Symposium G Poster Session

Thursday, May 2, 2013 5:00 PM in Room Grand Hall

GP2 Preparation of Phosphor-doped TiO2 Particle/Passivating Layer and their Applications in Dye-sensitized Solar Cells
TaeSung Eom, KyungHwon Kim, ChungWung Bark, HyungWook Choi (Gachon University, Republic of Korea)
The Dye-sensitized solar cell (DSSC) are composed of a dye-adsorbed nanoporous TiO2 layer on a fluorine-doped tin oxide (FTO) glass substrate, redox electrolytes and a counter electrode. DSSC were constructed by application of phosphor-doped and TiO2 nanoparticle composite particles with various percentages. phosphor-doped TiO2 nanoparticle have been synthesized by introducing a trace amount of silicate phosphor to the reaction system. TiO2 passivating layer was deposited on the substrate by hydrolysis of TiCl4 aqueous solution. TiO2 layer was coated on FTO glass by screen printing method. The crystal structure and the morphology were characterized by X-ray diffraction (XRD), and a Scanning Electron Microscope (SEM). The transmittance and the absorbance of TiO2 films and phosphor scattering were characterized by UV-vis. The TiO2 films were calcinated by the conventional method and a Rapid Thermal Annealing system. It was found that the conversion efficiency of the DSSC was highly affected by the crystalline structure of the scattering layer.
GP3 Dual Frequency ICP Discharge: Effect of Pressure and Gas Ratio on EEDF and Discharge Parameters
Anurag Mishra, TaeHyung Kim, Kyongnam Kim, Geun Yeom (Sungkyunkwan University, Republic of Korea)

Using a radio frequency compensated Langmuir probe, pressure and gas ratio dependent effects on plasma parameters and electron energy distribution functions (EEDFs) are investigated in Ar/CF4 discharge produced by dual frequency/dual antenna large area (450 mm) inductively coupled plasma (ICP) source, at an operating in the pressure range from 1 to 25 mTorr. A tungsten probe tip of 10 mm in length and 100 µm in diameter is located at the center of the substrate and 70 mm away from the plasma source.

It is observed that increasing pressure reduces energy spread of electron energy probability functions (EEPFs), due to increasing electron energy loss via collisions, from 20 eV at 1 mTorr to 13 eV at 25 mTorr. At a constant RF power, plasma density (ne) increases linearly with pressure between 1 to 10 mTorr and then (> 10 mTorr) decreases. The same trend has also been observed for electron temperature.

It has also been found that increasing Ar gas proportion in Ar/CF4 mixture significantly increases plasma density (ne), however plasma temperature and plasma potential influences marginally.

GP4 Failure Behavior of Thick Single and Multilayered TiSiCN Coatings under Impact-sliding Forces
Junfeng Su, Xueyuan Nie, Henry Hu (University of Windsor, Canada); Ronghua Wei (Southwest Research Institute, US)
With plasma-enhanced magnetron sputtering (PEMS) technology, a series of thick single and multilayered TiSiCN coatings have been successfully deposited on H13 steels. The thick TiSiCN coatings have been investigated in severe sliding wear, erosive and corrosion conditions. However, there is a lack of study on failure behavior of the coatings when subjected to cyclic impact-sliding loads. An impact-sliding coating fatigue wear testing method was used to evaluate the failures behavior of the coatings under high contact stress conditions caused by impact and sliding forces. The impact-sliding wear tracks were observed at both top view and cross-section view using scanning electron microscopy. The effects of thickness, multilayer structures, surface topography on failure mechanisms were particularly discussed.
GP5 Evolution of Reliability on Electroplated and Sputtered Ni-Zn films for Under Bump Metallization with Sn-3.0Ag-0.5Cu Solder Attached During Liquid Reactions
Hsiu-Min Lin, Jenq-Gong Duh (National Tsing Hua University, Taiwan, Republic of China)

The suitable Ni-rich alloy films could be fabricated by controlling parameter of electroplating, and the alternative Ni-Zn, Ni-Fe and Ni-Co films which act as under bump metallization (UBM) layer have been developed in flip chip electronic design. Flip chip structures are the better ideal to enhance the reliability of solder joint and pursue the small size, low cost, and multiple functionalities in electronics. Regarding the suppression of both intermetallic compounds (IMCs) formation and UBM consumption rates in the flip chip design of the solder joints, Ni-based films UBM with the slower elemental diffusion should be selected. This study aims to investigate and to evaluate the feasibility of electroplated Ni-Zn, Ni-Fe, Ni-Co films UBM. The doped Zn, Fe, Co might inhibit and affect the elemental diffusion in the solder joints. After fabricating these suitable Ni-rich alloy films, the intrinsic properties, i.e. residual stress, roughness, microstructure, texture were analyzed by curvature measurement, atomic force microscopy (AFM), field-emission scanning electron microscopy (FE-SEM), and X-ray diffractometry (XRD), respectively. Furthermore, the extrinsic properties of the IMC formation and composition re-distribution in those solder joints via different Ni-based films UBM attached with Sn3.0Ag0.5Cu (SAC305) solder were evaluated by a field emission electron probe microanalyzer (FE-EPMA) during various reflow time. Besides, the reliability of the SAC305/Ni-Zn, SAC305/Ni-Fe, and SAC305/Ni-Co joints was evaluated by high speed impact tests. This study demonstrated that the binary Ni-Zn, Ni-Fe, and Ni-Co film might be the potential alternatives for under bump metallization application. The possible mechanisms for correlation between intrinsic properties of these novel Ni-based films UBM and related extrinsic interfacial reaction were discussed and proposed.

GP6 Improvement of Air Plasma Spraying Parameters for the Fabrication of Thermal Barrier Coatings
Sugehis Liscano, Linda Gil, Miriam Romero (UNEXPO, Venezuela (Bolivarian Republic of))
In this research, ZrO2–10%Y2O3–18%TiO2,Al2O3–13%TiO2 thermal barrier coatings (TBCs) with NiCrAlCoY2O3 bond coats were sprayed by employing an air plasma thermal spray (APS) technique following factorials design experiments in order to obtain the best favorable spraying conditions able to enhance their properties. The powders particle size distribution analysis was obtained by mesh analysis using sonic sifter equipment. The morphology and microstructure of composites powders were analyzed by SEM (EDS) and X Ray Diffraction techniques. The effect of the spraying parameters on the porosity, microhardness, microstructure and morphology of coatings were determined by using different techniques such as optical microscopy (OP) with image analysis, Vickers indentation and scanning electron microscopy (SEM) technique, this latter coupled with X-Ray microanalysis (EDS). The adhesive strength of each TBCs System was measured according to the ASTM C633. It was found that both variables evaluated the arc voltage and the arc current, as well as their interaction, had a significant effect on the microstructure and mechanical properties of the coatings.
GP7 Surface Recrystallization of Tungsten Carbide by MPCVD due to Controlled Oxidation and Deoxidation in an Equilibrium Process
Manuel Mee, Sven Meier (Fraunhofer IWM, Germany)
Diamond coatings for hard metal tools have been used for years, but usually only inadequate adhesion appears. The approach to remove cobalt from the surface by a two-step chemical etching pretreatment has led to good results, but at the same time a strong weakening of the underground structure is a result of this approach. A newly developed process causes surface regeneration due to a balance of coincidental oxidation and deoxidation.
GP8 Understanding of Wear Mechanisms of Coated Solid Carbide Endmills During Machining of Ti-Al6-V4
Sebastian Stein, Richard Rachbauer, Mirjam Arndt (OC Oerlikon Balzers AG, Liechtenstein)

State-of-the-art cutting operations for difficult-to-cut materials, e.g. Ni- or Ti-based alloys, represent a challenging topic for research and development efforts of tool manufacturers and coating designers. Conventional process conditions involve high temperatures up to 1000°C at the cutting edge, which mostly stem from the low thermal conductivity of the workpiece materials. Moreover, the high-temperature toughness and high material strength of Ni- and Ti-based alloys at elevated temperatures demand optimized process conditions and coating solutions.

In order to understand the apparent wear mechanisms during solid carbide milling of Ti-Al6-V4 in more detail, the present work explores the complex interaction of the tool micro and macro geometry, including edge and corner shapes, as well as different coating systems and the impact of liquid coolants. The adhesive wear behaviour during the machining of Ti-Al6-V4 is analyzed by experimental work, utilizing optical and electron microscopy. Furthermore, currently available coating concepts, that only exhibit marginal benefits in comparison to uncoated tools, are discussed with special focus on roughing operations.

The present contribution emphasizes the importance of a holistic process knowledge and gives a contribution to the understanding of wear mechanisms in context of cooling lubrication and coating design.