Investigation of a Possible Material-Saving Approach of Sputtering Techniques for Radiopharmaceutical Target Production

Magnetron sputtering (MS) is a relatively new deposition technique, which is being considered among the cyclotron solid target (CST) manufacturing options now available, aiming at the medical radioisotopes yield for radiopharmaceutical production. However, the intrinsic high material losses during the deposition process do not permit its use with extremely expensive target materials, such as isotopically enriched metals/oxides. In this study, R&D technology for a new recovering shield is instead proposed to assess the dissipation of target material during the sputtering processes and, thus, an estimate of the material recovery that may be feasible and the related amount. The weight-loss analysis method is used to assess the material losses level inside the chamber during processing. In all tests carried out, a high-purity copper (99.99%) was used as a target material. As a result of this study, the material distribution for both magnetron and diode sputtering depositions can be calculated. The feasibility of the ultra-thick coatings growing, devoted to CST production, is demonstrated.

High Temperature Cycling Behavior of Novel Thermal Barrier Coatings Deposited by High Enthalpy Plasma Torch

This study presents the results of thermal cycling experiments on thermal barrier coatings deposited using hybrid water/argon-stabilized plasma (WSP-H) torches. Topcoats produced from YSZ suspensions and powders were successfully prepared and evaluated by thermal fatigue testing. Quad-layer coatings with topcoats consisting of yttria stabilized zirconia, gadolinium zirconate, and yttrium aluminum garnet were also prepared and tested at high temperatures and thermal gradients. The results obtained show the potential of WSP-H technology for applications where protection of large components or deposition of thick coatings are required.

Fabrication of Thermal Plasma Sprayed NiTi Coatings Possessing Functional Properties

Thick NiTi shape memory alloy coatings (300–500 µm) were produced on graphite and AISI 304 substrates by radio frequency inductively-coupled plasma spray technology (RF-ICP) from feedstock NiTi powders. Their microstructure as well as chemical and phase composition were characterized and a methodology for the characterization of functional shape memory properties of the thick coatings was developed. The coatings exhibited cubic to monoclinic martensitic transformation and shape memory effect. The presented results prove that NiTi coatings with functional thermomechanical properties can be easily produced on structural materials by RF-ICP. Further optimization will be needed to prepare NiTi coatings with better microstructural and chemical homogeneity.

Influence of Groundwater pH on Water Absorption and Waterproofness of Polymer Modified Bituminous Thick Coatings

Polymer modified bituminous thick coatings are increasingly used in the construction industry to protect underground parts of buildings from groundwater. When assessing their durability, one vital issue related to their functional properties is the influence of water absorption on the waterproofness of the applied solution as a result of the action of groundwater with different pH values. As part of the research, the water absorption of the products in question was assessed using the method of total immersion in water with pH of 4.0, 7.0 and 7.5 as well as comparatively, as a result of one-way exposure to demineralized water under successively increasing pressure up to 0.5 MPa. The moisture susceptibility of the coatings was assessed both concerning the local surface damage and the continuous waterproofing coating. It was established that the coatings show the highest water absorption when the water pH is 4.0, which simulates the groundwater aggressiveness on construction products. It was proven that moisture absorbed by the coatings is retained within this layer and is not transferred to the substrate on which the coatings are laid. It was also found that water in contact with the tested coatings changes its reaction to alkaline, which can result in contamination of groundwater in the area of waterproofing coating. A modification of the method of assessing the water absorption of polymer modified bituminous thick coatings was proposed, taking into account their use in conditions of use.

Nanostructural Characterisation and Optical Properties of Sputter-Deposited Thick Indium Tin Oxide (ITO) Coatings

Indium tin oxide (ITO) thin films, used in many optoelectronic applications, are typically grown to a thickness of a maximum of a few hundred nanometres. In this work, the composition, microstructure and optical/electrical properties of thick ITO coatings deposited by radio frequency magnetron sputtering from a ceramic ITO target in an Ar/O2 gas mixture (total O2 flow of 1%) on unheated glass substrates are reported for the first time. In contrast to the commonly observed (200) or (400) preferential orientations in ITO thin films, the approximately 3.3 μm thick coatings display a (622) preferential orientation. The ITO coatings exhibit a purely nanocrystalline structure and show good electrical and optical properties, such as an electrical resistivity of 1.3 × 10−1 Ω·cm, optical transmittance at 550 nm of ~60% and optical band gap of 2.9 eV. The initial results presented here are expected to provide useful information for future studies on the synthesis of high-quality thick ITO coatings.

Strain-Induced Cracking Behavior of Coating/Substrate Systems and Strain Tolerant Design for Thick Coatings

The life span for a coating attached to its substrate is basic support for their desired protective function. Therefore, it is necessary to find out the causes responsible for the failure of coatings during service. This paper developed a finite element model to investigate the cracking behavior of plasma-sprayed ceramic coatings induced by the mismatch strain of thermal expansion between coating and substrate. Crack propagation affected by coating thicknesses was realized by the virtual crack closure technique (VCCT). The residual stresses (σ22 and σ12) and the strain energy release rate (SERR) induced at the tip of pre-crack in ceramic coatings are calculated. Results show that the σ22 and σ12 at the tip of the pre-crack increases continuously with the thickening ceramic coatings. The SERRs at the tip of the pre-crack in top-coat (TC) were increased with the thickness of ceramic coatings, resulting in the propagation of cracks. The crack length increases with the thickening of ceramic coatings. The crack propagation and coalescence lead to coating spallation, which is one of the main failure modes for plasma sprayed ceramic coatings during service. Given that, strain tolerant design was developed by inserting vertical pores in coatings. It was found that the SERRs were decreased with the increase in the number of vertical pores, as well as their depth. Moreover, the coatings with vertical pores appear to be crack-resistant, in particular for the thicker coatings. This suggests that the strain tolerant design is helpful to extend the life span of thick coatings, which makes a fundamental contribution to the design and preparation of advanced protective coatings in future applications.