Complicated Microstructure Research Articles

Recent Advances in Domain Analysis

Recent progress in domain analysis, which has been attained by the notable advancement of transmission electron microscopy (TEM), is reviewed by selecting certain topics related to displacive and magnetic phase transformations. Energy-filtered TEM, which separates the elastic scattering from the unwanted inelastic one, enabled us to explore the complex phenomena in the precursor state of martensitic transformations. In particular, the discovery of the peculiar nano-scaled domains in the parent phase has offered a novel picture on the lattice distortion in the precursor state and the subsequent nucleation process of martensite. With respect to the analysis of magnetic domains, the authors have devised a technique that precisely evaluates the magnetization distribution based on electron holography. The method was applied to the complicated magnetic microstructure as observed near the Curie temperature and/or Neel temperature in hole-doped manganites. In addition to these topics, similarities of crystallographic domains between martensites and charge-ordered manganites, correlations between crystallographic microstructures (e.g., antiphase boundaries) and magnetic domains, and future challenging issues regarding domain analysis will also be mentioned.

The study of mass transport of acetone in polycarbonate

The mechanism of mass transport and associated crystallization in polycarbonate (PC) were studied. Based on Harmon’s model for case I (or Fickian), case II (or swelling), and anomalous transport, the data of the initial period of mass uptake were analyzed. Due to the initially small dimensional variation of the PC and the initially small amount of crystallization, the influence of crystallinity on the mass transport can be ignored. The diffusivity in case I and the velocity in case II both followed the Arrhenius relationship. Case II dominated the transport process as the activation energy of case II is lower than that of case I. This finding was further verified by measuring the movement of diffusion fronts with a carefully selected observation coordinate. A distinct transport front was identified from the measurements of optical microscope and the microhardness. This investigation addresses more complicated microstructures of PC during mass transport.

Ultra-water-repellent surface: fabrication of complicated structure of SiO2 nanoparticles by electrostatic self-assembled films

Ultra-water-repellent surface requires a high surface roughness and low surface energy. We designed surface complicated microstructure of SiO 2 nanoparticles by using electrostatic self-assembly process. The films that were prepared by the alternate adsorption of poly(allylamine hydrochloride), SiO 2 nanoparticles mixture solution and poly(acrylic acid) on the substrates were very complicated in surface structure. After surface hydrophobic treatment by dichlorodimethylsilane, the film surface showed a contact angle of larger than 160° for water droplets. The value was much larger compared with the contact angle on silicon wafer treated by dichlorodimethylsilane. The difference was strongly dependent on the surface structure. In this paper, we changed deposition conditions to fabricate the water-repellent surfaces with various surface structures by using three types of silica nanoparticles, and we found that the nanoscale structure was very important for the ultra-water-repellency.

Three-dimensional micro-structures consisting of high aspect ratio inclined micro-pillars fabricated by simple photolithography

This paper presents a fabrication method of three-dimensional micro-structures consisting of high aspect ratio inclined micro-pillars using simple photolithography. The width and height of micro-pillars were 10 μm and 200 μm (the aspect ratio was about 20). The SU-8 coated on the Cr patterned Pyrex glass substrate was exposed from the backside with an angle to fabricate inclined micro-pillars. The 3-D micro-structures were fabricated by repeating the backside exposure with different angles. The shape of the micro-structure was defined by the number of exposures and the UV irradiation angles. The complicated micro-structures were fabricated by multi-angle exposures around two axes, as well as around one axis.

Stress Analysis of Ceramic Component Having Complicated Microstructure Using Finite Element Method

Stress Analysis of Ceramic Component Having Complicated Microstructure Using Finite Element Method

Sorption purpose lime hydrate grinding

The lime is a typical material for the building industry. The grinding of such material is connected with the hundreds of years of human experience. However, present activities using lime as the sorption material for exhalations show that the knowledge of the lime grinding process is very poor. Several methods as classical sedimentation, the remains on the 90- and 63-μm sieves, BET, CILAS diffraction, SEM photographs and the microstructure relieves were used to reply the question: “Where are hidden all the enormous energy requirements of the pre-grinding, the ball mills and the separators in the lime hydrate grinding circuits, when the material with its complicated micro-structure before and after grinding seems to be nearly the same?” The paper marks the basic technology outlook for the lime hydrate sorption surface enlargement.

Ultra-water-repellent surface: fabrication of complicated structure of SiO2 nanoparticles by electrostatic self-assembled films

Ultra-water-repellent surface requires a high surface roughness and low surface energy. We designed surface complicated microstructure of SiO2 nanoparticles by using electrostatic self-assembly process. The films that were prepared by the alternate adsorption of poly(allylamine hydrochloride), SiO2 nanoparticles mixture solution and poly(acrylic acid) on the substrates were very complicated in surface structure. After surface hydrophobic treatment by dichlorodimethylsilane, the film surface showed a contact angle of larger than 160° for water droplets. The value was much larger compared with the contact angle on silicon wafer treated by dichlorodimethylsilane. The difference was strongly dependent on the surface structure. In this paper, we changed deposition conditions to fabricate the water-repellent surfaces with various surface structures by using three types of silica nanoparticles, and we found that the nanoscale structure was very important for the ultra-water-repellency.

Development of practical system for laser-induced plasma-assisted ablation (LIPAA) for micromachining of glass materials

The laser-induced plasma-assisted ablation (LIPAA) process developed by us, in which only a single conventional pulsed laser is used, makes it possible to perform high-quality and high-speed glass microfabrication. We developed the LIPAA system, which uses the second harmonic of a diode pumped Q-switched Nd:YAG laser, for practical use in industry. The system comprises two optical components, which are the objective lens for high-resolution microfabrication and the galvano mirror type scanner for high-speed patterning of complicated microstructures. In addition to surface microstructuring of the glass, selective metallization of the glass by the LIPAA process, followed by electroless Cu plating, is demonstrated .

Photothermal depth profilometry of heat-treated hardened 0.15%–0.2%C, 0.6%–0.9%Mn Steels

The thermal-diffusivity depth-profilometric properties of hardened AISI1018 steel samples (0.15%–0.2%C and 0.6%–0.9%Mn) are investigated from experimental data and compared to their microhardness depth profiles. To fully understand the effect of the individual steps of the heat-treating process on the thermal-diffusivity of the steels, the thermal-diffusivity depth profiles are reconstructed using laser infrared photothermal radiometry. The inverted depth profiles are compared to the results of microhardness testing after each step of carbonitriding and quenching. The comparison shows that there is a good to excellent anticorrelation between hardness and thermal-diffusivity profiles for both carbonitrided and quenched samples with 0.02in. case depth and gradually worsening anticorrelation trends for 0.04 and 0.06in. case depths. It is concluded that for this particular steel, both carbon diffusion and the complicated carbonitrided microstructure affect the absolute values of the thermal-diffusivity profiles as well as their depth distribution.

Dislocation mechanisms of mean stress effect on cyclic plasticity

Abstract The dislocation mechanisms behind sagging behavior of auto-suspension spring steels are far from being understood due to their complicated microstructures. In this study, systematic cyclic...

Dislocation mechanisms of mean stress effect on cyclic plasticity

Abstract The dislocation mechanisms behind sagging behavior of autosuspension spring steels are far from being understood due to their complicated microstructures. In this study, systematic cyclic loading tests were carried out on two model materials - industrial pure iron and spheroidized 1045 steel – to understand the mechanisms behind sagging. It is found that it is the different dislocation microstructures that control the cyclic creep behavior of different materials. With iron samples with low mean stress values, higher mean stresses do not trigger cell structure formation mainly due to the little requirement for high plastic strain amplitude and hence the lack of necessity for high dislocation density, and a large number of dislocation interactions through large mobile dislocations. In the case of the 1045 steel samples, the collapse of pre-existent substructures and the movement of newly generated mobile dislocations are the main reasons for the cyclic softening observed. The massive reorganization process of dislocation configurations and the competition between softening and hardening both carry on throughout the entire cycling process, but the softening process is found to be the predominant factor.

Local potential measurements with the SKPFM on aluminium alloys

Nowadays several measuring techniques, like SVET, SRET and Kelvin probe, exist to study local potential differences on alloys surfaces. One very sensitive technique with good spatial resolution is scanning Kelvin probe force microscopy. This technique enables direct measurement of the local Volta potential differences resulting from very complicated microstructures due to the thermal history of the produced aluminium alloys. In combination with SEM, EDS and electrochemical techniques detailed mechanistic studies on the relation between the microstructure and the corrosion behaviour have now become possible. Local electrochemical measuring techniques do show that local Volta potential differences in many cases are clearly reflected in local corrosion behaviour.

Spectral representation theory for higher order nonlinear responses in random composites with arbitrary nonlinearity

AbstractThe higher order nonlinear responses of random two‐phase composite media are investigated within spectral representation theory. The first component with the volume fraction p is assumed to have the nonlinear displacement (D)‐electric field (E) relation of the form D = ε1E+ χ1 |E|βE, where ε1 is the linear dielectric constant and χ1 is the (β + 1)th order nonlinear response; the second component is linear with the volume fraction 1–p and the dielectric constant ε2. The effective nonlinear responses of the composite media can be defined as 〈D〉 = εeE0 + χe|E0|βE0 + ηe|E0|2βE0, where εe, χe and ηe are the effective linear dielectric constant, the effective (β + 1)th order nonlinear response and (2β + 1)th order nonlinear response respectively. Based on spectral representation theory and the perturbative expansion method, general expressions for χe and ηe are derived as a function of the material parameters and the spectral density function m(x), which are indeed valid for arbitrary β and for any complicated microstructures. For the dilute limit and the Maxwell‐Garnett microstructures, our expressions yield the same formulae as those in previous works. Moreover, the theoretical results for Bruggeman effective medium microstructures are compared with numerical simulations, good agreement is found. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

04/00685 Formation and dissociation studies for optimizing the uptake of methane by methane hydrates: Link, D. D. et al. Fluid Phase Equilibria, 2003, 211, (1), 1–10

Samples of metamorphosed and deformed granitic rocks were collected from two Alpine complexes with well-constrained metamorphic history: Western Tauern Window and Ötztal-Stubai Crystalline Complex. Zircon grains from these samples were investigated in situ by a combination of scanning electron microscope techniques, cathodoluminescence (CL) imaging and Raman spectroscopy. The aims were: to describe and interpret complicated secondary textures and microstructures in zircon; based on cross-cutting relationships between secondary microstructures, reconstruct the sequence of processes, affecting zircon crystals; link the evolution of zircon with the history of the host rocks.The results indicate that zircon in the sampled granitic rocks forms growth twins and multi-grain aggregates, which are unusual for this mineral. Moreover, various secondary textures have been found in the sampled zircon, often cross-cutting each other in a single crystal. These include: distorted oscillatory CL zoning with inner zones forming inward-penetrating, CL-bright embayments, which are the evidence of dry recrystallization via annealing/lattice recovery; CL mosaicism with no preservation of growth zoning, but abundant nano- and micro-scale pores and mineral inclusions, which are the evidence of recrystallization by coupled dissolution–reprecipitation and/or leaching; embayed zircon boundaries filled with apatite, monazite, epidote and mylonitic matrix, indicating mineral-fluid reactions resulting in zircon dissolution and fragmentation; overgrowth CL-dark rims, which contain nano-pores and point to transport and precipitation of dissolved zircon matter. We conclude that zircon in our meta-granites is sensitive to metamorphism/deformation events, and was reactive with metamorphic fluids. Additionally, we have found evidence of crystal-plastic deformation in the form of low angle boundaries and bent grain tips, which is a result of shearing and ductile deformation of the host rock. We suggest that the observed complicated secondary textures in zircon can be linked to the evolutionary stages of the host rocks such as magmatic crystallization, prograde metamorphism, peak of amphibolite-facies metamorphism, post-peak cooling and exhumation, formation of ductile shear zones and final cooling to ~ 250 °C.

Mechanical properties of three-dimensional braided composites

Recently developed digital element approach, which treats textile composite manufacturing process as a nonlinear solid mechanics problem, was successfully used to investigate the complicated microstructure of 3D braided rectangular preform. The yarns interaction and cross-sectional deformation, which were neglected in traditional topological model, could be analyzed exactly. Results showed that yarns inside 3D braided preform were curvy, which was opposite to the straight-yarns assumption of topological model and, yarns curvature inside the preform, which was very difficult to be explored before both experimentally and theoretically, was investigated numerically. After that, the mechanical properties of 3D rectangular braided composites, such as tensile stiffness, shear stiffness and Poisson ratio were calculated through the volume-average-compliance method. Comparison was conducted for those from the topological model and digital element approach, and topological model was found to underestimate greatly both the tensile stiffness and shear stiffness.

Effect of Electric Field on Hydrostatic Piezoelectric Coefficients of Single Domain PZN-PT Crystals

The effect of dc bias electric field on the hydrostatic piezoelectric coefficient dh in Lead Zinc Niobate-Lead Titanate (PZN:PT) single crystal solid solutions in the vicinity of the morphotropic phase boundary (MPB) is studied. The hydrostatic measurements can be very important to gain insight into these materials. In particular, the discrepancy between sum of piezoelectric coefficients d33+ 2 d31 vs. hydrostatic dh coefficient measured directly suggests the importance of extrinsic contributions. Limiting values of measured hydrostatic piezoelectric coefficients dh for high electric fields are compared with calculated theoretic values from the Landau-Devonshire-Ginzburg (LGD) phenomenological theory. The influence of complicated microstructure within the single domain region is studied. Such microstructure could possibly account for the inability of the LGD phenomenology to give correct electric field bias dependence of dielectric constant.

Adhesion Strength Evaluation of Low-k Interconnect Structures Using a Nanoscratch Method

AbstractA convenient nanoscratch method was combined with atomic force microscope (AFM) and transmission electron microscope (TEM) observations to conduct the first-ever evaluation of the adhesion strength of a complicated microstructure Cu/Ta/TaN/pSiO2/low-k/SiC/pSiO2/Si-substrate with the aim of correlating the fracture strength with the results of chemical mechanical polishing (CMP) tests. Concretely, this evaluation focused on the fact that specimens having a low-k layer pretreated with rare-gas plasma prior to the deposition of the SiO2 layer exhibited low delaminated densities in the Cu CMP process. It was found that a specimen with the rare-gas plasma pretreatment exhibited a higher friction coefficient, a higher critical load and brittle adhesive failure resulting from delamination at the interface between the low-k and SiC layers. A specimen without the rare-gas plasma pretreatment displayed a lower friction coefficient, a lower critical load, and ductile cohesive failure in the low-k layer. Because less plastic deformation was observed in the low-k layer subjected to the rare-gas plasma pretreatment, it is assumed that the pretreatment reinforced the mechanical properties of the low-k layer, making it more resistant to ductile cohesive failure. These results agreed with the CMP test data and indicated that the nanoscratch method makes it possible to predict the ability of complicated Cu/low-k interconnect structures to withstand the CMP process.

An enhanced asymptotic homogenization method of the static and dynamics of elastic composite laminates

The homogenization method has been used often in analyzing the composite materials but has had limited use with the laminated structures. This is due to a limitation of the homogenization theory, which assumes the unit cell should be periodically represented in any specific area. The main attraction of the homogenization method is its systematic capability to develop the homogenized macroscopic constitutive relation of composite materials and to compute the stresses in the microstructure of composites. In other words, both the macro- and micromechanics can be treated in the same context. In this paper, we will develop an enhanced asymptotic homogenization method (EHM); this method is developed from the partial asymptotic expansion and the condensed third-order shear deformation theory. This theory uses the reduced matrix method to consolidate all the stiffness matrices into four stiffness matrices (the extension; coupling; bending and transverse shear stiffness matrices) in the same manner as with the first-order shear deformation theory (FSDT). Two FORTRAN programs PRELAM and POSTLAM [Int. J. Comput. Struct. 76 (2000) 319; An enhanced asymptotic homogenization method of elastic composite laminates, Ph.D. Thesis, The University of Michigan, 1999] were also developed from the finite element implementation of the enhanced homogenization method. The pre-processor, PRELAM, reads the unit cell model and generates the homogeneous material stiffness matrix for a laminated structure. The post-processor, POSTLAM, calculates the local stress distribution based on the strains and curvatures obtained from the global structure analysis generated by the commercial finite element software, i.e., ABAQUS or MSC/NASTRAN. By the nature of homogenization method, these computational methods are capable of handling geometrically complicated microstructures and predicting the microscopic stress distributions. Since, the number of unknown variables for EHM and FSDT are the same, this implies that the results from EHM is easily utilized by ABAQUS in the global analysis. Therefore, one of the main benefits to EHM is that it is readily applied in commercial FEM packages, but not that it is as accurate as other methods. Numerical examples are also presented to validate these two programs.

Anion Rearrangements in Fluorinated Nd2CuO3.5.

AbstractFor Abstract see ChemInform Abstract in Full Text.

A New Estimation Method of Coke Strength by Numerical Multiscale Analysis

The homogenization method is proposed as new numerical approach to understand the fracture mechanism of the microscopic behavior in coke because the evaluations of the strength has been still difficult for the improvement of coke qualities in coke making process. The conditions for the stress concentration and relaxation effect are investigated by homogenization method. These results show that the distribution of micro cracks and pores in coke is important factor for the microscopic fracture. Also, the digital image technique is applied to the actual coke with the complicated microstructure and the improvement mechanism of coke strength by the carbon deposition is clarified by using homogenization method. The effect of carbon deposition on the coke strength is illustrated from the stress distribution while calculating the homogenized elastic modulus. Although the stress concentration between large pores is caused in the case of carbon deposited coke, the maximum stress becomes smaller than the tensile strength of coke because of large homogenized elastic modulus. As a result, the microscopic fracture does not easily occur for carbon deposited coke.