Effect Of Interfacial Stress Research Articles

Effect of interfacial stress on the crystalline structure of the matrix and the mechanical properties of high‐density polyethylene/CaCO3 blends

AbstractA series of high‐density polyethylene (HDPE)/CaCO3 blends were prepared with different kinds of coupling agents, with CaCO3 particles of different sizes, and with matrixes of different molecular weights during the melt‐mixing of HDPE and CaCO3 particles. The mechanical properties of these blends and their dependence on the interfacial adhesion and matrix crystalline structure were studied. The results showed that the Charpy notched impact strength of these blends could be significantly improved with an increase in the interfacial adhesion or matrix molecular weight or a decrease in the CaCO3 particle size. When a CaCO3 surface was treated with a compounded coupling agent, the impact strength of the HDPE/CaCO3(60/40) blend was 62.0 kJ/m2, 2.3 times higher than that of unimproved HDPE; its Young's modulus was 2070 MPa, 1.07 times higher than that of unimproved HDPE. The heat distortion temperature of this blend was also obviously improved. The improvement of the mechanical properties and the occurrence of the brittle–tough transition of these blends were the results of a crystallization effect induced by the interfacial stress. When the interfacial adhesion was higher and the CaCO3 content was greater than 30%, the interfacial stress produced from matrix shrinkage in the blend molding process could strain‐induce crystallization of the matrix, leading to an increase in the matrix crystallinity and the formation of an extended‐chain (or microfibrillar) crystal network. The increase in the critical ligament thickness with an increasing matrix molecular weight was attributed to the strain‐induced areas becoming wider, the extended‐chain crystal layers becoming thicker, and the interparticle distance that formed the extended‐chain crystal network structure becoming larger with a higher matrix molecular weight. The formation of the extended‐chain crystal network and the increase in the matrix crystallinity were also the main reasons that Young's modulus and the heat distortion temperature of this blend were improved. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 87: 2120–2129, 2003

Warpage measurement comparison using shadow Moire and projection Moire methods

Microelectronic and photonic packaging are progressing toward integrating more devices with more functions into a smaller confined space, while requiring higher yield and superior reliability. New electronic components, materials, fabrication processes, and configurations are emerging to achieve these goals. As expected, surface flatness is playing a more crucial role in integrated circuits and integrated optics manufacturing. Out-of-plane displacement (warpage) is a global effect of interfacial stress and displacement. It is also the cause of mis-registration and noncontact between components and their substrates. Moire methods offer noncontact, full-field, high-resolution approaches for measuring warpage. In this paper, two types of Moire methods are introduced and analyzed. They carry distinct features and grant more options to measure warpage under various scenarios. It has been shown through system analysis and experimental results that these systems are powerful tools for studying warpage mechanisms. Specifically, they can help to investigate the effects of materials, manufacturing processes, and packaging configurations on warpage.

Structural relaxation of SiO 2/Si interfacial layer during annealing

We have studied the structural evolution of the high density interfacial layer around 10 Å thick in 40 Å thermal oxide observed by difference X-ray reflectivity (DXR) techniques during thermal annealing. Effects of interfacial stress are evaluated by grazing incidence X-ray diffraction. As the annealing proceeds, density of the interfacial layer decreased and got close to the value of the upper SiO 2 layer after 2 h of annealing in Ar at 800°C. At the same time, a slight increase in the thickness of the interfacial layer and the flattening of the Si interface are observed. These results indicate that during annealing, both the structural relaxation of oxide in the direction normal to the interface and an atomic rearrangement at the Si interface proceeds. Elastic deformation by stress can not be the dominant origin of the density change. The observed decrease of the interface state density D it along annealing may be linked to the decrease of structural defects accompanied with the structural relaxation at the interface.

Mechanism of silica-metal mixing by ion irradiation

The application of ion-beam mixing to the doping of silica films with metals either in solution or in the form of nanoclusters requires a preliminary investigation of the mixing mechanisms. This was undertaken by means of RBS and XRD for Au, Pt, W, Ag and Cu films mixed with silica by 4.5 MeV Au or 200 keV Ar ions, at 100 or 300 K. In all cases metal atoms migrated preferentially inwards. At room temperature, the radiation enhanced diffusion of Au, Pt, Ag and Cu in the silica matrix competed with their coalescing into coarser particles, under the effect of interfacial stresses. The mixing rate was proportional to the ion dose or to its square, depending on the system and temperature. This unusual quadratic law is attributed to the formation of solute metal-vacancy complexes.

Effects of interfacial stress on oxidation of mild steel

The effects of a compressive stress on the oxidation rate of mild steel have been investigated through the use of novel equipment designed to measure the extension of specimens during scaling. Preliminary results are described for mild steel oxidised in 2% CO–CO2. The rate of breakaway scaling is found to be lower at constrained interfaces by comparison with the free surfaces of the specimens and the rate of oxidation is shown also to decrease as the interfacial stress increases. The microstructures of the various breakaway scales formed with and without an external load, as examined in cross-section in the transmission electron microscope, are also described and possible reasons to account for the observed reduction in the oxidation rate are discussed.MST/1146

Effects of interfacial stress on oxidation of mild steel

AbstractThe effects of a compressive stress on the oxidation rate of mild steel have been investigated through the use of novel equipment designed to measure the extension of specimens during scaling. Preliminary results are described for mild steel oxidised in 2% CO–CO2. The rate of breakaway scaling is found to be lower at constrained interfaces by comparison with the free surfaces of the specimens and the rate of oxidation is shown also to decrease as the interfacial stress increases. The microstructures of the various breakaway scales formed with and without an external load, as examined in cross-section in the transmission electron microscope, are also described and possible reasons to account for the observed reduction in the oxidation rate are discussed.MST/1146

A unified description of two-layer flow over topography

Observations of the flow of a two-layer fluid resulting from the motion of a towed streamlined two-dimensional obstacle are described in some detail. The experiments were designed to further our understanding of the factors governing the nature and magnitude of upstream disturbances in the general flow of stratified fluid over two-dimensional topography, and predictions for arbitrary two-dimensional flows are made from the results of these experiments. In particular, the relationship between uniformly stratified flow and single-layer flow over topography is suggested. Most of the observed features of interest in these experiments are nonlinear in character. Relatively complete descriptions of the observed flows are presented over a wide range of parameter values, and the phenomena observed include upstream undular and turbulent bores, bores with zero energy loss, ‘rarefactions’ (in which the interface height changes monotonically over a transition region of continuously increasing length), and downstream hydraulic drops and jumps. Their properties are shown to be broadly consistent with predictions from a two-layer hydrostatic model based on continuity and momentum considerations, which employs jump criteria and rarefaction equations where appropriate. Bores occur because of nonlinear steepening when the layer containing the obstacle is thinner than the other, and rarefactions occur when this layer thickness is comparable with or greater than that of the other layer. The speed and amplitude of the upstream bores are governed by nonlinear effects, but their character is determined by a balance between nonlinear steepening, wave dispersion and interfacial friction when the bore is non-turbulent.Experimental evidence is presented for two types of hysteresis or ‘multiple equilibria’ - situations where two different flow states may exist for the same external steady conditions. In the first of these hysteresis types, the upstream flow may be supercritical or consist of an upstream bore state. It is analogous to the type anticipated for single-layer flow by Baines & Davies (1980) and described numerically by Pratt (1983), but it is only found experimentally for part of the expected parameter range, apparently because of interfacial stress effects. The second hysteresis type is new, and involves the presence or absence of a downstream hydraulic drop and following jump.

Effect of interfacial stress at the Si/SiO2, interface on the diffusion of Ga in Si through SiO2

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The effect of interfacial stress on the propagation of stoneley waves

Surface waves centred on the interface between two homogeneous linearly-elastic half-spaces which remain in non-slipping contact have been extensively investigated. Here, for isotropic half-spaces, account is taken of interfacial elasticity, inertia and residual stress which may originate in a departure from material homogeneity of either body near the surface of contact and/or the bonding process which ensures that non-slipping contact is maintained. The possibility of the propagation of disturbances having the character of Love and Rayleigh waves is investigated and shown to depend upon the relative values of interfacial and bulk parameters. It is demonstrated that such waves exist in almost all cases, in contrast to the classical theory which precludes the propagation of Love-type waves and requires for the existence of Rayleigh-type waves that the two bodies have similar acoustical properties. Attention is drawn to the relevance of the discussion to ultrasonic signal-processing devices.