Controlled atmosphere pyrolysis of polyureasilazane for tailored volume fraction Si3N4/SiC nanocomposites powders

Abstract

A controlled atmosphere pyrolysis process is used to develop processing protocols for controlled volume fraction Si 3 N 4 /SiC composites from a polyureasilazane. Various processing protocols are explored such as gas composition (Argon, NH 3 and a 10%NH 3 /Argon mix) and a gas switching process where gas is switched from NH 3 to Argon at specified temperatures and specified times to quench the reaction. Results showed an accurate control of the volume fraction of SiC in 0-30 volume % range in a Si 3 N 4 matrix. FTIR spectroscopic results confirmed that a substitution reaction occurs between NH 3 and the polyureasilazane. Raman spectroscopy shows a free carbon phase present up until 1850 ˚C and carbon present in specimens that do not show observable XRD peaks of SiC.

Hybrid polymer matrix composite (UHMWPE‐HPMC) as solid particle erosion resistant coating for sharp pipe elbows using numerical simulation and experimental analysis

“…Continuous decrease in the mass of samples indicates the lack of erodent particles indentation into the coatings or embedment of particle in the target surface. Coefficients of friction conform to Archard's equation estimations 12 with slight decrease by increasing hardness between samples. Trends in COF for each sample showed a noticeable increase at higher distance, probably the result of particle plowing and matrix degradation.…”

“…As the erosion calculation is mainly particle velocity related, the relative particle concentration towards the centerline of pipes and channels (φ p ) was matched with velocity profile (Vp) to make simulation and empirical results more compatible. As the HPMC composite design was hardness related, the wear in inner pipe wall was calculated using Archard wear equation 12 :…”

“…The results were checked with hardness independent wear low equation (Equation (5)) to ensure that local measured hardness can be attributed to whole surface. 12…”

“…2,[7][8][9] The erosion resistance of PMC coatings is affected by parameters of the environment such as shape and size of eroding solids, impact velocity at contacting angle, 4 impacting flux rate and ceramic filler parameters in the composite coating like content, 6 size orientation, and hardness profile. [10][11][12][13] For PMC composite coatings, the factors affecting the SPE can be categorized to the nature of hybrid polymer matrix, ductility, and quality of different interfaces like particle-matrix or matrix-metal. Metal-hybrid polymer matrix composite (HPMC) coating interface comprises of coupling agent (CA)/metal interphase, high density CA, polymer/CA, and high density HPMC.…”

β-Si3N4 Microcrystals Prepared by Carbothermal Reduction-Nitridation of Quartz

“…The most prevalent methods for preparing Si 3 N 4 powders include direct nitridation method, carbothermal reduction-nitridation (CRN) method and thermal decomposition method [5,6,7]. By CRN method, Si 3 N 4 powders or columnar grains with excellent size distribution and physical properties could be synthesized and used as thermal conductive fillers or commercial applications for manufacturing engineering devices [8,9].…”