Effect of chlorine purification on oxidation resistance of some mechanical carbons

Oxidation experiments were conducted with some experimental and commercial mechanical carbons at 650 C in dry air flowing at 28 cc/sec (STP). In general, purification of these carbon-graphites with chlorine at 2800 C improved oxidation resistance. Additional improvements in oxidation resistance were obtained from purification followed by an antioxidant (zinc phosphate) treatment. For the commercial materials, purification alone gave greater oxidation resistance than the antioxidant treatment alone. The reverse, however, was the case for the experimental materials

Optimalisation of evaluation methods for phosphating bathes

Tato práce se zabývá technologii fosfatizace oceli. V teoretické části jsou nejprve shrnuty poznatky z oboru konvenčního fosfatizačního procesu, kde jsou předloženy i příklady přípravy povrchu oceli před samotným fosfátováním. V následující kapitole je rozvinuta problematika moderní metody fosfatizačního procesu, elektrolytického fosfátování. Tato kapitola pojednává o principech a charakteristice této metody. Následuje shrnutí a srovnání všech ekonomických a ekologických pozitiv elektrolytického fosfátování oproti konvenčním metodám vylučování fosforečnanů. V experimentální části je nejprve uveden popis nynějšího stavu analýzy fosfatizační lázně pro elektrolytické fosfátování ocelového drátu. Cílem experimentální části je nalezení analytické metody proveditelné v provozních podmínkách fosfatizační linky. V další kapitole jsou popsány všechny provedené analytické metody – měření hustoty, indexu lomu, vodivosti, redoxního potenciálu, pH, turbidimetrie a stanovení obsahu síranů, železa a fosforečnanů. Vyvrcholením práce je diskuze všech provedených metod v souvislosti s praktickým využitím v provozních podmínkách fosfatizační linky a konkrétní návrh vybraných analytických metod.This work deals with phosphating technology of steel. In theoretical part are summarized facts about conventional phosphating process, including steel surfaces pretreatment. In the next chapter the latest contemporary technology of phosphating is discussed, i.e. electrolytic phosphating. This chapter contains principles and characteristics of this technique. Than follow comparisons of electrolytic phosphating and conventional process, concerning economical and ecological aspects. In experimental part is firstly stated nowaday situation of process analyses of phosphating bath for electrolytic phosphating. Intention of experimental part is finding of analytical technique which can be used in operating conditions of phosphating production line. Next chapter render an account of all analytical techniques – measuring of density, refractive index, conductance, reduction potential, pH, turbidity and determination of sulphate, iron and phosphate by indicator papers. Discussion of all results leads to conclusions on tested techniques in connection with practical use in operating conditions of phosphating production line and recommendations for use of individual analytical techniques.

Study on properties of geopolymers for application in transport means

Disertační práce je věnovaná studiu alkalicky aktivovaných materiálů na bázi elektrárenského popílku, zejména možnosti jejich využití jako vysokoteplotních tmelů pro aplikace v dopravní technice. Adheze geopolymerů s kovem nebyla dodnes široce studovaná. Tato práce je zaměřena zejména na vyhledávání optimálního složení tmelu, které by odpovídalo požadavkům na vysokoteplotní tmely a kromě toho aby byly cenově srovnatelné podobnými materiály již existujícími na trhu.This doctoral thesis deals with a study of alkali activated materials based on fly ash, above all the possibility of their application as high temperature sealants in transport means. Adhesive bonding of geopolymers with steel haven?t been studied widely till nowadays. This work is mainly concentrated on optimal sealant composition search, which would respond to main requirements to high temperature sealants, besides would have a competitive price in comparison with the similar materials existent in the market.Katedra mechaniky, materiálů a částí strojůPrezentace doktorské dizertační práce Přečtení posudků Odpovědi na připomínky oponentů Rozprava Tajné hlasování Vyhlášení výsledku tajného hlasován

Towards the production of 50'000 tonnes of low-carbon steel sheet for the LHC superconducting dipole and quadrupole magnets

A total of 50'000 tonnes of low-carbon steel sheet has been ordered for the LHC main magnets. After three years of production, about 10'000 tonnes of steel sheet have been produced by Cockerill-Sambre Groupe Usinor. This paper gives a summary of the manufacturing process and improvements implemented as well as an overview of the difficulties encountered during this production. Preliminary statistics obtained for the mechanical and magnetic steel properties are presented

Agriculture in the Clermont Silt Loam Area

Exact date of bulletin unknown.PDF pages: 2

Hybrid sol-gel coatings: smart and green materials for corrosion mitigation

Corrosion degradation of materials and metallic structures is one of the major issues that give rise to depreciation of assets, causing great financial outlays in their recovery and or prevention. Therefore, the development of active corrosion protection systems for metallic substrates is an issue of prime importance. The promising properties and wide application range of hybrid sol-gel-derived polymers have attracted significant attention over recent decades. The combination of organic polymers and inorganic materials in a single phase provides exceptional possibilities to tailor electrical, optical, anticorrosive, and mechanical properties for diverse applications. This unlimited design concept has led to the development of hybrid coatings for several applications, such as transparent plastics, glasses, and metals to prevent these substrates from permeation, mechanical abrasion, and corrosion, or even for decorative functions. Nevertheless, the development of new hybrid products requires a basic understanding of the fundamental chemistry, as well as of the parameters that influence the processing techniques, which will briefly be discussed. Additionally, this review will also summarize and discuss the most promising sol-gel coatings for corrosion protection of steel, aluminium, and their alloys conducted at an academic level.info:eu-repo/semantics/publishedVersio

Performance and Analysis of Perfluoropolyalkyl Ether Grease Used on Space Shuttle Actuators--A Case Study

Actuators used on the United States space shuttle fleet are lubricated with unspecified amounts of Braycote 601 (Castrol Braycote) grease consisting of a perfluoropolyalkyl ether (PFPAE) base oil thickened with a polytetrafluoroethylene (PTFE) filler. Each shuttle has four body flap actuators (BFAs) (two on each wing) on a common segmented shaft and four rudder speed brake (RSB) actuators. The actuators were designed to operate for 10 years and 100 flights without periodic relubrication. Visible inspection of two partially disassembled RSB actuators in continuous use for 19 years raised concerns over possible grease degradation due to discoloration of the grease on several places on the surfaces of the gears. Inspection revealed fretting, micropitting, wear and corrosion of the bearings and gears. A small amount of oil dripped from the disassembled actuators. Whereas new grease is beige in appearance, the discolored grease consisted of both grey and reddish colors. Grease samples taken from the actuators together with representative off-the-shelf new and unused grease samples were analyzed by gravimetry for oil content; by inductively coupled plasma spectroscopy (ICP) for metals content; Fourier transform infrared (FTIR) spectroscopy for base oil decomposition; and by size exclusion chromatography (SEC) for determination of the molecular weight distributions of the grease oil. The Braycote 601 grease was stable after 19 years of continuous use in the sealed RSB actuators and was fit for its intended purpose. There were no significant chemical differences between the used grease samples and new and unused samples. Base oil separation was not significant within the sealed actuators. No corrosive effect in the form of iron fluoride was detected. The grey color of grease samples was due to metallic iron. The red color was due to oxidation of the metallic wear particles from the gears and the bearings comprising the actuators