富含光诱导氧空位Bi12O17Br2的制备及其高效光催化固氮性能

采用一步水热法制备了Bi₁₂O₁₇Br₂光催化剂,其平均微片尺寸为1.2μm,比表面积约为29 m²·g^-1。Bi₁₂O₁₇Br₂的禁带宽度为2.42 eV,能够响应可见光。值得注意的是,在光照条件下Bi₁₂O₁₇Br₂表面能够产生氧空位;光诱导氧空位不仅能促进氮气在催化剂表面的吸附,而且对吸附的氮气分子的活化起到至关重要的作用。实验结果表明在可见光照射下,Bi₁₂O₁₇Br₂光催化剂上的氨生成速率为337.6μmol·g^-1·h^-1。在可见光的驱动下,Bi₁₂O₁₇Br₂光催化剂能够实现氮气与水反应生成氨的过程。     

Nanostructured AgPb(m)SbTe(m+2) system bulk materials with enhanced thermoelectric performance

Nanostructured Ag0.8Pbm+xSbTem+2 (m = 18, x = 4.5) system thermoelectric materials have been fabricated by combining mechanical alloying (MA) and spark plasma sintering (SPS) methods followed by annealing for several days to investigate the effect on microstructure and thermoelectric performance. It was found that appropriate annealing treatment could reduce both the electrical resistivity and the thermal conductivity at the same time, consequently greatly enhancing the thermoelectric performance. A low electrical resistivity of 2 x 10-3 Ohm-cm and low thermal conductivity of 0.89 W m-1 K-1 were obtained for the sample annealed for 30 days at 700 K. The very low thermal conductivity is supposed to be due to the nanoscopic Ag/Sb-rich regions embedded in the matrix. A high ZT value of 1.5 at 700 K has been achieved for the sample annealed for 30 days.     

HPA/Bi_2WO_6光催化剂的制备及其脱氮性能研究

以Na2WO4·2H2O和Bi(NO3)3·5H2O为原料,通过不同表面活性剂为模板剂对所制备催化剂的形貌进行调控,将调控形貌后的催化剂固载不同种类杂多酸(HPA),再进行超临界流体干燥制得HPA/Bi2WO6光催化剂。并采用X射线衍射(XRD)、紫外-可见漫反射(UV-vis)、扫描电镜(SEM)、比表面积测定仪(BET)对所制备的催化剂进行表征,通过含氮模拟油对固载杂多酸后的催化剂的脱氮性能进行评价。结果表明,十二烷基硫酸钠(SDS)能起到更好的模板导向作用,从而获得由二维纳米片组装成的三维中空花状结构。采用超临界流体萃取干燥技术对催化剂进行提纯干燥,可有效地避免孔塌陷、团聚等现象,进一步增大了催化剂的比表面积,其脱氮效果有了进一步的提高。固载磷钨酸能有效地提高催化剂的表面酸性位点,从而显著提高了催化剂的催化活性,磷钨酸固载量为10%、剂油比为1∶100时、氙灯光照3 h脱氮率可达92.08%。     

Synthesis and study of Bi2Ti2O7/TiO2 composites as efficient visible-light-active photocatalysts in the reduction of aqueous Cr(VI)

In this work, Bi_2Ti_2O_7/TiO_2 composites were synthesized and studied as potential visible-light-activated photocatalysts in the reduction of aqueous Cr(VI). Bi_2Ti_2O_7/TiO_2 composites with tunable compositions were synthesized via a solvothermal-calcination two-step method, simply by changing the molar ratios of Bi(NO_3)_3·5H_2O to tetrabutyl titanate in the reactants. The compositions, structures and optical properties of the as-synthesized Bi_2Ti_2O_7/TiO_2 composites were characterized by X-ray diffraction, field emission scanning electron microscopy and UV–vis diffuse reflectance spectra. The photocatalytic activity of the as-synthesized Bi_2Ti_2O_7/TiO_2 composites was tested in the reduction of aqueous Cr(VI)under visible-light(λ420 nm) irradiation, and compared with that of TiO_2 nanoparticles. It was observed that the as-synthesized Bi_2Ti_2O_7/TiO_2 composites exhibited much higher photocatalytic activity than TiO_2 nanoparticles, and the most efficient composite(300 mg) can achieve the complete reduction of Cr(VI) in 300 mL of 50 mg/L K_2Cr_2O_7 aqueous solution under visible-light(λ420 nm)irradiation in 90 min.     

超临界水热极速合成异质结构H4SiW12O40/Bi2WO6光催化剂及其脱氮性能

采用超临界水热合成方式极速合成一种H_4SiW_(12)O_(40)/Bi_2WO_6光催化剂,通过X射线衍射(XRD)、场发射扫描电子显微镜(SEM)、透射电子显微镜(TEM)、比表面积及孔隙度(BET)测定对所合成催化剂的结构和性质进行了考察,并以吡啶含量为15 mg/g的模拟油对光催化剂的脱氮效果进行评价。结果表明,该光催化剂为二维纳米片自组装成的三维球状结构,其中,H_4SiW_(12)O_(40)与Bi_2WO_6不是简单的固载关系而是在超临界水热条件下生成一种新的晶相,正是由于这种晶相的存在,使得H_4SiW_(12)O_(40)牢固固载在Bi_2WO_6光催化剂本体上的同时,对光生载流子进行了有效疏导,提升了H_4SiW_(12)O_(40)/Bi_2WO_6光催化剂的使用寿命和光催化活性。本研究针对光催化剂制备周期与晶形发育的矛盾,将超临界水热技术与光催化剂模板导向合成技术有机结合,在获得良好晶形异质结构H_4SiW_(12)O_(40)/Bi_2WO_6光催化剂的同时明显缩短了光催化剂的制备周期,从而降低了催化剂的制备成本,攻克了光催化剂工业化应用的主要矛盾,所制备的H_4SiW_(12)O_(40)/Bi_2WO_6光催化剂轻质油脱氮效率达97%以上。     

Lotus-stalk Bi4Ge3O12 as binder-free anode for lithium and sodium ion batteries

The synthesized lotus-stalk Bi₄Ge₃O₁₂ utilized as binder-free anode for LIBs demonstrates excellent cycling performance. The synthesized lotus-stalk Bi₄Ge₃O₁₂ is composed of nanosheets, which is contribute to outstanding lithium storage performance.     

Bi_(20)TiO_(32)/聚丙烯腈复合纳米纤维的制备及其对异丙隆的光催化降解性能

采用溶剂热法制备了可见光响应型光催化剂Bi_(20)TiO_(32),为了实现该光催化剂的固定化负载,进一步以Bi_(20)TiO_(32)和聚丙烯腈(PAN)为原料,通过同轴静电纺丝法制备了不同光催化剂含量的Bi_(20)TiO_(32)/PAN复合纳米纤维。通过这一途径一方面可以便于光催化剂的回收利用,另一方面纳米纤维结构可以提高光催化剂与有机污染物反应的接触面积。采用X射线衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)、紫外-可见漫反射光谱(UV-Vis DRS)和氮气吸附-脱附法对样品的物相组成、形貌结构、光谱吸收和比表面积等进行表征。研究了在可见光照射下Bi_(20)TiO_(32)/PAN复合纳米纤维膜对苯脲类农药异丙隆的光催化降解性能。结果显示,制备的Bi_(20)TiO_(32)光催化剂禁带宽度为2.35 eV,属于典型的可见光响应型光催化剂。制备的Bi_(20)TiO_(32)/PAN复合纳米纤维直径在600~700 nm,Bi_(20)TiO_(32)可以在纳米纤维表面均匀负载,复合纳米纤维膜对可见光具有明显的响应性,对异丙隆具有很好的光催化降解效果,其中光催化剂质量分数为25.7%的样品S3对异丙隆的降解率最高可达到87%。这一研究表明,通过同轴静电纺丝法将光催化剂负载于有机纳米纤维表面,可以保持光催化剂原有光催化效果,是实现光催化剂固定化一条较好的途径。     

Ag/Yb掺杂对Ca3Co3.9Cu0.1O9-δ热电性能的影响

采用溶胶凝胶及冷压方法, 通过在Ca₃Co_3.9Cu_0.1O_9-δ体系中引入不同量的Ag⁺或Yb³⁺离子来调控体系的热电性能, 制备了可在300~880 K下稳定存在且热电性能优良的陶瓷材料Ca_3-xAg_xCo_3.9Cu_0.1O_9-δ(x=0.1, 0.15, 0.2, 0.3)和Ca_3-yYb_yCo_3.9Cu_0.1O_9-δ(y=0.05, 0.1, 0.2, 0.3). 通过X射线衍射(XRD)和扫描电子显微镜(SEM)等测试手段对产物进行了表征, 结果显示所制备的样品纯度较高, 晶粒均匀, 晶粒间较致密. 适量的Ag⁺, Yb³⁺离子取代Ca²⁺离子固溶到晶体中使制备的双掺杂材料晶胞体积发生了变化, 但并未引起晶体对称结构的变化. 电阻率和Seebeck系数的表征结果说明双掺杂优化了载流子的浓度, 随着温度的升高电阻率不断减小, Seebeck系数不断增大. 经过计算可知Seebeck系数的增大还有电子有效质量的贡献. 热导率表征结果显示双掺杂体系的热导率随着温度的升高而减小, 其中声子热导依然起主要作用, 这与单掺杂体系的结果一致. 随着温度的升高, 双掺杂样品Ca_2.7Ag_0.3Co_3.9Cu_0.1O_9-δ在880 K下ZT值达到最大, 为0.2.     

Thermoelectric properties of Cu-doped n-type (Bi2Te3)0.9–(Bi2−xCuxSe3)0.1(x=0–0.2) alloys

n-Type (Bi₂Te₃)_0.9–(Bi_2−xCu_xSe₃)_0.1 (x=0–0.2) alloys with Cu substitution for Bi were prepared by spark plasma-sintering technique and their structural and thermoelectric properties were evaluated. Rietveld analysis reveals that approximate 9.0% of Bi atomic sites are occupied by Cu atoms and less than 4.0 wt% second phase Cu_2.86Te₂ precipitated in the Cu-doped parent alloys. Measurements show that an introduction of a small amount of Cu (x0.1) can reduce the lattice thermal conductivity (κ_L), and improve the electrical conductivity and Seebeck coefficient. An optimal dimensionless figure of merit (ZT) value of 0.98 is obtained for x=0.1 at 417 K, which is obviously higher than those of Cu-free Bi₂Se_0.3Te_2.7 (ZT=0.66) and Ag-doped alloys (ZT=0.86) prepared by the same technologies.     

钨酸铋量子点和纳米片修饰石墨相氮化碳复合催化剂的制备及其可见光催化活性增强

利用超声-水热法、使用油酸钠辅助合成钨酸铋(Bi₂WO₆)量子点/纳米片修饰的石墨相氮化碳(g-C₃N₄)(Bi₂WO₆/g-C₃N₄)复合光催化剂。 通过X射线粉末衍射(XRD)、透射电子显微镜(TEM)、傅里叶变换红外光谱(FT-IR)、紫外可见漫反射光谱(UV-Vis DRS)、N₂吸附-脱附等技术手段获得Bi₂WO₆/g-C₃N₄催化剂的组成、结构和光吸收性能,分析合成机理。 以罗丹明B(RhB)水溶液为模拟污染物,考察Bi₂WO₆/g-C₃N₄复合催化剂的可见光催化活性。 结果表明:g-C₃N₄和Bi₂WO₆的质量比为3:7的Bi₂WO₆/g-C₃N₄-30具有最有效的异质界面,电化学阻抗和光电流测试结果显示该催化剂的光生载流子传输速率快、复合率低,可见光照射120 min对RhB的降解率达到95.8%;通过活性物质捕捉实验获知光生空穴是光催化反应中的主要活性物质,分析异质界面对光催化活性的影响,进而提出光催化反应机理。     

p-Type thermoelectric properties of the oxygen-deficient perovskite Ca2Fe2O5 in the brownmillerite structure

Brownmillerite calcium ferrite was synthesized in air at 1573 K and thermoelectric properties (direct current electrical conductivity σ, Seebeck coefficient α, thermal conductivity κ, thermal expansion α_L) were measured from 373 to 1050 K in air. Seebeck coefficient was positive over all temperatures indicating conduction by holes, and electrical properties were continuous through the Pnma-Imma phase transition. Based on the thermopower and conductivity activation energies as well as estimated mobility, polaron hopping conduction was found to dominate charge transport. The low electrical conductivity, <1 S/cm, limits the power factor (α²σ), and thus the figure of merit for thermoelectric applications. The thermal conductivity values of ∼2 W/mK and their similarity to Ruddlesden-Popper phase implies the potential of the alternating tetrahedral and octahedral layers to limit phonon propagation through brownmillerite structures. Bulk linear coefficient of thermal expansion (∼14×10⁻⁶ K⁻¹) was calculated from volume data based on high-temperature in situ X-ray powder diffraction, and shows the greatest expansion perpendicular to the alternating layers.     

Nanostructured Bi(2-x)Cu(x)S3 bulk materials with enhanced thermoelectric performance

Nanostructured Bi(2-x)Cu(x)S(3) (x = 0, 0.002, 0.005, 0.007, 0.01, 0.03) thermoelectric polycrystals were fabricated by combining mechanical alloying (MA) and spark plasma sintering (SPS) methods. The effect of Cu content on the microstructure and thermoelectric property of Bi(2-x)Cu(x)S(3) bulk samples was investigated. It was found that the subtle tailoring of Cu content could reduce both the electrical resistivity and the thermal conductivity at the same time, and consequently enhancing the thermoelectric property. A low electrical resistivity of 1.34 × 10(-4)Ω m(-1) and a low thermal conductivity of 0.52 W m(-1) K(-1) were obtained for the Bi(1.995)Cu(0.005)S(3) sample at 573 K. The low thermal conductivity is supposed to be due to the nanoscopic Cu-rich regions embedded in the host matrix. A peak ZT value of 0.34 at 573 K was achieved for the Bi(1.995)Cu(0.005)S(3) composition, which is the highest value in the Bi(2)S(3) system reported so far.     

Solid-solutioned homojunction nanoplates with disordered lattice: a promising approach toward "phonon glass electron crystal" thermoelectric materials

The concept of "phonon glass electron crystal" (PGEC) was proposed in the mid-1990s to maximize the ZT value for thermoelectric materials, based on its combined advantages of low thermal conductivity as in a glass but high electricity as in a well-ordered crystal. Although a great amount of research in complex materials systems for achieving this concept has been done, a perfect "PGEC" material has not been acquired yet. Herein, we first put forward a solid-solutioned homojunction in high temperature phase with disordered lattice, which possesses both high electrical conductivity and low thermal conductivity, as an effective way to optimize the low/mid-temperature thermoelectric property. As an example, nonambient cubic phase AgBiSe(2) was successfully stabilized to room temperature through the formation of a solid solution by Sb incorporation for the first time, and furthermore, in situ formed homojunctions on the surface of solid-solutioned nanoplates were also first achieved through a simple colloidal method. A significant enhancement of thermoelectric performance at low/mid-temperature was realized through synergistical regulation on electronic and thermal transport. As a result, compared to that of original AgBiSe(2) (ZT = 0.03 at 550 K), the ZT value of AgBi(0.5)Sb(0.5)Se(2) was increased to 0.51 at 550 K by the formation of a solid solution, and then further increased to 1.07 at 550 K by the formation of solid-solutioned homojunction.     

微波液相法一步合成H3PW12O40/Bi2WO6光催化剂及其脱氮性能

采用微波液相法一步合成了固载型H₃PW₁₂O₄₀/Bi₂WO₆光催化剂. 通过紫外-可见漫反射光谱(UV-Vis)、 场发射扫描电子显微镜(SEM)、 表面积及孔隙度(BET)测定、 氨气程序升温脱附(NH₃-TPD)、 吡啶吸附红外光谱(Py-FTIR)和X射线衍射(XRD)对所合成催化剂的结构和性质进行了考察, 并以吡啶浓度为15 mg/g的模拟油对光催化剂的脱氮效果进行评价. 结果表明, 与传统浸渍固载法相比, 微波液相一步法不仅能高效合成H₃PW₁₂O₄₀/Bi₂WO₆光催化剂, 且所合成的催化剂能被低能量的光激发. 固载H₃PW₁₂O₄₀不但能提高Bi₂WO₆纳米颗粒的表面酸量, 还能通过改变Bi₂WO₆前驱液的酸强度来调控催化剂形貌. 在H₃PW₁₂O₄₀固载量为15%(质量分数), 微波功率为800 W, 反应时间为90 min条件下得到的H₃PW₁₂O₄₀/Bi₂WO₆的光催化脱氮活性最高, 在催化剂与模拟油质量比为1/300, 500 W氙灯光照60 min的最佳光催化反应条件下, 模拟油脱氮率达到92.63%.     

Thermal studies on the electrical conductivity of some (CnH2n+1NH3)2CuCl4 (n = 1,2) and (CH2)(CH3)2CuCl4 complexes

The electrical conductivities of the compounds (CH₃NH₃)₂CuCl₄, (C₂H₅NH₃)₂CuCl₄ and (CH₂)₂(NH₃)₂CuCl₄ were measured in the temperature range which includes their structural phase transition. The values of the activation energies as calculated from the Arrhenius equation are reported. Confirmation of the phase transition temperatures is carried out using differential thermal analysis in the same temperature range as the conductivity measurements.     

Ag复合对LaCoO_3陶瓷热电性能的影响

<正>0引言热电材料是利用热电效应实现电能和热能相互转化的功能材料,在废热发电和无氟制冷等方面有广泛的应用前景。其中氧化物热电材料是近年来备     

TiO2/Bi2O3纳米复合体的制备及可见光催化产氢性能

首先采用相分离的水解-溶剂热法制备了Bi₂O₃纳米粒子,然后利用简单的湿化学法在Bi₂O₃表面负载不同比例的TiO₂纳米颗粒,进而得到TiO₂/Bi₂O₃纳米复合体。通过气氛调控的表面光电压谱(SPS)等测试表明,表面负载适量的TiO₂后能够提高Bi₂O₃光生电荷分离。可见光催化产氢和降解污染物测试结果进一步证明,表面负载适量的TiO₂后可显著提高其可见光催化活性,其中Ti/Bi摩尔比为7%时具有最高的光催化活性。这主要归因于TiO₂具有较为合适的导带能级位置,可以接收Bi₂O₃在可见光激发下所产生的高能级电子,从而抑制光生电子-空穴对复合,并且维持了高能级电子较高的还原能力。     

The effect of Cu substitution on microstructure and thermoelectric properties of LaCoO(3) ceramics

La(Co, Cu)O(3-δ) ceramics were prepared by pressureless sintering of citrate precursor powders, and their thermoelectric properties were investigated with an emphasis on the influence of Cu doping and phase structure as well as microstructure. It was found that a secondary phase first appeared in the form of a network along the grain boundaries and then changed to dispersion with increasing Cu content, which effectively reduced the lattice thermal conductivity of the materials. The thermal conductivity was only 1.21 W m(-1) K(-1) for the sample LaCo(0.75)Cu(0.25)O(3-δ), being much lower as for the thermoelectric oxide materials. In addition, a small amount of Cu substitution for Co increased the electrical conductivity greatly and the absolute Seebeck coefficient, whose sign was also reversed from negative to positive. The dimensionless figure of merit, ZT, of LaCoO(3-δ) oxides at low and middle temperatures can be remarkably enhanced by substituting Co with Cu.     

A novel method for the preparation of Bi4Ti3O12 nanoparticles in w/o microemulsion

Nanometer-sized Bi₄Ti₃O₁₂ particles have been prepared by chemical reaction of bismuth nitrate pentahydrate, titanium sulfate and ammonia solution in a reverse microemulsion system consisting of water, OP (P-octyl polyethylene glycol phenylether, non-ionic surfactant), n-butanol (co-surfactant), and cyclohexane (oil). Precursor hydroxides precipitated in the droplets of water-in-oil (w/o) microemulsion were calcined at 800 °C for 4 h to form Bi₄Ti₃O₁₂ nanoparticles. The samples were investigated with X-ray diffraction (XRD), transmission electron microscopy (TEM), fourier transform infrared spectrophotometer (FT-IR) and ultraviolet visible spectrophotometer (UV–vis). It was found that the as-prepared Bi₄Ti₃O₁₂ nanoparticles had small particle sizes (35 nm), high crystallinity, narrow size distributions and strong light absorption properties not only in the ultraviolet light but also in the visible light region.     

Thermal stability of osmium mixed oxides I. CaOsO3 decomposition products: A new orthorhombic phase Ca2Os2O7

The thermal decomposition of CaOsO₃ by differential thermal analyses, thermogravimetry and X-ray powder diffraction has been studied. In nitrogen CaOsO₃ decomposes at 880 ± 10°C into CaO, osmium metal and oxygen due to the reaction CaOsO₃ → CaO + Os + O₂. In static air the decomposition occurs in three stages: 2CaOsO₃ + 1/2O₂ → Ca₂Os₂O₇ (in region 775–808°C), Ca₂Os₂O₇ → Ca₂Os₂O_6,5 + 1/4O₂ (at a temperature interval of 850–1000°C) and in the third stage Ca₂Os₂O_6,5 → 2CaO + OsO₄ ÷ 1/4 O₂ (at 1005 ± 5°C). The first intermediate Ca₂Os₂O₇ is isostructural with orthorhombic Ca₂Nb₂O₇ and its cell parameters are: a₀ = 3.745 Å, b₀ = 25.1 Å, c₀ = 5.492 Å, Z = 4, space group Cmcm or Cmc2. Ca₂Os₂O₇ exhibits metallic conductivity and its electrical resistivity is 4.6 × 10⁻² ohm-cm at 296K.