The effects of concentration and surface modification of two Brazilian bentonite clays on nanocomposites' properties based on polylactic acid – (PLA) were investigated. The samples were prepared by the extrusion/injection method to obtain biodegradable packaging plastics. The raw materials and their bionanocomposites were characterized by various techniques. Natural clay samples presented a size of around 2 μm while the modified ones' size was 5–6 μm, probably due to the presence of cetyltrimethylammonium bromide in the interlayer space. The particle size and the contact angle increased with the treatment and the clay's density decreased. The organoclays were homogeneously dispersed in PLA, which can be associated with the interactions between PLA chains' carbonyl groups and the organoclays. The bionanocomposites present modified clay particles axis aligned to the flow direction of the extruder/injector. Chocolate organoclay acts as a nucleating agent to PLA crystal growth, increasing the sample's crystallinity, while Bofe organoclay interferes with the amorphous chain's mobility and diminishes the sample's crystallization. The addition of both organoclays to PLA diminished the sample's elongation at break and strength, although the organoclays increased the sample's Young modulus, even though Bofe organoclay is more active in PLA amorphous phase and Chocolate organoclay on the crystalline one.

No abstract

No abstract

ResumoA superliga de níquel 718 é uma superliga endurecida por precipitação, com alta resistência mecânica sob condições extremas e ambientes agressivos. Encontra aplicações como componentes críticos para indústrias aeroespacial, óleo e gas e nuclear. Seu alto teor de elementos de liga promove a ocorrência de diversas fases com consequente impacto nas propriedades. O presente trabalho foca na comparação por análise de imagens na morfologia, fração volumétrica, tamanho médio e distribuição de partículas de carbonetos (Nb,Ti)C após duas rotas de processamento termomecânico. Sua quantidade, distribuição e morfologia podem ter um papel em processos de degradação como corrosão e fragilização ao hidrogênio. Portanto, é importante saber como se desenvolve sob diferentes rotas de processamento. Palavras-chave: Superliga 718; Inconel 718; Carboneto; Processamento termomecânico. ANALYSIS OF (NB,TI)C CARBIDE MORPHOLOGY IN NICKEL-BASE SUPERALLOY 718 AFTER THERMOMECHANICAL PROCESSING AbstractNickel base superalloy 718 is a precipitation hardened Ni-base superalloy, with high strength under extreme temperatures and harsh environments. It finds applications as critical components for airspace, oil and gas and nuclear industries. Its high content of allying elements promotes several phases with impact on properties. The present work aims to compare by image analysis the morphology, volume fraction, average size and distribution of (Nb,Ti)C particles after two different routes of thermomechanical processing. Its amount, distribution and morphology can play a role on degradation processes such as corrosion and hydrogen embrittlement. It is, then, important to know how it develops under different processing routes.

No abstract