Phase Behavior and dewetting for polymer blend films studied by in situ AFM and XPS: From thin to ultrathin films

In this work, the film thickness (l(0)) effect on the phase and dewetting behaviors of the blend film of poly(methyl methacrylate)/poly (styrene-ran-acrylonitrile) (PMMA/SAN) has been studied by in situ atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The thinner film shows the more compatibility of the blend, and the phase separation of the film occurs at l(0) > 5R(g) (radius of gyration). An initially time-independent q*, the characteristic wavenumber of the phase image, which is in good agreement of Cahn's linearized theory for the early stage of spinodal decomposition, has been obtained in real space and discussed in detail. For 5R(g) > l(0) > 3R(g), a "pseudo-dewetting/(phase separation + wetting)" behavior occurs, where the pseudo-wetting is driven by the concentration fluctuation mechanism. For 10 < 3R(g), a "real dewetting/(phase separation + wetting)" behavior occurs.

IN-SITU AFM STUDY OF THE SURFACE-MORPHOLOGY OF POLYPYRROLE FILM

In this paper we focus on the surface morphology of polypyrrole film by using in situ atomic force microscopy (AFM). The formation process of polypyrrole film and the transformation process of the film from the oxidized to reduced state were clearly observed.

In situ study of nanostructure and morphological development during the crystal-mesophase transition of poly(di-n-hexylsilane) and poly(di-n-butylsilane) by X-ray and hot-stage AFM

Nanostructure and morphology and their development of poly(di-n-hexylsilane) (PDHS) and poly(di-n-butylsilane) (PDBS) during the crystal-mesophase transition are investigated using small angle X-ray scattering (SAXS), wide angle X-ray diffraction and hot-stage atomic force microscopy. At room temperature, PDHS consists of stacks of lamellae separated by mesophase layers, which can be well accounted using an ideal two-phase model. During the crystal-mesophase transition, obvious morphological changes are observed due to the marked changes in main chain conformation and intermolecular distances between crystalline phase and mesophase. In contrast to PDHS, the lamellae in PDBS barely show anisotropy in dimensions at room temperature. The nonperiodic structure and rather small electronic density fluctuation in PDBS lead to the much weak SAXS. The nonperiodic structure is preserved during the crystal-mesophase transition because of the similarity of main chain conformation and intermolecular distances between crystalline phase and mesophase.

Effect of in situ thermal treatment during growth on crystal quality of GaN epilayer grown on sapphire substrate by MOVPE

GaN epilayers on sapphire substrate grown by metalorganic vapor-phase epitaxy (MOVPE) in a horizontal-type low-pressure two-channel reactor were investigated. Samples were characterized by X-ray diffraction (XRD), Raman scattering, atomic force microscopy (AFM) and photoluminescence (PL) measurements. The influence of the temperature changes between low temperature (LT) deposited GaN buffer and high temperature (WT) grown GaN epilayer on crystal quality of epilayer was extensively studied. The effect of in situ thermal annealing during the growth on improving the GaN layer crystal quality was demonstrated and the possible mechanism involved in such a growth process was discussed. (C) 2001 Elsevier Science B.V. All rights reserved.

Microstructure and wear resistance of in situ TiCp composite coating by laser cladding

A new in situ method was realized by one step laser cladding to produce Ni-base alloy composite coating reinforced by in situ reacted and gradiently distributed TiCp particles. The submicron TiCp particles were formed and uniformly distributed because of the in situ reaction and trapping effect under the rapid solidification condition. And, TiCp particles were of gradient distribution on a macro scale and their volume fraction increased from 1.86% at the layer/substrate interface to a maximum 38.4% at the surface of the layer. Furthermore, the in situ generated TiCp/gamma-Ni interfaces were free from deleterious surface reactions. Additionally, the clad coating also revealed a high microhardness of gradient variation with the layer depth and the superior abrasive wear resistance.

Laser Melted TiC Reinforced Nickel Aluminide Matrix in situ Composites

Titanium carbide reinforced nickel aluminide matrix in situ composites were produced using a newly patented laser melting furnace. Microstructure of the laser melted TiC/(Ni3Al–NiAl) in situ composites was characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and transmission electron microscopy (TEM). Results showed that the constituent phases in the laser melted in situ composites are TiC, Ni3Al and NiAl. Volume fraction of TiC and NiAl increase with increasing content of titanium and carbon. The growth morphology of the reinforcing TiC carbide has typically faceted features, indicating that the lateral growth mechanism is still predominant growth mode under rapid.

Adlayer Structures of DL-Homocysteine and L-Homocysteine Thiolactone on Au(111) Surface: an in situ STM Study

The adsorption Of DL-homocysteine (Hcy) and L-homocysteine thiolactone (HTL) on Au(1 1 1) electrode was investigated in 0.1 M HClO4 by cyclic voltammetry and in situ scanning tunneling microscopy (STM). Hcy and HTL molecules formed highly ordered adlayers on Au(1 1 1) surface. High-resolution STM images revealed the orientation and packing arrangement in the ordered adlayers. Hcy molecules formed (2root3 x 3root3)R30degrees adlayer structure and H-bonds between carboxyl groups were assumed to be responsible for the origin of tail-to-tail or head-to-head molecular arrangement, while HTL molecules formed (4 x 6) adlayer structure, and two different orientations and appearances in the ordered adlayer were found. Structural models were proposed for the two adlayers.

In situ formation by laser cladding of a TiC composite coating with a gradient distribution

An in situ method was developed to produce an Ni alloy composite coating reinforced by in situ reacted TiC particles with a gradient distribution, using one-step laser cladding with a pre-placed powder mixture on a 5CrMnMo steel substrate. Dispersed and ultra-fine TIC particles were formed in situ in the coating. Most. of the TiC particles, with a marked gradient distribution, were uniformly distributed within interdendritic regions because of the trapping effect of the advancing solid-liquid interface. In addition, the TiC-gamma-Ni interfaces generated in situ were found to be free from any deleterious surface reaction. Finally, the microhardness also showed a gradient variation, with the highest value of 1250 Hv0.2 and the wear properties of the coating were significantly enhanced.

In Situ Synthesis Of Nanocrystalline Intermetallic Layer During Surface Plastic Deformation Of Zirconium

By means of a surface plastic deformation method a nanocrystalline (NC) intermetallic compound was in situ synthesized on the surface layer of bulk zirconium (Zr). Hardened steel shots (composition: 1.0C, 1.5Cr, base Fe in wt.%) were used to conduct repetitive and multidirectional peening on the surface layer of Zr. The microstructure evolution of the surface layer was investigated by X-ray diffraction and scanning and transmission electron microscopy observations. The NC intermetallic layer of about 25 gm thick was observed and confirmed by concentration profiles of Zr, Fe and Cr, and was found to consist of the Fe100-xCrx compound with an average grain size of 22 nm. The NC surface layer exhibited an extremely high average hardness of 10.2 GPa. The Zr base immediately next to the compound/Zr interface has a grain size of similar to 250 nm, and a hardness of similar to 3.4 GPa. The Fe100-xCrx layer was found to securely adhere to the Zr base. (c) 2007 Elsevier B.V All rights reserved.

Fracture Mechanisms And Size Effects Of Brittle Metallic Foams: In Situ Compression Tests Inside Sem

In situ compressive tests on specially designed small samples made from brittle metallic foams were accomplished in a loading device equipped in the scanning electron microscopy (SEM). Each of the small samples comprises only several cells in the effective test zone (ETZ), with one major cell in the middle. In such a system one can not only obtain sequential collapse-process images of a single cell and its cell walls with high resolution, but also correlate the detailed failure behaviour of the cell walls with the stress-strain response, therefore reveal the mechanisms of energy absorption in the mesoscopic scale. Meanwhile, the stress-strain behaviour is quite different from that of bulk foams in dimensions of enough large, indicating a strong size effect. According to the in situ observations, four failure modes in the cell-wall level were summarized, and these modes account for the mesoscopic mechanisms of energy absorption. Paralleled compression tests on bulk samples were also carried out, and it is found that both fracturing of a single cell and developing of fracture bands are defect-directed or weakness-directed processes. The mechanical properties of the brittle aluminum foams obtained from the present tests agree well with the size effect model for ductile cellular solids proposed by Onck et al. (C) 2008 Elsevier Ltd. All rights reserved.

An In-Situ Observation On Initial Aggregation Process Of Colloidal Particles Near Three-Phase Contact Line Of Air, Water And Vertical Substrate

The self-assembling process near the three-phase contact line of air, water and vertical substrate is widely used to produce various kinds of nanostructured materials and devices. We perform an in-situ observation on the self-assembling process in the vicinity of the three phase contact line. Three kinds of aggregations, i.e. particle-particle aggregation, particle-chain aggregation and chain-chain aggregation, in the initial stage of vertical deposition process are revealed by our experiments. It is found that the particle particle aggregation and the particle-chain aggregation can be qualitatively explained by the theory of the capillary immersion force and mirror image force, while the chain-chain aggregation leaves an opening question for the further studies. The present study may provide more deep insight into the self-assembling process of colloidal particles.

In Situ Observations On The Fracture Process Of Metallic Glassy Ribbons

Crack propagation and strain field evolution in two metallic glassy ribbons are studied using in situ scanning electron microscopy and the white digital speckle correlation method. Strain state at the crack tip, which depends heavily on the fracture toughness, plays a key role in fracture. A high degree of shear strain concentration in tough glassy ribbon can satisfy the critical shear strain, resulting in shear fracture, whereas a high degree of linear strain concentration in brittle glassy ribbon can initiate normal tensile fracture. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

In Situ Synthesis of Nanocrystalline Intermetallic Compound Layer During Surface Mechanical Attrition Treatment of Zirconium

The surface mechanical attrition treatment (SMAT) technique was developed to synthesize a nanocrystalline (NC) layer on the surface of metallic materials for upgrading their overall properties and performance. In this paper, by means of SMAT to a pure zirconium plate at the room temperature, repetitive multidirectional peening of steel shots (composition (wt%): 1C, 1.5Cr, base Fe) severely deformed the surface layer. A NC surface layer consisting of the intermetallic compound FeCr was fabricated on the surface of the zirconium. The microstructure characterization of the surface layer was performed by using X-ray diffraction analysis, optical microscopy, scanning and transmission electron microscopy observations. The NC surface layer was about 25 mu m thick and consisted of the intermetallic compound FeCr with an average grain size of 25 +/- 10 nm. The deformation-induced fast diffusion of Fe and Cr from the steel shots into Zr occurred during SMAT, leading to the formation of intermetallic compound. In addition, the NC surface layer exhibited an ultrahigh nanohardness of 10.2 GPa.

Measurements Of In Situ Stress And Mining-Induced Stress In Beiminghe Iron Mine Of China

In order to obtain the distribution rules of in situ stress and mining-induced stress of Beiminghe Iron Mine, the stress relief method by overcoring was used to measure the in situ stress, and the MC type bore-hole stress gauge was adopted to measure the mining-induced stress. In the in situ stress measuring, the technique of improved hollow inclusion cells was adopted, which can realize complete temperature compensation. Based on the measuring results, the distribution model of in situ stress was established and analyzed. The in situ stress measuring result shows that the maximum horizontal stress is 1.75-2.45 times of vertical stress and almost 1.83 times of the minimum horizontal stress in this mineral field. And the mining-induced stress measuring result shows that, according to the magnitude of front abutment pressure the stress region can be separated into stress-relaxed area, stress-concentrated area and initial stress area. At the -50 m mining level of this mine, the range of stress-relaxed area is 0-3 m before mining face; the range of stress-concentrated area is 3-55 m before mining face, and the maximum mining-induced stress is 16.5-17.5 MPa, which is 15-20 m from the mining face. The coefficient of stress concentration is 1.85.

Measurement technique for in situ characterizing aberrations of projection optics in lithographic tools

As the feature size decreases, degradation of image quality caused by wavefront aberrations of projection optics in lithographic tools has become a serious problem in the low-k1 process. We propose a novel measurement technique for in situ characterizing aberrations of projection optics in lithographic tools. Considering the impact of the partial coherence illumination, we introduce a novel algorithm that accurately describes the pattern displacement and focus shift induced by aberrations. Employing the algorithm, the measurement condition is extended from three-beam interference to two-, three-, and hybrid-beam interferences. The experiments are performed to measure the aberrations of projection optics in an ArF scanner. (C) 2006 Optical Society of America.