Profile control of plastic sheet in an industrial polymer processing process

A control system was developed using a two-degree of freedom control structure with four input variables in the feedforward, and two inputs, the screw rotation speed and the gap of the forming roller, in the feedback loop. The feedforward signals were predetermined from first principles and the operators' heuristic rules for each changeover operation and prepared in a database. At the end of each changeover operation, the values in the database were rewritten by evaluating control performance. The magnitude of the true dead time changed as the production rate was changed. The rate of sampling and control action in the feedback control was adapted in each changeover operation so that the changing time delay was always expressed by a one-sampling-step time delay in the discrete models and dealt with by the controller robustness against parameter uncertainty. The developed control system was applied to an actual industrial plastic sheet production line and allowed one to easily perform the changeover operation and reduce material consumption.     

Modeling of Droplet-Based Processing for the Production of High-Performance Particulate Materials using the Level Set Method

The dynamic and thermal processes of an Mg-Zn-Y alloy droplet's spreading and solidification are investigated using the level set method in order to understand their effects on the phase change process in a uniform droplet spray process. The level set method, driven with the solidification velocity predicted by a free dendritic growth model, is capable of tracking the evolution of the solidification front within the deformed droplet. It is found that the solidification process heavily depends on the initial thermal state of the droplet, the latent heat released during solidification, and the heat loss to the substrate. A rapid solidification occurs in the initial microseconds before a slow solidification process takes place.     

Electrical conduction properties of Sr-doped Bi<Subscript>4</Subscript>(SiO<Subscript>4</Subscript>)<Subscript>3</Subscript> with the eulytite-type structure

Electrical conduction in 1 mol% Sr-doped Bi₄(SiO₄)₃ with the eulytite-type structure at elevated temperatures was investigated with conductivity measurements. Conductivity of the material under wet condition was higher than that under dry condition, and were 1.2 × 10⁻⁶ – 9.7 × 10⁻⁵ S cm⁻¹ at 500–850 ^°C. From H/D isotope effects and p(O₂)-dependencies of the conductivity, it was found that the Sr-doped Bi₄(SiO₄)₃ exhibited protonic conduction at all the temperatures investigated while contribution of p-type conduction became significant with increasing p(O₂) and/or temperature. Protonic and p-type conductions in the material were discussed in terms of defect equilibria.     

High-speed oxide coating by laser chemical vapor deposition and their nano-structure

Oxide thick films, partially yttria-stabilized zirconia (YSZ) and titania (TiO₂), were prepared by laser chemical vapor deposition (LCVD). The assistance of laser tremendously increased the deposition rate for YSZ and TiO₂ films up to 660 and 2500 μm/h, respectively. The increase in the deposition rate was accompanied by plasma formation around the deposition zone, and the plasma was observed over critical values of laser power and substrate pre-heating temperature. A wide variety of morphologies of films from feather-like columnar to dense microstructures were obtained depending on deposition conditions. The columnar structure contained a large amount of nano-pores at columnar boundary and inside grains. These columnar structure and nano-pores were advantageous for applying YSZ films to thermal barrier coatings.     

Characterization of Al Skeletal Structures Fabricated by Ultrasonic Powder Consolidation

Metallurgical and Materials Transactions A - Skeletal aluminum structures were fabricated by ultrasonic powder consolidation (UPC) of NaCl—15&nbsp;mass&nbsp;pct Al and...     

Spray deposition of a Sn-40 Wt Pct Pb alloy with uniform droplets

An apparatus capable of producing and depositing uniform droplets (100 to 200 μm in diameter) was developed and used to study the relationship between spray deposition parameters and the microstructures of Sn-40 wt pct Pb alloy spray deposits. The sprays used in the study consisted of uniform droplets, either 103 or 178 μm in diameter, that were in identical thermal and solidification states as they impacted the substrate. The thermal and solidification states of the uniform droplets were determined as a function of the flight distance (the distance from the metal pouring orifice) by model calculations and calorimetric measurements assuming equilibrium solidification. Although a fair agreement was noted between the model and the calorimetric measurements at small flight distances, corresponding to large liquid fractions, the calorimetric measurements indicated 10 to 20 pct higher liquid fractions at larger flight distances. The resultant microstructures comprised either a mixture of the Pb-rich and Sn-rich phases, both in an equiaxed morphology, or a lamellar eutectic structure with a small amount of the Pb-rich primary phase in a coarse spherical morphology. The mostly lamellar eutectic structure resulted from an excessive enthalpy flux and/or slow heat extraction from the deposit. Fine, equiaxed, two-phase microstructures and high deposit density resulted from optimal combinations of droplet enthalpy, deposition rate, droplet size, and deposit cooling rate which gave short local solidification times.     

Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel

In an attempt to investigate Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in high chromium steel, Cs–Te corrosion out-pile tests of two 9Cr steels with different distributions of chromium carbide were carried out at 975 K for 100 h, and their corrosion depths were compared. The corrosion is obviously more advanced in a specimen which has grain boundary carbide than in the one that does not. A considerable reason of the result is that the carbide distributed at grain boundaries promoted the corrosion reaction and the corrosion extended along the grain boundary. This is the first case in which the Cs–Te corrosion depth dependence on distribution of chromium carbide precipitation in Fe–Cr steel is clarified experimentally.     

Heat Capacity Study on Anharmonicity in Ae<Subscript>8</Subscript>Ga<Subscript>16</Subscript>Ge<Subscript>30</Subscript> (Ae = Sr and Ba)

The heat capacity of single-crystalline samples of Sr₈Ga₁₆Ge₃₀ (SGG) and Ba₈Ga₁₆Ge₃₀ (BGG) clathrates was measured to investigate the anharmonicity of the encapsulated atoms. At low temperatures, BGG can be well described by a standard Debye model, and the C _p/T ³ versus T plot can be fitted with two Einstein temperatures: θ _E1 = 42 K and θ _E2 = 74 K. On the other hand, SGG shows deviation from the Debye model. Moreover, neither the Einstein model nor the soft potential model (SPM) alone can fit the peak in the C _p/T ³ versus T plot, and the peak should be fitted by employing both models. Our results indicate that the effective electron mass is enhanced by the anharmonic phonons.     

Development of electrospray laser chemical vapour deposition for homogenous alumina coatings

Electrospray,as a liquid source supply system,has been applied to chemical vapour deposition(CVD).In thermal CVD,the microstructure of the obtained films changes from dense to coarse granular because of the decreasing surface temperature during deposition.Using the electrospray laser chemical vapour deposition method,we prepared homogenous alumina coatings.We found that laser irradiation was effective in compensating the surface temperature decrease,and an alpha-alumina coating with dense columnar microstructures was obtained at a deposition rate of 200 μm/h using 200 W Nd:YAG laser irradiation.