Synthesis and Characterization of Electrospun Mullite Nanofibers

Abstract

Mullite (3Al 2 O 3 Á2SiO 2 ) is well-known as superior engineering ceramic materials owing to its relatively high chemical stability, good refractory properties, high temperature mechanical strength, and low thermal expansion coefficient. [1,2] Fabrication of continuous mullite nanofibers is highly desired because it is an important candidate used as reinforcement of metals, ceramics, and resins. [3,4] Several traditional methods such as sol-gel, melt spinning, and solution spinning methods have been used to fabricate mullite fibers. [5][6][7] Electrospinning is a promising technique that utilizes electric forces along to drive the spinning process and to produce fibers. Unlike sol-gel fabricated nanofibers, most of which contain foreign cations as catalysts and require further expensive purification, electrospun nanofibers are more pure, inexpensive, continuous, and relatively easy to align, assemble, and process into applications. [8][9][10][11] Unlike conventional spinning techniques (e.g., melt spinning and solution spinning methods) that are capable of producing fibers with diameters in the micrometer range ($5-15 mm), electrospinning is capable of producing fibers with diameters in the nanometer range ($50-1000 nm) with less cracks. In the recent decade, numerous electrospun ceramic nanofibers including silica, titania, and zirconia, have been fabricated and studied throughout the world. [12][13][14] However, very little literatures have been reported about electrospinning approach fabricating mullite nanofibers due to its more complicated stoichiometry/microstructure and relatively higher synthesis temperature. Recnetly, Dharmaraj et al. have reported the fabrication of electrospun mullite nanofibers, which focused on the sintering process, studying the effect of calcination temperature on the morphology evolution of mullite nanofibers. [15] However, much less attention has been paid to the electrospinning process.In the present work, electrospinning method is introduced to fabricate mullite nanofibers. Three different solvent systems including de-ionized water (DI) (solution A), DI/ absolute alcohol (EtOH) (solution B), and DI/N, N-dimethylformamide (DMF) (solution C) were used to prepare precursor spinning solutions. The effect of different solvents on the micromorphological evolution, crystallization sequence, and structural properties of both the as-electrospun fibers and the final sintered mullite nanofibers will be primarily focused and systematically investigated.

Production of submicrometric fibers of mullite by solution blow spinning (SBS)

“…This diameter reduction is due to the burning-out of PVC followed by the densification and mullitization processes. Studies [4,6,8,9] on electrospinning of mullite obtained fibers with diameters ranging from 85 nm up to 1mm, indicating that the confidence interval of the mean achieved by SBS in this work (788 up to 860 nm) is in agreement with electrospinning technology.…”

“…The production of mullite fibers, mostly nanometric and submicrometric fibers, has attracted considerable interest of many technological sectors, because of the excellent properties they exhibit and the large number of applications, ranging from reinforcements for metals, ceramics, and polymers, high temperature structural materials, high temperature plasticizing structural ceramics and insulating systems to membrane technology [4][5][6][7][8][9].…”

Influência da composição e das variáveis de processamento deformulações à base de argilas - uso em materiais refratários

“…A refratariedade é a propriedade que o material tem de suportar altas temperaturas sem se deformar ou fundir. Dentre as diversas aplicações da mulita em materiais refratários, destacam-se: cadinhos, peças de isolamentos térmicos, revestimentos de fornos e reatores (para altas temperaturas), matriz e reforço de material compósito, componentes de motores de turbina, vedação elástica em altas temperaturas, catalisadores, membranas de filtração, acessórios para aeronaves espaciais e materiais leves, entre outras [17,18]. Diante desse contexto, este trabalho teve como objetivo avaliar o efeito da composição, tempo de maturação e da temperatura nas propriedades físico-mecânicas de peças cerâmicas obtidas a partir de formulações à base de argilas para uso na fabricação de materiais refratários mulíticos.…”

Electrospun mullite nanofibers derived from diphasic mullite sol

“…In Zadeh's work, electrospun mullite nanofibers derived from mullite monophasic sol exhibited a uniform microstructure when the sintering temperate was below 1200°C; however, when the sintering temperature increased to 1400°C, mullite fibers showed a porous structure due to the growth of mullite grains. In Lin's work, mullite fibers derived from monophasic sol exited a rough surface when the sintering temperature was only 1200°C. Compared to the mullite fibers derived from monophasic sols, fibers in our work derived from a diphasic sol exhibited a smooth surface even when the sintering temperature was 1400°C (Figure G1) and the mullite grain size in mullite fibers after sintering at 1500°C is only about 100 nm (Figure C), which is similar to that of mullite fibers fabricated by the sol‐gel method (commercially Nextel 720 fibers and laboratory‐produced mullite fibers) .…”

“…Although many groups, such as Lin, Zadeh, and Peng, have successfully fabricated nanoscale mullite fibers by electrospinning a monophasic mullite sol, the results indicated that mullite nanofibers derived from the monophasic sol cannot be used at high temperatures (higher than 1400°C) due to the dramatic growth of mullite grains and therefore is unsuitable for being used as the starting material for the fabrication of mullite nanofibrous ceramics. Mullite sol can be divided into the monophasic sol and the diphasic sol according to their homogeneity, and the general agreement of the extensive works is that the homogeneity level of mullite sols actually controls the phase transformation sequence, mullite formation temperature, as well as the properties of sintered bodies.…”