微纳米Sb_2O_3的制备与生长机理研究进展

Sb_2O_3作为间接带隙半导体功能材料,在众多领域表现出卓越的性能。晶型和形貌的差异,会影响Sb_2O_3微纳米材料的性能及应用。本文基于负离子配位多面体生长基元模型,分析了Sb_2O_3两种晶型的结构特点,综述了不同晶型和形貌Sb_2O_3微纳米材料的制备方法,详细探讨了制备过程中温度、溶剂等条件对材料晶型、形貌及尺寸的影响,概述了不同形貌Sb_2O_3微纳米材料的晶体生长机理,并对其发展前景进行了展望。     

导电高分子基柔性应变传感材料研究进展

随着人机交互、电子皮肤、可穿戴电子等新兴领域的迅速发展,作为核心部件之一的柔性应变传感材料成为人们关注的热点。由导电材料与柔性高分子复合而成的导电高分子基复合材料具有柔韧性好、质轻、易加工成型等优势,且材料导电性能在应变刺激下发生改变,因此可用作柔性应变传感材料。综述了基于导电高分子复合材料的柔性应变传感材料的分类及特点,详细介绍了该类传感材料的应变响应机理,并总结了影响导电高分子复合材料应变传感性能的因素。     

铝基非晶合金的玻璃形成能力、热稳定性以及应用展望

Al基非晶合金良好的综合性能表现,使其正在成为新一代工程材料,得到了人们的广泛关注和应用研究,但获得大尺寸的非晶材料成为其得到工业应用的一项难题。本文对铝基非晶合金的发展历史、综合性能、玻璃形成能力及其热稳定性进行了介绍,并对大块铝基非晶合金的探索及应用进行了展望。     

氢敏感材料:钯镍合金纳米线条阵列的制备与性能

为了获得钯镍合金纳米线条优秀的氢敏感性能,采用不同方法获得不同形貌的钯镍合金纳米线条阵列.用AAO模板可以制得连续光滑的纳米线条,在石墨阶梯边上沉积可以得到纳米粒子链,在铂微电极上交流电沉积能够得到多孔纳米线条和枝晶状纳米线条.氢传感实验表明,钯镍合金纳米粒子链和多孔纳米线条结构具有高的氢敏感性和快速响应能力,因此应使用这2种钯镍合金纳米结构材料制备氢传感器才能获得更好的性能.     

纳米Fe_3O_4水泥基复合材料的制备和吸波性能

以FeCl_3·6H_2O(AR)、FeSO_4·7H_2O(AR)、NH_3·H_2O(AR)为原料,采用水热法制备得到纳米Fe_3O_4,采用X射线衍射仪、扫描电镜和矢量网络分析仪对其相组成、形貌与电磁性能进行了表征,将纳米四氧化三铁掺入到水泥基材料中制备水泥基吸波材料,采用弓形法测试水泥基吸波材料在8~18 GHz频段内的吸波性能。结果表明:纳米四氧化三铁的平均尺寸在80~90 nm之间;电损耗角正切tanδe和磁损耗角正切tanδm分别在0.03~0.29和0.01~0.41之间;当其掺量为10%,试样厚度为30 mm时,水泥基复合吸波材料在8~18 GHz频段范围内的吸波性能最佳,反射率小于-10 d B的频带宽为4.7 GHz。     

二氧化硅气凝胶的常压低温快速制备和表征

二氧化硅气凝胶凭借其极高的孔隙率和低导热性能已成为近年的热门研究材料之一。文章在常压低温条件下以正硅酸四乙酯为硅源,异丙醇和正己烷溶液为溶剂,通过低表面能溶剂置换以及粒子表面改性的方法快速制备无机气凝胶材料,并采用FE-SEM、HR-TEM、FTIR-ATR光谱及X射线衍射分析等手段对所制备气凝胶材料的表观形貌、化学结构以及结晶性能进行表征。研究表明:制得的二氧化硅气凝胶表面连有疏水的Si—CH3基团、存在丰富的介孔结构,粒子和孔隙的尺寸较小,是一种孔隙率高、轻质、且热稳定性较高的微晶纳米材料,具有广泛的应用前景。     

功能化核-壳式结构Fe_3O_4/聚合物的合成及应用

核-壳式结构的Fe_3O_4/聚合物结合了Fe_3O_4的磁性和聚合物壳层具有功能基的特点,在药物载体、固定化酶、DNA纯化、催化、传感和金属离子分离等领域得到了科研工作者的广泛研究,表面含羟基、羧基、氨基、巯基、磷酸根及多种官能团修饰的Fe_3O_4/聚合物的合成方法及应用是研究的重要方面。     

纤维素基可穿戴压力传感材料的制备与应用

随着科技水平的提高,具有良好力学响应性能的柔性传感器被广泛应用于健康监测、电子皮肤和虚拟现实等领域。本文以微纤化纤维素为主要原料,先通过物理吸附和化学键合的协同作用将二维纳米导电颗粒(多壁碳纳米管)负载在微纤化纤维素纤维表面;再利用冷冻干燥技术制备了具有多孔结构的纤维素基复合压力传感材料,并验证了其应用于压电传感领域的可行性。结果表明,当微纤化纤维素用量为2%,交联剂(N,N-二甲基甲酰胺)用量为1.5%,多壁碳纳米管用量为0.05%时,制备的传感材料的密度约为0.06 g/cm~3;当该复合材料的应变为10%时,产生的应力约为10 kPa;当压缩次数达到500次时,材料的回复率仍高达90%以上;经线性回归得到材料的灵敏度为3.33 kPa~(-1);人体穿戴测试结果表明,该新型微纤化纤维素复合压力传感材料的灵敏度较高、适应性较强。     

金属/硅基纳米复合体系制备技术

金属/硅基纳米复合材料作为一种新型材料,获得了比相应单纯的纳米硅更为优越的材料性能.为更好地发挥这些材料的性能,需要解决材料表面的形貌(尺寸和形状)、效率及反应条件的可控制性.为此,针对金属/硅基复合纳米体系的制备技术及进展作了概述.     

活性粉末混凝土微观层面的研究进展

作为新型水泥基复合材料,活性粉末混凝土具有高强度,高韧性以及高耐久性等优异性能,在桥梁与路面工程、建筑工程、水利工程和特种结构等领域拥有广阔的应用前景.但由于组成中活性组分多,内部结构复杂,微观机理研究尚不够明确,难以为材料的宏观性能提供明确的理论依据.介绍了活性粉末混凝土的基本组成、各组分产生的反应及影响因素,总结了国内外学者对活性粉末混凝土微观形貌及孔结构等的研究成果,更进一步地提出了现阶段微观层面研究和材料本身所存在的问题,指出了发展趋势,并进行了分析和讨论.     

Sensing characterization of Sn/In/Ti nanocomplex oxides for CO,CH<Subscript>4</Subscript> and NO<Subscript>2</Subscript>

The nanocomplex oxides of Sn-In and Sn-In-Ti were prepared by controlled co-precipitation method as sensing materials of semiconductor gas sensors for detection of CO, CH4 and NO2. Through manipulating the Sn/In cation ratio, metal salt total concentration, precipitation pH value and aging time, the nanocrystalline powders were successfully derived with chemical homogeneity and superior thermal stability, compared with the single component oxides. The particle size and morphology, surface area, and thermal and phase stabilities were characterized using TEM, TG-DTA, BET and XRD. The sensing tests showed that the Sn-In composites exhibit high sensitivity and selectivity for CO and NO2. The introduction of TiO2 enhanced CH4 sensitivity and selectivity, particularly, additives of Pd and Al2O3 as a dopant and surface modification greatly enhanced the sensing properties. The sensitivity depended on the composition of composites, calcination temperature and operating temperature. The optimal values were (25%In2O3- 75%SnO2)-20%TiO2 for ternary composite, 600 and 300℃, respectively. Temperature-programmed desorption (TPD) studies were employed to explain the gas adsorption behavior displayed by the surface of nanocomposites and X-ray photoelectron spectroscopic (XPS) analysis was used to confirm the electronic interactions existing between oxide components. The sensing mechanism of the nanocomposites was attributed to chemical and electronic synergistic effects.     

Fabrication of Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-NaCl composite heat storage materials by one-step synthesis method

Thermal energy storage is an attractive option for effectiveness since it gives flexibility and reduces energy consumption and costs. New composite materials for storage and transformation of heat of NaCl-Al₂O₃ composite materials were synthesized by one-step synthesis method. The chemical composition, morphology, structure, and thermal properties were investigated by XRD, EDS, SEM, and DSC. The results show that NaCl can be absorbed by Al₂O₃ particle from 800 to 900 °C for Al₂O₃ particle surface is rich active structure. The results also indicate that the leakage of NaCl when the phase change can be prevented by Al₂O₃ particles and the enthalpy of phase change of NaCl-Al₂O₃ material is 362 J/g. The composites have an excellent heat storage capacity. Therefore, this study contributes to one new thought and method to prepare high temperature heat storage material and this material can be applied in future thermal engineering.     

Development of magnetocaloric materials in room temperature magnetic refrigeration application in recent six years

Some magnetocaloric materials were used successfully in magnetic refrigeration application and became one of the critical parts of magnetic refrigeration technology whose delightful progresses were made worldwide in the past 30 years. At the same time, the research on giant magnetocaloric materials will accelerate the development of room temperature magnetic refrigeration. In this paper, the new theoretical and experimental investigations on magnetic materials in room temperature application were described, including Gd and its binary and ternary intermetallic compounds, Mn-based compounds, La(Fe_13−x M _x )-based compounds and manganites. Based on the analysis of hysteresis, corrosion, cost and heat process, the comparison between different families of magnetic materials was discussed. Further research of room temperature magnetic refrigerant was suggested. Foundation item: Project(50876082) supported by the National Natural Science Foundation of China; Project (IRT0746) supported by the Changjiang Scholars and Innovative Research Team in University     

Synthesis and characterization of Cu-Cr-O nanocomposites

Cu-Cr-O nanocomposites that can be used as additives for the catalytic combustion of AP（ammonium perchlorate）-based solid-state propellants were synthesized via a citric acid（CA） complexing approach. Techniques of TG-DTA, XRD as well as TEM were employed to characterize the thermal decomposition procedure, crystal phase, micro-structural morphologies and grain size of the as-synthesized materials respectively. The results show that well-crystallized Cu-Cr-O nanocomposites can be produced after the CA-Cu-Cr precursors are calcined at 500℃ for 3 h. Phase composition of the as-obtained Cu-Cr-O nanocomposites depends on the molar ratio of Cu to Cr in the starting reactants. Addition of the as-synthesized Cu-Cr-O nanocomposites as catalysts enhances the burning rate as well as lowers the pressure exponent of the AP-based solid-state propellants considerably. Noticeably, catalyst with a Cu/Cr molar ratio of 0.7 exhibits promising catalytic activity with high burning rate and low pressure exponent at all pressures, due to the effective phase interaction between the spinel CuCr2O4 and delafossite CuCrO2 contained in the as-synthesized Cu-Cr-O nanocomposites.     

Preparation and electrochemical performance of spherical Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> as anode materials for Li-ion batteries

Fe₃O₄ nano-powder was prepared by the hydrothermal method. The structure and morphology of the product were characterized by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The as-prepared powder has regularly spherical morphology, and the average size of product is about 25 nm. The possible application use of this material as the active mass of anode for rechargeable Li batteries was examined by cyclic voltammeter (CV), galvanostatic charge/discharge. The experimental results showed that this material exhibited large specific capacity at the first cycle, and the discharge and charge capacity retention of this electrode are 37.04% and 48.76%, respectively. Furthermore, the impedance change of Fe₃O₄ electrode under different cycle number and potential was examined.     

Structure and Electric Conductivity of Ce-doped Bi<Subscript>2</Subscript>O<Subscript>3</Subscript> Electrolyte Synthesized by Reverse Titration Chemical Coprecipitation

Ce-doped Bi₂O₃ nanopowders were prepared by reverse titration chemical coprecipitation from Bi³⁺ and Ce⁴⁺ containing aqueous solution. Techniques of X-ray diffraction (XRD), transmission electron microscopic (TEM) and Fourier transform infrared spectroscopy (FTIR) were employed to characterize the as-synthesized materials. The XRD patterns indicated that the peaks can be easily indexed to β-Bi₂O₃ and no diffraction peaks of Ce or other impurity phases were detected in the prepared samples. The calculated average crystalline size decreased from 31.72 to 11.96 nm when the Ce content increased from 1 wt% to 10 wt%. The morphology changed from flake-like into the spherical-like with increase in Ce content. The electric conductivity of Ce-doped Bi₂O₃ electrolyte was also investigated by two probe DC method. Conductivity analysis exhibited that the rate of conductivity increased with increasing Ce²⁺ ratio, when the Ce concentration was up to 5 wt%, the as-synthesized Ce-doped Bi₂O₃ electrolyte showed the maximum value of conductivity(0.295 S·cm^–1).     

Catalytic graphitization of Mo-B-doped polyacrylonitrile （PAN）-based carbon fibers

A novel carbon fiber pretreatment was proposed. Polyacrylonitrile (PAN)-based carbon fibers were first anodized in H₃PO₄ electrolyte to achieve an active surface, and then coated with Mo-B catalysts by immersed the carbon fibers in a uniformly dispersed Mo-B sol. The as-treated carbon fibers were then graphitized at 2 400 °C for 2 h. The structural changes were characterized by X-ray diffractometry (XRD), Raman spectroscopy, scanning electron microscopy (SEM) and high-resolution transmission electronic microscopy (HRTEM). The results show that much better graphitization can be achieved in the presence of Mo-B, with an interlayer spacing (d ₀₀₂) of 0.335 8 nm and a crystalline size (L _c) of 28 nm.     

Cl 掺杂提升N-PbS 热电性能的实验研究

铅基硫属化合物在中高温热电领域具有广泛的应用。相较于Te 和Se 元素, S 元素具有含量丰富, 价格低廉,且PbS 热稳定性高等优点, 近年来PbS 热电材料引起了研究人员的广泛兴趣。然而, PbS 热电材料本体固有高晶格 热导率, 导致其较低的热电转化效率, 严重限制了其在热电领域的应用。为了降低其晶格热导率, 采用Cl 掺杂方法改善PbS 的热电性能。实验结果表明, 通过水热法制备了形貌可控的树枝状PbS 基纳米材料, 在烧结过程中形成了 多孔结构PbS 基块体材料。通过测试结果可知, Cl 掺杂后的多孔PbS 材料的致密度和晶格热导率显著降低, 载流子浓度升高, 热电性能明显改善, 其中PbCl_0.02S_0.98 材料在773 K 时zT 值达到0.71, 较纯PbS 提升了约108.8%。     

Mechanical properties of individual core-shell-structured SnO<Subscript>2</Subscript>@C nanofibers investigated by atomic force microscopy and finite element method

Although SnO₂-based nanomaterials used to be considered as being extraordinarily versatile for application to nanosensors, microelectronic devices, lithium-ion batteries, supercapacitors and other devices, the functionalities of SnO₂-based nanomaterials are severely limited by their intrinsic vulnerabilities. Facile electrospinning was used to prepare SnO₂ nanofibers coated with a protective carbon layer. The mechanical properties of individual core-shell-structured SnO₂@C nanofibers were investigated by atomic force microscopy and the finite element method. The elastic moduli of the carbon-coated SnO₂ nanofibers remarkably increased, suggesting that coating SnO₂ nanofibers with carbon could be an effective method of improving their mechanical properties.     

Preparation and characterization of Bi4Ti3O12 platelets by a novel low-temperature molten salt system

Bismuth titanate (Bi₄Ti₃O₁₂) platelets were prepared by molten salt method in a new salt system of CaC_l2-NaCl at 650–750 °C, using bismuth nitrate pentahydrate (Bi(NO₃)₃―H₂O) and titanium butoxide (Ti (OC₄H₉)₄) as raw materials. The synthesis temperature of Bi₄Ti₃O₁₂ platelets was decreased to 650 °C from 900–1100 °C. The phase compositions and crystalline morphology of Bi₄Ti₃O₁₂ platelets were investigated by XRD and SEM. The experimental results indicate that Bi₄Ti₃O₁₂ platelets containing tetragonal and orthorhombic phase with the size of 1–3 μm can be synthesized at 650 °C for 2 h, and the orthorhombic phase becomes the dominant phase at 750 °C for 5 h. The size and proportion of Bi₄Ti₃O₁₂ platelets increase with the increment of the calcining temperature and holding time. The proportion of platelets increases to about ninety percent, and the platelets grow up to about 3–10 μm at 750 °C for 5 h from 1–2 μm at 650 °C for 2 h. This technical route provides a new low-temperature molten salt system for preparing platelets by molten salt methods.