Nonextensive treatment of nucleation and growth in a thin layer

In this study, a generalized method based upon nonextensive statistics is presented for nucleation and growth processes in a thin layer between two interfaces. It is shown that the presented mathematical model, which uses an index called the entropic index that measures the nonextensivity of the physical system, successfully deals with the nucleation and growth processes, and works better than Johnson–Mehl–Avrami–Kolmogorov model. The presented model also contains Austin–Rickett model as a special case.     

The Effect of Space Dimensions on a Generalized Hydrogen-Atom Specific Heat in the Generalized Boltzmann-Gibbs Statistics

In this article, the effect of the space dimensions on the generalized hydrogen-atom specific heat in the generalized Boltzmann-Gibbs statistics is studied. The temperature dependence of the specific heat for a few different values of q and for different low space dimensions using Tsallis statistics is numerically calculated. The results indicate that for a fixed value of q, as the space dimension increases the temperature range where the specific heat has a nonzero value, decreases, while the general behavior of the specific heat does not show any change. Also, there exits a q-independent quantity related to two specific temperatures of the system which is almost linearly dependent on the space dimensions.     

Protein photoimmobilizations on the surface of quartz glass simply mediated by benzophenone

In this paper, photoinduced protein immobilizations on quartz glass slides utilizing benzophenone as photoinitiator without any photoactive group derivatizations involved were developed. Three different methods mediated by benzophenone were investigated, including protein photo-attachment onto untreated glass surface, protein attachment onto glass surface by reacting with pre-photografted maleic anhydride, and protein photo-attachment onto alkylamino silane functionalized glass surface, respectively. Protein immobilizations were characterized by fluorescence microscopy and atomic force microscopy. The preservation of biological activity after protein photo-attachments was confirmed by immunoassays. Area-defined protein immobilization was also primarily investigated. Comparative studies demonstrated that in respect of immobilization density, coverage homogeneities and photo-localization, protein photocoupling to amino-terminated quartz glass surfaces remarkably outperformed other photoinduced methods, as well as one kind of 3-(triethoxysilyl) propyl isocyanate chemical protein immobilization. The feasibility of this protein photo-immobilization on silicon-based materials is promising for widespread application because of its simplicity and effectiveness.     

Effect of surface treatment of nanoclay on the mechanical properties of epoxy/glass fiber/clay nanocomposites

A new method of silane treatment of nanoclays is reported where in the clay is nanodispersed in hydrolyzed silanes. The surface functionalization of Cloisite^® 15A nanoclay has been carried out using two different silane coupling agents: 3-aminopropyltriethoxy silane and 3-glycidyloxypropyltrimethoxy silane using varied amounts of silane coupling agents, e.g. 10, 50, 200, and 400 wt% of clay. The surface modification of Cloisite^® 15A has been confirmed by Fourier transform infrared spectroscopy. The modified clays were then dispersed in epoxy resin, and glass fiber-reinforced epoxy clay laminates were manufactured using vacuum bagging technique. The fiber-reinforced epoxy clay nanocomposites containing silane modified clays have been characterized using small angle X-ray scattering, transmission electron spectroscopy and differential scanning calorimetry. The results indicate that the silane treatment of nanoclay aided the exfoliation of nanoclay and also led to an increase in mechanical properties. The optimized amount of silane coupling agents was 200 wt%. The nanocomposites containing clay modified in 200 wt% of silanes exhibited an exfoliated morphology, improved tensile strength, flexural modulus, and flexural strength. The improved interfacial bonding between silane modified nanoclays and epoxy matrix was also evident from significant increase in elongation at break.     

Nb添加对Cu-Zr非晶合金玻璃转变和晶化动力学的影响

采用铜模吸铸法制备出直径为2 mm的Cu_50.3Zr_49.7-xNb_x(x=0,2)大块非晶合金，利用示差扫描量热分析(DSC)研究了2at%Nb元素添加对Cu-Zr非晶合金玻璃转变动力学和晶化动力学的影响，发现含Nb合金具有较低的脆性指数，和较高的晶化激活能.这表明微量Nb的添加提高了该二元Cu基非晶合金过冷金属液相的热稳定性，从而有利于其非晶合金的形成. 关键词： Cu-Zr非晶合金 Nb添加 玻璃转变动力学 晶化动力学     

Synthesis, characterization of ceria-coated silica particles and their chemical mechanical polishing performance on glass substrate

Nano-sized ceria particles were coated on the silica surface by the precipitation method using ammonium cerium nitrate and urea as precipitant with poly(vinylpyrrolidone) (PVP) as assistant. The structures and compositions of ceria-coated silica particles were characterized using X-ray diffraction (XRD), field-emission scanning microscopy (FE-SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements. The results show that nano-size ceria particles were coated uniformly around the surface of silica particles when PVP was used as assistant during coating process, while without PVP, the ceria particles were grown sparsely on the silica particle surface and many ceria particles grow up through independent nucleation in the solution. Then, the chemical mechanical polishing (CMP) behaviors of the as-prepared ceria-coated silica particles on glass substrate were investigated. The CMP test results suggest that the as-prepared ceria-coated silica particles exhibit higher removal rate than pure silica particles without deteriorating the surface quality. In addition, online coefficient of friction (COF) was conducted during the polishing process. The COF data indicate that the COF values of ceria-coated silica particles are larger than those of pure silica particles due to their surface properties.     

Heterogeneous nucleation and growth of silver nanoparticles on unmodified polystyrene spheres by in situ reduction

The in situ reduction growth of Ag nanoparticles (NPs) on unmodified polystyrene (PS) spheres is investigated via controlling Ag nucleation and growth rates by continuous dripping addition of reductant solution in the absence of surfactants. The sub-micro PS spheres were coated by a uniform coverage of Ag NPs with several shapes like elongated islands, spherical particles, and particle aggregates. The reaction temperature and reductant concentration are demonstrated to influence the crystal structure, distribution, and stability of the Ag NPs on the PS substrates. The heterogeneous nucleation and growth of Ag NPs on PS spheres are found to depend on the inhibition of in-solution reduction and homogeneous nucleation.     

磁控溅射ZnO薄膜的成核机制及表面形貌演化动力学研究

利用原子力显微镜分析了ZnO薄膜在具有本征氧化层的Si(100)和Si(111)基片上的表面形貌 随沉积时间的演化. 通过对薄膜生长形貌的动力学标度表征，研究了射频反应磁控溅射条件 下，ZnO薄膜的成核过程及生长动力学行为. 研究发现，ZnO在基片表面的成核过程可分为初 期成核阶段、低速率成核阶段和二次成核阶段. 对于Si(100)基片，三个成核阶段的生长指 数分别为β₁=1.04，β₂=0.25±0.01，β₃=0.74；对 于Si(11 关键词： ZnO薄膜 磁控溅射 生长动力学 成核机制     

Preparation and growth mechanism of micro spherical ammonium dinitramide crystal based on ultrasound-assisted solvent-antisolvent method

Micro-sized spherical ammonium dinitramide (ADN) crystals are successfully prepared by a facile ultrasound-assisted solvent-antisolvent recrystallization method without introducing any additives. The influences of the volume ratio of solvent to antisolvent, the antisolvent temperature and the ultrasound power on the micro-morphologies and properties of ADN crystals are studied systematically. The changes of morphology, particle size, crystal structure and melting point of the ADN crystals are characterized through scanning electron microscopy (SEM), laser particle size analyzer (LPSA), X-ray diffraction (XRD) and differential scanning calorimetry (DSC), respectively. The results show that the optimal experimental parameters for the ADN crystal of spherical morphology are as follows: the volume ratio of solvent to antisolvent is 1:50, the antisolvent temperature is 20 ℃, and the ultrasound power is 70 W. The predicted hexagonal-flake and spherical morphologies for the ADN are close to the experimental morphologies. The growth mechanism of the spherical ADN crystal changes with supersaturation of the ADN solution. As the degree of supersaturation increases, the growth models of the spherical ADN change from the spiral growth to the rough growth, and the morphologies of ADN change from the large-sized ADN ball to the small-sized ADN ball.     

The fabrication of Ag nanoflake arrays via self-assembly on the surface of an anodic aluminum oxide template

Vertical-aligned Ag nanoflake arrays are fabricated on the surface of an anodic aluminum oxide (AAO) template under a hydrothermal condition for the first time. The porous surface of AAO templates and the precursor solution may play key roles in the process of fabricating Ag nanoflakes. The rim of pores can provide many active sites for nucleation and growth, and then nanoflake arrays gradually form through self-assembly of Ag on the surface of AAO membranes. The product is characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM), and a growth mechanism of nanoflake is deduced. This work demonstrates that it is possible to make ordered nanoarrays without dissolving templates using the hydrothermal method, and this interesting Ag nanoflake arrays may provide a wider range of nanoscale applications.     

The influence of repellent coatings on surface free energy of glass plate and cotton fabric

The aim of this research was to determine the influence of chemical finishes on the surface properties of glass plate, considered as a model homogeneous smooth surface and cotton fabric as a non-ideal heterogeneous rough surface. Microscopic slides and 100% cotton fabric in plain weave were coated with fluorocarbon polymers (FCP), paraffin waxes with zirconium salts (PWZ), methylolmelamine derivatives (MMD), polysiloxanes with side alkyldimethylammonium groups (PSAAC) and aminofunctional polysiloxanes (AFPS). From the goniometer contact angle measurements of different liquids, the surface free energy of the coated glass plates was calculated according to approaches by Owens-Wendt-Kaelble, Wu, van Oss-Chaudhury-Good, and Li-Neumann-Kwok. The results showed that all the coatings decreased the surface free energy of the substrate, which was also influenced by the liquid combination and the theoretical approach used. In spite of the fact that the liquid contact angles were much higher on the coated fabric samples than on glass plates and resulted in the lower values of work of adhesion, a very good correlation between the coatings deposited on both substrates was obtained. The presence of repellent coatings FCP, PWZ and MMD converted the solid surface from polar to highly apolar by masking the functional groups of glass and cellulose. PSAAC and AFPS coatings did not decrease the solid surface free energy to such an extent as the former three coatings due to their monopolar character.     

Effect of gamma-ray irradiation on isothermal crystallization of biodegradable poly(ethylene succinate)

The effects of gamma-ray irradiation on the isothermal crystallization of biodegradable poly(ethylene succinate) (PESu) and the growth behavior of PESu spherulites have been studied by differential scanning calorimetry and polarized optical microscopy. The irradiation doses used in the study are 0, 200, 400, and 600 kGy. The kinetic parameters for the isothermal crystallization have been determined, using the Avrami relationship. The nucleation constants and activation energy for the growth of the PESu spherulites have been analyzed, using the Lauritzen-Hoffman growth theory. Triple melting points have been observed for all the irradiated PESu. The gamma irradiation has no observable effect on the Avrami exponent, and the composite rate constant increases first with the increase of the crystallization temperature, reaches maximum at the crystallization temperature of ~35 °C, and then decreases with the increase of the crystallization temperature for both the non-irradiated and irradiated PESu. There exists a transition of the growth of the PESu spherulites from regime II to regime III. Both the nucleation constants and activation energy increase with increasing the irradiation dose. The gamma irradiation increases the energy barrier for the migration of polymer chains.     

Effect of ZnO on phase emergence, microstructure and surface modifications of calcium phosphosilicate glass/glass-ceramics having iron oxide

The effect of ZnO on phase emergence and microstructure properties of glass and glass-ceramics with composition 25SiO₂-50CaO-15P₂O₅-(10 − x)Fe₂O₃-xZnO (where x = 0, 2, 5, 7 mol%) has been studied. They have been characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). Surface modifications of these glass-ceramics in simulated body fluid have been studied using Fourier transform infrared reflection spectroscopy (FTIR), XPS and SEM. Results have shown a decrease in the fraction of non-bridging oxygen with increase in zinc oxide content. Emergence of crystalline phases in glass-ceramics at different heat treatment temperatures was studied using XRD. When glass is heat treated at 800 °C calcium phosphate, hematite and magnetite are developed as major phases in the glass-ceramics samples with ZnO up to 5 mol%. In addition to these, calcium silicate (Ca₃Si₂O₇) phase is also observed when glass is heat treated at 1000 °C. The microstructure of the glass-ceramics heat treated at 800 °C exhibits the formation of nano-size (40-50 nm) grains. On heat treatment at 1000 °C crystallites grow to above 50 nm size and more than one phase are observed in the microstructure. The formation of thin flake-like structure with coarse particles is observed at high zinc oxide concentration (x = 7 mol%). In vitro studies have shown the surface modifications and formation of Ca-P-rich layer on the glass-ceramics when immersed in simulated body fluids (SBF) for different durations. The bioactive response was found to depend on ZnO content.     

Energetics of Ge nucleation on SiO2 and implications for selective epitaxial growth

We have measured the time evolution of Ge nucleation density on SiO₂ over a temperature range of 673–973 K and deposition rates from 5.1 × 10¹³ atoms/cm² s (5 ML/min) to 6.9 × 10¹⁴ atoms/cm² s (65 ML/min) during molecular beam epitaxy. The governing equations from mean-field theory that describe surface energetics and saturation nucleation density are used to determine the size and binding energy of the critical Ge nucleus and the activation energy for Ge surface diffusion on SiO₂. The critical nucleus size is found to be a single Ge atom over substrate temperatures from 673 to 773 K, whereas a three-atom nucleus is found to be the critical size over substrate temperatures from 773 to 973 K. We have previously reported 0.44 ± 0.03 eV for the Ge desorption activation energy from SiO₂. This value, in conjunction with the saturation nucleation density as a function of substrate temperature, is used to determine that the activation energy for surface diffusion is 0.24 ± 0.05 eV, and the binding energy of the three-atom nucleus is 3.7 ± 0.1 eV. The values of the activation energy for desorption and surface diffusion are in good agreement with previous experiments of metals and semiconductors on insulating substrates. The small desorption and surface diffusion activation barriers predict that selective growth occurring on window-patterned samples is by direct impingement of Ge onto Si and ready desorption of Ge from SiO₂. This prediction is confirmed by the small integral condensation coefficient for Ge on SiO₂ and two key observations of nucleation behavior on the window-patterned samples. The first observation is the lack of nucleation exclusion zones around the windows, and second is the independence of the random Ge nucleation density on patterned versus unpatterned oxide surfaces. We also present the Ge nucleation density as a function of substrate temperature and deposition rate to demarcate selective growth conditions for Ge on Si with a window-patterned SiO₂ mask.     

Effect of surface treatment on sand erosion behavior of glass beads-filled epoxy resin

Effects of the adhesion between filler particle and matrix on the erosion rate were studied in cured epoxy resin filled with glass beads having mean diameter 17 um. In order to observe the effect of adhesion on erosion rate. the filler particles were treated with silane coupling agent, silicone oil and washed by acetone as well. The filler content of the specimen was varied and also the specimens were attacked by different size angular particles. The comparison of each type of specimen shows that by using acetone and silicone oil for surface treatment, the erosion rate is relatively high. Whereas the specimen in which the filler was treated by silane have low erosion rate. The difference of erosion behavior is influenced by impacting particle size and filler content. Using small impacting particles and also low filler content, the erosion behavior between silane and acetone treated was quite different. On the other hand, using large impacting particles and high filler content, the erosion behavior between them was similar.     

Spectroscopic studies of thermal treatment effect on the composition and size of CdS1−xSex nanocrystals in borosilicate glass

The effect of heat treatment parameters on the chemical composition and average size of CdS_1−xSe_x nanocrystals obtained in borosilicate glass by diffusion-limited growth is studied by optical absorption and Raman scattering spectroscopy. An increase of selenium content from 0.75 to 0.83 in the nanocrystals with the heat treatment temperature and duration is observed. Three lowest-energy optical transitions in CdS_1−xSe_x nanocrystals are assigned to corresponding electronic transitions based on the observed dependence of the confinement-related absorption maxima on the nanocrystal size.     

各向异性界面动力学与各向异性表面张力的相互作用对定向凝固过程中深胞晶生长的影响

通过应用匹配渐近展开法和多变量展开法研究了各向异性界面动力学与各向异性表面张力的相互作用对定向凝固过程中深胞晶生长的影响.结果表明:当各向异性界面动力学与各向异性表面张力的偏好方向之间相差角度为θ_0时,θ_0会对深胞晶生长形态产生影响;当0≤θ_0≤π/4时,随着θ_0的增大,深胞晶的指状界面全长减小,深胞晶根部的深度减小,根部附近界面的曲率减小,而曲率半径增大;当π/4≤θ_0≤π/2时,随着θ_0的增大,深胞晶的指状界面全长增大,深胞晶根部的深度增大,根部附近界面的曲率增大,而曲率半径减小.     

Simulation of ultrasound influence on melt convection for the growth of GaxIn1−xSb and Si single crystals by the Czochralski method

The flow simulation for Ga_xIn_1−xSb and Si melts was conducted for quasi-steady conditions. The maximum velocity was under the solid–liquid interface near periphery of the crystals. An introduction of ultrasound into the liquid formed a standing wave channel under the solid–liquid interface, which acted on melt particles. The calculations of convective and ultrasonic forces acting on the particles in the melt showed that the ultrasonic force is much higher than the convective force.     

Effect of surface treatment of magnetic particles on the preparation of magnetic polymer microspheres by miniemulsion polymerization

Surface treated magnetic particles were used to prepare well encapsulated submicron polystyrene/magnetic (PS/Fe₃O₄) composite microspheres via miniemulsion polymerization. The effects of the different surface treatment agents Disperbyk-106, Disperbyk-111, KH550, sodium dodecyl sulfate (SDS) and oleic acid were investigated on the encapsulation of polymer via miniemulsion polymerization. The interface interactions between magnetic particles, dispersants and coupling agents were analyzed from their IR spectra. It was found that Disperbyk-106 was the best dispersant in terms of preparing magnetic polymer microspheres with high encapsulation efficiency. The effect of wet or dry magnetic particles on encapsulation was also discussed.     

A simple model for the growth kinetics of Fe2B iron boride on pure iron substrate

The present work evaluates the growth kinetics of Fe₂B iron boride forming on iron substrate by means of a diffusion model in the temperature range 1223-1323 K. The model takes into account the effect of the boride incubation time during the formation of Fe₂B phase. The parabolic growth constant at the (Fe₂B/Fe) interface and the mass gain generated by this treatment were estimated. Likewise a simple relationship was proposed to describe the variation of the parabolic growth constant as a function of both the temperature and the boron content in the Fe₂B phase. Furthermore, the simulation results show a good agreement with our experimental results.