Time-Temperature Effect for Preparation of SnO2 Nanostructures Using Carbon Assisted

We studied the effect of time and temperature for preparation of SnO2 nanostructures by chemical vapor deposit methods. SnO2 nanostructures were synthesized using Sn powder with carbon charcoal as starting materials. The source materials and Si substrates were heated with various times, temperatures under atmosphere of nitrogen and oxygen. The synthesized products were characterized using scanning electron microscopy (SEM), X-ray diffraction (XRD) techniques. The results showed the nanostructures of prepared products were very uniformly of SnO2 nanowires with diameter about 100-300 nm and length around more 1-2 μm depending on times and temperatures.

Foreign Object Damage (FOD) of Ceramic Thermal Barrier Coatings (TBCs) in Gas Turbine Airfoils

Ceramic thermal barrier coatings (TBCs), attributed to their inherent brittle nature, are highly susceptible to damage by impacting foreign particles when the impacting kinetic energy exceeds certain limits. The damage is termed foreign object damage (FOD) in related turbine components and results in various issues/problems to coatings as well as to substrates from delamination to spallation to cracking to catastrophic failure depending on the severity of impact. The FOD testing was performed using a ballistic impact gun for turbine airfoil components coated with 7% yittria stabilized zirconia (7YSZ) by electron beam physical vapor deposit (EB-PVD). A range of impact velocities up to Mach 1 was applied with three different projectile materials of steel, silicon nitride, and glass balls. The damage was assessed and characterized in terms of impact velocity, projectile material, and remaining life of turbine components. An energy-balance approach was made to develop a model to predict delamination of the TBCs upon impact.

Spark Plasma Sintering of CBN-WC-10Co Composites

Nanocomposite WC-10Co powder produced by spray pyrolysis-continuous reduction & carbonization technology and cubic boron nitride (CBN) plated with titanium by vacuum vapor deposit were used, and this paper adopted spark plasma sintering (SPS) process to prepare CBN enhanced ultrafine WC-10Co cemented carbide cermets composite material. The microstructure and mechanical properties of CBN-WC-10Co composites were investigated. The results show that CBN-WC-10Co composites consolidated by spark plasma sintering can reach 95.0 % relative density, and transverse rupture strength (TRS) is 1050 MPa, the average grain size of cermets matrix is less than 420 nm, and CBN-WC-10Co composites with excellent properties are achieved. The CBN still remains very good crystal shape after 1240°C spark plasma sintering, and there is not obvious clearance between CBN plated with titanium and the cermets matrix, the coated titanium layer can not only improve the thermal stability of CBN, but also increase the properties of CBN-WC-10Co composites.

Evaluation of CVD Diamond Coating Using Back-Reflected Rayleigh Surface Wave

The propagation characteristics of the back-reflected Rayleigh surface wave in chemical vapor deposit (CVD) diamond coated specimens were investigated experimentally using the ultrasonic backward radiation measurement. The deliberated delaminations produced between the coating layer and the substrate decreased Rayleigh surface wave velocity. This initial experimental result obtained in the present study demonstrates the high potential of the backward radiated ultrasound as a tool for nondestructive evaluation of very thin CVD diamond coating layer.

Effect of Surface Treatment on the Formation of Oxygen Enriched Brittle Layer in A Ti3A1-Nb Alloy

Effect of surface treatment on the formation of oxygen enriched brittle layer in a Ti3Al-Nb alloy was investigated. The results show that a mixed Ti2N and TiN layer was formed at the surface by the titanium nitride vapor deposit treatment, and this titanium nitride layer makes it possible to suppress the formation of the oxygen enriched brittle layer during thermal exposure. An Al2O3 film was formed at the surface of the alloy, when the surface treatment was conducted under a low partial pressure oxygen atmosphere. However, such surface treatment is not able to depress the formation of the oxygen enriched brittle layer during thermal exposure, due to the higher affinity of α2 phase for oxygen as well as the higher diffusivity of titanium in Al2O3.

MOCVD Growth of Copper and Copper Oxide Films from Bis-β-Diketonate Complexes of Copper. The Role of Carrier Gas on Deposit Composition.

An examination of thermal chemical vapor deposit elemental composition by EDAX has been completed for material films grown from Cu(acac)2 and Cu(tmhd)2 (acac = pentane-2,4-dionate; tmhd = 2,2,6,6-tetramethylheptane-3,5-dionate), using both hydrous and anhydrous carrier gas steams each of reducing (H2), inert (H2), and oxidizing (O2) composition.

Calculation of Transport-Shifted CVD Phase Diagrams

A non-iterative method is presented for constructing CVD phase diagrams which include the systematic effects of chemical element segregation in mass-transfer controlled flow reactors. Element segregation is shown to substantially shift predicted deposit phase boundaries when the vapor/deposit interface equilibrium is calculated using the local element fractions instead of the feed gas elemental composition, as is usually done. The mass transfer analysis developed here accounts for both Fick and Soret multicomponent diffusion acting across a non-isothermal boundary layer. The gas phase is assumed to be chemically frozen, with local thermochemical equilibrium imposed only at the vapor/deposit interface (as in a cold wall reactor with a hot substrate). As a specific example, this model is applied to the chemical vapor deposition of titanium diboride from TiCl4(g), BC13(g) and H2(g) in an Ar(g) carrier gas for ceramic composite material applications. These calculations, which account for boron and titanium transport via 17 chemical species, are illustrated for a long cylindrical reactor with a resistively heated coaxial fiber deposition substrate and coaxial annular flow. However, the method presented here is general in that both the chemical system and CVD reactor geometry can be changed to any other system of interest, provided: i) adequate themochemical and thermophysical data are available, ii) the deposition rate is vapor transport controlled, and iii) convective-diffusion heat and mass transfer coefficients are estimable.