Model-based analysis of the silica glass film etch mechanism in CF4/O2 inductively coupled plasma

The analysis of the Er-doped silica glass films (62%SiO₂–30%B₂O₃–8%P₂O₅ + 0.2 wt%. Er₂O₃) etch mechanism in the CF₄/O₂ inductively coupled plasma was carried out using the combination of simplified models for plasma chemistry and etch kinetics. As the O₂ mixing ratio in the CF₄/O₂ plasma increases from 0% to 30%, the etch rate decreases monotonically in the range of 385–190 nm/min that contradicts with the behavior of F atom density and flux. From the model-based analysis, it was found that, at low ion bombardment energies, the etch process followed the formal kinetics of ion-assisted chemical reaction and was controlled by both neutral and ion fluxes.     

Self-sensing of carbon fiber/carbon nanofiber–epoxy composites with two different nanofiber aspect ratios investigated by electrical resistance and wettability measurements

Electro-micromechanical techniques, wettability test, and acoustic emission (AE) were use to compare self-sensing and stress-transferring effects in single carbon fiber embedded in carbon nanofiber (CNF)–epoxy composites with two different aspect ratios. Electrical resistivity and standard deviation were used as indirect measures of comparative dispersion degree of CNF. The dispersion was observed to decrease with increasing CNF content due to an increase in the electrical contacts. Composites with higher aspect ratio exhibited better self-sensing than lower aspect ratio case. This was attributed to differences in dispersion, orientation, coagulation of CNF with different aspect ratios. The opposite effect was observed for apparent Young’s modulus, which was larger for composites with lower aspect ratio. This is probably related to better stress transfer linked to orientation effects. Work of adhesion consistently followed same trend as apparent Young’s modulus. Single carbon fiber pull-out tests and AE provided additional information on the effects of aspect ratio.     

Crack initiation and propagation behavior of zirconium cladding under an environment of iodine-induced stress corrosion

Tests of iodine-induced stress corrosion cracking (ISCC) were carried out to elucidate the initiation and propagation of cracks in the claddings of zirconium alloys. Zircaloy-4 cladding and Nb-contained zirconium cladding were pressurized with and without a pre-cracked state at 350°C in an iodine environment. The results show that pitting nucleation and growth play an important role in initiating ISCC. Pits preferentially grow and agglomerate around the grain boundary, where the number of pits increases with the iodine concentration and the hoop stress of the claddings. A model of grain-boundary pitting coalescence and a model of pitting-assisted slip cleavage, which were proposed to clearly elucidate the crack initiation and propagation process under ISCC, produce reasonable results. The Nb-contained zirconium cladding exhibits higher ISCC resistance than Zircaloy-4 from the standpoint of a higher threshold stress-intensity factor and a lower crack propagation rate.     

Effects of the Surface Contact on the Uncertainty in Indentation Yield Strength: Surface Roughness and Angular Misalignment

Metals and Materials International - We suggest a method for accurately estimating the uncertainty of indentation yield strength determined from the modified Meyer relation as a mathematical...     

Measurements and correlation of effect of cosolvents on the solubilities of complex molecules in supercritical carbon dioxide

A new transparent microscale circulation-type high pressure equilibrium cell with on-line sampling was devised. With this apparatus, experimental solubility of molecularly complex species such as steroids (cholesterol, stigmasterol and ergosterol) and fatty acids (palmitic acid and stearic acid) in supercritical carbon dioxide(sc-C0₂) were measured. Also, to find an appropriate substance for enhancing both the polarity and the solubility power of the SC-CO₂ solvent, we arbitrarily selected three polar substances such as acetone, methanol and water and the effect of these cosolvents on the solubility of solutes in SC-CO₂ are examined. The supercritical phase equilibrium data of solute-cosolvent-sc-CO₂ systems were quantitatively correlated using a new equation of state based on the lattice fluid theory incorporated with the concept of multibody interaction. We found that the addition of tracer amount of acetone or methanol to SC-CO₂ enhances the solubility of all solutes about thirty to sixty times when compared with the case of pure sc-CO₂ However, for the case of cosolvent water, no further enhancement of the solubility of solutes was realized. Also, the versatile fittability of the equation of state proposed in this work was demonstrated with the newly measured ternary supercritical equilibrium data.     

Adjustment of CNC machine tool controller setting values by an experimental method

This paper presents an adjustment technique on controller setting values in CNC machine tools by measurement of servo induced feed drive errors. At high feed rate operations of CNC machine tools, servo induced errors are usually dominant and large compared with geometric errors. For measurement of the servo induced errors, an experimental equipment which incorporates two linear displacement sensors and a steel cube was developed, and servo feed drive errors were evaluated along a square corner test path. Based on evaluations of servo feed drive errors with different combination of parameters in machine control system, optimum setting parameters were found. The measuring equipment and optimisation method are described.     

Evaluation of structural reliability of mems device in digital video disk systems

In this paper, we describe the reliability evaluation for MEMS devices, especially designed tbr DVD(Digital Video Disk) application. These MEMS devices are fabricated as a mirror plane (shutter plane) used in DVD data picking up. This micromachined annular shutter mirror (ASM) acts as an adjusting means of the numerical aperture. The electrostatic force can drive the upper plane up and down for focusing or defocusing of incident laser beam to the selected recording plane. So we need to evaluate the micromechanical properties of thin film structural materials to ensure the reliability of those MEMS devices. For those, we perfl)rm the fatigue tests onto the devices in the conditions of much accelerated than those of normal driving. The applied electrostatic force can induce the change of the thin film properties, and those are observed by direct and indirect methods (XRD and electrical system). And then, we compare the fatigue effects with electrical, optical data from the intentionally-fatigue-applied specimen and as-fabricated one under accelerated conditions. Consequently, we can estimate the structural reliability and will provide the effective suggestion data for the fabrication of stable mirror material before commercialization.     

Determination of texture and estimation of anisotropie properties of metallic uranium rods by neutron diffraction

Textures of metallic uranium rods were measured by neutron diffraction. From experimentally measured single and composite pole figures, the crystallite orientation distribution function (ODF) was determined by the harmonic method using a computer program developed for the fiber texture with orthorhombic crystal symmetry. The composite pole figures measured at overlapped peak positions of the diffraction pattern were assumed to be a linear combination of several neighboring single pole figures. The calculated results show that the harmonic method based on this conjecture well recovers the experimentally measured composite pole figures. Anisotropie physical properties such as thermal expansion coefficients and elastic constants due to the texture were evaluated by numerically averaging the second and fourth rank tensors with the calculated ODF, respectively.     

Assessment of fracture characteristics from revised small punch test using pre-cracked specimen

Small punch (SP) test has been utilized to analyze the neutron irradiation damage of nuclear vessels. Since this technique is easy, simple, and nondestructive, it can be applied to evaluate the mechanical properties and material degradation of in-service components. Conventional SP test has evaluated the ductile-brittle transition temperature and the equivalent fracture strain by the interpretations of load-deflection curve and the change of specimen thickness, respectively. The assumption that fracture occurs at maximum load is, however, not reasonable because the crack initiates at smaller load. In this study, in order to evaluate quantitatively fracture characteristics based on fracture mechanics, the pre-crack is introduced to SP specimen and acoustic emission is used to determine the crack initiation point. Using the load at crack initiation point, the fracture toughness of thin plate is calculated through bending theory. Therefore, the fracture characteristics of thin plate can be evalualed more reliably by using revised SP test.     

Observability analysis of alignment errors in GPS/INS

Misalignment can be an important problem in the integration of GPS/INS. Observability analysis of the alignment errors in the integration of low-grade inertial sensors and multiantenna GPS is presented in this paper. A control-theoretic approach is adopted to study the observability of time-varying error dynamics models. The relationship between vehicle motions and the observability of the errors in the lever arm and relative attitude between GPS antenna array and IMU is given. It is shown that alignment errors can be made observable through maneuvering. The change of acceleration makes the components of the relative attitude error that are orthogonal to the direction of the acceleration change observable. The change of angular velocity makes the components of the lever arm error that are orthogonal to the direction of the angular velocity observable. The motion of constant angular velocity has no influence on the estimation of the lever arm.