Processing, characterisation and oxidation resistance of βNiAl bond coat: Al and Zr effects

Platinum-modified-?NiAl is a bond coat (BC) material for thermal barrier coatings (TBCs) applications applied on aero-engine hardware to reduce their surface temperatures. However, it is desirable to minimize its production and material costs by the low-cost alternatives of similar performance. As, it has been acknowledged that the small concentration of the reactive elements (REs), such as Zr, Hf, and Y, could tremendously enhance the oxide adhesion even in some cases better than Pt modified counterparts. The present study aims to design and fabricate the Zr-modified-?NiAl bond coat on CMSX-4 superalloy using an aluminizing method. Moreover, the study focuses on the development of a systematic understanding of underlying mechanisms behind the beneficial effects of REs. Initially, three sets of BCs were prepared: Zr-free ?NiAl (undoped), Al and Zr co-deposited in a single-step process (1SP), and Zr and Al, which were individually deposited in two processing steps (2SP): zirconizing and aluminizing. Such three sets of BCs help to understand the processing, as well as Zr and Al effects on scale adhesion. In particular, 1SP/2SP BCs showed uniformity of Zr in the form of precipitates and networks that caused hardness enhancement. All BCs were isothermally oxidized at 1150oC for 100 hours wherein 2SP revealed the best spallation resistance, microstructural stability and its Zr-oxide pegs were extended to substrates. In addition to the Zr effect, BC Al content was found to affect the oxide adhesion equally. Under identical Zr contents (of 1SP and 2SP = 1at %), the higher Al showed the better spallation resistance while lower Al caused the inverse effect of Zr owing to its reactive nature that is termed as over doping. Moreover, it has been established that over-doping either local or into entire BC, accelerates the Al depletion that destabilizes the ?NiAl into ??-Ni3Al phase. An extensive discussion is presented in the light of observed results.

Quenching of Fluorescence Caused by Graphene Oxide as an Immunosensing Platform in a Microwell Plate Format

Immunoassays are, at present, an important tool for diagnostics, drug development, and environmental monitoring. However, most immunoassays involve procedures that require many elements for their development. We introduce a novel biosensing platform based on fluorescence quenching caused by graphene oxide (GO) for the detection of Human-IgG and Prostate-Specific Antigen (PSA). We employ a single antibody for the capture and detection processes, avoiding washing steps. FITC fluorophore was conjugated with antibodies for H-IgG detection, whereas quantum dots were conjugated with antibodies for PSA detection. The simple biosensing platform consists of covering a 96-well microplate (with a polystyrene bottom) with GO. The graphene oxide adhesion is possible by way of electrostatic interactions between the plate surface modified with amino groups (positively charged) and the graphene oxide (negatively charged). This proposal showed an excellent response for the detection of Human-IgG, with acceptable precision (from 0.27% to 5%). The limit of detection reached for H-IgG was 3.35 ng mL-1. In the same manner, for PSA detection, the limit of detection reached was 0.02 ng mL-1 and the precision range was from 0.7% to 15.2%. Furthermore, this biosensing platform was demonstrated to operate with real samples of human urine doped with different concentrations of prostate-specific antigen.

Using a Metal Oxide Adhesion Layer and Wet Chemical Cu Metallization for Fine Line Pattern Formation on Glass

With the trends towards miniaturization and heterogeneous integration, both IC and advanced substrate manufacturers are striving to meet the needs of next generation platforms, to increase the density of interconnects, and generate conductors featuring finer lines and spaces. Advanced manufacturing technologies such as Semi-Additive-Processing (SAP) and Advanced Modified-Semi-Additive-Processing (amSAP) were devised, realized and implemented in order to meet these requirements. Line and space (L/S) requirements of copper conductors will be below 5/5μm for advanced substrates, with 2/2μm L/S required for chip to chip connections in the near future. Herein we report about the performance of the new developed ferric sulfate based EcoFlash™ process for SAP and amSAP application with the focus on glass as the substrate and VitroCoat as thin metal oxide adhesion promotion layer. The adhesion promotion layer (about 5–10 nm thickness) is dip-coated by a modified sol-gel process followed by sintering which creates chemical bonds to the glass. The sol-gel dip coating process offers good coating uniformity on both Though-Glass-Via (TGV) and glass surfaces under optimized coating conditions. Uniform coating can be achieved up to aspect ratios of 10:1 by using a 300μm thick glass with 30μm diameter TGV. The thin adhesive layer enables electroless and electrolytic copper plating directly onto glass substrates. Excellent adhesion of electroless plated copper seed layer on glass can be achieved by using the adhesive layer and annealing technology. The thin adhesive layer is non-conductive and can be easily removed from the area between circuit traces together with the electroless copper seed layer by etching with a ferric sulfate based process. We have successfully integrated the adhesion layer and electroless and electrolytic copper plating technologies into semi-additive process and seed layer etching capable producing L/S below 10 μm.

Adhesion of Oxides Grown in Supercritical Water on Selected Austenitic and Ferritic/Martensitic Alloys

A series of austenitic alloys (800H, H214, I625, 310S, and 347) with different surface finishes were exposed to supercritical water (SCW) at 550 °C and 2.5 × 107 Pa for 120 h, 260 h, and 450 h in a static autoclave with an initial level of dissolved oxygen of 8 ppm. Indentation with a hardness indenter was used for assessment of oxide adhesion. This was compared with the results of a similar test on SCW-oxidized ferritic alloys. Delamination in all the tested ferritic alloys was insufficient for quantification of the results but allowed for qualitative comparison within this group. In the set of austenitic alloys, oxide on stainless steel (SS) 347 exfoliated during cooling from 550 °C, and from the remaining four alloys, only oxide on H214 delaminated, which made the qualitative comparison across the whole group impossible. Energy dispersive X-ray spectroscopy (EDX) revealed that under delaminated external Cr2O3 on H214 alloy, there was a submicron thick layer of Al-rich oxide. To investigate a possible oxide spallation on austenitic samples during exposure, mass loss obtained through descaling was compared with mass gain due to SCW exposure. The results indicated that the applied descaling procedure did not, in most cases, fully remove the scale. Apart from one case (SS 347 with alumina surface finish), there was no clear indication of oxide spallation.

A metal oxide adhesion layer prepared with water based coating solution for wet Cu metallization of glass interposer

Inorganic interposers made of glass are attractive for advanced high frequency applications and ultra- fine line patterning technology. Because glass combines a couple of benefits like large form factor, good coefficient of thermal expansion (CTE) matching to silicon, smooth surface and a low dielectric constant and loss tangent. Recently much progress has been made with respect to glass electrical and physical properties. This allows for handling of thin glass sheets down to 100 μm in a typical PCB panel format. Also advances have been made in the area of laser drilling allowing aspect ratio up to 1:10 for 25 μm diameter of through glass via (TGV). Another major challenge is the cost competitive and reliable metallization of smooth glass, a critical prerequisite for the use of glass substrates in the electronic packaging market. Plated copper does not adhere directly to glass. Sputtering technology typically also requires a 50 nm thick adhesion promoting metal layer (like Ti) before copper can be seeded. This metal layer could not be etched together with the copper and needs to be removed between traces by etching in an additional step. A volatile flammable solvent based metal oxide precursor coating solution has been used to make an adhesive metal oxide layer by a modified sol-gel process. To prevent potential safety issue for mass production water based metal oxide precursor coating solution so called VitroCoat GI W has been developed. The VitroCoat GI W solution can be dip-coated on flat glass surface and TGVs followed by sintering to form an ultrathin metal oxide adhesion layer (about 10nm). The thin adhesive layer enables electroless and electrolytic copper plating directly onto glass substrates without changing any of the glass properties or impacting high frequency performance. The thin metal oxide adhesive layer is non-conductive and can be easily removed from the area between circuit traces. This paper will focus on the coating uniformity and capability of VitroCoat GI W on flat glass surface and TGVs and the adhesion of wet chemical metallization on glass interposer. This adhesion layer can be used for copper fine line patterning on glass and radio frequency (RF) device fabrication.