3D nanoporous nanowire current collectors for thin film microbatteries

Conventional thin film batteries are fabricated based on planar current collector designs where the high contact resistance between the current collector and electrodes impedes overall battery performance. Hence, current collectors based on 3D architectures and nanoscale roughness has been proposed to dramatically increase the electrode-current collector surface contact areas and hence significantly reduce interfacial resistance. The nanorod-based current collector configuration is one of several 3D designs which has shown high potential for the development of high energy and high power microbatteries in this regard. Herein we fabricate a nanoporous nanorod based current collector, which provides increased surface area for electrode deposition arising from the porosity of each nanorods, yet keeping an ordered spacing between nanorods for the deposition of subsequent electrolyte and electrode layers. The new nanostructured 3D current collector is demonstrated with a polyaniline (PANI)-based electrode system and is shown to deliver improved rate capability characteristics compared to planar configurations. We have been able to achieve stable capacities of ~32 μAh/cm(2) up to 75 cycles of charge/discharge even at a current rate of ~0.04 mA/cm(2) and have observed good rate capability even at high current rates of ~0.8 mA/cm(2).     

Simultaneous control of size and surface functionality of silica particle via growing method

Although silane treatment has been studied as a simple and powerful tool to modify the surface of silica particle, there are still several difficulties in terms of controlling surface functionality and size of nanoparticles. Here we develop a growing method to overcome above drawback. The method was processed by continuously injecting precursor using syringe pump. According to the continuous injection, the concentration of precursors in media are properly controlled, and then the continuous injection of precursor promotes the growth of silica particles. When the functional silanes (silane coupling agents) are used, the method can control the amount of surficial functional groups on the silica particle, and can adjust diameter of the particle simultaneously. Furthermore, well-controlled functional silica particles made by growing method are used for catalytic reaction, Knoevenagel reaction, as a solid state catalyst.     

Two steps bulk-surface functionalization of nanoporous alumina by methyl and vinyl-silane adsorption. Evidence for oxide surface highly reactive sites creation

Functionalization of a novel nanoporous monolithic alumina synthesized from amalgam is investigated. The structure is studied by X-ray diffraction, BET, MEB and IR spectroscopy, before and after chemical functionalization by trimethylethoxy silane adsorption and annealing at high temperature. These treatments retain both monolith microstructure and nanostructure while strongly improving material mechanical properties. Allyldimethoxysilane and alcohol adsorption on the annealed samples, proves that highly reactive sites are available for further polymer grafting, as demonstrated by a significant shift of allyldimethoxysilane ν_SiH to 2,215 cm⁻¹ and adsorbed acetate formation. Simple quantum computations on model systems support this conclusion. Chemical processes reported in this paper, allow a nanostructured alumina monoliths functionalization to optimize ceramics-polymer bonds, and to tune new hybrid biomaterial properties.     

Slippery pores: anti-adhesive effect of nanoporous substrates on the beetle attachment system

Traction experiments with adult seven-spotted ladybird beetles Coccinella septempunctata (L.) were carried out to study the influence of surface structure on insect attachment. Force measurements were performed with tethered walking insects, both males and females, on five different substrates: (i) smooth glass plate, (ii) smooth solid Al₂O₃ (sapphire) disc, and (iii–v) porous Al₂O₃ discs (anodisc membranes) with the same pore diameter but different porosity. The traction force of beetles ranged from 0.16 to 16.59 mN in males and from 0.32 to 8.99 mN in females. In both sexes, the highest force values were obtained on smooth solid surfaces, where males showed higher forces than females. On all three porous substrates, forces were significantly reduced in both males and females, and the only difference within these surfaces was obtained between membranes with the highest and lowest porosity. Males produced essentially lower forces than females on porous samples. The reduction in insect attachment on anodisc membranes may be explained by (i) possible absorption of the secretion fluid from insect adhesive pads by porous media and/or (ii) the effect of surface roughness. Differences in attachment between males and females were probably caused by the sexual dimorphism in the terminal structure of adhesive setae.     

Impact Damage of 3D Orthogonal Woven Composite Circular Plates

The damages of 3D orthogonal woven composite circular plate under quasi-static indentation and transverse impact were tested with Materials Test System (MTS) and modified split Hopkinson bar (SHPB) apparatus. The load vs. displacement curves during quasi-static penetration and impact were obtained to study the energy absorption of the composite plate. The fluctuation of the impact stress waves has been unveiled. Differences of the load-displacement curves between the quasi-static and impact loading are discussed. This work also aims at establishing a unit-cell model to analyze the damage of composites. A user material subroutine which named VUMAT for characterizing the constitutive relationship of the 3-D orthogonal woven composite and the damage evolution is incorporated with a finite element code ABAQUS/Explicit to simulate the impact damage process of the composite plates. From the comparison of the load-displacement curves and energy absorption curves of the composite plate between experimental and FEM simulation, it is shown that the unit-cell model of the 3D woven composite and the VUMAT combined with the ABAQUS/Explicit can calculate the impact responses of the circular plate precisely. Furthermore, the model can also be extended to simulate the impact behavior of the 3D woven composite structures.     

Gas-tight alumina films on nanoporous substrates through oxidation of sputtered metal films

The fabrication of ultrathin oxide films without gas leakage was investigated for the application to low-temperature solid oxide fuel cells (SOFCs). Aluminum thin films were deposited onto two types of anodic nanoporous alumina substrates with pore diameter of 20 and 200 nm, respectively, using dc-magnetron sputter at room temperature. By subsequent oxidation at temperatures over 500 °C, the metal films were successfully transformed into oxide films with thickness of about 35 and 410 nm. Volume expansion induced from oxidation of metal resulted in dense thin films that are free from hydrogen permeation.     

三维正交机织复合材料厚向压缩性能试验研究

采用方柱形试样对UHMWPE/乙烯基酯三维正交机织复合材料进行了压缩试验。研究了该类材料的厚向压缩强度和压缩模量与z向增强纤维细度的关系,并讨论了材料的压缩破坏失效模式。结果表明:z向增强纤维细度的增加导致材料厚向压缩性能的下降。降低z向增强纤维束的细度,有利于提高材料厚向抗压性能。三维正交机织复合材料的压缩破坏具有塑性特征。三维正交机织复合材料主要的破坏模式是z向纤维在试样表面的应力集中、纤维束的剥离和剪切破坏。     

Nanomechanical and surface behavior of polydimethylsiloxane-filled nanoporous anodic alumina

In this article, the mechanical and wetting behavior of anodic aluminum oxide (AAO) and nanoporous-filled AAO were investigated using nanoindentation and contact angle measurements. The results showed that the nanoporous AAO was hydrophobic with a contact angle of 105°. The polymer filling affected the surface property and reduced the contact angle to 84°. The effects of the nanoporous filling on the Young’s modulus and the hardness are investigated and discussed. A three-dimensional finite element model was also successfully developed to understand the nanoindentation-induced mechanism. A maximum von Mises stress of 1058 MPa occurred beneath the indenter.     

多巴胺的自聚-附着行为与膜表面功能化

多巴胺(dopamine)是一种生物神经递质,在水溶液条件下,它能在溶解氧的作用下发生氧化-交联反应,形成强力附着于固体材料表面的聚多巴胺复合薄层.基于多巴胺的这一特性,近年来膜技术研究者们通过多巴胺在固体基膜上的自聚-复合,对膜进行表面改性,并以具有反应活性的聚多巴胺复合层为平台,对膜进行进一步的表面修饰,实现膜的功...     

Electron beam surface treatment. Part I: surface hardening of AISI D3 tool steel

The effects of electron beam surface hardening treatment on the microstructure and hardness of AISI D3 tool steel have been investigated in this paper. The results showed that the microstructure of the hardened layer consisted of martensite, a dispersion of fine carbides and retained austensite while the transition area mainly consisted of tempered sorbite. Also, the microhardness of the hardened layer on the surface increased dramatically compared to that of base material. Finally, the hardening response of AISI D3 tool steel to electron beam surface treatment is closely related to the scanning speed of the electron beam.     

Surface functionalization of silver nanoparticles: novel applications for insect vector control

Every day, people and animals contract debilitating and life threatening diseases due to bites from infected flies, ticks, and mosquitoes. The current methods utilized to fight against these diseases are only partially effective or safe for humans and animals. When it comes to insect vector control, a conceptual paradigm shift is urgently needed. This work proposes a novel synthetic scheme to produce a nanoparticle-pesticide core-shell conjugate to be used as an active agent against arthropod vectors, such as mosquitoes. As a proof of concept, we conjugated nanosilver to the pyrethroid pesticide deltamethrin. First, electron microscopy and Fourier transform infrared spectroscopy verified the presence of a 15 nm nanosilver core surrounded by deltamethrin. Second, when the conjugate was exposed to mosquitoes for a 24 h bioassay, mortality was observed at 9 × 10(-4) M. Silver was detected in the hemolymph of mosquitoes exposed to the conjugate. We concluded that the newly developed nanoconjugate did not inactivate the primary function of the pesticide and was effective in killing mosquitoes at low concentrations. These results demonstrate the potential to use nanoparticle surfaces to kill insects, specifically vectors of human pathogens.     

Controlled functionalization of graphene oxide through surface modification with acetone

The facile method to functionalize graphene oxide through surface modification with acetone was studied and improved. The resulting nanomaterials showed variable characteristics as the surface energy could be tailored according to the combination (proportion of H₂O to acetone) of mixed solvent under sonication. Stability test and contact angle measurement showed that the treated graphene oxide exhibited different dispersibility and wettability. SEM images of graphene oxide films corroborated the changes in chemical composition of the sheets. FT-IR, XPS, and TGA observation provided direct evidence for chemical composition changes occurred on the surface. The presence of alkyl chain could decrease the surface energy and obviously control the hydrophilicity of the graphene oxide sheets. These results will provide significant guidance for the study of graphene-based bio-materials and nano-composites.     

Characteristics evaluation of calcium carbonate particles modified by surface functionalization

Calcium carbonate (CaCO₃) particles were modified by a direct blending method using different coupling agents. The changes in the CaCO₃ particles were determined using different techniques. Compared with pristine particles, the modified CaCO₃ particles show good dispersion, particularly those modified by γ-methacryloxypropyl trimethoxy silane. Results of the thermogravimetric analysis indicated that the coupling agents were adsorbed or anchored on the surface of the CaCO₃ particles, thereby hindering aggregation. The formation of covalent bonds [CaOSi] or [CaOTi] was verified using Fourier transform infrared spectroscopy and X-ray diffraction. The modified CaCO₃ particles showed more stable colloidal dispersion in ethyl acetate than that of pristine CaCO₃ particles. Some silane or titanate coupling agents can be combined with CaCO₃ by covalent bonds, thereby changing the surface properties of CaCO₃ and enhancing dispersion in many organic media. The hydroxyl groups on the surface of CaCO₃ particles can interact with silanol groups or titanate coupling agents forming an organic coating layer.     

多壁碳纳米管的表面功能化及分散性研究

多壁碳纳米管(MWCNTs)分别经混合、强酸氧化浸泡和酰氯化处理后,再与9,10-二氢-9-氧杂-10-磷杂菲-10-氧化物(DOPO)的衍生物(DHDOPO)进行接枝反应得到表面功能化的MWCNTs。利用傅里叶变换红外光谱仪(FT-IR)、透射电子显微镜(TEM)、扫描电子显微镜(SEM)、热重分析仪(TGA)、紫外-可见分光光度仪(UV-Vis)和沉降实验等分别表征改性前后MWCNTs的结构和表面形态,估算DHDOPO在MWCNTs表面的相对接枝率,研究改性前后MWCNTs在乙醇中的分散性。结果表明,MWCNTs经混合强酸氧化后表面出现羧基;DHDOPO在MWCNTs上的相对接枝率为51%;混合强酸氧化和表面接枝DHDOPO的MWCNTs在无水乙醇中具有良好的分散性。     

Selective surface functionalization of silicon nanowires via nanoscale joule heating

In this letter, we report a novel approach to selectively functionalize the surface of silicon nanowires located on silicon-based substrates. This method is based upon highly localized nanoscale Joule heating along silicon nanowires under an applied electrical bias. Numerical simulation shows that a high-temperature (>800 K) with a large thermal gradient can be achieved by applying an appropriate electrical bias across silicon nanowires. This localized heating effect can be utilized to selectively ablate a protective polymer layer from a region of the chosen silicon nanowire. The exposed surface, with proper postprocessing, becomes available for surface functionalization with chemical linker molecules, such as 3-mercaptopropyltrimethoxysilanes, while the surrounding area is still protected by the chemically inert polymer layer. This approach is successfully demonstrated on silicon nanowire arrays fabricated on SOI wafers and visualized by selective attachment of gold nanoparticles.     

All-(111) surface silicon nanowires: selective functionalization for biosensing applications

We demonstrate the utilization of selective functionalization of carbon-silicon (C-Si) alkyl and alkenyl monolayers covalently linked to all-(111) surface silicon nanowire (Si-NW) biosensors. Terminal amine groups on the functional monolayer surfaces were used for conjugation of biotin n-hydroxysuccinimide ester. The selective functionalization is demonstrated by contact angle, X-ray photoelectron spectroscopy (XPS), and high-resolution scanning electron microscopy (HRSEM) of 5 nm diameter thiolated Au nanoparticles linked with streptavidin and conjugated to the biotinylated all-(111) surface Si-NWs. Electrical measurements of monolayer passivated Si-NWs show improved device behavior and performance. Furthermore, an analytical model is presented to demonstrate the improvement in detection sensitivity of the alkyl and alkenyl passivated all-(111) Si-NW biosensors compared to conventional nanowire biosensor geometries and silicon dioxide passivation layers as well as interface design and electrical biasing guidelines for depletion-mode sensors.     

Fatigue of a 3D Orthogonal Non-crimp Woven Polymer Matrix Composite at Elevated Temperature

Tension-tension fatigue behavior of two polymer matrix composites (PMCs) was studied at elevated temperature. The two PMCs consist of the NRPE polyimide matrix reinforced with carbon fibers, but have different fiber architectures: the 3D PMC is a singly-ply non-crimp 3D orthogonal weave composite and the 2D PMC, a laminated composite reinforced with 15 plies of an eight harness satin weave (8HSW) fabric. In order to assess the performance and suitability of the two composites for use in aerospace components designed to contain high-temperature environments, mechanical tests were performed under temperature conditions simulating the actual operating conditions. In all elevated temperature tests performed in this work, one side of the test specimen was at 329 °C while the other side was open to ambient laboratory air. The tensile stress-strain behavior of the two composites was investigated and the tensile properties measured for both on-axis (0/90) and off-axis (±45) fiber orientations. Elevated temperature had little effect on the on-axis tensile properties of the two composites. The off-axis tensile strength of both PMCs decreased slightly at elevated temperature. Tension-tension fatigue tests were conducted at elevated temperature at a frequency of 1.0 Hz with a ratio of minimum stress to maximum stress of R = 0.05. Fatigue run-out was defined as 2 × 10⁵ cycles. Both strain accumulation and modulus evolution during cycling were analyzed for each fatigue test. The laminated 2D PMC exhibited better fatigue resistance than the 3D composite. Specimens that achieved fatigue run-out were subjected to tensile tests to failure to characterize the retained tensile properties. Post-test examination under optical microscope revealed severe delamination in the laminated 2D PMC. The non-crimp 3D orthogonal weave composite offered improved delamination resistance.     

Synthesis and surface acoustic wave properties of AlN films deposited on LiNbO3 substrates

The c-axis-oriented aluminum nitride (AlN) films were deposited on z-cut lithium niobate (LiNbO₃) substrates by reactive RF magnetron sputtering. The crystalline orientation of the AlN film determined by x-ray diffraction (XRD) was found to be dependent on the deposition conditions such as substrate temperature, N₂ concentration, and sputtering pressure. Highly c-axis-oriented AlN films to fabricate the AlN/LiNbO₃-based surface acoustic wave (SAW) devices were obtained under a sputtering pressure of 3.5 mTorr, N₂ concentration of 60%, RF power of 165 W, and substrate temperature of 400°C. A dense pebble-like surface texture of c-axis-oriented AlN film was obtained by scanning electron microscopy (SEM). The phase velocity and the electromechanical coupling coefficient (K²) of SAW were measured to be about 4200 m/s and 1.5%, respectively. The temperature coefficient of frequency (TCF) of SAW was calculated to be about -66 ppm/°C