含钨介孔SBA-15催化新材料的表征

孔道排列有序的介孔分子筛材料因在催化、环境和传感等众多领域的潜在用途而日益受到人们的关注。但是纯二氧化硅分子筛材料是没有酸性活性中心的 ,因而难以应用于催化反应中[1] 。为了制备具有催化活性的介孔分子筛材料 ,人们常常将不同性质的杂原子引入到介孔二氧化硅分子筛的基体以赋予分子筛一些酸性位和催化活性中心。SBA 15介孔分子筛作为一种新型的介孔材料 ,具有大的孔径、高的热稳定性和水热稳定性[2 ] ,相对M4 1S材料更具应用前景 ;但其产生于强酸性条件 ,氧化硅骨架中很难引入杂原子。鉴于SBA 15介孔材料优良的物化性能 ,为…     

石墨烯量子点/介孔SiO2复合材料的研究进展

石墨烯量子点/介孔SiO2复合材料的发光效率是影响其应用的重要指标,文章从实验和理论两个方面总结了量子点/介孔复合材料发光效率的研究现状,分析了其发光效率的影响因素和理论预测方法,提出了建立石墨烯量子点/介孔SiO2复合材料发光效率模型的方法和亟待解决的关键问题。     

介孔微孔分子筛的电子显微表征

介孔分子筛对大分子的转化有独特的催化作用 ,但通常的介孔分子筛稳定性差 ,成为限制其工业应用的最大障碍。最近 ,提高介孔分子筛水热稳定性的探索取得了重大进展 ,高稳定性的ＳＢＡ 15 [1,2 ] 、ＭＡＳ 7[3 ] 相继制成。尤其是后者 ,在沸水中稳定时间比ＳＢＡ 15还高出 4 0 %。已有实验表明 ,ＳＢＡ 15介孔分子筛中可能存在 1ｎｍ以下的微孔。为了更直接的研究ＳＢＡ 15中的介孔微孔结构 ,以及从微结构方面找出ＭＡＳ 7高稳定性的可能原因 ,我们利用透射电子显微镜对这两种材料进行了比较研究。材料制备方法参照文献[3 ] 。样品粉末分散于…     

介孔SnO_2的制备及气敏性能研究

采用CTAB模板法制备了具有介孔结构的SnO2。通过小角X射线衍射,BET法对其进行了表征。采用静态配气法对介孔SnO2的气敏性能进行了研究。结果表明:随着煅烧温度的升高,介孔SnO2的比表面积从105.54m2/g降到38.11m2/g。通过延长陈化时间和进一步水热处理可以增加介孔SnO2材料的比表面积。气敏测试表明:在4.5V加热电压下,气敏元件对体积分数为50×10-6酒精蒸气有较好的气敏性能,灵敏度为9.4,响应-恢复时间均为8s。     

三类金属氧化物热电材料的研究进展

综述了NaxCo2O4系、ZnO系和CuAlO2系氧化物热电材料的晶体结构、制备方法和研究现状,发现这三类热电材料均具有较好的热电性能,具有进一步研究的价值。阐述了金属氧化物热电材料未来的研究方向。     

金属氧化物基丙酮气体传感器研究进展

丙酮是一种具有毒性、易挥发性以及易燃性的有机化工原料,会对人们的身体健康造成危害。在特定环境中,丙酮的含量可以通过气体传感器进行快速检测。详细介绍了金属氧化物基丙酮气体传感器的工作机理,并对以ZnO、WO₃、Co₃O₄、SnO₂四种金属氧化物为基质的半导体型气体传感器在丙酮检测方面的研究进展进行了综述,重点总结了其微观形貌、金属掺杂及复合对传感器选择性和灵敏度的影响,并对现阶段研究中可能存在的问题以及未来可能的研究方向进行了简单概述。这将有助于提高金属氧化物基丙酮气体传感器的性能,为环境监测和工业安全领域提供更可靠、更高效的丙酮检测手段。     

介孔NiO纳米片/泡沫镍复合电极的构建及其在超级电容中的应用

随着世界的快速发展,能源储存器件的发展显得尤为重要,具有长的循环寿命、较高的功率密度以及快的充放电速率的超级电容器是最有前途的储能器件之一,过渡金属氧化物及氢氧化物具有较高的理论比电容,但较低的导电性限制其在实际中的应用。本文采用简单的水热法和热处理工艺将多孔NiO纳米片生长在泡沫镍(NF)基底上,利用NF提高了其导电性和电化学稳定性。结果表明,该电极在1 A/g的电流密度下,比电容达到728. 0 F/g,在5 A/g条件下循环2000次仍保留原有比电容的76%。组装的对称电容工作电压达0. 45 V,在功率密度为224. 9 W/kg能量密度达到最大为11. 3 Wh/kg,在能量密度为5 Wh/kg功率密度达到最大为4500 W/kg。     

C60/硅基介孔复合物的发光研究

用化学沉积法制备了C60/多孔硅以及C60/硅基多孔氧化铝两种硅基介孔复合物,并研究了它们的发光性质.结果表明C60的毗联可以影响多孔硅的发光性质,但对硅基多孔氧化铝的发光基本不产生影响.这种现象可以从多孔硅以及硅基多孔氧化铝的发光机理进行解释.     

C_(60)/硅基介孔复合物的发光研究

用化学沉积法制备了 C6 0 /多孔硅以及 C6 0 /硅基多孔氧化铝两种硅基介孔复合物 ,并研究了它们的发光性质 .结果表明 C6 0 的毗联可以影响多孔硅的发光性质 ,但对硅基多孔氧化铝的发光基本不产生影响 .这种现象可以从多孔硅以及硅基多孔氧化铝的发光机理进行解释     

Photoconductivity of Hf-based binary metal oxides

In order to explore the possibility of bandgap engineering in binary oxide insulators we studied photoconductivity of nanometer-thin Hf oxide layers containing different fractions of cations of another sort (Si, Al, Sr, or Ce) deposited on (1 0 0)Si. The smallest bandgaps of the Hf:Al and Hf:Ce oxides are close to the values found in elemental Al₂O₃ (6-6.2 eV) and HfO₂ (5.6 eV), respectively, and show little sensitivity to the concentration of Al or Ce. This result suggests that the oxide sub-network with the largest bandgap preserves its gap energy, while development of a narrower gap is prevented, likely, by dilution of the second cation sub-network. In Hf:Si oxide samples photoconductivity thresholds of 5.6-5.9 eV, corresponding to the bandgap of HfO₂, were observed for all studied Si concentrations, suggesting phaseseparation to occur during deposition. Photoconductivity of SrHfO₃ exhibits two thresholds, at 4.4 and 5.7 eV, which are close to the bandgaps of elemental SrO₂ and HfO₂, respectively. These gap values indicate the phase separation also to occur in this binary oxide. Through this work photoconductivity is demonstrated to be a feasible method to trace phase separation in binary oxides, even in nanometer-thin layers.     

二维半导体光电性质与器件研究进展简述

二维半导体材料,如过渡金属硫族化合物,以其在光电器件方面展现出的独特性能与巨大潜力,成为后摩尔时代有极大发展前景的新半导体材料.二维材料具有独特的光电性质,如直接带隙的电子结构,谷自旋电子学特性,强激子效应等,而利用以上性质,此类材料可用于光探测器、场效应晶体管、高效微纳传感器、光电子电路等微纳光电器件中.因此,以过渡金属硫族化合物为代表的二维半导体材料无论在基础科学与未来应用方面,都是重要的备选材料.     

脉冲激光烧蚀金属氧化物的物理化学过程及反应机理

本文回顾了前人有关脉冲激光烧蚀过程的各种理论模型，重点综述了脉冲激光烧蚀金属氧化物的物理化学过程及反应机理，并对激光能量不很高时金属氧化物的烧蚀过程提出了热控制机制的新观点。     

二次电池金属锂负极的研究进展

金属锂负极具有极高的比容量、极低的密度和最负的电势,被认为是最有希望的下一代高能量密度型电池的负极材料。然而,在反复充放电过程中,锂负极会出现严重的粉化和枝晶生长,造成安全隐患,极大地降低了电池的性能,缩短了使用寿命。综述了近年来国内外针对金属锂负极存在问题进行的改性研究进展,从锂负极存在问题的根源、锂枝晶的生长模式以及近年来改善锂负极的举措三个方面出发,重点针对锂枝晶问题开展分析,并予以展望,为高能量密度锂电池的商业化研究提供借鉴。     

VGF法生长半导体晶体的研究进展

VGF法可实现晶体生长条件可控,晶体重复性好,所生长晶体尺寸大、位错密度低、应力小,是一种很有前景的晶体生长方法。本文综述了VGF法生长半导体晶体、数值模拟和磁场应用的国内外研究进展。     

Synthesis,characterization and photo-catalytic studies of mixed metal oxides of nano ZnO and SnOx

Novel mixed metal oxides of Zinc and Tin (MZOTO) were synthesized by a simple co-precipitation method. The effect of blending varying compositions of SnO_x (x=1, 2) to ZnO has been evaluated, and it was found that the crystal structure, morphology, optical properties and photo-catalytic behavior were dependent on the percentage of SnO_x. The obtained samples were characterized using XRD, EDAX, FESEM, UV–vis spectroscopy, Photoluminescence, etc. XRD data revealed that the ZnO and SnO_x co-exist as mixture and their structures were found as hexagonal and cubic/orthorhombic respectively. FESEM image intricate about the morphology of the MZOTO prepared in 1:0.5 ratio providing nano flower structures that resemble like Chrysanthemum species. The band gaps of all the obtained MZOTOs were determined from UV–vis reflectance spectra using Kubelka-Munk relation. Photoluminescence emission studies revealed that the recombination of excited e⁻ with the h⁺ of ZnO is greatly influenced by SnO_x nanoparticles. Visible light photo-catalytic activities of MZOTOs were followed spectrophotometrically against the degradation of crystal violet solution. MZOTO2 obtained in the ratio of 1:0.5 shows better catalytic efficiency compared to other samples, degrading crystal violet completely within 40 min. The reusability and free radical trapping experiments were performed to study the performance and mechanism of MZOTO2 as the photo-catalyst. The photo catalytic efficiency of 1:0.5 MZOTO was higher due to the presence of flower-like structures that effectively captivated more photons from the sunlight.     

Bandwidth Control and Symmetry Breaking in a Mott-Hubbard Correlated Metal

In Mott materials strong electron correlation yields a spectrum of complex electronic structures. Recent synthesis advancements open realistic opportunities for harnessing Mott physics to design transformative devices. However, a major bottleneck in realizing such devices remains the lack of control over the electron correlation strength. This stems from the complexity of the electronic structure, which often veils the basic mechanisms underlying the correlation strength. This study presents control of the correlation strength by tuning the degree of orbital overlap using picometer-scale lattice engineering. This study illustrates how bandwidth control and concurrent symmetry breaking can govern the electronic structure of a correlated SrVO₃ model system. This study shows how tensile and compressive biaxial strain oppositely affect the SrVO₃ in-plane and out-of-plane orbital occupancy, resulting in the partial alleviation of the orbital degeneracy. The spectral weight redistribution under strain is derived and explained, which illustrates how high tensile strain drives the system toward a Mott insulating state. Implementation of such concepts can push correlated electron phenomena closer toward new solid-state devices and circuits. These findings therefore pave the way for understanding and controlling electron correlation in a broad range of functional materials, driving this powerful resource for novel electronics closer toward practical realization.     

Hydride Anion Substitution Boosts Thermoelectric Performance of Polycrystalline SrTiO3 via Simultaneous Realization of Reduced Thermal Conductivity and High Electronic Conductivity

The development of environmentally benign thermoelectric materials with high energy conversion efficiency (ZT) continues to be a long-standing challenge. So far, high ZT has been achieved using heavy elements to reduce lattice thermal conductivity (κ_lat). However, it is not preferred to use such elements because of their environmental load and high material cost. Here a new approach utilizing hydride anion (H⁻) substitution to oxide ion is proposed for ZT enhancement in thermoelectric oxide SrTiO₃ bulk polycrystals. Light element H⁻ substitution largely reduces κ_lat from 8.2 W/(mK) of SrTiO₃ to 3.5 W/(mK) for SrTiO_3−xH_x with x = 0.216. The mass difference effect on phonon scattering is small in the SrTiO_3−xH_x, while local structure distortion arising from the distributed Ti−(O,H) bond lengths strongly enhances phonon scattering. The polycrystalline SrTiO_3−xH_x shows high electronic conductivity comparable to La-doped SrTiO₃ single crystal because the H⁻ substitution does not form a grain boundary potential barrier and thus suppresses electron scattering. As a consequence, SrTiO_3−xH_x bulk exhibits maximum ZT = 0.11 at room temperature and the ZT value increases continuously up to 0.22 at T = 657 K. The H⁻ substitution idea offers a new approach for ZT enhancement in thermoelectric materials without utilizing heavy elements.     

Synthesis,physical properties and antibacterial activity of metal oxides nanostructures

Metal oxides (MOs) nanostructures represent a new class of materials which have been explored for the health related applications. Highly ionic MOs nanostrucrures are important for their unique physicochemical properties as well as antibacterial activity. In this work, MOs nanostructures (ZnO, CuO, SnO₂ and CeO₂) have been synthesized by chemical co-precipitation technique and characterized by XRD, SEM, EDS, FTIR and UV–visible spectroscopy analysis. XRD results reveal the single-phase formation of all metal oxides. Spherical nanoparticles are observed in case of ZnO, SnO₂ and CeO₂ samples, while hierarchal nanostructures are observed in case of CuO sample. Antibacterial activity of four different MOs nanostructures against E. coli bacterium has been assessed by agar disc method. The antibacterial activity results have shown that the ZnO nanostructures exhibit maximum sensitivity (10 mm ZOI) towards E. coli bacterium. The order of antibacterial activity for different MOs nanostructures is found to be the following: ZnO>SnO₂>CeO₂>CuO. Our findings suggest that the particle size, morphology and type of MOs nanostructures play vital role in their antibacterial activity. It is concluded from the present findings that ZnO nanostructures can be used as an efficient antibacterial agent.     

Understanding the Structural Evolution and Redox Mechanism of a NaFeO2–NaCoO2 Solid Solution for Sodium‐Ion Batteries

Na‐ion batteries have become promising candidates for large‐scale energy‐storage systems because of the abundant Na resources and they have attracted considerable academic interest because of their unique behavior, such as their electrochemical activity for the Fe³⁺/Fe⁴⁺ redox couple. The high‐rate performance derived from the low Lewis‐acidity of the Na⁺ ions is another advantage of Na‐ion batteries and has been demonstrated in NaFe_1/2Co_1/2O₂ solutions. Here, a solid solution of NaFeO₂‐NaCoO₂ is synthesized and the mechanisms behind their excellent electrochemical performance are studied in comparison to those of their respective end‐members. The combined analysis of operando X‐ray diffraction, ex situ X‐ray absorption spectroscopy, and density functional theory (DFT) calculations for Na_{1– x} Fe_1/2Co_1/2O₂ reveals that the O3‐type phase transforms into a P3‐type phase coupled with Na⁺/vacancy ordering, which has not been observed in O3‐type NaFeO₂. The substitution of Co for Fe stabilizes the P3‐type phase formed by sodium extraction and could suppress the irreversible structural change that is usually observed in O3‐type NaFeO₂, resulting in a better cycle retention and higher rate performance. Although no ordering of the transition metal ions is seen in the neutron diffraction experiments, as supported by Monte‐Carlo simulations, the formation of a superlattice originating from the Na⁺/vacancy ordering is found by synchrotron X‐ray diffraction for Na_0.5Fe_1/2Co_1/2O₂, which may involve a potential step in the charge/discharge profiles.