Rapid replication of nanostructures made with a polymer using simple injection molding

It is possible to fabricate nanostructures of 25.5 nm by replication using injection molding. In this study, a silicon calibration grating was used as a mold insert to replicate high‐quality nanostructures with a simple custom‐made injection machine. The replicated grating with 25.5‐nm nanofeatures made with a polymer was of high quality when a high mold temperature was employed and the mold was evacuated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Formation of Expandable Mica from Talc Using the Intercalation Procedure

To investigate the transformation process from talc to expandable micas, mixtures of talc and Na₂SiF₆ were heated from 600° to 900°C and air-quenched at 50°C intervals. The air-quenched product at 800°C mainly consisted of expandable micas with a basal spacing of 1.25 nm, nonexpandable materials with a basal spacing of 0.96 nm, and a small amount of talc used as the starting material. A lattice fringe image by HRTEM of the product shows that the layer spacing at the edges surfaces is about 1.2 nm, but the layer spacing inside of the particles is close to that of talc. Such a nanostructure indicates a topotactic reaction from talc to expandable micas and confirms that Na⁺ ions intercalate into the structure from the edge to the core.     

电沉积Ni-W梯度镀层及其结构表征

The Ni-W gradient deposit with nano-structure was prepared by an electrochemical deposition method.X-ray diffraction (XRD) and energy dispersive X-ray analysis (EDXA) indicate that the crystallite size of the deposit decreases from 10.3nm to 1.5nm and the crystal grating aberrance increases with the increase of W content in the growing direction of the deposit. The structure of deposit changes from crystalline to amorphous stepwise with associated increase of crystal grating aberrance, and presents gradient distribution. These show that the deposit isgradient with nano-structure.     

Synthesis of multilayered hexagonal boron nitride microcrystals as a potential hydrogen storage element

Top-down approach has been used to synthesize pure, highly crystalline, multilayered micron size crystals of hexagonal boron nitride (BNMCs) at the top of Silicon substrate at 800 °C by using bulk boron nitride powder as a precursor. The synthesized crystals have different interlayers spacing from left to right (0.33 nm, 0.37 nm and 0.35 nm) and at the center (~0.24 nm). The former spacing corresponds to d₍₀₀₂₎ spacing whereas the later corresponds to d₍₀₁₀₎ spacing in h-BN. The sharpness of the peaks in XRD, Raman and FTIR spectrums correspond to highly crystalline nature of BNMCs whereas the locations of the peaks verify the h-BN nature of BNMCs. The B-N bonded BNMCs with larger surface area can be an excellent choice as a hydrogen storage element.     

Enhancement of dye-sensitized photocurrents by gold nanoparticles: effects of dye-particle spacing

Photocurrents of a ruthenium dye-TiO(2) system are enhanced by gold nanoparticles (100 or 40 nm diameter) embedded in TiO(2). As dye-particle spacing decreases to 10 nm, enhancement factor and intensity of localized electric fields at the TiO(2) surface increase. A further decrease in the spacing suppresses the enhancement.     

Graphite oxide intercalation compounds with rotator hexagonal order in the intercalated layers

Graphite oxide intercalation compounds (GOIC), exhibiting a large distance between graphite oxide sheets as well as a long-range order in the organization of guest species, are obtained by intercalation of organic cations containing two long hydrocarbon tails. In particular, graphite oxide layers with interlayer spacing of 0.84 nm, when ionically bonded with cations with two C18 chains, lead to GOIC with interlayer spacing of 3.4 nm and with a hexagonal rotator order in the packing of the long hydrocarbon tails. The intercalation of a second guest species with one or two long hydrocarbon tails not only leads to a further large increase of the interlayer spacing (from 3.4 nm up to 5.8 nm, for guests with C18 alkyl chains) but also, surprisingly, improves the order in the stacking of the layers as well as in the organization of the hydrocarbon chains in the interlayer space. X-ray diffraction measurements on powders and oriented films indicate that these ordered GOIC present intercalate structures with inclined and perpendicular bilayers of guest molecules. Differential scanning calorimetry associated with X-ray diffraction measurements show the occurrence of reversible loss of the hydrocarbon rotator order, which can be associated with significant changes of the interlayer spacing.     

Stearyl Amine Ethoxylate (SAM) Grafted Montmorillonite Clay-Styrene Butadiene Rubber (SBR) Nanocomposites

The present study describes the modification of montmorillonite clay (kunipia F) surface by grafting Stearyl Amine Ethoxylate (SAM). Wide-angle X-ray diffraction (WAXD) and transmission electron microscopy (TEM) provided the evidence of formation of a nanocomposite. The interlayer spacing of the kunipia clay was increased from 1.22 nm (unmodified) to 1.53 nm (modified). The TEM study revealed the intercalated and partially exfoliated nature of the nanocomposites. When the modified clay was compounded with SBR rubber, the interlayer spacing was further increased to 1.88 nm. Remarkable improvements in the mechanical properties were found by the addition of a small amount of modified clay.     

Holographic polymer dispersed liquid crystals (HPDLCs) containing triallyl isocyanurate monomer

The morphology and corresponding performance of holographic polymer dispersed liquid crystals (HPDLCs) based on thiol-ene polymer are dependent on a number of factors including the gel point conversion of the polymer, polymerization kinetics, and extent of liquid crystal (LC) phase separation. Previous research of HPDLC reflection gratings made from thiol-allyl ether polymer indicates that increasing polymerization rate in systems with moderate gel point conversion can improve diffraction efficiency (DE). This work examines HPDLC reflection gratings that contain the ene monomer triallyl isocyanurate (TATATO). In HPDLCs, thiol-TATATO polymerization is two times faster than the thiol-ene polymerization of triallyl ether. By substituting TATATO for triallyl ether, the LC droplet size within HPDLC reflection gratings decreases from 100 nm to 25 nm. The dramatic reduction in LC droplet size for thiol-TATATO HPDLCs increases baseline transmission from 55% in thiol-triallyl ether HPDLCs to 90% at 450 nm. Unfortunately, the DE of thiol-TATATO HPDLCs is only approximately 10% due to poorly defined lamellae in the grating morphology. As determined with real-time IR (RTIR) spectroscopy, thiol-TATATO HPDLCs have significantly faster LC demixing kinetics in comparison to thiol-allyl ether HPDLCs. During holographic photopolymerization, the increased rate of LC demixing causes formation of LC droplets throughout the grating. The low DE of thiol-TATATO HPDLCs can be improved by mixing TATATO and allyl ether monomer. The morphology of ternary thiol-ene HPDLC formulations containing TATATO and allyl ether has a well-defined grating structure due to increased LC solubility in the system, an average LC droplet size of 50 nm, and baseline transmission of nearly 85% at 450 nm.     

溶液法制备有机蛭石

为了获得层间距较大的有机蛭石,将蛭石在酸介质中,用十六烷基三甲基溴化铵(CTAB)作阳离子交换剂,以1.5倍阳离子交换容量与蛭石进行阳离子交换反应。通过X衍射实验,将有机化蛭石前后情况进行对比分析。结果表明:蛭石通过有机化之后,层间距由1.76 nm增大至4.01 nm。通过分析之后得出,蛭石有机化的影响因素主要是有机化环境的和蛭石原料形态。     

Carbons from furan-polymers prepared in the presence of a double-chain amphiphile

Furfuryl alcohol was polymerized in the presence of a double-chain amphiphile using malonic acid or phosphoric acid as the catalyst, leading to an aggregate of spherical particles with a long period of 2.6 nm. On calcination at 1000 °C in nitrogen gas, the polymer particles were converted into lamella-patterned carbons with a long spacing of some micrometers that are composed of carbon layers 0.4 nm in spacing. The lamella-patterned carbon particles were further developed into a highly ordered structure in an appreciable portion on calcination at 2800 °C in argon gas. The present results demonstrate that the presence of a double-chain amphiphile in the polymerization process is effective for the synthesis of such a structurally modified carbon from non-graphitizable furan polymers.     

The gram-scale synthesis of carbon onions

The combustion of naphthalene has been found to yield gram-scale quantities of carbon onions that are free of impurities and furthermore without the use of catalysts. X-ray diffraction (XRD) indicates that the interlayer spacing between concentric shells of the carbon onions is not uniform across the particle; rather it decreases from a graphite-like 0.34 nm and approaches a diamond-like 0.29 nm interlayer spacing towards the inner layers. The dispersion in the interlayer spacing is believed to result from differing external pressures exerted on the individual nanometer-sized graphitic membranes during formation of the onions. Electron microscopy techniques such as high-resolution transmission electron microscopy (HRTEM) and scanning electron microscopy demonstrate the extensive formation of carbon onions. The HRTEM indicates that the onions consist of 50–54 shells, found to be in good agreement with the XRD data.     

Improving optical and electrical performances of aluminum-doped zinc oxide thin films with laser-etched grating structures

A laser etching method was performed to achieve the dual purpose of fabricating grating structures and laser annealing on aluminum-doped zinc oxide (AZO) thin films, and thus improve the film photoelectric performances. Different line spacings and laser fluences were adopted to systematically explore the optimal laser etching condition. Too narrow line spacings or too high laser fluences led to light reflections at the grating external surface to cause more light dissipation, and too wide line spacings or too low laser fluences resulted in relatively small total grating lateral areas being detrimental to multiple internal light reflections. Moreover, too narrow line spacings brought about laser-caused lattice disorder and too high laser fluences produced laser-ablated spots or overburned traces. Therefore, using the medium line spacing and laser fluence, e.g. 40 μm and 0.6 J/cm² in the present work, was more suitable for synchronously realizing grating structure fabrication and laser annealing. The corresponding AZO film exhibited the maximum figure of merit of 2.89 × 10^?2 Ω^?1, which was 1.6 times that of the untreated AZO film. This study is expected to expand performance improvement methods of TCO films and promote the application of laser-etched grating structures.     

Chromophore concentration effect on holographic grating formation efficiency in novel azobenzene‐functionalized polymers

Optically active photochromic poly(amideimide)s containing azobenzene side groups in the repeating unit were prepared. The polymers were designed and synthesized specifically for this work in order to evaluate chromophore concentration effect on holographic grating recording. The poly(amideimide)s with mono‐ and bis‐azobenzene moieties were obtained via direct high temperature polycondensation and compared with respect to their ability of diffraction grating formation due to the light‐induced optical anisotropy effects. Holographic gratings were fabricated in polymer films upon exposure to an interference pattern of two polarized Ar⁺ laser beams at 514.5 nm wavelength. Different geometries of laser beams polarization were applied. It should be emphasized that although the azobenzene moieties are rigidly connected to the polymers backbone, some of polymers exhibited the unusually high light diffraction efficiency of around 40%. The created surface relief gratings (SRGs) were successfully observed using the atomic force microscopy (AFM). AFM images show regularly defined and aligned grating structures. It should be stressed that the SRGs with maximum of relief height up to 260 nm in polyimide derivatives with side azobenzene group were observed for the first time. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

High performance surface-enhanced Raman scattering substrates of Si-based Au film developed by focused ion beam nanofabrication

ABSTRACT: A novel method with high flexibility and efficiency for developing SERS substrates is proposed by patterning nanostructures on Si substrates using Focused Ion Beam Direct Writing (FIBDW) technology following with precise thermal evaporation of gold film on the substrate. The effect of SERS on the substrate was systematic investigated by optimizing the processing parameters and the gold film thickness. The results proved that small dwell time could improve the machining accuracy and obtained smaller nanogap. The Raman-enhanced performance of the substrate was investigated with 10-6 mol/L Rhodamine 6G solution. It was indicated that the elliptic nanostructures with 15nm spacing on Si substrates, coated with approximate 15nm thickness gold film have exhibited a high-enhanced performance. But dramatic performance degradation was found as the gold film thickness further increased, which most probably resulted from changes of the nanostructures' morphological such as elliptical tip and spacing. To avoid the morphological changes effectively after depositing gold film, optimization design of the nanostructures for FIBDW on Si substrates was proposed. Besides, a similar phenomenon was found when the gold film was less than 15nm because there was little gold remaining on the substrate. The method proposed in this paper shows a great potential for the higher performance SERS substrates development, which can further reduce the spacing between hot spots.     

X‐ray diffraction studies and phase volume determinations in poly(ethylene glycol)–montmorillonite nanocomposites

Poly(ethylene glycol)–montmorillonite nanocomposites were prepared by both solution and melt intercalation methods with a range of polymer molecular weights and at a range of polymer loadings. Particular attention was given to the reliability of low‐angle X‐ray diffraction results for basal plane spacing and a sound correlation between three diffractometers was obtained (±0.005 nm). Expansion of the basal plane spacing from 1.23 nm to 1.82 nm by solution intercalation was independent of polymer molecular weight in the range 300–20 000. Furthermore, the clay expansion was independent of the method of intercalation; melt intercalation also gave d₀₀₁ = 1.82 nm irrespective of polymer molecular weight. The maximum amount of polymer intercalated by clay and the maximum loading of clay that polymer can sustain were also studied for the determination of nanocomposite formulations. The confined polymer exerts a reduced effective density (670 kg m^?3) in the galleries. Copyright © 2005 Society of Chemical Industry     

Unusual exfoliation of layered silicate clays by non-aqueous amine diffusion mechanism

The organic ionic exchange intercalation of smectite clays is conventionally performed in water swelling conditions. Here we report a different mechanism for modifying the smectite clays in alcohol solvents. The modification of sodium montmorillonite with poly(oxyethylene-oxypropylene)-amines (POA-amine) were compared for the differences between in water and in alcohol. In water, the intercalation of hydrophobic poly(oxypropylene)-rich amines in the silicate galleries expands the interlayer spacing up to 10 nm and even to exfoliation (featureless in X-ray diffraction pattern) with over 5 amine equivalents, where as hydrophilic poly(oxyethylene)-rich amines could only intercalate in a low spacing of 1.8 nm. On the other hand, all of the POA-amines in isopropanol afford the exfoliation with over, 3 amine equivalents. The mechanism of this unexpected exfoliation is explained by the thermodynamic formations of an imaginary membrane surrounding the clay units, followed by amine diffusion from the solvent into the clay galleries.     

Phase structure in segmented polyurethanes having fatty acid-based soft segments

Structural studies on two segmented polyurethanes prepared from modified oleic acid soft segments and butane diol/diphenylmethane diisocyanate hard segments, were performed. Polyurethanes were thermoplastic elastomers with 50% and 70% soft segment concentration (SSC) for TPU-50 and TPU-70, respectively. DMA revealed the co-continuous morphology in TPU-50 and dispersed hard domains in the soft matrix in TPU-70. AFM showed micron size globules in TPU-70 ascribed to hard segment-rich superstructures. Alternating small soft and hard domains were present in TPU-50, with ～15 nm lateral dimensions and local modulus deviations from 40 to 50 MPa, consistent with co-continuous morphology. The dispersed hard domains in the soft matrix of TPU-70, and co-continuous phases in TPU-50 morphology was confirmed. USAXS showed the domain spacing of TPU-50 was about 13.3 nm. TPU-70 demonstrated domain spacing of about 11.3 nm. USAXS revealed that the interface between phase-separated domains exhibited surface-fractal-like behavior.     

Iridium wire grid polarizer fabricated using atomic layer deposition

In this work, an effective multistep process toward fabrication of an iridium wire grid polarizer for UV applications involving a frequency doubling process based on ultrafast electron beam lithography and atomic layer deposition is presented. The choice of iridium as grating material is based on its good optical properties and a superior oxidation resistance. Furthermore, atomic layer deposition of iridium allows a precise adjustment of the structural parameters of the grating much better than other deposition techniques like sputtering for example. At the target wavelength of 250 nm, a transmission of about 45% and an extinction ratio of 87 are achieved.     

Field emission characteristics of a single free standing carbon nanotube with gate electrode

In this paper, we have constructed and analyzed the field emission behavior of a single vertically aligned free standing carbon nanotube (CNT) with a gate electrode in order to verify the feasibility of using a single CNT as the low-voltage field emission electron source. The single vertically aligned CNT with gate electrode was fabricated by combining optical lithography, electron beam lithography (EBL) and inductively coupled plasma chemical vapor deposition (ICP-CVD) processes. A self-aligned process with a single mask was utilized to define the gated structure and the nano-size catalyst for CNT growth. A single vertically aligned CNT was then grown within the gate hole by ICP-CVD. The length-to-diameter ratio of CNT could be varied by adjusting the e-beam exposure time, and the CNT height was controlled to equal to the gate-to-cathode spacing (800) nm in one gated device and less than the spacing (530 nm) in another device. The field emission characteristics of the integrated gate electrode devices were then measured under a scanning electron microscopy (SEM) with a three-axis nano-positioning device. The turn-on field of the gated devices with 800 and 530 nm height CNT were 2.77 and 3.57 V/μm, respectively, with applying − 10 V gate voltage, and 0 V anode voltage.     

表面活性剂和硅烷偶联剂有机复合改性蒙脱土的制备及性能表征

为增加蒙脱土与有机物的相容性,采用十六烷基三甲基溴化铵(CTAB)与硅烷偶联剂(KH-560)对蒙脱土进行了有机复合改性。X-射线衍射和红外光谱的结果表明,CTAB已插入蒙脱土片层,平均层间距离从1.54 nm增大到3.98 nm和2.08 nm,而KH-560未插入蒙脱土片层,只是覆盖在蒙脱土表面,未改变蒙脱土的插层结构;分散性实验表明,表面活性剂和硅烷偶联剂有机复合改性的蒙脱土在苯乙烯、液体石蜡中的分散性好于其他改性蒙脱土;有机复合改性不仅增大了蒙脱土层间距,且改善了蒙脱土与聚氯乙烯的界面效果,提高了蒙脱土在聚氯乙烯基体中的分散均匀性,从而使聚氯乙烯/蒙脱土复合材料玻璃化转变温度的提高和力学性能的改善更明显。