Fluoride coatings make effective lubricants in molten sodium environment

Coating bearing surfaces with calcium fluoride-barium fluoride film provides effective lubrication against sliding friction in molten sodium and other severe environments at high and low temperatures

Method of making carbide/fluoride/silver composites

A composition containing 30 to 70 percent chromium carbide, 5 to 20 percent soft noble metal, 5 to 20 percent metal fluorides, and 20 to 60 percent metal binder is used in a powdered metallurgy process for the production of self-lubricating components, such as bearings. The use of the material allows the self-lubricating bearing to maintain its low friction properties over an extended range of operating temperatures

N‐heterocyclic carbene catalyzed photoenolization/Diels–Alder reaction of acid fluorides

The combination of light activation and N‐heterocyclic carbene (NHC) organocatalysis has enabled the use of acid fluorides as substrates in a UVA‐light‐mediated photochemical transformation previously observed only with aromatic aldehydes and ketones. Stoichiometric studies and TD‐DFT calculations support a mechanism involving the photoactivation of an ortho‐toluoyl azolium intermediate, which exhibits “ketone‐like” photochemical reactivity under UVA irradiation. Using this photo‐NHC catalysis approach, a novel photoenolization/Diels–Alder (PEDA) process was developed that leads to diverse isochroman‐1‐one derivatives

Biomaterial Properties of Titanium in Dentistry

Background Among various dental materials and their successful restorative uses, titanium provides an excellent example of integrating science and technology involving multiple disciplines of dentistry including biomaterials, prosthodontics and surgical sciences. Titanium and its alloys have emerged as a material of choice for dental implants fulfilling all requirements biologically, chemically and mechanically. Several excellent reviews have discussed the properties of titanium and its surface characteristics that render it biocompatible. However, in most patients, titanium implants are used alongside several other metals. Presence of different metals in the same oral environment can alter the properties of titanium. Other influencing factors include intra-oral pH, salivary content, and effect of fluorides. Highlight This review discusses the effect of the above-mentioned conditions on the properties of titanium and its alloys. An extensive literature search encompassing the properties of titanium in an altered oral environment and its interaction with other restorative materials is presented. Specific conditions that could cause titanium to corrode, specifically due to interaction with other dental materials used in oral rehabilitation, as well as methods that can be employed for passivation of titanium are discussed. Conclusion This review presents an overview of the properties of titanium that are vital for its use in implant dentistry. From a restorative perspective, interaction between implant restoration metals, intra-oral fluorides and pH may cause titanium to corrode. Therefore, in order to avoid the resulting deleterious effects, an understanding of these interactions is important for long-term prognosis of implant restorations

Self-lubricating coatings for high-temperature applications

Solid lubricants with maximum temperature capabilities of about 1100 C are known. Unfortunately, none of the solid lubricants with the highest temperature capabilities are effective below 400 C. However, research at NASA's Lewis Research Center shows that silver and stable fluorides such as calcium and barium fluorides act synergistically to provide lubrication from below room temperature to about 900 C. This paper describes plasma-sprayed composite coatings that contain these solid lubricants in combination with a metal-bonded chromium carbide. The lubricants control friction, and the carbide matrix provides wear resistance. Successful tests of these coatings as backup lubricants for compliant gas bearings in turbomachinery and as self-lubricating liners in a four-cylinder Stirling engine are discussed

Additions to fused-fluoride lubricant coatings for reduction of low-temperature friction

Additions to fused-fluoride lubricant coatings for reduction of low temperature frictio

High temperature rare earth solid lubricants

Rare earth trifluorides have potential use as lubricating fillers for mechanical carbons and as coatings on metallic substrates. Friction experiments show that they are effective in reducing metallic wear