Synthesis of MgSiN2 under 0.1 MPa of nitrogen pressure via combustion

This paper describes combusting loose powder beds of mixtures of aluminum metal powders and aluminum oxide powders with various grain sizes under various nitrogen pressure. The synthesis conditions required at least 20/80 weight ratio of aluminum metal powder to alumina powder in the mix to reach approximately 80 wt% of γ-AlON in the products. Finely ground fused white alumina with a mean grain size of 5 μm was sufficient to achieve results similar to very fine alumina with 0.3 μm grains. A lower nitrogen pressure of 1 MPa provided good results, allowing a less robust apparatus to be used. The salt-assisted combustion synthesis upon addition of 10 wt% of ammonium nitrite resulted in a slight increase in product yield and allowed lower aluminum metal powder content in mixes to be ignited. Increasing the charge mass five times resulted in a very similar γ-AlON yield, providing a promising technology for scaling up. Synthesis in loose powder beds could be utilized for effective production of relatively cheap and uniform AlON powder, which could be easily prepared for forming and sintering without intensive grounding and milling, which usually introduce serious contamination.

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Densification of Ceramic Matrix Composite Preforms by Si2N2O Formed by Reaction of Si with SiO2 under High Nitrogen Pressure. Part 2: Materials Properties

Journal of Composites Science ◽

10.3390/jcs5070179 ◽

2021 ◽

Vol 5 (7) ◽

pp. 179

Author(s):

Brice Taillet ◽

René Pailler ◽

Francis Teyssandier

Keyword(s):

Elastic Modulus ◽

Yield Strength ◽

Room Temperature ◽

Outer Part ◽

Ceramic Matrix Composites ◽

Ceramic Matrix ◽

Nitrogen Pressure ◽

High Nitrogen ◽

Yield Strain ◽

High Nitrogen Pressure

Ceramic matrix composites (CMCs) have been prepared and optimized as already described in part I of this paper. The fibrous preform made of Hi-Nicalon S fibers was densified by a matrix composed of Si2N2O prepared inside the CMC by reacting a mixture of Si and SiO2 under high nitrogen pressure. This part describes the oxidation resistance and mechanical properties of the optimized CMC. The CMC submitted to oxidation in wet oxygen at 1400 °C for 170 h exhibited an oxidation gradient from the surface to almost the center of the sample. In the outer part of the sample, Si2N2O, Si3N4 and SiC were oxidized into silica in the cristobalite-crystallized form. The matrix microstructure looks similar to the original one at the center of the sample, while at the surface large pores are observed and the fiber/matrix interphase is consumed by oxidation. The elastic modulus and the hardness measured at room temperature by nano-indentation are, respectively, 100 and 8 GPa. The elastic modulus measured at room temperature by tensile tests ranges from 150 to 160 GPa and the ultimate yield strength from 320 to 390 MPa, which corresponds to a yield strain of about 0.6%. The yield strength identified by acoustic emission is about 40 MPa.

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Pressure Assisted Sintering of an Aluminium Alloy

Materials Science Forum ◽

10.4028/www.scientific.net/msf.618-619.627 ◽

2009 ◽

Vol 618-619 ◽

pp. 627-630

Author(s):

Stephen J. Bonner ◽

Graham B. Schaffer ◽

Ji Yong Yao

Keyword(s):

Aluminium Alloy ◽

Gas Flow ◽

Isothermal Holding ◽

Horizontal Tube ◽

Elevated Pressure ◽

Nitrogen Pressure ◽

Gas Pressure ◽

Densification Rate ◽

Conventional Press ◽

Gas Pressures

An aluminium alloy was sintered using a conventional press and sinter process, at various gas pressures, to observe the effect of sintering gas pressure on the densification rate. Compacts of aluminium alloy 2712 (Al-3.8Cu-1Mg-0.7Si-0.1Sn) were prepared from elemental powders and sintered in a horizontal tube furnace under nitrogen or argon at 590°C for up to 60 minutes, and air cooled. The gas flow was adjusted to achieve specific gas pressures in the furnace. It has been found that increasing the nitrogen pressure at the start of the isothermal holding stage to 160kPa increased the densification rate compared to standard atmospheric pressure sintering. Increasing the nitrogen pressure further, up to 600kPa, had no additional benefit. The densification rate was increased significantly by increasing the gas pressure to 600kPa during both heating and isothermal holding. Under argon the elevated pressure did not increase the densification rate. Results seem to suggest that the beneficial effect of the elevated pressure on the rate of densification is related to nitride formation.

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Chemically activated combustion synthesis of AlON under high nitrogen pressure

Combustion and Flame ◽

10.1016/j.combustflame.2021.111560 ◽

2021 ◽

Vol 232 ◽

pp. 111560

Author(s):

Tigran G. Akopdzhanyan ◽

Sergey I. Rupasov ◽

Stepan Vorotilo

Keyword(s):

Combustion Synthesis ◽

Nitrogen Pressure ◽

High Nitrogen ◽

High Nitrogen Pressure

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Effect of nitrogen pressure on preparation of β-Si3N4 whiskers

Ceramics International ◽

10.1016/j.ceramint.2017.05.038 ◽

2017 ◽

Vol 43 (13) ◽

pp. 10610-10613 ◽

Cited By ~ 4

Author(s):

Xiuan Xi ◽

Hao Xiong ◽

Weiming Guo ◽

Qiangguo Jiang ◽

Yanling Cheng ◽

...

Keyword(s):

Nitrogen Pressure

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Mechanical and Structural Properties of Superhard TiAlSiN Coatings Deposited by Arc Ion Plating of Cylindrical Cathode

Materials Science Forum ◽

10.4028/www.scientific.net/msf.783-786.1426 ◽

2014 ◽

Vol 783-786 ◽

pp. 1426-1431

Author(s):

Wang Ryeol Kim ◽

Min Chul Kwon ◽

Jung Hoon Lee ◽

Uoo Chang Jung ◽

Won Sub Chung

Keyword(s):

Structural Properties ◽

Nitrogen Pressure ◽

Structural Features ◽

X Ray Diffraction ◽

X Ray ◽

Ion Plating ◽

Arc Current ◽

Cathode Arc ◽

Cathodic Arc ◽

Tialsin Coating

TiAlSiN coatings were deposited on WC-Co metal by using a cathodic arc ion deposition method of cylindrical cathode. We used Ti / Al (50 / 50 at.%) arc target and silicon sputter target. The influence of the nitrogen pressure, TiAl cathode arc current, bias voltage, and deposition temperature on the mechanical and the structural properties of the films were investigated. The structural features of the films were investigation in detail using X-ray diffraction. And coatings were characterized by means of FE-SEM, nanoindentation, Scratch tester, Tribology tester, XRD and XPS. The hardness of the film reached 43 GPa at the cathode arc current of 230 A and decreased with a further increase of the arc current. And the adhesion of the film reached 34 N. The results showed that the TiAlSiN coating exhibited an excellent mechanical properties which application for tools and molds.

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Production of lactic acid from cellulose using solid catalyst

MATEC Web of Conferences ◽

10.1051/matecconf/201926807006 ◽

2019 ◽

Vol 268 ◽

pp. 07006 ◽

Cited By ~ 1

Author(s):

Sujitra Doungsri ◽

P. Rattanaphanee ◽

Aatichat Wongkoblap

Keyword(s):

Lactic Acid ◽

Batch Reactor ◽

Nitrogen Pressure ◽

Reaction Pathways ◽

Solid Catalyst ◽

One Pot ◽

Solid Catalysts ◽

Platform Chemicals ◽

Acid And Base ◽

The One

Lactic acid (LA), one of the important biomass derived platform chemicals, has been used in food and chemical industries, especially in biodegradable polymer as polylactic acid (PLA). The aim of this work is to study the one-pot production of LA from cellulose by using different solid catalysts. The reaction was conducted in a high pressure batch reactor and the catalyst used in this study were ZrO2 and Al2O3. The reaction was carried out at temperature of 200oC for 6 hr. and under nitrogen pressure of 1 MP. It was found that the production yield of LA were 8.02% and 6.63%, when the ZrO2 and Al2O3 catalysts were used respectively. The result indicated that the ZrO2 may effect on the LA production because of the acid and base sites of the ZrO2. Therefore, the reaction pathways for conversion of cellulose into lactic acid have been investigated, and developed the new conditions to achieve the higher yield.

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Combustion Synthesis of Si3N4 from Si/NH4Cl at Low Nitrogen Pressure

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.368-372.1767 ◽

2008 ◽

Vol 368-372 ◽

pp. 1767-1770 ◽

Cited By ~ 3

Author(s):

Yi Xiang Chen ◽

Jiang Tao Li ◽

Zhi Ming Lin ◽

Guang Hua Liu ◽

S.L. Yang ◽

...

Keyword(s):

Combustion Synthesis ◽

Combustion Temperature ◽

Profile Analysis ◽

Combustion Velocity ◽

Nitrogen Pressure ◽

Analysis Method ◽

Α Phase ◽

Steady Combustion ◽

Combustion Wave Velocity ◽

Low Nitrogen

Combustion synthesis (CS) of Si3N4 was accomplished by using as-milled Si/NH4Cl as reactants at low nitrogen pressure. The additive of NH4Cl decreased the combustion temperature and promoted the Si nitridation. Full nitridation of Si was achieved by burning Si in pressurized nitrogen with 10 ~ 25 wt. % NH4Cl as additives while no Si3N4 diluent added. The maximum combustion temperature (Tc), the combustion velocity (u) together with the α-Si3N4 content and mean particle size (d50) of the powder products were found to be great dependent on the NH4Cl content added in the reactants. Fine Si3N4 powder products with α-phase content up to 85 wt. % were obtained via steady combustion mode. A mathematical approach named combustion wave velocity methods for the analysis of temperature profiles in CS was proposed and the reaction kinetics was discussed. The apparent activation energy calculated according to the temperature profile analysis method is 29.7 kJ/mol, which agrees well with the corresponding low temperature nitriding combustion of Si.

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Influence of additive composition on thermal and mechanical properties of β–Si3N4 ceramics

Journal of Materials Research ◽

10.1557/jmr.2004.0416 ◽

2004 ◽

Vol 19 (11) ◽

pp. 3270-3278 ◽

Cited By ~ 31

Author(s):

Xinwen Zhu ◽

Hiroyuki Hayashi ◽

You Zhou ◽

Kiyoshi Hirao

Keyword(s):

Mechanical Properties ◽

Thermal Conductivity ◽

Fracture Toughness ◽

Nitrogen Pressure ◽

High Fracture Toughness ◽

Oxygen Impurity ◽

Thermal And Mechanical Properties ◽

High Fracture ◽

Doped Materials ◽

Gas Pressure Sintering

Dense β–Si3N4 ceramics were fabricated from α–Si3N4 raw powder by gas-pressure sintering at 1900 °C for 12 h under a nitrogen pressure of 1 MPa, using four different kinds of additive compositions: Yb2O3–MgO, Yb2O3–MgSiN2, Y2O3–MgO, and Y2O3–MgSiN2. The effects of additive composition on the microstructure and thermal and mechanical properties of β–Si3N4 ceramics were investigated. It was found that the replacement of Yb2O3 by Y2O3 has no significant effect on the thermal conductivity and fracture toughness, but the replacement of MgO by MgSiN2 leads to an increase in thermal conductivity from 97 to 113 Wm-1K-1and fracture toughness from 8 to 10 MPa m1/2, respectively. The enhanced thermal conductivity of the MgSiN2-doped materials is attributed to the purification of β–Si3N4 grain and increase of Si3N4–Si3N4 contiguity, resulting from the enhanced growth of large elongated grains. The improved fracture toughness of the MgSiN2-doped materials is attributed to the increase of grain size and fraction of large elongated grains. However, the same thermal conductivity between the Yb2O3- and Y2O3-doped materials is related to not only their similar microstructures, but also the similar abilities of removing oxygen impurity in Si3N4 lattice between Yb2O3 and Y2O3. The same fracture toughness between the Yb2O3- and Y2O3-doped materials is consistent with their similar microstructures. This work implies that MgSiN2 is an effective sintering aid for developing not only high thermal conductivity (>110 Wm−1K−1) but also high fracture toughness (>10 MPa m1/2) of Si3N4 ceramics.

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