Ultra-thick Film Research Articles

Design of an Ultra-Thick Film and Its Friction and Wear Performance under Different Working Conditions

Tantalum (Ta)/Ti/TiN/Ti/diamond-like carbon (DLC) (referred to as TTTD film) and Ta/Ti/TiN/TiCuN/Ti/DLC (referred to as ultra-thick film) films were designed in this study, and the factors affecting the friction and wear properties of DLC films in sodium bicarbonate and lactic acid solutions were analyzed. Moreover, a thin film with a thickness exceeding 50 microns was prepared. Morphology and tribological and mechanical properties were analyzed by scanning electron microscopy, friction and wear testing machine, and nanoindentation instrument, respectively. The results show that the presence of a TiCuN interlayer increases the defects in the DLC film and the roughness of surface, reaching a roughness of 0.19 µm. Compared with the TTTD film, the TiCuN interlayer reduces the hardness and increases the residual stress, which is 0.52 Gpa and −6.08 GPa, respectively. The TTTD film has a smooth and dense surface structure and high hardness, causing it to more easily form boundary lubrication. However, the ultra-thick film has lower hardness and rough surface, which cannot effectively form boundary lubrication. Therefore, the friction coefficient of the ultra-thick film is higher than that of the TTTD film under different working conditions. In sodium bicarbonate solution, a double-hydrolysis reaction is more likely to occur, resulting in a higher friction coefficient than in lactic acid solution. The friction coefficient of the TTTD film has a longer running-in period, which is attributed to the oxides generated by the double-hydrolysis reaction and the precipitated sodium bicarbonate crystals. Finally, it was concluded that the surface quality and the internal bond structure of DLC film have a significant impact on the friction and wear properties. This provides a theoretical basis for the design of multilayer structures.

High Performance Electrode Architectures By Laser Structuring of Silicon-Graphite Anodes and Ultra-Thick Film NMC-Type Cathode Materials

Laser structuring of battery materials such as electrodes, current collectors, and separator materials becomes more and more a versatile tool for a flexible designing of battery performance with regard to high rate capability, reduced impedance and diffusion over-potential, enhanced battery lifetime, and a tremendous improvement of electrode wetting with liquid electrolyte. Especially structuring of thick film composite electrodes with film thickness up to 300 µm is of great interest for combining high energy and high power applications. Laser ablation by using ultrafast laser radiation ensures a high aspect ratio structuring without damaging or modifying the material properties of the active material, inactive compounds, and current collector. Thermal induced material modification and laser-induced material splatter on top of the electrode surfaces have been so far a major problem by using conventional nanosecond lasers. However, in recent years high power OEM-type ultrafast laser beam sources became available for industrial production. Those lasers provide powers of several 100 W up to the kW-regime with repetition rates of several tenfold MHz, which makes high-speed parallel material processing feasible. Finally, after introducing high-speed nanosecond laser cutting of electrodes almost one decade ago, we forecast that with regard to recent technical approaches quite soon high-speed electrode ultrafast laser structuring will entering the pilot line level. For this purpose, at KIT, parallel processing of cathode and anode materials with large foot print area is being developed in a roll-to-roll (R2R) environment in order to meet the process speed requirements of cell production. Furthermore, we are developing thick film electrode concepts for anodes made of graphite and silicon-graphite and cathodes based on Lithium-Nickel-Manganese-Cobalt-Oxide (NMC) with varying nickel content and water-based slurries. Electrode thicknesses in the range of 100-300 µm were synthesized for subsequent laser processing, cell assembly, and electrochemical characterization such as galvanostatic measurements, galvanostatic intermittent titration technique, cyclic voltammetry, and electrochemical impedance spectroscopy. Large area laser structuring in R2R environment for generation of three-dimensional (3D) electrode architectures with increased active surface area, enhanced mechanical integrity for high energy materials such as Si-graphite anodes and an overall boost in electrochemical performances on pouch cell level will be presented. Laser-induced breakdown spectroscopy (LIBS) was applied for elemental mapping of entire electrodes in order to characterize binder migration in ultra-thick film electrodes, and in post-mortem studies to evaluate degradation processes in unstructured, damaged, and structured thick film electrodes with large footprint (pouch cell level). Post-mortem studies show that significant chemical modifications across from electrodes with macroscopic surface defects could be detected while laser structured electrodes provide less inhomogeneity in lithium distribution in comparison to cells with unstructured electrodes. Furthermore, an inhomogeneity in mechanical load on cells could be identified as a main reason for cell degradation. LIBS is presented as a perfect tool to rapidly characterize and identify starting points for cell degradation on coin cell and pouch cell level. In summary, ultrafast laser structuring of electrodes provides a new manufacturing tool for next generation battery production to overcome current limitations in electrode design and cell performances.

Cyclotron solid targets preparation for medical radionuclides production in the framework of LARAMED project

LARAMED project aims to set up an advanced science and technology facility to develop new and efficient methods to produce medical radioisotopes at Legnaro National laboratories of National Institute of Nuclear Physics. Waiting for the facility full operation, LARAMED group has already started working on the cyclotron production of several conventional and emerging radionuclides. Suitable target preparation is one of the most critical aspects in cyclotron production of radioisotopes. LARAMED group has investigated a set of non-classical techniques for metallic target preparation. Magnetron sputtering technique developed for ultra-thick film deposition was applied for the preparation of the Mo solid targets for 99mTc production, and Y ones for 89Zr production. Spark plasma sintering method provides efficient sintering of powders and good bonding of metallic pellet to a backing. Like magnetron sputtering, it was tested for natl00Mo and natY targets, as well as for natCr targets preparation aimed at 52Mn production. The High energy Vibration Powders Plating technique was instead applied for natural (Mo, Ti) and enriched 48Ti metallic powders with >95% deposition efficiency. All three techniques tested provided the cyclotron solid targets with high thermomechanical performance under the beam (IkW/cm2).

Medical Cyclotron Solid Target Preparation by Ultrathick Film Magnetron Sputtering Deposition

Magnetron sputtering is proposed here as an innovative method for the deposition of a material layer onto an appropriate backing plate for cyclotron solid targets aimed at medical radioisotopes production. In this study, a method to deposit thick, high-density, high-thickness-uniformity, and stress-free films of high adherence to the backing was developed by optimizing the fundamental deposition parameters: sputtering gas pressure, substrate temperature, and using a multilayer deposition mode, as well. This method was proposed to realize Mo-100 and Y-nat solid targets for biomedical cyclotron production of Tc-99m and Zr-89 radionuclides, respectively. The combination of all three optimized sputtering parameters (i.e., 1.63 × 10−2 mbar Ar pressure, 500 °C substrate temperature, and the multilayer mode) allowed us to achieve deposition thickness as high as 100 µm for Mo targets. The 50/70-µm-thick Y targets were instead realized by optimizing the sputtering pressure only (1.36 × 10−2 mbar Ar pressure), without making use of additional substrate heating. These optimized deposition parameters allowed for the production of targets by using different backing materials (e.g., Mo onto copper, sapphire, and synthetic diamond; and Y onto a niobium backing). All target types tested were able to sustain a power density as high as 1 kW/cm2 provided by the proton beam of medical cyclotrons (15.6 MeV for Mo targets and 12.7 MeV for Y targets at up to a 70-µA proton beam current). Both short- and long-time irradiation tests, closer to the real production, have been realized.

The development of quartz crystal microbalance

Quartz crystal microbalance (QCM), which is a sensitive and practical tool for measurement of the changes of interface, has got certain applications in the study of interface problems in physical, chemical, biological, pharmaceutical, clinical medicine and environmental science. However, the application and promotion of QCM in liquid phase has been limited by the difficulties of quantitative interpretation of QCM data. To solve this problem, researchers have developed a variety of advanced QCM, such as the QCM with the impedance analysis (impedance QCM, i-QCM) or the QCM that can monitor the energy dissipation (QCM with dissipation, QCM-D). At the same time, many corresponding theoretical models also have been developed. However, for most biological and chemical researchers, these theories are too complicated, which greatly limits the potential of QCM study. This review classified the reported methods, models and equations of QCM into five categories by application conditions with a clue of our groups research work in the QCM and provided a clear definition of criteria: i) solid-gas interface; ii) Newtonian fluid; iii) solid-liquid interface of thin film studies; iv) solid-liquid interface of thick film studies; v) solid-liquid interface of ultra-thick film studies. For each type of situation, we will describe how to simplify the QCM data and ensure the accuracy of quantitative analysis in simple language that chemists and biologist can understand. For QCM data analysis in liquid environment, we emphatically introduce the “solidified liquid” model, which allows QCM become a molecular ruler under certain conditions with the working range from nanometers to micrometers. The molecular ruler has a good application in some innovative interface researches. Finally, we theoretically analyze the defects of QCM as a biosensor -- the sensitivity of protein concentration detection is limited by the “detection of surface average mass” at only 1 μg mL^-1. Furthermore, we propose the development direction and potential applications of QCM, and hope that QCM can be extended in various problems of the interface application.

Fabrication of high-aspect-ratio microstructures using SU8 photoresist

SU8 photoresists are used widely in the development and fabrication of the high-aspect-ratio micro-structure. However, SU8 process is difficult to repeat when the film thickness and aspect ratio are increasing. In this paper, the soft bake is investigated. The retained solvent level in SU8 film is studied by using the theory of free volume and diffusion process. The result shows that the proper and uniform solvent level in the photoresist film is crucial to achieve good SU8 microstructures in the ultra-thick film process. The microstructure with 5 μm linewidth and aspect ratios larger than 50 was obtained.

Ultra thick film open tubular traps with an increased inner diameter

In this paper, the concept of open tubular traps, coated with a very thick film of polydimethyldisiloxane for enrichment of trace volatile components has been further explored. From theoretical calculations as well as practical experiments it is demonstrated that it can be advantageous to increase the inner diameter of such traps. For a given sampling flow rate and phase ratio, the plate number of the traps is not dependent on the inner diameter, provided that the linear flow velocity remains sufficiently high to offset the effect of axial diffusion. It is shown that this is due to the basic fact that for a given sampling flow rate, the average linear flow velocity in the trap is inversely proportional to the square of the inner diameter of the trap. However, in contrast to chromatographic separations, the linear flow velocity is not important. Under conditions of a constant phase ratio, an increased inner diameter also increases the amount of sorbent in the trap, which is a key parameter for obtaining high breakthrough volumes. Open tubular traps with an expanded inner diameter have very low pressure drop characteristics, which provides the possibility to construct new, simplified sampling systems.

Thick film traps with an irregular film: Preparation and evaluation

A new method for preparation of sorbent-based ultra-thick film traps for concentration of trace volatile components from gaseous matrices is described. The procedure is based on blowing a prepolymer (polydimethylsiloxane) through a capillary tube, forming an irregular film of stationary phase. Subsequently, the prepolymer is immobilized in a few seconds by heating to 200 °C. Evaluation of the performance of the new traps showed that the loss of efficiency, compared to regular smooth film traps is only on the order of 20–30%. In terms of breakthrough volume, this loss in performance is rather insignificant. The technology is extremely simple and allows a rapid and cheap production of a large number of ultra-thick film traps, even in non-specialized laboratories. The method can be applied to any type of cross-linkable stationary phase, thereby expanding the scope of sorbent-based trapping and preconcentration concept. Many applications are anticipated in trace and ultra-trace analysis in a wide range of fields, such as environmental chemistry, polymers, food and process analysis.

Headspace gas analysis: Comparison of the efficiency of thick film, ultra thick film, and activated charcoal open tubular capillary traps for the concentration of volatile, airborne, organic compounds

AbstractDetermination of the rate at which volatile organic molecules diffuse through the wall of a polysiloxane rubber tube, shows that the full depth of the rubber lining of ultra‐thick film open tubular traps is utilized for the retention of volatile organic compounds in headspace gas analysis. Small apolar molecules migrate rapidly through the rubber, but larger molecules and polar compounds diffuse relatively slowly into the rubber. Neither traps with a thick film of an apolar stationary phase, nor those with an ultra thick polysiloxane rubber lining retain highly volatile compounds very effectively. Traps containing activated charcoal particles fused into their inside glass surface have a much higher capacity than those with activated charcoal particles embedded in a layer of stationary phase.