利用超细化方法制备超级热辐射涂料

本文详细地分析了热辐射在介质中的吸收过程，以及超细化对物体辐射性能的影响，提出了提高材料热辐射性能的超细化方法。实际应用和理论分析都表明将材料超细化后可以增加热辐射的透射深度，从而能够提高材料的发射率与吸收率。辐射节能涂料今后的研究方向之一就是朝着超细化、纳米化的方向发展。     

微纳米疏水结构表面纳米流体的动态行为

以荷叶作为二级微纳米结构表面,对纳米流体在荷叶表面上的动态行为特性进行了研究。通过控制垂直振动台施加能量,驱动液滴在微纳米结构表面运动。由高速摄影捕捉图片,发现在液滴受迫振动过程中,在一定的振动频率(30~90 Hz)和振动幅值(0.2~2.0 mm)下,液滴会从微纳米结构表面跃起而脱离,即液滴在微纳米结构表面运动过程中,液滴的浸润状态发生了向Cassie(液滴悬浮在表面微结构上)状态的转变。此外,由于施加的外界振动频率不同,液滴的振动模式阶数j出现j=3/2向j=2的转变。结合实验以及液滴固有频率模型,发现振动液滴在共振频率(40 Hz)时发生脱离所需能量最小(0.39 mm)。通过对液滴三相接触线进行力学分析,得到了液滴在共振时发生浸润状态转变的力学特征。     

微米-纳米分层阵列结构减反膜的制备

介绍一种基于聚二甲基硅氧烷(PDMS)材料的微米-纳米分层阵列结构双重减反膜.微米阵列结构模板图案由常规的激光直写光刻机光刻而成.微米阵列结构被复制到PDMS薄膜上,对PDMS薄膜进行等离子体表面修饰处理后在微米阵列结构上形成纳米褶皱结构,从而低成本制备出微米-纳米分层阵列结构双重减反膜.测试结果显示,所制备的微米-纳...     

利用结构化工具刻印方法对硬脆材料进行纳米表面制备

本文介绍了利用钻石结构工具刻印方法来制备硬脆材料纳米表面。超细粉末材料主要是由碳酸纳玻璃、耐火玻璃、石英玻璃、硅以及石英晶片构成。最近一种专门用于制备该类表面的先进压痕试验机和钻石工具被研制出来了，该试验机是由一种聚焦离子束（Focused Ion Beam）的系统所操纵。本文将研究压痕点和超细粉末表面结构的几何形状和精度，并且还讨论作用在成形表面的载荷和压痕深度之间的关系。试验机压头进入材料表面后材料从塑性变形到脆性变形的临界点深度称为临界深度，利用它可以估测脆性材料的性能。由此，本文着重研究了脆性材料压痕变形极限值的大小，此外还讨论了压痕处深度的变化量。     

载体SiO_2上纳米TiO_2膜的制备及光催化性能

以SiO2 为载体 ,在酸性条件下 ,用TiCl4 水解法制备了TiO2 纳米膜催化剂TiO2 /SiO2 。以IR、XRD、SEM和吸光光度法对其进行了表征 ,所制TiO2 膜的平均粒径在 12nm以内 ,并能在很宽的煅烧温度范围内保持锐钛矿晶体结构 ;将TiO2 /SiO2 应用于光催化降解敌敌畏 (DDVP) ,具有高的光催化活性 ,且易回收及反复使用。探讨了不同条件对光催化活性的影响。     

微纳米气泡制备技术及应用研究

微纳米气泡表现出的不同于普通气泡的特点,使其在环境、医疗以及水处理等方面具有较好的优势和发展前景。通过对微纳米气泡进行深入研究,有利于促进该技术在相关领域的发展应用。围绕电解法、光催化法、超声空化法、分散空气法等微纳米气泡的制备方法,概述了气泡的特性与气泡分析测量技术之间的对应关系,综述了微纳米气泡在曝气、气浮、消毒、高精度传递等的应用现状及前景,并对微纳米气泡的发展进行了展望。     

纳米流体在电子冷却中的应用研究进展

随着新型电子元件产生热量的增加,纳米流体特性与微通道特性的结合成为研究热点。这种技术的发展可以使电子设备进一步小型化,并提高能源效率。从纳米颗粒材料和散热器几何结构两方面综述了近年来纳米流体在电子冷却中的应用研究进展,总结了这一领域未来的研究机会和存在的挑战。研究发现,将纳米流体作为新型冷却液应用于不同的散热器中可以提升电子冷却技术的工作效率。     

纳米硅锗热电材料和纳米器件的研究进展

近年来,纳米技术逐渐被用来设计和制备硅锗（Si−Ge）热电材料和新型器件。为了提高Si−Ge热电材料的热电性能,研究学者利用各种纳米结构对Si−Ge热电材料进行了理论研究。其中,利用纳米线、超晶格和量子点等结构中的能带机理与散射机理,从理论上设计了降低Si−Ge纳米结构热导率和提高其功率因子的途径。同时,高效的Si−Ge纳米热电材料被制备出来,包括纳米块体材料的热电性能得到大幅度提高,室温下薄膜和纳米线的热电性能实现了重大突破。在高性能材料的基础上,新型Si−Ge纳米热电器件的研发除了关注于制备工艺优化外,还包括传热结构和原型器件的设计。     

纳米润滑油添加剂的研究进展

阐述了纳米润滑油添加剂的种类及其作用机理,并简要介绍了纳米粒子的制备方法以及纳米粒子在润滑油中分散性和稳定性,分析指出了纳米润滑油添加剂的未来研究方向.     

Methanation of carbon dioxide over Ni/CeO2 catalysts: Effects of support CeO2 structure

The CeO₂, which were prepared by hard-template method, soft-template method, and precipitation method, were used as support to prepare Ni/CeO₂ catalysts (named as NCT, NCS, and NCP catalysts, respectively). The prepared catalysts were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), and Brunauer–Emmett–Teller (BET). Hydrogen temperature-programmed reduction (H₂-TPR) was also used to study the reducibility of the support nickel precursors. Moreover, CO₂ catalytic hydrogenation methanation was used to investigate the catalytic properties of the prepared NCT, NCS, and NCP catalysts. H₂-TPR and XRD results showed that the NiO can be reduced by H₂ to produce metal Ni species, and the surface oxygen species existing on the surface of the support CeO₂ can also be reduced by H₂ to form surface oxygen vacancies. Low-angle XRD, TEM, and BET results indicated that the NCT and NCS catalysts had developed mesoporous structure and high specific surface area of 104.7 m² g^?1 and 53.6 m² g^?1, respectively. The NCT catalyst had the highest CO₂ methanation activity among the studied NCT, NCS, and NCP catalysts. The CO₂ conversion and CH₄ selectivity of the NCT catalyst can reach 91.1% and 100% at 360 °C and atmospheric pressure. The NCP catalyst, which had low specific surface area and low porosity, performed less CO₂ conversion and higher CH₄ selectivity than the NCT and NCS catalysts till 400 °C.     

Influence of CeO2 morphology on WO3/CeO2 catalyzed NO selective catalytic reduction by NH3

WO₃/CeO₂ catalysts with different support morphologies were fabricated by incipient wetness technique and applied to selective catalytic reduction of NO by NH₃ (NH₃-SCR). WO₃/CeO₂ rod (WCR) displayed higher catalytic activity and resistance to SO₂ and H₂O compared with WO₃/CeO₂ polyhedron (WCP) and WO₃/CeO₂ cube (WCC). N₂-BET, XRD, Raman, H₂-TPR, TEM, HRTEM, NH₃-TPD, XPS and in situ DRIFTS were conducted to investigate the physicochemical properties of the catalysts and the adsorption of NH₃ and NO_x species on the catalytic surface. These characterization results demonstrated that the larger BET surface area, the smaller CeO₂ particle size, the higher surface acidity, the more oxygen defects, the better redox performance, and the higher Ce³⁺ and O_α ratios of the catalysts played critical functions in obtaining more outstanding NH₃-SCR catalytic performance. All of these characterization results were also closely related to the CeO₂ morphology. The results of the in situ DRIFTS showed that the WCR had the highest intensities of the adsorbed NO_x and NH₃ species among these three catalysts. The reactions between adsorbed species attributed to NO_x and NH₃ on the catalyst surface can also be a key factor in the NH₃-SCR catalytic performance enhancement.     

Environmental effect of CeO2 nanoadditive on biodiesel

The role of additives for biodiesel has gained most reliable position in the current scenario as they reasonably formulate base fuel composition that contribute to efficiency reliability and long life of an engine. They also can have surprisingly large effects even when used in low (ppm) range. With the use of fuel additives for blending the biodiesel in compression ignition engine, one can expect diminished engine exhaust emission characteristics and also improved fuel properties, which could enhance the combustion characteristics. There are many reports based on the biodiesel blended with nanoparticles additive; however, there is a vacuum in the research pertaining to the use of the most common, low-cost, and eco-friendly CeO₂ nanoparticles as additive to prepare blended canola biodiesel fuel. Moreover, there are very few literatures available on the usage of CeO₂ blended biodiesel. In the present study, an attempt has been made to reduce and understand the engine emission of biodiesel blended with CeO₂ nanoparticles.     

Increased interface effects of PtFe alloy/CeO2/C with PtFe selective loading on CeO2 for superior performance in direct methanol fuel cell

Here, a simple two-step solvothermal approach has been employed to synthesize PtFe alloy (or Pt)/CeO₂/C with PtFe (or Pt) selective loading on CeO₂ nanoparticles. In addition, the selective loading of PtFe alloy or Pt nanoparticles on the surface of CeO₂ is achieved under weak alkaline environment, which is mainly attributed to the opposite electrostatic force between H⁺ enriched on the surface of CeO₂ particles and OH⁻ covered with carbon supporters. As-prepared PtFe alloy (or Pt)/CeO₂/C catalysts with two-stage loading structures show more excellent electro-catalytic efficiency for methanol oxidation as well as duration compared with commercial Pt/C and PtCeO₂/C with random loading structure. Further, single-cell assembly based on Pt₃Fe/CeO₂/C as the anode catalyst exhibits a maximum power density of 31.1 mW cm⁻², which is 1.95 times that of an analogous cell based on the commercial Pt/C. These improved performances with considerable low Pt content (<0.3 mg cm⁻²) are mainly ascribed to the abundant three phase interfaces (PtCeO₂ carbon) induced by the selective and efficient dispersion of Pt nanoparticles on ceria.     

Effect of the CeO2 synthesis method on the behaviour of Pt/CeO2 catalysis for the water-gas shift reaction

A comparative study of three different ceria synthesis procedures (template- and MW- assisted hydrothermal synthesis and urea homogeneous precipitation) is reported in this paper. The obtained materials were employed as supports for Pt nanoparticles, and the Pt/CeO₂ catalysts were evaluated in the WGS reaction under model and realistic conditions. The influence of the support, e.g., its morphology and electronic properties, has been studied in detail by means of XRD, H₂-TPR, XPS, UV–Vis spectroscopy and toluene hydrogenation (for metal dispersion assessment). The catalytic performance of the samples is directly correlated with the modification of the electronic properties, as a result of the preparation method used. The conventional homogeneous precipitation method with urea resulted to be the best option, leading to enhanced ceria reducibility and adequate Pt dispersion, which in turns resulted in a very efficient WGS catalyst.     

The application of MOF-derived CeO2 to synthesize the Cu/CeO2 catalyst for the hydrogen production via water gas shift reaction

The development of catalysts for the water-gas shift (WGS) reaction is attracting attention because of the increased interest in on-site small-scale hydrogen production, which requires highly active and stable catalytic performance under severe conditions. In this study, metal–organic frameworks (MOF), which have been adopted in various fields because of their high surface area, diversity of assemblies, and uniform porosity, were applied to prepare Cu/CeO₂ catalysts for the WGS reaction. MOF-derived CeO₂ (MDC) was obtained from a Ce-BTC-based MOF calcined at different temperatures. Various techniques were used to investigate the physicochemical properties of the Cu/MDC catalysts. Important properties that determine the catalytic performance, such as crystallinity, surface area, Cu dispersion, reducibility, and oxygen storage capacity (OSC), were affected by the treatment temperature of MDC. Among the Cu/MDC catalysts, Cu/MDC prepared with MDC that was treated at 400 °C (Cu/MDC(400)) exhibited the highest CO conversion at reaction temperatures of 200–400 °C. In addition, Cu/MDC(400) maintained 80% of its initial CO conversion after 48 h on stream, even at a very high gas hourly specific velocity of 50,233 mL·g_cat⁻¹·h⁻¹. This result was attributed to the high surface area, Cu dispersion, OSC, and easier reducibility of the Cu/MDC(400) catalyst compared to Cu supported on MDC calcined at other temperatures.     

Polyvinyl alcohol-induced low temperature synthesis of CeO2-based powders

Ce_0.8Sm_0.2O_1.9 (SDC) powders have been synthesized by a combustion method with polyvinyl alcohol (PVA) as the fuel and nitrate as oxidizer. A calcination temperature of 350 °C was found to be sufficient for the formation of pure SDC powders. The cell parameters were calculated using the peak positions determined from the XRD patterns, and it was found that stoichiometric SDC powder could be obtained only when stoichiometric PVA fuel contents were used. The as-prepared SDC pellets exhibited 98% of the theoretical density sintered at 1300 °C. This shows that the SDC powders obtained by this combustion method have excellent sintering properties, which can densified at a relatively low sintering temperature. The powders made by this method, due to its high conductivity of 0.033 S cm⁻¹ at 700 °C, are suitable for intermediate temperature solid oxide fuel cells (IT-SOFCs).     

Metal-organic framework-derived CeO2 nanosheets confining ultrasmall Pd nanoclusters catalysts with high catalytic activity

An in-situ assembly method was successfully constructed to encapsulate Pd clusters within CeMOF matrix. This method involved the protection of nanoclusters with PVP and the assembly of CeMOF around Pd nanoclusters under mild condition. The small size and high dispersion resulting from physical confinement effect were inherited in the derivates as CeO₂ nanosheets confining Pd nanoclusters catalysts. The relative position of Pd and Ce was regulated via varying pyrolysis parameter, which determined the confinement state of Pd clusters. A critical state was found where Pd clusters were maintained at high dispersion and possessed unlimited accessibility for CO. The specific confining structure and low surface concentration depressed the oxygen supply, resulting in the formation of substoichiometric PdO_x, which interacted with CeO₂ and formed Pd–Ce–O(s) clusters. With the improved dispersion and high content of Pd–Ce–O(s) clusters, the catalyst converted 100% CO at 63 °C with a Pd loading of 1.07%. The reaction followed Mars-van Krevelen mechanism, in which CO adsorbed on Pd–Ce–O(s) clusters and reacted with the highly active oxygen species.     

CeO2 coated NaFeO2 proton-conducting electrolyte for solid oxide fuel cell

Nowadays, the low-temperature operation has become an inevitable trend for the development of SOFCs. Transition metal layered oxides are considered as promising electrolyte materials for low-temperature solid oxide fuel cells (LT-SOFCs). In this work, we report the CeO₂ coated NaFeO₂ as an electrolyte material for LT-SOFC. The study results revealed that the piling of CeO₂ significantly influenced the open-circuit voltage (OCV) as well as the power output of the fuel cells. In comparison with pure NaFeO₂, the denser structure of CeO₂ coated NaFeO₂ leads to higher OCV (1.06 V, 550 °C). The electrochemical impedance spectrum (EIS) fitted results showed that NaFeO₂–CeO₂ composites possessed higher ionic boundary conductivity. This is because that the hetero-interfaces between NaFeO₂ and CeO₂ provide fast ion conducting path. The high ionic conductivity of CeO₂ coated NaFeO₂ lead to admirable fuel cell power output of 727 mW cm^?2 at 550 °C.     

Morphologies dependence of hydrogen evolution over CeO2 via ultrasonic triggering

Ultrasonic field can lead to cavitation bubbles explosion, which rises a high-frequency oscillation and generates a high-frequency current in semiconductor nanoparticles in suspension. However, the effect of nanoparticle morphology on ultrasonic-triggered H₂ production is still unclear. To this end, herein, nanorods CeO₂ (nrCeO₂), CeO₂ nanocubes (ncCeO₂), and CeO₂ nanospheres (nsCeO₂) were successfully synthesized. Among them, one-dimensional nrCeO₂ had the most abundant O-vacancies. As revealed by the COMSOL simulation, nanoparticle deformation was easier in nanorods compared with nanocubes and nanospheres, resulting in more efficient charge separation and facilitating H₂ production reaction in nrCeO₂. In detail, within a 5 h’ period, nrCeO₂ presented the highest H₂ production activity of 983.1 μmol g^?1 h^?1 with the positive charge (q+) trapping agent of CH₃OH, and that of 278.1 μmol g^?1 h^?1 in pure water. This work presents a new understanding about the relationship between nanoparticle morphology and H₂ production activity, and provides a promising, efficient, and clean H₂ production approach, which can be further extended to multi-field coupling reactor.