银纳米线电极微结构对柔性压力传感器灵敏度的影响

新型柔性压力传感器具有类似人体皮肤的可拉伸性以及对外力的感知特性,可被用于仿生电子皮肤及各种可穿戴电子设备,近年来引起了学术界和产业界的广泛关注。开发具有优异的传感灵敏度且制作工艺简单、节能、成本低廉的柔性压力传感器具有重要的科学与实际意义。本文以银纳米线(AgNWs)为电极材料,聚二甲基硅氧烷(PDMS)为柔性基底,分别采用PDMS相纸原位固化和抽滤转移固化2种方式制备银纳米线/PDMS复合电极,以聚酰亚胺薄膜(PI)为介电层,将两电极面对面层压封装,得到电容式柔性压力传感器。利用激光共聚焦显微镜和扫描电镜比较了2种制作工艺得到的电极微结构,并研究了上述电极微结构结构对传感器灵敏度的影响。研究结果表明,电极表面银纳米线的蓬松程度及粗糙度能显著影响器件灵敏度。电极表面银纳米线处于较密实状态、粗糙度为0.4μm的传感器灵敏度约为0.43kPa-1;当电极表面银纳米线较为蓬松且粗糙度增大为0.7μm时,传感器灵敏度增大到0.65kPa-1。本文制作的柔性压力传感器具有高灵敏度、低成本的特点,可用于诸如脉搏、心率,发声震动,细微压力变化监控等方面。     

Multilayer Actuator Composed of PZN–PZT and PZN–PZT/Ag Fabricated by Co-Extrusion Process

A multilayer ceramic actuator composed of piezoelectrically active Pb(Zn_1/3Nb_2/3)_0.2–Pb(Zr_0.5Ti_0.5)O_0.8 (PZN–PZT) layers and electrically conducting PZN–PZT/Ag layers was fabricated by the co-extrusion process. For the piezoelectric layers, PZN–PZT, which is sinterable at a low temperature (900°C), was used. For the conducting layers, a PZN–PZT/Ag composite, made by mixing silver particles with the PZN–PZT matrix, was employed. For the co-extrusion process, piezoelectric and conducting feedrods were made by mixing the PZN–PZT and PZN–PZT/Ag, respectively, with a thermoplastic polymer. The initial feedrods, which were composed of five 3 mm-thick PZN–PZT layers, two 1.5 mm-thick PZN–PZT layers, and six 1 mm-thick PZN–PZT/Ag layers, were co-extruded through a 24 mm × 2 mm reduction die at 105°C to produce continuous multilayered green sheets. The sheets were stacked, warm pressed, and sintered at 900°C for 4 h after binder burnout. The sintered multilayer actuator showed distinct layers without any reaction products or cracks at the interface. The thicknesses of the piezoelectric and conducting layers were about 200 and 70 μm, respectively. The displacement of the multilayer actuator, composed of 40 piezoelectric layers (with a total height of 10.8 mm), was about 10 μm at an applied voltage of 500 V.     

纳米Ag/TiO2复合材料的抗菌性能

采用Sol gel法制备掺杂不同质量分数银的纳米Ag/TiO2复合材料,研究了其对抗菌性能的影响。结果表明,银掺杂后的复合材料和应用其整理的纺织品不需紫外光照射就具有较强的抗菌性能,对大肠杆菌和金黄葡萄球菌的透明抑菌圈达到13～17mm。复合材料中银的掺杂能抑制粒径的长大,促进TiO2从锐钛型向金红石相的转移,但其质量分数对复合材料的抗菌性能影响不大。n(Ti)∶n(Ag)=20∶1时,复合材料的抗菌性能最佳,透明抑菌圈达到17mm。     

Synthesis of Ceramic Nanocomposite Powders with in situ Formation of Nanowires/Nanobelts

A significant challenge in synthesizing nanowire/nanobelt-reinforced ceramic nanocomposites is to uniformly disperse these reinforcements. Here, we report the synthesis of amorphous silicon carbonitride powders containing in situ- formed single-crystal Si₃N₄ nanowires and nanobelts via the catalyst-assisted pyrolysis of a polymeric precursor. The nanowires/nanobelts are uniformly dispersed within the powder matrix. The ratio of nanomaterials to powder can be controlled by tailoring the experimental conditions. The novel powders could be useful for fabricating nanowire/nanobelt-reinforced ceramic nanocomposites.     

湿化学法制备氧化铜纳米棒

湿化学技术在工业上有着广泛的应用，而纳米材料也已成为科学研究的热点。本文报道了用湿化学技术制备氧化铜纲米棒。通过透射电镜(TEM)观察和X—射线粉末衍射(XRD)表征：所得氧化铜产品具有单斜晶形氧化铜纳米棒，其直径在20～90nm，长约500-1000nm长径比约为30。     

Ag/PAMAM树形分子纳米复合材料对PTFE膜性能的影响

以第4.0代端氨基聚酰胺-胺型树形分子(G4.0-NH2PAMAM)为模板制备Ag/PAMAM纳米复合材料(Ag·DENPs), 利用了Ag·DENPs与聚四氟乙烯(PTFE)膜表面的氢键作用,通过超声沉积的方法制备出了PTFE-Ag/PAMAM复合膜.通过研究沉积时间对Ag·DENPs在PTFE膜表面沉积量的影响,得到饱和沉积时间是60min,沉积量约为2.32mg.通过UV-vis光谱和SEM对其化学组成和微观形貌进行了表征.复合膜的水接触角为105.3°,较纯PTFE膜降低了23.6°,显著改善PTFE膜表面亲水性.复合膜对水和牛血清白蛋白的通量比纯PTFE膜低,但傅立叶变换衰减全反射红外光谱(FRR)为88.2%,比纯PTFE膜的35.4%高出了52.8%,且对大肠杆菌及金黄色葡萄球菌具有抑菌作用.表明Ag·DENPs的引入可以改善PTFE的抗污染性及抑菌性.     

以SDS为原料并作模板合成水溶纳米棒

通过引入Ca^2＋、NO3^-、Cl^-和十六烷基三甲基溴化胺,成功地合成了水溶性的Na2SO4纳米棒。XRD结果表明,实验制得的Na2SO4纳米棒纯度较高;SEM结果表明不同的外加物质对Na2SO4晶体的生长有显著影响。     

氧化铝模板中Ag纳米线阵列的选择性生长

利用Ag离子与Br离子之间的化学沉积作用在孔隙中充满明胶的阳极氧化铝（AAO）模板中制备了AgBr/AAO纳米介孔复合材料.材料选择性曝光后,利用原位显影液对其进行化学显影,在AAO模板中选择性得到Ag纳米线阵列.实验结果表明：Ag纳米线是连续的、致密的,且具有多晶结构,充满了曝光部分的模板孔隙.本文还对影响Ag纳米线选择性生长的因素进行了简单讨论.     

New Preparation Method for PZT Films Using Electrochemical Reduction

PZT perovskite films on stainless steel were prepared by electrochemical reduction in solutions containing TiO²⁺, ZrO²⁺, and Pb²⁺ ions. Heat treatment at temperatures higher than about 500°C was necessary for crystallization, because the as-deposited oxide films were amorphous. The deposited oxides consisted of a mixture of hydroxides and oxide produced by an increase of pH due to some electrochemical reduction reactions of NO₃⁻, H⁺, and H₂O on the electrode surface. The composition of the PZT films was easily controlled by the composition in solution during the electrolysis. The mechanism of the PZT precursor deposition is discussed.     

Rattle‐Structured Ag/TiO2 Nanocomposite Capsules with Bactericide and Photocatalysis Activities

A structural design featuring rattle‐type silver/titania (Ag/TiO₂) core/shell, that is, Ag@TiO₂, composite microcapsules is produced. The TiO₂ shell protects the encapsulated, movable Ag nanoparticles from breaking away under moderate loading, minimizing hence adverse environmental and biological exposure due to the metal loss, whereas the mesoporous shell serves as conduits for Ag ions released from the caged Ag nanoparticles to kill Escherichia coli in aqueous solutions under dark condition. The anatase TiO₂ shell imparts an additional, synergistic photocatalysis activity under ultraviolet irradiation. A pronouncedly enhanced photocatalysis activity results when the Ag@TiO₂ composite capsules were thermally annealed under vacuum. This “rattle‐in‐ball” hybrid architecture enables bifunctional bactericide and photocatalysis capability under both light and dark conditions, as well as mitigated environmental and biological impact in practical use.     

Improved Photocatalytic Activity Using Ternary Au-ZnO/rGO Nanocomposite

In the present study, ternary Au-ZnO/rGO nanocomposite was prepared using a modified polyol protocol. The ternary structure was attained by deposition of both gold nanoparticles (AuNPs) and ZnO NPs on the rGO surface. No surfactants or ligands are used in this chemical process. On the other hand, 1,3-propanediol was used as solvent, reducing agent and surfactant to ensure the formation of NPs and inhibit particles accumulation. The XRD data confirm the successful formation of the three materials and the high crystallinity of the as-prepared sample. Moreover, the XPS measurements confirmed the high purity of the nanocomposite. TEM images show the formation of ternary Au/ZnO/rGO nanostructure. However, Au and ZnO NPs exhibited spherical shape with an average size of 20 nm and homogeneously distribution onto the rGO surface. The ternary Au-ZnO/rGO nanocomposite exhibited optical response in both UV and visible region due to the plasmonic properties of AuNPs. The BET data revealed an increase of the surface area of Au-ZnO/rGO nanocomposite compared to bare ZnO and hybrid Au-ZnO NPs which render it a promising system for high photocatalytic activity. The preliminary photodegradation measurements against MB molecules prove the high performance of the ternary Au-ZnO/rGO nanocomposite to decompose pollutant molecules compared to bare ZnO. The observed photocatalytic activity enhancement could be attributed to the apport given by both plasmonic properties of AuNPs and the high surface area of rGO.

     

Thermochemical Reactions Between PZT and Ag/Pd Powders: Relevance to Cofiring of Multilayer Actuators

Mixtures of Ag_{1− x} Pd _x ( x =0.2, 0.3) and doped PZT ceramic powders have been heat treated in air and the resulting phase content has been analyzed by X-ray diffraction and transmission electron microscopy. Beginning around 400°C, a phase similar to PbPdO₂ is formed on the surface of the Ag_{1− x} Pd _x particles and subsequently decomposes at temperatures <700°C. Consequently, the remaining Ag_{1− x} Pd _x powder becomes significantly silver-rich while the reaction progresses. After decomposition the Pd appears to realloy and the initial Ag_{1− x} Pd _x composition is recovered. We show that the reaction is all but eliminated in a nitrogen atmosphere. The occurrence of this reaction was also investigated in PZT multilayer actuators cofired with Ag_0.7Pd_0.3 electrodes. Transmission electron microscope analysis revealed the presence of distinct crystallites at the electrode–ceramic interface, most likely nucleated from a PbO liquid phase arising from the decomposition of PbPdO₂.     

用EDGE法制备羟基磷灰石/明胶交联纳米复合材料

钙化组织,比如骨头和牙齿,是一种由无机磷灰石纳米晶体嵌入胶原[COL]和非胶原蛋白有机基体以生物和化学结合所构成的复合材料[1,2]。在这些有机基体上的阴离子和阳离子侧链很容易地与磷灰石表面上的钙和磷酸盐相结合。羟基赖氨酸含量较高的骨胶原对羟基磷灰石[Hap]具有优良的化     

Tungsten Oxide Nanorods Array and Nanobundle Prepared by Using Chemical Vapor Deposition Technique

Tungsten oxide (WO₃) nanorods array prepared using chemical vapor deposition techniques was studied. The influence of oxygen gas concentration on the nanoscale tungsten oxide structure was observed; it was responsible for the stoichiometric and morphology variation from nanoscale particle to nanorods array. Experimental results also indicated that the deposition temperature was highly related to the morphology; the chemical structure, however, was stable. The evolution of the crystalline structure and surface morphology was analyzed by scanning electron microscopy, Raman spectra and X-ray diffraction approaches. The stoichiometric variation was indicated by energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy.     

Direct Synthesis of Alumina Nanowires on Ceramic Substrates Using Sn Catalysts

Direct integration of nanostructures into macroscopic substrates is very important for their practical applications. In this work, we report a simple method that can be introduced for the Sn‐catalyzed growth of alumina nanowires on ceramic substrates such as porous disk, monolith, and foam. Our study focuses on the role of the Sn catalysts in the formation mechanisms governing nanowire growth. Using the proposed approach, hair‐ or grass‐like tufts of 20 nm diameter nanowires grow on the surface of the ~3 μm diameter Sn particles, in a tip growth mechanism. The nanowires of α‐phased polycrystalline structure grow and are packed via a complex process involving batch‐by‐batch, branching, and amalgamation growth. The detailed observations reveal that the Sn catalyst is key to tailoring the growth patterns of the nanowires. In addition, cathodoluminescence studies highlight the potential optical applications of the alumina nanowires.     

Refined Model of Electromigration of Ag/Pd Electrodes in Multilayer PZT Ceramics Under Extreme Humidity

The phenomenon of silver electromigration has been examined in multilayer structures comprised of a low-firing PZT-based ceramic with inner Ag_{1− x} Pd _x electrodes (0< x <0.3). Under high humidity and dc bias, the time-to-failure was found to increase significantly with Pd content for x >0.1. Failed samples exhibited metallic-like transport properties including Ohmic behavior and a low temperature coefficient of resistance. Subsequently, electron microscopy of cross-sectioned samples revealed high concentrations of Ag in grain boundaries confirming Ag migration as the failure mechanism. Furthermore, it was found that the failure rate did not improve substantially by replacing a pure Ag anode with a higher Pd composition. This observation appears to conflict with previous conceptual models in which Ag migration originates mainly from the anode. It is suggested that Ag diffusion during sintering results in a background concentration of Ag within the ceramic which later contributes to the electrolytic flux of Ag⁺ ions under high humidity. This effect may be more apparent in low temperature sintered materials where residual grain boundary phases become vulnerable pathways for moisture penetration.     

Flexible IZO/Ag/IZO/Ag multilayer electrode grown on a polyethylene terephthalate substrate using roll-to-roll sputtering

We investigated the optical, electrical, structural, and surface properties of roll-to-roll [R2R] sputter-grown flexible IZO/Ag/IZO/Ag [IAIA] multilayer films on polyethylene terephthalate substrates as a function of the top indium zinc oxide [IZO] thickness. It was found that the optical transmittance of the IAIA multilayer was significantly influenced by the top IZO layer thickness, which was grown on identical AIA multilayers. However, the sheet resistance of the IAIA multilayer was maintained between the range 5.01 to 5.1 Ω/square regardless of the top IZO thickness because the sheet resistance of the IAIA multilayer was mainly dependent on the thickness of the Ag layers. Notably, the optimized IAIA multilayer had a constant resistance change (ΔR/R ₀) under repeated outer bending tests with a radius of 10 mm. The mechanical integrity of the R2R-sputtered IAIA multilayer indicated that hybridization of an IZO and Ag metal layer is a promising flexible electrode scheme for the next-generation flexible optoelectronics.     

Novel Core–Shell Nanostructure in Percolative PZN−PZT/Ag Ferroelectric Composites

Novel percolative PZN?PZT/Ag ferroelectric composites with intragranular structure were prepared with micro‐PZN?PZT and nano‐Ag particles. The typical core–shell nanostructures were systematically investigated by TEM, in which, the nanoscale shells act as interlayers between the Ag cores and the ceramic matrix. Excellent dielectric properties, such as high dielectric constant (ε_r ~16600) and low dielectric loss (< 0.056) were reported. The high dielectric constant originates from the coeffect of “microcapacitors” and Maxwell–Wager–Sillars (MWS) polarization. Especially, the core?shell structure may reinforce the MWS effect. Meanwhile, the insulating interlayers reduce the tunnel current between neighboring Ag cores by causing potential barriers, endowing the nanocomposites with low dielectric loss. This approach can be used to realize a novel material with high dielectric constant over a wide frequency and temperature range.