Chemical looping gasification of biomass char for hydrogen-rich syngas production via Mn-doped Fe2O3 oxygen carrier

Because of its low cost, an iron-based oxygen carrier is a promising candidate for hydrogen-rich syngas production from the chemical looping gasification of biomass. However, it needs modification from a reactivity point of view. In this study effect of Mn doping on Fe₂O₃ has been investigated for hydrogen-rich syngas production from biomass char at different temperatures (700–900 °C) and steam flow rates (60–100 μL/min). Several techniques (XRD, XPS, BET, and TPR-H₂) have been utilized to characterize fresh and spent oxygen carriers. The result demonstrated Mn-doing boosted the redox activity and the amount of oxygen vacancies, which increased hydrogen gas generation. Hydrogen production displayed different behavior across temperatures due to detecting Fe₂O₃ and MnFeO₃ phases for spent oxygen carriers. For the Fe₂O₃ oxygen carrier hydrogen gas yield is 1.67 Nm³/kg which is due to reduction of Fe₂O₃ phase to Fe₃O₄. However, the MnFe₂O₄ spinel phase detected in the spent MnFeO₃ oxygen carrier is a reason for improving hydrogen gas yield to 1.84 Nm³/kg. Change reaction temperature from 900 °C to 850 °C reduced hydrogen gas yield from 1.84 Nm³/kg to 1.83 Nm³/kg for with MnFeO₃ oxygen carrier. Regarding different steam flows, the proper flow rates that can maintain the formed phases and obtained best hydrogen gas yield are 80 and 90 μL/min, respectively. Meanwhile, the best hydrogen gas yield (2.21Nm³/kg) are obtained with MnFeO₃ oxygen carrier at optimum conditions (850 °C and 90 μL/min).     

锰掺杂氧化镍薄膜的电沉积及性能

通过有机体系电化学沉积法制备了未掺杂及锰掺杂氧化镍薄膜,并通过SEM、EDS、紫外-可见分光光度计和电化学工作站对其形貌、成分、光学及电化学性能进行了研究。结果显示:薄膜由团聚颗粒构成,锰的掺入使团聚颗粒细化,随锰掺入量的增大,薄膜颗粒出现择优方向聚集,形成蠕虫状;锰掺杂还使薄膜的光学及电学性能得到改善,薄膜在550nm处的透光率差值由68%提高到93%,着色效率增至30.9mC·cm-2;电致变色可逆性得到明显改善,响应(消色/着色)时间有所减小。     

草酸盐共沉淀法合成Mn掺杂的BaTiO3陶瓷微球

用草酸盐共沉淀法制备了Mn掺杂的BaTiO3陶瓷微球,并探索了用此方法制备Mn掺杂的BaTiO3微球的最佳工艺条件。借助差热-热重、X射线衍射和扫描电子显微镜等手段对样品进行了表征。实验结果表明:该方法可以制备出掺Mn钛酸钡陶瓷微球,并且在适宜的掺杂量,反应温度和煅烧温度等反应条件下,可以制得平均直径1.5μm的Mn掺杂的BaTiO3陶瓷微球。     

Mn离子掺杂对Ba_(0.2)Sr_(0.8)Zr_(0.18)Ti_(0.82)O_3陶瓷烧结和电学性能的影响

采用溶胶凝胶法制备x Mn-Ba0.2Sr0.8Zr0.18Ti0.82O3(BSZT)(x=0mol%、1mol%、2mol%、3mol%)的陶瓷粉末,以传统工艺制备Mn离子掺杂的BSZT陶瓷。研究Mn离子掺杂浓度对BSZT陶瓷烧结特性、物相结构、介电性能、击穿场强以及储能密度的影响。结果表明,Mn离子掺杂降低了BSZT陶瓷的烧结温度,同时降低其介电常数以及介电损耗,提高了击穿场强和储能密度。在1400℃下烧结的2mol%Mn离子掺杂BSZT陶瓷较未掺杂BSZT陶瓷的烧结温度降低了100℃,相对密度为96.3%;1 k Hz处介电常数约为497、介电损耗为3.6%;最大击穿场强为12.595 k V/mm;最大储能密度为0.374 J/cm3。     

Eco-friendly Mn-doped CsPbCl3 perovskite nanocrystal glass with blue-red emission for indoor plant lighting

Mn-doped CsPbCl₃ perovskite nanocrystal (PeNC) glass was prepared by melt quenching and in situ crystallization. Under the protection of robust glass, PeNCs exhibit excellent moisture resistance and thermal stability. The combination effect of thermal quenching and energy transfer of exciton to Mn²⁺ enables its promising applications in the field of temperature sensor. Interestingly, by matching with ultraviolet chips, all-inorganic blue-red emitting conversion device consisting of PeNC glass was prepared for light-emitting diodes (LEDs), which can meet the light requirements of plant growth. The cultivation results indicated that the growth of cabbages using PeNC plant cultivation LEDs was greater than those cultivated using commercial w-LEDs (white light-emitting diodes). Therefore, Mn-doped CsPbCl₃ PeNCs can be used as a new generation of solid fluorescent materials in the field of indoor plant cultivation LEDs.     

Magnetic properties of low Mn-doped NiCuZn nanocrystalline ferrites

Low Mn-doped NiCuZn ferrites with compositions of (Ni_0.6Zn_0.3Cu_0.1)_1−xMn_xFe₂O₄ (where x = 0, 0.01, 0.02 and 0.03) were synthesized directly with sol–gel method. The influence of the Mn²⁺ content (parameter x) and the sintered temperature on the microstructure and the magnetic properties of these ferrites were mainly discussed. With the increasing Mn²⁺ content, saturation magnetization (M_s) of the powder samples decreased. Saturation magnetic flux density (B_s) and remnant magnetic flux density (B_r) of the toroidal specimens decreased with the Mn²⁺ content up to x = 0.02, followed by increasing. B_r and B_s both increased with the increasing sintered temperature, while coercivity (H_c) decreased. The real part of permeability (μ′) of the toroidal specimens increased up to x = 0.01, followed by decreasing. The sintered temperature also affected the resonance frequency and the useable frequency (from which the value of tan δ increased more) obviously. Furthermore, the low-frequency permeability and the secondary maximum (the maximum of the permeability appearing the secondary time) both increased with the sintered temperature from 70 to 120 and 150 to about 600.     

Fabrication and Electrical Characterization of Heterojunction Mn-Doped GaN Nanowire Diodes on <Emphasis Type="Italic">n</Emphasis>-Si Substrates (GaN:Mn NW/<Emphasis Type="Italic">n</Emphasis>-Si)

We demonstrated that manganese (Mn)-doped GaN nanowires (NWs) exhibit p-type characteristics using current–voltage (I–V) characteristics in both heterojunction p–n structures (GaN:Mn NWs/n-Si substrate) and p–p structures (GaN:Mn NWs/p-Si). The heterojunction p–n diodes were formed by the coupling of the Mn-doped GaN NWs with an n-Si substrate by means of an alternating current (AC) dielectrophoresis-assisted assembly deposition technique. The GaN:Mn NWs/n-Si diode showed a clear current-rectifying behavior with a forward voltage drop of 2.4 V to 2.8 V, an ideality factor of 30 to 37, and a parasitic resistance in the range of 93 kΩ to 130 kΩ. On the other hand, we observed that other heterojunction structures (GaN:Mn NWs/p-Si) showed no rectifying behaviors as seen in p–p junction structures.     

Structures and pyroelectric properties for [111]-oriented Mn-doped rhombohedral 0.36PIN-0.36PMN-0.28PT crystal

The crystal structures, pyroelectric properties, and thermal stability of [111]-oriented 0.5 mol% Mn-doped 0.36Pb(In_1/2Nb_1/2)O₃-0.36Pb(Mg_1/3Nb_2/3)O₃-0.28PbTiO₃ (Mn-0.36PIN-0.36PMN-0.28PT) ternary single crystal were investigated. The temperature dependence of the Raman spectra and dielectric properties revealed that the crystal exhibited a rhombohedral (R) structure at room temperature, and ferroelectric R → tetragonal (T) and ferroelectric T to paraelectric cubic (C) phase transitions at 130 and 175°C respectively. The single crystal had a high remnant polarization of P_r = 38 μC cm^–2 and coercive field of E_C = 12 kV cm^–1 at room temperature and a frequency of f = 100 Hz. The values of P_r and E_C decreased with increasing temperature, exhibiting anomalies near their phase-transition temperatures, which coincided with changes in the Raman spectra and dielectric properties. Furthermore, at 25°C and f = 100 Hz, the single crystal had high pyroelectric coefficients of p = 8.7 × 10⁻⁴ C m⁻² K⁻¹, figures of merit for the current responsivity of F_i = 3.5 × 10⁻¹⁰ m V⁻¹, the voltage responsivity of F_v = 0.08 m² C⁻¹, and the detectivity of F_d = 30.1 × 10⁻⁵ Pa^−1/2. These values were weakly dependent on temperature below 120°C. In addition, the room-temperature pyroelectric coefficients of the ternary single crystal maintain over 83% of the original value at thermal annealing temperatures below 120°C. These outstanding pyroelectric properties, together with high thermal stability, indicate that [111]-oriented rhombohedral Mn-0.36PIN-0.36PMN-0.28PT ternary single crystal is a new potential candidate for infrared detection applications.     

Optical properties of Mn-doped ZnS semiconductor nanoclusters synthesized by a hydrothermal process

Undoped and Mn-doped ZnS nanoclusters have been synthesized by a hydrothermal approach. Various samples of the ZnS:Mn with 0.5, 1, 3, 10 and 20 at.% Mn dopant have been prepared and characterized using X-ray diffraction, energy-dispersive analysis of X-ray, high resolution electron microscopy, UV-vis diffusion reflection, photoluminescence (PL) and photoluminescence excitation (PLE) measurements. All the prepared ZnS nanoclusters possess cubic sphalerite crystal structure with lattice constant a = 5.408 ± 0.011 ?. The PL spectra of Mn-doped ZnS nanoclusters at room temperature exhibit both the 495 nm blue defect-related emission and the 587 nm orange Mn²⁺ emission. Furthermore, the blue emission is dominant at low temperatures; meanwhile the orange emission is dominant at room temperature. The Mn²⁺ ion-related PL can be excited both at energies near the band-edge of ZnS host (the UV region) and at energies corresponding to the Mn²⁺ ion own excited states (the visible region). An energy schema for the Mn-doped ZnS nanoclusters is proposed to interpret the photoluminescence behaviour.     

ZnS:Mn荧光粉的溶剂热法制备及其发光性能

采用溶剂热法合成了ZnS∶Mn荧光粉,讨论了锰掺杂量对硫化锌发光性能的影响。通过扫描电镜(SEM)、X射线粉末衍射仪(XRD)、紫外可见分光光度计(UV-Vis)和荧光分光光度计(PL)对合成的ZnS∶Mn荧光粉的结构和光学性能进行了表征。结果表明:ZnS∶Mn荧光粉的平均粒径为13.5nm,在波长340nm~200nm处有强吸收,Mn离子浓度在所研究范围内,锰掺杂量对硫化锌的晶型、结晶度、粒径无影响,但对其能级结构影响显著,且随着Mn离子掺杂量的增加,发光强度先增加后减小,掺杂量为5%时达到最大值。