Where ppm Quantities of Silsesquioxanes Make a Difference—Silanes and Cage Siloxanes as TiO2 Dispersants and Stabilizers for Pigmented Epoxy Resins

In this work, silsesquioxane and spherosilicate compounds were assessed as novel organosilicon coupling agents for surface modification of TiO2 in a green process, and compared with their conventional silane counterparts. The surface-treated TiO2 particles were then applied in preparation of epoxy (EP) composites and the aspects of pigment dispersion, suspension stability, hiding power, as well as the composite mechanical and thermal properties were discussed. The studied compounds loading was between 0.005–0.015% (50–150 ppm) in respect to the bulk composite mass and resulted in increase of suspension stability and hiding power by over an order of magnitude. It was found that these compounds may be an effective alternative for silane coupling agents, yet due to their low cost and simplicity of production and manipulation, silanes and siloxanes are still the most straight-forward options available. Nonetheless, the obtained findings might encourage tuning of silsesquioxane compounds structure and probably process itself if implementation of these novel organosilicon compounds as surface treatment agents is sought for special applications, e.g., high performance coating systems.

Overview of Silica-Polymer Nanostructures for Waterborne High-Performance Coatings

Combining organic and inorganic components at a nanoscale is an effective way to obtain high performance coating materials with excellent chemical and physical properties. This review focuses on recent approaches to prepare hybrid nanostructured waterborne coating materials combining the mechanical properties and versatility of silica as the inorganic filler, with the flexural properties and ease of processing of the polymer matrix. We cover silica-polymer coupling agents used to link the organic and inorganic components, the formation of hybrid films from these silica-polymer nanostructures, and their different applications. These hybrid nanostructures can be used to prepare high performance functional coatings with different properties from optical transparency, to resistance to temperature, hydrophobicity, anti-corrosion, resistance to scratch, and antimicrobial activity.

Design and Synthesis of a High Performance Coating

High performance coatings are needed for downhole drilling applications. The main challenge in developing such coatings is to impart desirable surface characteristics such as low friction, high wear and corrosion resistance, while retaining structural integrity and consistency. Most coatings do not sustain the conditions in harsh environments resulting in failure and safety hazards. In this research, we designed high temperature coatings with integration of components that display wear resistance. After synthesis, they exhibited promising lubrication performance. Specifically, a simple and low-cost method was developed that can process the coating consisting high-temperature ceramics such as BN, SiC. Hybridizing graphite and α-zirconium phosphate as friction modifiers ideal for use with metals, alloys and ceramics, this coating is durable in a wide range of temperatures. Experimental results showed that the friction coefficient obtained for our coating was 0.17 as against the 0.50 value obtained for steel on steel sliding contact. In this work, we detail about the composition, microstructure, and tribological evaluation of the coatings tailored for drilling applications.

Micro/Nano Technologies for High-Density Retinal Implant

During the past decades, there have been leaps in the development of micro/nano retinal implant technologies, which is one of the emerging applications in neural interfaces to restore vision. However, higher feedthroughs within a limited space are needed for more complex electronic systems and precise neural modulations. Active implantable medical electronics are required to have good electrical and mechanical properties, such as being small, light, and biocompatible, and with low power consumption and minimal immunological reactions during long-term implantation. For this purpose, high-density implantable packaging and flexible microelectrode arrays (fMEAs) as well as high-performance coating materials for retinal stimulation are crucial to achieve high resolution. In this review, we mainly focus on the considerations of the high-feedthrough encapsulation of implantable biomedical components to prolong working life, and fMEAs for different implant sites to deliver electrical stimulation to targeted retinal neuron cells. In addition, the functional electrode materials to achieve superior stimulation efficiency are also reviewed. The existing challenge and future research directions of micro/nano technologies for retinal implant are briefly discussed at the end of the review.

Optimizating Spray Parameters of High Velocity Oxy Fuel (HVOF) for Cr3C2 - NiCr Coating

Porosity, hardness, and adhesion mainly affect the performance of thermal spray coating and significantly depend on spray parameters. Therefore, determining value of the spray parameters and their effects on the coating properties are always taken into consideration. This paper studies optimization as well as evaluates influences of HVOF spray parameters which include powder feed rate (M), rotational speed of the details per minute (N) and step movement of the nozzle per revolution (S) to the adhesion, porosity, micro-hardness of Cr3C2 - 20(80Ni20Cr) coating on 40Cr steel shaft substrate. Taguchi experimental design L9 combined with analysis of variance (ANOVA) was used to determine optimum spray parameters and percentage of effect of each spray parameter on properties of the coating. From obtained results, the optimal spray parameters are m = 35 g.min-1, n = 130 rpm, S = 6 mm for the highest hardness coating of 658.2 HV; with m = 45g.min-1, n = 130rpm, S = 3 mm for the smallest porosity of 1.27%; with m = 35g.min-1, n = 130 rpm, S = 3 mm for the coating with a maximum adhesion of 44.07 MPa. The percent effects of the parameters m, n, S to adhesion, porosity and hardness were (2.8%, 33.6%, 63.6%), (0.1%, 1.3%, 98.6%), (32.7%, 43.3%, 24%), respectively. The percent effects of spray parameters on corresponding coating property allows adjustment of spray parameters to obtain the desired coating. Verified experiment results shows that the results are reliable. Taguchi method and ANOVA can find optimal parameters of the HVOF spray to acquire high-performance coating.