Processing sodium tellurite melts in low gravity drop shaft: part I Melt evaporation and formation of solid particles from vapor

Glasses of Na₂O·8TeO₂ and Na₂O·4TeO₂ compositions adhered to a small platinum heating coil (2 to 3 mm ID, 5 to 6 mm long) were melted and evaporated in low gravity using the drop shaft at the Japan Microgravity Center (JAMIC). The gravity level attained during the 10 s free fall was in the order of 10^–3 g. The species evaporated from the melt in low gravity generally formed a spherical smoke cloud surrounding the melt, whose size depended on the melt temperature and also on the time the melt evaporated in low gravity. The shape of the cloud was found to depend on several other factors, namely, the uniformity of heating, amount of melt, and the presence of gas bubbles in the melt. The evaporating species formed nearly perfect spheres of pure TeO₂ whose diameter ranged from 0.05 to 20 m. The size of TeO₂ microspheres increased with increasing melt temperature and time in low gravity, and was 5 to 10 times larger than that of similar particles prepared at 1-g.     

Gold nanoparticles assisted structural and spectroscopic modification in Er3+-doped zinc sodium tellurite glass

Achieving enhanced spectroscopic properties of rare earth doped inorganic glasses by embedding metallic nanoparticles of controlled sizes is a challenging task. We report the gold (Au) NPs assisted modifications in structural and spectroscopic properties of melt-quench synthesized Er³⁺ doped zinc sodium tellurite glass. The growth of NPs is stimulated via time varying heat treatment at 300 °C. XRD patterns confirm the amorphous nature of glasses and TEM images manifest the growth of gold NPs with sizes between 6.1 and 10.7 nm. The heat treatment time dependent variations in physical properties are ascribed to the alteration in bonding of non-bridging oxygen ions. The UV–VIS–NIR spectra reveal six absorption peaks centered at 488, 523, 655, 800, 973 and 1533 nm corresponding to the transition from ground state of ⁴I_15/2 to ⁴F_7/2, ²H_11/2, ⁴F_9/2, ⁴I_9/2, ⁴I_11/2, and ⁴I_13/2 excited states of Er³⁺ ions, respectively. Surface plasmon resonance (SPR) bands are observed in the range of 618–632 nm. Judd–Ofelt analyses demonstrate a significant increase of spectroscopic quality factors (0.86–1.05) and branching ratio (0.62–92.38%). The up-conversion emission spectra of Er³⁺ exhibit three prominent peaks of reasonable green (502 nm), a moderate green (546 nm) and a strong red (629 nm). An enhancement in the red band luminescence intensity by a factor of 8.19 and 8.54 times are achieved for 2 and 4 h of heat treatments, respectively. This enhancement is attributed to the SPR effects of gold NPs producing an intense local field in the proximity of Er³⁺ ions and subsequent energy transfer between RE ions and NPs. The FTIR spectra display the presence of vibrational modes for ZnO₄ bonds, Te–O bond in TeO₃ (tp) and TeO₄ (tbp) units and the hydroxyl groups. Excellent features of the results suggest that our method constitute a basis for tunable growth of gold NPs which is exceedingly useful for the optimization of optical and structural properties.     

Crystallization of glass forming melts under hydrostatic pressure and shear stress: Part II Flow induced melt crystallization: a new method of nucleation catalysis

In this second part of a thorough investigation into the influence of external pressure and shear stress on melt crystallization the effect of shear stress is analysed. Both pseudoplastic and dilatant liquids are examined, and are possible effects of the respective rheological behaviour are discussed. It is shown that the very nature of pseudoplastic liquids leads to a reduction of their viscosity, which results in increased nucleation and crystal growth rates, whilst the non-steady-state time lag is, on the contrary, reduced. Experimental evidence supporting the above idea is discussed. This revised version was published online in November 2006 with corrections to the Cover Date.     

Fatigue crack growth in thin notched woven glass composites under tensile loading. Part II: Modelling

Fatigue propagation of a through-the-thickness crack in thin woven glass laminates is difficult to model when using homogeneous material assumption. Crack growth depends on both the fatigue behaviour of the fibres and of the matrix, these two phenomena occurring at different time and space scales. The developed finite element model is based on the architecture of the fabric and on the fatigue behaviours of the matrix and the fibre, even if the pure resin and fibre behaviours are not used. That thus limits the physical meaning of this model. Basically, the objective of this simulation is to illustrate and to confirm proposed crack growth mechanism. The fatigue damage matrix is introduced with user spring elements that link the two fibre directions of the fabric. Fibre fatigue behaviour is based on the S-N curves. Numerical results are compared to experimental crack growth rates and observed damage in the crack tip. Relatively good agreement between predictions and experiments was found.     

Growth of silver nano-particle embedded in tellurite glass: Interaction between localized surface plasmon resonance and Er ions

In this paper we show a systematic study of the growth of silver nano-particles (NPs) embedded in an Erbium-doped tellurite glass with annealing time, aiming to a photoluminescence enhancement. The results indicate an improved or quenching of the photoluminescence due to an energy transfer mechanism in the coupling between NP’s electric dipoles and Er⁺³ transitions (⁴S_3/2 → ⁴I_15/2, ⁴F_9/2 → ⁴I_15/2 and ⁴I_13/2 → ⁴I_15/2).     

Advances in the mechanism of cleavage fracture of low alloy steel at low temperature. Part II: Fracture model

The authors discuss in detail the existing cleavage fracture model including the physical model and the statistical model. Based on the discovery that a minimum distance for initiating the cleavage fracture was revealed to have a definite physical meaning, that the stress triaxiality reaches the critical value Tc at this distance instead of that the presence of an eligible carbide crack within this distance is assured; a combined criterion for cleavage fracture, i.e. a critical plastic strain (εp ≥ εpc) for initiating a crack nucleus, a critical stress triaxiality (σ m/σ ≥ Tc) for preventing it from blunting and a critical normal stress (σyy ≥ σ) for its propagation has been proposed to substitute for the criterion of σyy ≥ σ over a ‘characteristic distance’ suggested by the RKR model. With regard to the statistical model the authors suggested that it is not necessary to describe the fracture stress distribution by Weibull function. The fracture probability at a given applied load was modified by multiplying a ‘remaining probability’ taking account of the effect of the preceding loading process. The authors also discuss the mechanism of transition from a fibrous to a cleavage crack within the toughness transition temperature range. This revised version was published online in August 2006 with corrections to the Cover Date.     

Electron beam surface treatment. Part II: microstructure evolution of stainless steel and aluminum alloy during electron beam rapid solidification

Surface rapid solidification microstructures of AISI 321 austenitic stainless steel and 2024 aluminum alloy have been investigated by electron beam remelting process and optical microscopy observation. It is indicated that the morphologies of the melted layer of both stainless steel and aluminum alloy change dramatically compared to the original materials. Also, the microstructures were greatly refined after the electron beam irradiation.     

Experimental study on pressure drop and heat transfer in pipelines for brine based ice slurry Part II: Dimensional analysis and rheological model

The rheological behaviour of the ice slurry made from 9% NaCl brine has been experimentally studied in this work. Starting from the dimensional analysis of pressure drop and heat transfer processes, the minimum numbers of non-dimensional parameters present in these processes have been determined. Rheological behaviour has been adjusted to the experimental data on ice slurry pressure drop. Two different behaviours were observed depending on the shear rate values, with a clear yield stress recognizable in the low shear rate region and a shear thickening behaviour for high shear rate values. A modified Herschel–Bulkley rheological model has been proposed, which is able to predict ice slurry behaviour in both, low and high shear rate region. The influence of the parameters involved has been determined and an analytical equation for the Darcy friction factor has been obtained from the model proposed and compared to experimental results. The comparison showed a very good agreement between these data.     

Transverse crack growth in glass/epoxy composites with exactly positioned long fibres. Part II: numerical

Using finite element as the basis, transverse crack growth in long fibre composites have been investigated. Three criteria concerning pure matrix growth, fibre/matrix interface growth and crack kinking out of a fibre/matrix interface have been implemented to form a Crack Propagation Module for a software package. Numerically obtained crack paths have been compared to the ones obtained experimentally in Part I, and finally the Crack Propagation Module has been used on constructed examples in order to obtain information about the influence of various fibre distributions on the crack growth process.     

Processing of 3D sheet metal components in STEP AP-203 format. Part II: feature reasoning system

Both feature recognition and reasoning are needed for automating manufacturing planning activities for 3D sheet metal components. The feature reasoning system proposed here generates manufacturing information (e.g. flat pattern, locations of various features, internal cuts and blank profiles, type of tools required, operation sequence, bending sequence, etc.) for the features recognized in Part I of this paper. The issues related to flat pattern developments as experienced while using commercial software have been addressed in this work. A tool selection approach that uses standard tools for single and multiple blow features in punch presses is suggested. A zigzag method for operation sequencing and a virtual bend sequencing system are included. The system has been tested with various components and the results are compatible with industrial practices.     

Fe-Zn phase formation in interstitial-free steels hot-dip galvanized at 450°C: Part II 0.20 wt% Al-Zn baths

The effect of solute additions of titanium, titanium and niobium and phosphorus on interstitial-free steels on Fe-Zn phase formation after immersion in a 0.20 wt% Al-Zn bath was studied to determine the morphology and kinetics of the individual Fe-Zn phases formed. These results were contrasted to the previous study using a pure zinc (0.00 wt% Al) bath in Part I. It was found that in the 0.20 wt% Al-Zn bath, an iron-aluminide inhibition layer prevented uniform attack of the steel substrate. Instead, localized Fe-Zn phase growth occurred, termed outbursts, containing a two-phase layer morphology. Delta-phase formed first, followed by gamma-phase. Zeta-phase did not form in the 0.20 wt% Al-Zn bath, in contrast with zeta-phase formation in the pure zinc bath. As in the pure zinc bath, the growth kinetics of the total layer was controlled by the Fe-Zn phase in contact with the liquid zinc during galvanizing. For the 0.20 wt% Al-Zn bath, the Fe-Zn phase in contrast with the liquid zinc was the delta-phase, whereas the zeta-phase was in contact with liquid zinc in the pure zinc bath. The delta-phase followed t1/2 parabolic growth, while the gamma-phase showed essentially no growth after its initial formation. Titanium and titanium + niobium solute additions, which enhance grain-boundary reactivity, resulted in more rapid growth kinetics of the gamma- and delta-phases. Phosphorus additions, which decrease grain-boundary reactivity, generally increased the incubation time and retarded the growth rate of the gamma-phase. These results further confirm the concept that solute grain-boundary reactivity is primarily responsible for Fe-Zn phase growth during galvanizing in a liquid Zn-Al bath in which an iron aluminide inhibition layer forms prior to Fe-Zn phase formation. This revised version was published online in November 2006 with corrections to the Cover Date.     

Quality and exposure control in semiconductor manufacturing. Part II: Evaluation

The purpose of this article is to test the performance of a heuristic algorithm that computes a quality control plan. The objective of the tests reported in this paper is twofold: (1) to compare the proposed heuristic algorithm (HA) to an optimal allocation (OA) method; and (2) to analyse the behaviour and limitations of the proposed HA on a scale-1 test with a before/after test. The method employed to evaluate this algorithm is based on comparisons: 1. The first test illustrates the method and its sensitivity to internal parameters. It is based on a simplified case study of a product from the semiconductor industry. The product is made up of 1000, 800 and 1200 wafers incorporating three different technologies. The production duration is 1 week, and three tools were involved in this test. The behaviour of the proposed algorithm is checked throughout the evolution of the model parameters: risk exposure limit (R_L ) and measurement capacity (P). The quality control plan for each tool and product are analysed and compared to those from a one stage allocation process (named C ⁰) that does not take into account risk exposure considerations. A comparison is also performed with OA.

2. The second scale-1 test is based on three scenarios of several months of regular semiconductor production. Data were obtained from 23 etching and 12 photolithographical tools. The outputs provided by the HA are used in the sampling scheduler implemented at this plant. The resulting samples are compared against three indicators.

The results of these comparisons show that, for small instances, OA is more relevant than the HA method. The HA provides realistic limits that are suitable for daily operations. Even though the HA may provide far from optimal results, it demonstrates major MAR improvement. In terms of the maximum inhibit limit, the HA achieves better performances than C ⁰, and they are strongly correlated to R_L and to the control capacity. The article concludes that the proposed algorithm can be used to plan controls and to guide their scheduling. It can also improve the insurance design for several levels of acceptance of risk.     

Experimental and numerical studies in model composites Part II: Numerical results

A numerical approach using the boundary element method for strength and toughness of a composite with long aligned fibers is reported. The three-dimensional problem is reduced to a two-dimensional one by substituting the rows of fibers with layers of appropriate width and elastic constants. The configuration examined in this work is a compact tension specimen similar to that used in the experimental studies (Part I, [1]). The experimental results on strength and apparent fracture toughness are compared with the numerical results. For the particular geometry and fiber spacing, the numerical simulations are in good agreement with the experimental findings, i.e. the composite's strength _A , scales with the fiber spacing , in the form of _A . Using the numerical formalism a number of different geometries was examined. The simulations suggested that if the external specimen characteristics remain the same and the fiber spacing in the direction of crack advance is changed, then the strength of the composite specimen can be expressed _A . If the fiber spacing varies in both directions simultaneously, for a certain range of , it can be considered that the composite's strength _A , is proportional to _A .     

Does sodium fluoride in bone cement affect implant fixation Part II: Evaluation of the effect of sodium fluoride additions to acrylic bone cement and the fixation of titanium implants in ovariectomized rabbits

Bone integration of threaded implants made of cured polymethylmethacrylate containing sodium fluoride or commercially pure (c.p.) titanium were studied in normal and estrogen deficient New Zealand white rabbits. Nine had been ovariectomized through laparoscopy and nine served as controls. Four weeks after the ovariectomy two threaded implants made of cured bone cement with or without sodium fluoride addition were inserted in each tibia. One threaded commercially pure titanium implant was inserted in each patello–femoral joint flush to the cartilage. Six weeks after implant insertion measurement of the peak removal torque necessary to loosen the implants and light microscopical histomorphometrical investigations of tissue integration were performed. In the ovariectomized rabbits addition of sodium fluoride to the cement resulted in increased area of bone in the threads (p=0.04), but no corresponding effect could be noted in the controls. The removal torque was lower in the ovariectomized rabbits compared to the non-ovariectomized when comparing implant with sodium fluoride addition (p=0.02). The bone tissue response and the removal torque of the titanium implants were not influenced by ovariectomy in these rabbits. ©2002 Kluwer Academic Publisher     

Crack formation in mesophase pitch-based carbon fibres: Part II Detailed structure of pitch-based carbon fibres with some types of open cracks

Several mesophase pitch-based carbon fibres showing radial textures in their transverse alignments were observed by high resolution scanning electron microscope (HR-SEM) to elucidate the principal factor that induces the open crack in the transverse sections of the fibre along its fibre axis. The HR-SEM images of transverse sections exhibited various features in the alignment and shapes of the domains, although they were approximately arranged in the radial direction. The alignment of the domains was often variable in the locations from the outer part to the centre. Linear domains radially oriented in the outer part of the transverse section, that induce the circumferential shrinkage at the spinning and further heat-treatment steps, were essential for the development of open cracks with the PAC-man shaped fibre. Non-radial alignment or non-linear, bent or loop domains in the outer parts prohibited the development of the crack; these are observed in the fibres with the radial skin-random core and the onion skin-radial core alignments. Fibres without cracks in their as-spun or stabilized states usually showed shallow cracks even after the graphitization because the bent and loop domains in the intermediate and centre parts prohibited cracks from propagating into the centre part because the graphitic shrinkage along the domain shapes cannot be linear. This revised version was published online in November 2006 with corrections to the Cover Date.     

Diffusion in materials with variable temperature: Part II Two- and three-dimensional problems

The analogy between the differential equations which describe diffusion with constant diffusivity, time-dependent diffusivity, and temperature-dependent diffusivity in non-isothermal conditions is now extended to obtain solutions for two- and three-dimensional problems. The solutions for non-isothermal conditions are derived by substitution of independent variables, and correspond to a change in scale of radial distances on varying the cooling or heating rate. The dependence of the amount transferred across the interface on the rate of change in temperature is also described, and the relative effects can be predicted by selecting suitable combinations of experimental conditions. This conclusion can be extended to diffusion-controlled growth or dissolution of particles.