Huibin Zhang

Pore Formation Process of Porous Ti3SiC2 Fabricated by Reactive Sintering

Porous Ti3SiC2 was fabricated with high purity, 99.4 vol %, through reactive sintering of titanium hydride (TiH2), silicon (Si) and graphite (C) elemental powders. The reaction procedures and the pore structure evolution during the sintering process were systematically studied by X-ray diffraction (XRD) and scanning electron microscope (SEM). Our results show that the formation of Ti3SiC2 from TiH2/Si/C powders experienced the following steps: firstly, TiH2 decomposed into Ti; secondly, TiC and Ti5Si3 intermediate phases were generated; finally, Ti3SiC2 was produced through the reaction of TiC, Ti5Si3 and Si. The pores formed in the synthesis procedure of porous Ti3SiC2 ceramics are derived from the following aspects: interstitial pores left during the pressing procedure; pores formed because of the TiH2 decomposition; pores formed through the reactions between Ti and Si and Ti and C powders; and the pores produced accompanying the final phase synthesized during the high temperature sintering process.

Direct separation of arsenic and antimony oxides by high-temperature filtration with porous FeAl intermetallic

A temperature-controlled selective filtration technology for synchronous removal of arsenic and recovery of antimony from the fume produced from reduction smelting process of lead anode slimes was proposed. The chromium (Cr) alloyed FeAl intermetallic with an asymmetric pore structure was developed as the high-temperature filter material after evaluating its corrosive resistance, structural stability and mechanical properties. The results showed that porous FeAl alloyed with 20wt.% Cr had a long term stability in a high-temperature sulfide-bearing environment. The separation of arsenic and antimony trioxides was realized principally based on their disparate saturated vapor pressures at specific temperature ranges and the asymmetric membrane of FeAl filter elements with a mean pore size of 1.8μm. Pilot-scale filtration tests showed that the direct separation of arsenic and antimony can be achieved by a one-step or two-step filtration process. A higher removal percentage of arsenic can reach 92.24% at the expense of 6∼7% loss of antimony in the two-step filtration process at 500∼550°C and 300∼400°C. The FeAl filters had still good permeable and mechanical properties with 1041h of uninterrupted service, which indicates the feasibility of this high-temperature filtration technology.

Development and characterization of microporous Ti3SiC2 ceramic membranes for filtration of microorganisms

A novel porous filter material was fabricated by element reactive synthesis method. The synthesized porous Ti3SiC2 membrane material presents a microstructure of both large substrate pores and small membrane pores, indicating large filtration flux and high filtration accuracy simultaneously. Microorganism filtration properties of the porous Ti3SiC2 membrane material were investigated by filtering the Escherichia coli suspension, which demonstrates excellent performance of the porous materials on filtration.

Factors affecting the property of porous Ti3SiC2 metal ceramic fabricated through pressureless sintering

Abstract In this paper, micrometer-sized porous Ti3SiC2 metal ceramic was fabricated through a reactive synthesis method using titanium hydride, silicon and graphite elemental powders. The factors including raw powders, pressing pressure, sintering procedure affecting the purity and the pore property of porous Ti3SiC2 were systematically studied. The results indicate that the purity, pore property including maximum pore size and porosity can be effectively controlled by adjusting the synthesis parameters.

Modification of the reactive synthesis of porous FeAl with addition of Si

Abstract Porous Fe25Al–xSi intermetallics with various contents of Si were fabricated via reactive synthesis using Fe + Al + Si powder mixtures, in which the elemental Si was added to control the self-propagating High-temperature Synthesis (SHS) occurred during sintering process. The Si element added in Fe25Al could make the exothermic reactions in the synthesis process become mild and the total heat release from the system decrease. With increasing Si content from 0 to 5 wt-%, the open porosity, the maximum pore size and permeability increased from 38·14 to 50·12%, 27·9 to 35·7 μm and 5·13 × 10−12 m2 to 11·9 × 10−12 m2, respectively. Si element could affect the microstructure and phase evolution during the middle temperature sintering. Scattered τ1 ((AlSi)5Fe3) phase surrounded Fe2Al5 layer transformed into loop-shape with increasing Si content. Fe(Al1−x Si x )3 and Al3FeSi phases substitute Fe2Al5 phase as the main intermediary phase when the Si content is beyond 3 wt-%.

Corrosion behavior of porous Ti 3 SiC 2 in nitric acid and aqua regia

Abstract Porous Ti3SiC2 with high purity was synthesized using TiH2, Si and C powders with mole ratio of Ti to Si to C being 3:1.2:2 by reactive synthesis method. The corrosion behaviors of porous Ti3SiC2 in nitric acid and aqua regia were investigated by immersing test. Scanning electron microscope (SEM), X-ray diffractometer (XRD), energy dispersive spectrometer (EDS) and X-ray photoelectron spectroscopy (XPS) were used to analyze the morphology, compositions and element contents of the samples before and after corrosion to determine the corrosion product and corrosion mechanism. The mass loss values of porous Ti3SiC2 are 26.9 and 132.5 μg/cm2, respectively after immersing in nitric acid and aqua regia for 600 h. The results indicate that Ti3SiC2 transforms to Ti5Si3 which has better corrosion resistance in nitric acid and aqua regia with mass loss values of 9.34 and 7.06 μg/cm2 under the same immersing time, respectively. The dramatic dissolution of porous Ti3SiC2 in the acids is due to its special microstructure.

In situ synthesis and strengthening of powder metallurgy high speed steel in addition of LaB 6

A novel technology which was characterized by the vacuum solid state sintering was developed for powder metallurgy high speed steels production. During sintering, both the WC and Mo2C reacted with Fe and transformed to W and Mo rich M6C carbides which were the common hard phases in high speed steels. Also, a high number of W, Mo and Fe were dissolved in VC, forming the MC carbides. The densification of the material mainly relied on the solubility effect during the M6C and MC carbides formation. By alloying with a 0.1 wt% of LaB6 to the steel, the bending strength and the fracture toughness were improved from 3290 MPa and 25.6 MPam1/2 to 4018 MPa and 29.4 MPam1/2, respectively. The TEM analysis demonstrated three types of reaction products by the LaB6 addition: the amorphous phase, the core-shell structure and the La2O3 phase. The impurity elements such as the Mg, Al, Si, S, Ca, and O were absorbed following the LaB6 addition. Moreover, the deoxidization effect caused by the LaB6 addition promoted the sintering at a high-temperature period which contributed to the bending strength and fracture toughness improvement.