Phase Transformation of MgAlON-SiAlON Powders Synthesized by Carbothermal Reduction-Nitridation from Ludwigite Tailings

2013 ◽  
Vol 365-366 ◽  
pp. 1095-1099
Author(s):  
Tao Jiang ◽  
Lu Zhang ◽  
Yi Tang ◽  
Yi Xia ◽  
Xiang Xin Xue
Keyword(s):  
Phase Transformation ◽  
Optimal Condition ◽  
Carbothermal Reduction ◽  
Intermediate Phase ◽  
Xrd Analysis ◽  
Synthesis Temperature ◽  
Holding Time ◽  
Experimental Results ◽  
Crystalline Phases ◽  
Influence Of Temperature

This paper focuses on the influence of temperature and holding time on synthesizing MgAlON-SiAlON powders applying CRN method. The results were analyzed by chemical and XRD analysis technology. The experimental results revealed that β-SiAlON, as an intermediate phase, appeared in the synthesized products at 1200°C. With the increase of synthesis temperature, β-SiAlON was translated into Mg-SiAlON polytypoid (Mg1.25Si1.25Al2.5O3N3) and reached the maximum at 1450°C. Increasing synthesis temperature was beneficial to generate MgAlON, and the optimal condition of temperature for powders synthesis was 1500°C. β-SiAlON disappeared with the increase of holding time. MgAlON and Mg-SiAlON polytypoid became the main crystalline phases with a holding time of 4h. Whats more, the phase compositions had no evident change with longer holding time. Flaky MgAlON grains and elongated Mg-SiAlON grains were observed in synthesized powders.

Influence of Amount of Nitrogen on Crystallisation of Y-SiAlON Glasses: In Situ XRD Analysis

2005 ◽  
Vol 287 ◽  
pp. 293-298 ◽  
Author(s):  
E. Dolekcekic ◽  
Michael J. Pomeroy ◽  
Stuart Hampshire
Keyword(s):  
Phase Transformation ◽  
Low Temperatures ◽  
Glass Composition ◽  
Xrd Analysis ◽  
Maximum Temperature ◽  
Crystalline Phases ◽  
In Situ Xrd ◽  
Powdered Glass ◽  
Nitrogen Contents

Y-SiAlON glasses of composition 36.5 Y: 42.3 Si: 21.2 Al with different amounts of N (0, 5, 8, 15 and 22 in e/o) were produced by melting appropriate mixtures of powders under flowing nitrogen at 1715°C. This composition is known to give B-phase (Y2SiAlO5N) on crystallisation at temperatures below 1050°C. In this work, the effect of nitrogen in the starting glass composition on the crystalline phases formed is discussed. High temperature in-situ XRD analysis was performed on powdered glass samples up to 1150°C by using a Philips X’pert PRO MPD (Multi Purpose Diffractometer) with a HTK1200 Oven Camera (Anton Paar, Austria). As expected, the results show that different nitrogen contents affect the crystalline phases formed. In all glasses, yttrium apatite silicate forms first, followed by crystallisation of B-phase. The phase transformation from B-phase to Iw-phase (Y3Si2Al[O,N10] i.e. 10 e/o N) takes place at relatively low temperatures (1050°C) for the lower nitrogen containing samples (5 and 8 e/o), whereas, the transformation does not take place for the glasses with higher nitrogen contents even at the maximum temperature studied (1150°C). This work also confirms that there is a correlation between the temperature where the first crystals appear and the amount of nitrogen in the starting glass.

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

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3622 ◽  
Author(s):  
Meng Zhang ◽  
Zhi Chen ◽  
Juntong Huang ◽  
Saifang Huang ◽  
Zhihui Hu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Formation Mechanism ◽  
Carbothermal Reduction ◽  
Single Phase ◽  
Heating Temperature ◽  
Holding Time ◽  
Spectral Emission ◽  
Reaction Parameters ◽  
Future Potential ◽  
Coke Powder

Single phase β-Si3N4 with microcrystals was synthesized via carbothermal reduction-nitridation (CRN) of quartz and carbon coke powder as starting materials. The effects of reaction parameters, i.e., heating temperature, holding time, C/SiO2 ratio, Fe2O3 additive and β-Si3N4 seeds on the phase transformation and morphology of products were investigated and discussed. Rather than receiving a mixture of both α- and β- phases of Si3N4 in the products, we synthesized powders of β-Si3N4 single polymorph in this work. The mechanism for the CRN synthesis of β-Si3N4 from quartz and the formation mechanism of Fe3Si droplets were discussed. We also firstly reported the formation of Fe3Si Archimedean solids from a CRN process where Fe2O3 was introduced as additive. Comparing to the gear-like short columnar morphology observed in samples without β-Si3N4 seeding, the addition of β-Si3N4 seeds led to an elongated morphology of final products and much finer widths. In addition, the β-Si3N4 microcrystals exhibited a violet‒blue spectral emission range, which could be highly valuable for their future potential optoelectronic applications.

scholarly journals A Response Surface Methodology (RSM) Approach for Optimizing the Attenuation of Human IgE-Reactivity to β-Lactoglobulin (β-Lg) by Hydrostatic High Pressure Processing

Foods ◽  
2021 ◽  
Vol 10 (8) ◽  
pp. 1741
Author(s):  
Xin Sun ◽  
Jialing Vivien Chua ◽  
Quynh Anh Le ◽  
Francisco Trujillo ◽  
Mi-Hwa Oh ◽  
...  
Keyword(s):  
Response Surface Methodology ◽  
Optimal Condition ◽  
Response Surface ◽  
High Pressure Processing ◽  
Molecular Structures ◽  
Holding Time ◽  
P Value ◽  
Molecular Change ◽  
Ige Reactivity ◽  
Β Lactoglobulin

The response surface methodology (RSM) and central composite design (CCD) technique were used to optimize the three key process parameters (i.e., pressure, temperature and holding time) of the high-hydrostatic-pressure (HHP) processing either standalone or combined with moderate thermal processing to modulate molecular structures of β-lactoglobulin (β-Lg) and α-lactalbumin (α-La) with reduced human IgE-reactivity. The RSM model derived for HHP-induced molecular changes of β-Lg determined immunochemically showed that temperature (temp), pressure (p2) and the interaction between temperature and time (t) had statistically significant effects (p < 0.05). The optimal condition defined as minimum (β-Lg specific) IgG-binding derived from the model was 505 MPa at 56 °C with a holding time of 102 min (R2 of 0.81 and p-value of 0.01). The validation carried at the optimal condition and its surrounding region showed that the model to be underestimating the β-Lg structure modification. The molecular change of β-Lg was directly correlated with HHP-induced dimerization in this study, which followed a quadratic equation. The β-Lg dimers also resulted in the undetectable human IgE-binding.

Phase transformation of high aluminium fly ash in carbothermal reduction–nitridation at high temperatures

2014 ◽  
Vol 32 (4) ◽  
pp. 399-403
Author(s):  
M. H. Fang ◽  
H. T. Liu ◽  
Z. H. Huang ◽  
J. T. Huang ◽  
Y. G. Liu ◽  
...  
Keyword(s):  
Phase Transformation ◽  
Fly Ash ◽  
High Temperatures ◽  
Carbothermal Reduction ◽  
High Aluminium

scholarly journals Sintering of alumina ceramics reinforced with a bioactive glass of 3CaO.P2O5-SiO2-MgO system

Cerâmica ◽  
2015 ◽  
Vol 61 (358) ◽  
pp. 160-167 ◽  
Author(s):  
A. W. Huang ◽  
C. Santos ◽  
R. O. Magnago ◽  
R. F. F. Silva ◽  
K. Strecker ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Relative Density ◽  
Transient Liquid Phase ◽  
Xrd Analysis ◽  
Alumina Ceramics ◽  
Crystalline Phases ◽  
Powder Mixtures ◽  
Solid State Sintering ◽  
Sintering Condition

<p>Alumina-based ceramics, Al<sub>2</sub>O<sub>3</sub>, exhibit a combination of properties which favor its use as biomaterial, specifically as structural dental prosthesis. Its most important properties as biomaterial are its elevated hardness, chemical stability and biocompatibility. Usually, Al<sub>2</sub>O<sub>3</sub> is processed by solid-state sintering at a temperature of about 1600 <sup>o</sup>C, but it is very difficult to eliminate the porosity due to its diffusional characteristics. The objective of this work was the development and characterization of sintered Al<sub>2</sub>O<sub>3</sub> ceramics, densified with a transient liquid phase formed by a bioactive 3CaO.P<sub>2</sub>O<sub>5</sub>-SiO<sub>2</sub>-MgO glass. Powder mixtures of 90 wt.% Al<sub>2</sub>O<sub>3</sub> and 10 wt.% bioglass were milled, compacted and sintered at 1200 <sup>o</sup>C to 1450 <sup>o</sup>C. Comparatively, monolithic Al<sub>2</sub>O<sub>3</sub> samples were sintered at 1600 <sup>o</sup>C/120 min. The sintered specimens were characterized by relative density, crystalline phases, microstructure and mechanical properties. The results indicate that the specimen sintered at 1450 <sup>o</sup>C/120 min present the best properties. Under this sintering condition, a relative density of 95% was reached, besides hardness higher than 9 GPa and fracture toughness of 6.2 MPa.m<sup>1/2</sup>. XRD analysis indicate alumina (αAl<sub>2</sub>O<sub>3</sub>), whitlockite (3CaO.P<sub>2</sub>O<sub>5</sub>) and diopsite [3(Ca,Mg)O.P<sub>2</sub>O<sub>5</sub>], as crystalline phases. Comparatively, monolithic sintered Al<sub>2</sub>O<sub>3</sub> samples presented 92% of relative density with 17.4 GPa and 3.8 MPa.m<sup>1/2</sup> of hardness and fracture toughness respectively.</p>

Hydrothermal Synthesis and Phase Formation Mechanism of TiO2(B) Nanorods via Alkali Metal Titanate Phase Transformation

2018 ◽  
Vol 283 ◽  
pp. 23-36 ◽  
Author(s):  
Yothin Chimupala ◽  
Rik Drummond-Brydson
Keyword(s):  
Phase Transformation ◽  
Intermediate Product ◽  
Intermediate Phase ◽  
Metastable Phase ◽  
Exchange Process ◽  
Titanium Isopropoxide ◽  
Growth Direction ◽  
Proton Exchange ◽  
Transformation Mechanism ◽  
Synthesis Conditions

Titanium dioxide (B phase) with 1-D structures was successfully fabricated via a hydrothermal method with a subsequent ion-exchange process and calcination. P25, titanium isopropoxide (TTIP), rutile and also anatase were used as Ti precursors in the alkali hydrothermal system. TTIP promoted an elongation of nanorod morphology whereas the other precursors produced short nanorod structures. The different types of titanium precursors did not have any influence on the phase transformation during the fabrication process. Na2Ti6O13 was the primary intermediate product after washing the hydrothermal sample. H2Ti3O7 was the secondary intermediate phase obtained following proton-exchange of Na2Ti6O13 in HNO3 solution. Finally, the TiO2(B) phase was the product of calcination of the secondary intermediate product at 400°C for 5 hr. A phase transformation mechanism is presented based on an investigation of products at each of the steps. The effects of the synthesis conditions on tailoring of the crystal morphology are discussed. The growth direction of the TiO2(B) nanorods was investigated by HR-TEM and SADP. Finally, the metastable phase of TiO2(B) was shown to be transformed to anatase during thermal treatment at temperatures higher than 400°C.

Synthesis and characterization of 50-50 wt. lanthanum aluminate-lanthanum zirconate composite dried by spray-drying

MRS Advances ◽  
2020 ◽  
Vol 5 (42) ◽  
pp. 2173-2179
Author(s):  
W. Hernández Muñoz ◽  
J. Zárate Medina ◽  
J. Serrato Rodríguez ◽  
J. Muñoz Saldaña
Keyword(s):  
Spray Drying ◽  
Phase Distribution ◽  
Pyrochlore Structure ◽  
Synthesis Temperature ◽  
Synthesis And Characterization ◽  
Precipitation Process ◽  
Lanthanum Zirconate ◽  
Crystalline Phases ◽  
Lanthanum Aluminate

AbstractLanthanum aluminate-lanthanum zirconate composite was synthesized by using coprecipitation and powders were dried by spray-drying. Pseudoboehmite was used as a precursor of lanthanum aluminate during the precipitation process. Highly crystalline phases were obtained. Lanthanum zirconate exhibits a pyrochlore structure at lower synthesis temperature (>1500°C). Due drying technique lanthanum aluminate particles appear surrounded by lanthanum zirconate. No other remaining phases were observed and the phase distribution in the composite was homogeneous.

Sign in / Sign up

Export Citation Format

Share Document