空心玻璃微球化学镀镍前处理工艺的研究

针对空心玻璃微球化学镀镍,研究了先偶联、再活化的前处理工艺.探讨了偶联处理对活化效果的影响,并通过正交试验确定了最佳偶联条件;采用优化的前处理工艺,再进行化学镀镍,得到镍包覆空心玻璃微球,分别使用扫描电镜(SEM)和X射线能谱仪(EDS)对镀镍层的形貌结构和成分进行了表征.研究发现:空心玻璃微球经过偶联处理以后对钯的吸附能力提高了很多,使得化学镀镍中微球表面的活性点大大增加,得到了包覆完整、均匀、致密的镍镀层.     

Palladium nanoparticle seeded electroless metallization of Al/Al2O3 surfaces

A simple method for the formation of palladium nanoparticles on aluminum and aluminum oxide surface is demonstrated. In the present method, the palladium nanoparticles obtained directly on the solid surface by immersing the specimen in palladium(II)acetate solution followed by reduction to metallic palladium by using sodium hypophosphite. In the investigation, as-received, boiled, electropolished and anodized aluminum was used as substrate. Additionally, the method is combined with the electroless nickel plating, which facilitates two steps metallization technique on the respective surfaces. In these cases, specimens were first immersed in palladium(II)acetate solution followed by immersion in electroless nickel plating solution, where, palladium reduced on the specimen surface providing catalytic site for the subsequent electroless nickel deposition. Using the technique, about 6 to 8.5 µm thick Ni-P metallic layer was deposited on the specimen surface.     

Growth of selenium thin films

Quantitative measurements of the formation and growth of selenium films on sapphire, glass, aluminium and nickel substrates have been made for various substrate temperatures (T) and evaporation times (t) using a scanning electron microscope (SEM). The film formation and growth process was thought to be a mechanism of the adsorption of impinging selenium atoms on the stable clusters, and the growth of these clusters as evaporation continues. The difference in the values of the activation energies for the growth of selenium on different substrates was explained by considering them as apparent energies which contain the adsorption, desorption, surface diffusion and binding energy terms. The experimental results also indicated an increase in there-evaporation of adatoms from the substrates at higher temperatures.     

Image contrast in polarization microscopy of magneto-optical disk data-storage media through birefringent plastic substrates

Using polarized-light microscopy, we have investigated the magnetic domains of perpendicularly magnetized media under several different conditions, including direct observation of the thin-film magnetic layer and observations through the glass or plastic substrates on which the magnetic film was deposited. The results show that the image contrast is reduced with an increasing numerical aperture of the objective lens. They also indicate that the polarization rotation caused by differences between the reflectivity-transmissivity of the p and s components of polarization deteriorate the magnetic image contrast. Furthermore, by comparing the image quality using the same objective lens on samples having different substrates, we found that the images obtained through plastic substrates are worse than those obtained through glass substrates. Birefringence of the plastic substrate is shown to be responsible for the additional degradation of the image contrast.     

Influence of substrates on the formation of the TiSi nanowire by atmosphere pressure chemical vapor deposition

TiSi nanowires were deposited on both Si(111) and glass substrates by using SiH4, TiCl4 and N2 as the Si, Ti precursors and diluted gas respectively through atmosphere pressure chemical vapor deposition (APCVD) method. Effects of the substrates on formation of the nanowires were investigated. The results show that the nanowires can be formed on both Si(111) and glass substrates at ratio of SiH4/TiCl4 of 4. However, the quantities of the TiSi nanowires that formed with glass substrate are less than that with Si(111) substrate. The nanowires formed with glass substrate has length of 2-3 microm and diameters of 15-25 nm while that is 4-5 microm and 25-35 nm respectively with Si(111) substrate. Great quantities of the titanium silicide nanowires with relative higher contents of the C54 TiSi2 crystalline phase underneath can be obtained through improving the deposition conditions.     

Single-Walled Carbon Nanotubes for Flexible Electronics and Sensors

This article reviews the use of electronic quality single-walled carbon nanotubes grown via chemical vapor deposition （CVD） approaches at high temperatures as building blocks for fabricating flexible field-effect devices, such as thin-film transistors （TFTs） and chemical sensors. Dry transfer printing technique is developed for forming films of CVD nanotubes on low-temperature plastic substrates. Examples of TFTs with the use of nanotubes and thin dielectrics and hydrogen sensors with the use of nanotubes decorated with palladium nanoparticles are discussed in detail to demonstrate the promising potentiality of single-walled carbon nanotubes for building high performance flexible devices, which can find applications where traditional devices on rigid substrates are not suitable.     

Designing plastic Cu-based bulk metallic glass via minor addition of nickel

A monolithic Cu-based bulk metallic glass (BMG), having plastic strain of more than 26% together with fracture strength of 2471 MPa, was fabricated by copper mold casting. This plastic strain has never seen in monolithic Cu-based BMGs containing more than 50 at.% Cu. The excellent plasticity is attributed to a large amount of free volume induced by minor addition of nickel, resulting in multiple shear bands formation, branching and interaction.     

Molecular dynamics simulation of incipient plasticity of nickel substrates of different surface orientations during nanoindentation

The present study aims to elucidate the anisotropic characteristics in material responses for crystallographic nickel substrates with (001), (011) and (111) surface orientations during nanoindentation. Molecular dynamic simulation is applied to compensate for the experimental limitation of nanoindentation, particularly for pure nickel substrates. Defect nucleation and evolution in Ni single crystal of these three crystal orientations was examined. Hardness and Young’s modulus are also extracted in different orientations. The Young’s modulus of (111) crystallographic orientation is the largest, while that of (001) surface is the smallest. The sensitivity of the yield point for face centred cubic crystals depends on the crystallographic orientation. The (001) crystallographic orientation reaches the yield point first, while the (111) crystallographic orientation is the most difficult in which to achieve yield. Using a visualisation method of centrosymmetry parameter, the homogeneous nucleation and early evolution of dislocations were investigated, deepening understanding of incipient plasticity at the atomic scale. The present results suggest that defect nucleation and evolution are the root of curve jitter. The indentation depth of the elastic–plastic transition point varies in the different crystallographic orientation models, and appears latest in the (111) model. The strain energy of the substrate exerted by the tip is stored by the formation of homogeneous nucleation and is dissipated by the dislocation slide in the {111} glide plane. The three nickel substrates with different crystallographic orientations exhibit different forms of dislocation propagation.     

Arrays of silicon micro/nanostructures formed in suspended configurations for deterministic assembly using flat and roller-type stamps

The ability to create and manipulate large arrays of inorganic semiconductor micro/nanostructures for integration on unconventional substrates provides new possibilities in device engineering. Here, simple methods are described for the preparation of structures of single crystalline silicon in suspended and tethered configurations that facilitate their deterministic assembly using transfer-printing techniques. Diverse shapes (e.g., straight or curved edges), thicknesses (between 55 nm and 3 μm), and sizes (areas of 4000 μm(2) to 117 mm(2) ) of structures in varied layouts (regular or irregular arrays, with dense or sparse coverages) can be achieved, using either flat or cylindrical roller-type stamps. To demonstrate the technique, printing with 100% yield onto curved, rigid supports of glass and ceramics and onto thin sheets of plastic is shown. The fabrication of a printed array of silicon p(+) -i-n(+) junction photodiodes on plastic is representative of device-printing capabilities.     

Designed Patterning of Mesoporous Metal Films Based on Electrochemical Micelle Assembly Combined with Lithographical Techniques

Mesoporous noble metals and their patterning techniques for obtaining unique patterned structures are highly attractive for electrocatalysis, photocatalysis, and optoelectronics device applications owing to their expedient properties such as high level of exposed active locations, cascade electrocatalytic sites, and large surface area. However, patterning techniques for mesoporous substrates are still limited to metal oxide and silica films, although there is growing demand for developing techniques related to patterning mesoporous metals. In this study, the first demonstration of mesoporous metal films on patterned gold (Au) substrates, prefabricated using photolithographic techniques, is reported. First, different growth rates of mesoporous Au metal films on patterned Au substrates are demonstrated by varying deposition times and voltages. In addition, mesoporous Au films are also fabricated on various patterns of Au substrates including stripe and mesh lines. An alternative fabrication method using a photoresist insulating mask also yields growth of mesoporous Au within the patterning. Moreover, patterned mesoporous films of palladium (Pd) and palladium–copper alloy (PdCu) are demonstrated on the same types of substrates to show versatility of this method. Patterned mesoporous Au films (PMGFs) show higher electrochemically active surface area (ECSA) and higher sensitivity toward glucose oxidation than nonpatterned mesoporous Au films (NMGF).     

Validity requirements of circumferentially notched tensile specimens for the determination of the interfacial fracture toughness of coatings

A simple method was developed for evaluating the interfacial fracture toughness of coatings on substrates using circumferentially notched tensile (CNT) specimens. Mild steel cylindrical substrates of 0°, 15°, 30°, 45° and 60° notch angles with electroplated nickel were tensile tested. A well defined pre-crack was introduced at the interface for the quantitative evaluation of adhesion. In situ acoustic signals and scanning electron microscope were used to analyze the crack initiation and propagation. Finite element analyses were used to evaluate the critical interface energy release rate. The size of the plastic zone was determined for different notch angles to validate application of the linear elastic approach in determining the interfacial fracture toughness. The validity requirements have been proposed for this specimen, considering the yield strength of the coating and substrate, pre-crack position, notch angle and plastic zone size. The obtained interfacial fracture toughness values using CNT specimens was found to be very close to the values obtained by others using standard specimens.     

Catalyst and its diameter dependent growth kinetics of CVD grown GaN nanowires

GaN nanowires were grown using chemical vapor deposition with controlled aspect ratio. The catalyst and catalyst-diameter dependent growth kinetics is investigated in detail. We first discuss gold catalyst diameter dependent growth kinetics and subsequently compare with nickel and palladium catalyst. For different diameters of gold catalyst there was hardly any variation in the length of the nanowires but for other catalysts with different diameter a strong length variation of the nanowires was observed. We calculated the critical diameter dependence on adatoms pressure inside the reactor and inside the catalytic particle. This gives an increasing trend in critical diameter as per the order gold, nickel and palladium for the current set of experimental conditions. Based on the critical diameter, with gold and nickel catalyst the nanowire growth was understood to be governed by limited surface diffusion of adatoms and by Gibbs–Thomson effect for the palladium catalyst.     

Precision compression molding of glass microlenses and microlens arrays--an experimental study

An innovative manufacturing process utilizing high-temperature compression molding to fabricate aspherical microlenses by using optical glasses, such as BK7, K-PG325, and soda-lime glass, is investigated. In a departure from conventional approaches, a unique hollow contactless mold design is adopted. Polished glass substrates and the mold assembly are heated above the glass transition temperature first, followed by initial forming, then annealing. The forming rate is controlled in real time to ensure mold position accuracy. Mold materials used include tungsten carbides, 316 stainless steel, 715 copper nickel, and aluminum alloys. The geometric control of the microlenses or microlens arrays can be precisely controlled by the forming temperature, forming speed, mold design, and annealing time.     

Scalable production of glass flakes via compression in the liquid phase

A comprehensive study on controlled shape formation with high yield of three commercially relevant SiO₂-based amorphous glasses in a stirred media mill is presented. Stressing under well-controlled conditions leads to micron-sized amorphous glass flakes with high aspect ratios. This unique result is quite contrary to the fundamental observation that comminution processes generally result in irregular shaped particles. The influences of glass composition, processing time, stirrer tip speed and grinding media size on the obtained products have been investigated. The size and shape of the obtained glass flakes have been characterized by scanning electron microscopy and atomic force microscopy. The glass flakes exhibit thicknesses as low as 155 nm while the lateral dimensions are well within the micrometer range. Our study shows that particle size reduction occurs within the first hour of grinding. Afterwards plastic deformation of the fragments, which can be accompanied by densification of the glass network, leads to the formation and further thinning of the glass flakes. To demonstrate the quality and applicability of the glass flakes interference pigments were realized by a TiO₂ coating via an aqueous titration process. The presented approach offers a simple, convenient and fully scalable top-down method to produce flake-like particles from various silica glasses. The obtained flakes are suitable substrates for further modifications and applications and the process can be transferred to other materials and glasses with tailor-made chemical compositions.     

Germanium‐Assisted Direct Growth of Graphene on Arbitrary Dielectric Substrates for Heating Devices

Direct growth of graphene on dielectric substrates is a prerequisite to the development of graphene‐based electronic and optoelectronic devices. However, the current graphene synthesis methods on dielectric substrates always involve a metal contamination problem, and the direct production of graphene patterns still remains unattainable and challenging. Herein, a semiconducting, germanium (Ge)‐assisted, chemical vapor deposition approach is proposed to produce monolayer graphene directly on arbitrary dielectric substrates. By the prepatterning of a catalytic Ge layer, the graphene with desired pattern can be achieved conveniently and readily. Due to the catalysis of Ge, monolayer graphene is able to form on Ge‐covered dielectric substrates including SiO₂/Si, quartz glass, and sapphire substrates. Optimization of the process parameters leads to complete sublimation of the catalytic Ge layer during or immediately after formation of the monolayer graphene, enabling direct deposition of large‐area and continuous graphene on dielectric substrates. The large‐area, highly conductive graphene synthesized on a transparent dielectric substrate using the proposed approach has exhibited a wide range of applications, including in both defogger and thermochromic displays, as already successfully demonstrated here.     

Machining of Glass Molds for Manufacturing Plastic Lenses

This paper reports research results on machining of glass molds for manufacturing plastic lenses. Aspherical and spherical plastic lenses are produced by replicating them on glass molds that are first ground (milled) and then lapped and polished. Results of surface texture analysis using the Form Talysurf instrument are presented together with scanning electron micrographs of the machined surfaces. Microstructure analysis conducted using scanning electron microscope reveals ductile streaks on ground (milled) and lapped glass surfaces. Polishing time versus surface roughness curves indicate the familiar knees, after which an increase in polishing time does not improve the surface finish. A moire deflectometer was used to observe fringe patterns on polished surfaces, in order to distinguish between acceptable polished surfaces and defective surfaces.     

On the mechanical weakness of glass seals to nickel-plated Remendur (Fe-Co-2 to 3% V) wire

Poor surface quality of wire can result in leaking glass-to-metal seals in sealed reed contacts. Nickel plating of Remendur reeds can be effective in eliminating this problem. However, the mechanical strength with nickel plated Remendur seals is significantly inferior to that for unplated reed seals. Measurement of breaking loads required for various types of sealed contacts, followed by examination of the fracture interfaces in a scanning electron microscope, indicates that the greater strength of seals with unplated reeds is due to a chemical bond at the Remendur/glass interface caused by interaction of constituents in the alloy with the glass. Furthermore, evolution or production of gases from the nickel plating during sealing causes the formation of large bubbles at the nickel/glass interface which reduce the area of contact and contribute to weakening. Outgassing of the nickel-plated Remendur reeds prior to sealing is impractical because the temperature required to achieve this results in degradation of the magnetic properties of the reeds. Seals made with barium oxide glasses, regardless of the reed material, appear to be stronger than those with the conventional lead oxide glass.     

Stress relief patterns of Co films deposited on circular silicone oil substrates

By using the expansive and mobile properties of silicone oil, circular liquid substrates with varied thicknesses naturally form on clean glass surfaces during deposition. Continuous cobalt (Co) films have been prepared on the circular liquid substrates by a direct current magnetron sputtering method, and the stress relief patterns of the Co films are investigated. The experiment shows that the Co film is susceptible to generating cracks due to thermal expansion of the silicone oil substrate during deposition. After deposition, subsequent cooling of the system creates a high compressive stress in the film, which is relieved by formation of various wrinkling morphologies. Based on the special growth mechanism and mechanical properties of the metal film deposited on a liquid substrate, the structural characteristics of the stress relief patterns and the underlying physical mechanisms are discussed in detail.     

Electron diffraction from periodic arrays of misfit dislocations formed during epitaxial growth

Changes in transmission electron diffraction patterns were examined during the epitaxial growth of copper and palladium on (111) gold substrates. Bicrystal patterns contain discrete reflections which can be explained by diffraction from uniformly strained deposit and substrate layers or by double diffraction between these two layers. Extra reflections are also observed, which vary markedly in intensity with increasing deposit thickness. It is shown that the extra reflections may be ascribed to periodic arrays of perfect edge misfit dislocations which are observed directly in both Cu/(111)Au and Pd/(111)Au films. The interpretation of these results is discussed and their significance for more general studies of epitaxial growth is briefly considered.     

Method for debonding of thin glass substrate and carrier for manufacturing thin flexible displays

Modern displays are becoming light, thin, and even curved and flexible. The thickness of glass substrates used in these displays has been reduced from its original value of 1.1 to 0.7 mm and eventually to 0.5 mm to create thinner displays. Glass substrates with a thickness of <?0.3 mm are extremely thin and fragile, can be easily deformed, and are therefore not suitable for direct incorporation into the display-manufacturing process. Glass-substrate suppliers bond thin glass substrates onto carrier glass substrates to form laminated glass substrates with increased overall thickness. The panel makers then manufacture the display on a laminated glass substrate. The carrier substrate is removed from the display to produce a thin panel. Glass-substrate makers debond the carrier from the thin glass substrate by applying mechanical force. However, the substrate may break during this debonding process. In this study, a novel method for bonding and debonding the carrier and glass substrates is proposed in which gas is injected between the carrier and thin glass substrate to separate them. This method effectively prevents the formation of edge defects in the thin glass substrate caused by breaks during the debonding process. We designed a debonding machine and established steps to debond the laminated glass substrate after a passive matrix organic light-emitting diode fabrication process. The results showed that this method can be used to efficiently debond the laminated glass substrate.