaxations and resistance of grain boundaries and grains. This excellent performance is expected to show great potential in electronic devices' miniaturization and high-density energy storage.