scholarly journals Synthesis of FeSi-Al2O3 Composites by Autowave Combustion with Metallothermic Reduction

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 258
Author(s):  
Chun-Liang Yeh ◽  
Kuan-Ting Chen
Keyword(s):  
Chemical Interaction ◽  
Molar Ratio ◽  
Aluminum Silicate ◽  
Metallothermic Reduction ◽  
Reaction Systems ◽  
High Temperature Synthesis ◽  
Combustion Wave Velocity ◽  
Co Reduction ◽  
Shs Method

Fabrication of FeSi-Al2O3 composites with a molar ratio of FeSi/Al2O3 ranging from 1.2 to 4.5 was conducted by the self-propagating high-temperature synthesis (SHS) method. The synthesis reaction involved metallothermic reduction of Fe2O3 and SiO2 by Al and the chemical interaction of Fe and Si. Two combustion systems were examined: one contained thermite reagents of 0.6Fe2O3 + 0.6SiO2 + 2Al, and the other had Fe2O3 + 2Al to mix with different amounts of Fe and Si powders. A thermodynamic analysis indicated that metallothermic reduction of oxide precursors was sufficiently exothermic to sustain the combustion reaction in a self-propagating mode. The SHS reaction carrying out co-reduction of Fe2O3 and SiO2 was less exothermic, and was applied to synthesize products with FeSi/Al2O3 = 1.2–2.5, while the reaction reducing only Fe2O3 was more energetic and was adopted for the composites with FeSi/Al2O3 = 2.5–4.5. Moreover, the former had a larger activation energy, i.e., Ea = 215.3 kJ/mol, than the latter, i.e., Ea = 180.4 kJ/mol. For both reaction systems, the combustion wave velocity and temperature decreased with increasing FeSi content. Formation of FeSi-Al2O3 in situ composites with different amounts of FeSi was achieved. Additionally, a trivial amount of aluminum silicate was detected in the products of high FeSi contents due to dissolution of Si into Al2O3 during the SHS process.

scholarly journals Intermetallic/Ceramic Composites Synthesized from Al–Ni–Ti Combustion with B4C Addition

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 873
Author(s):  
Chun-Liang Yeh ◽  
Chih-Yao Ke
Keyword(s):  
Combustion Velocity ◽  
Ceramic Composites ◽  
The Other ◽  
X Ray Diffraction ◽  
Temperature Synthesis ◽  
Reaction Systems ◽  
X Ray ◽  
High Temperature Synthesis ◽  
In Situ Formation

The fabrication of intermetallic/ceramic composites by combustion synthesis in the mode of self-propagating high-temperature synthesis (SHS) was investigated in the Al–Ni–Ti system with the addition of B4C. Two reaction systems were employed: one was used to produce the composites of xNiAl–2TiB2–TiC with x = 2–7, and the other was used to synthesize yNi3Al–2TiB2–TiC with y = 2–7. The reaction mechanism of the Al–Ni–Ti system was strongly influenced by the presence of B4C. The reaction of B4C with Ti was highly exothermic, so the reaction temperature and combustion velocity decreased due to increasing levels of Ni and Al in the reactant mixture. The activation energies of Ea = 110.6 and 172.1 kJ/mol were obtained for the fabrication of NiAl- and Ni3Al-based composites, respectively, by the SHS reaction. The XRD (X-ray diffraction) analysis showed an in situ formation of intermetallic (NiAl and Ni3Al) and ceramic phases (TiB2 and TiC) and confirmed no reactions taking place between Ti and Al or Ni. The microstructure of the product revealed large NiAl and Ni3Al grains and small TiB2 and TiC particles. With the addition of TiB2 and TiC, the hardness of NiAl and Ni3Al was considerably increased and the toughness was also improved.

In situ SHS-pseudo-HIP as an effective method to develop neutron shielding ceramic matrix composites from quaternary Ti-B-Cr-C system

2016 ◽  
Vol 1820 ◽  
Author(s):  
Marta Ziemnicka-Sylwester ◽  
Przemyslaw Litwa ◽  
Tomasz Czujko
Keyword(s):  
Solid Solutions ◽  
Volume Fraction ◽  
Ceramic Matrix Composites ◽  
Atomic Ratio ◽  
Molar Ratio ◽  
Matrix Composites ◽  
High Concentration ◽  
Neutron Shielding ◽  
High Temperature Synthesis

ABSTRACTHighly refractory composites with predominant volume fraction of TiB2, were “in situ” synthesized and consolidated. The production process was carried out using elemental powders by means of self-propagating high-temperature synthesis under pseudo-hot isostatic pressure (SHS-pseudo-HIP). The Ti:B atomic ratio corresponded to TiB2 formation, and Cr:C atomic ratio has been established in (3:2) molar ratio.Based on scanning electron images (SEI), very high relative density was obtained with nearly full densification in composite with intended 85vol.% of TiB2, which is sufficiently high concentration of boron from the perspective of neutron shielding. However XRD results indicated formation of CrB and TiC, next to TiB2. This clearly indicates no equilibrium in pseudo-binary TiB2-Cr3C2 system. Besides, broadened peaks in XRD patterns as well as gradient of composition in EDS maps may indicate solid solutions, especially (Ti,Cr)C. The existence of (Ti,Cr) solid solutions and ternary compounds is possible, considering Hume-Rothery rules for hypothetical mutual solubility.

scholarly journals Metallothermic Reduction of MoO3 on Combustion Synthesis of Molybdenum Silicides/MgAl2O4 Composites

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 4800
Author(s):  
Chun-Liang Yeh ◽  
Min-Chia Chen
Keyword(s):  
High Temperature ◽  
Combustion Synthesis ◽  
Xrd Analysis ◽  
Metallothermic Reduction ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Molybdenum Silicides ◽  
Front Temperature ◽  
In Situ Production

Combustion synthesis involving metallothermic reduction of MoO3 by dual reductants, Mg and Al, to enhance the reaction exothermicity was applied for the in situ production of Mo3Si–, Mo5Si3− and MoSi2–MgAl2O4 composites with a broad compositional range. Reduction of MoO3 by Mg and Al is highly exothermic and produces MgO and Al2O3 as precursors of MgAl2O4. Molybdenum silicides are synthesized from the reactions of Si with both reduced and elemental Mo. Experimental evidence indicated that the reaction proceeded as self-propagating high-temperature synthesis (SHS) and the increase in silicide content weakened the exothermicity of the overall reaction, and therefore, lowered combustion front temperature and velocity. The XRD analysis indicated that Mo3Si–, Mo5Si3– and MoSi2–MgAl2O4 composites were well produced with only trivial amounts of secondary silicides. Based on SEM and EDS examinations, the morphology of synthesized composites exhibited dense and connecting MgAl2O4 crystals and micro-sized silicide particles, which were distributed over or embedded in the large MgAl2O4 crystals.

Synthesis of Eu2+, Dy3+ Co-Doped Mal2O4 Phosphor (M = Ba, Sr) by In Situ Self-Propagating High Temperature Synthesis

2012 ◽  
Vol 626 ◽  
pp. 908-912
Author(s):  
Taschaporn Sathaporn ◽  
Sutham Niyomwas
Keyword(s):  
High Temperature ◽  
Broad Band ◽  
Rare Earth Ions ◽  
Temperature Synthesis ◽  
Co Doping ◽  
High Temperature Synthesis ◽  
Excited Luminescence ◽  
Co Doped ◽  
Shs Method

Eu2+, Dy3+ co-doped alkaline earth aluminates MAl2O4: Eu2+, Dy3+ (M = Ba, Sr) have been prepared by in situ self-propagating high temperature synthesis (SHS) method. The influence of co-doping rare earth ions (Eu2+, Dy3+) on the luminescence of MAl2O4:Eu2+, Dy3+ were described in this study. The particles morphology, photoluminescence and afterglow properties of the phosphors were studied. Broad band UV excited luminescence was observed for BaAl2O4:Eu2+, Dy3+ and SrAl2O4:Eu2+, Dy3+ in the green region peak at max = 503 nm and 523 nm, respectively. The dopant (Eu2+) and co-dopant (Dy3+) concentrations affect the crystallinity and luminescence properties of the materials.

On the dimorphism of Pr6Mo10O39

2017 ◽  
Vol 72 (11) ◽  
pp. 765-774
Author(s):  
Daniel Rudolph ◽  
Sonja Laufer ◽  
Ingo Hartenbach
Keyword(s):  
Crystal Structure ◽  
Thermal Decomposition ◽  
Single Crystals ◽  
Main Product ◽  
Molar Ratio ◽  
Coordination Environment ◽  
Space Group ◽  
Coordination Numbers ◽  
Dense Modification

AbstractAttempts to synthesize Pr4Mo7O27 using Pr, Pr6O11 and MoO3 in a molar ratio of 8:6:77 led to a main product of scheelite-type Pr0.667[MoO4] and few single crystals of the triclinic A-type Pr6Mo10O39. The latter crystallizes in space group P1̅ (a=945.25(1), b=1058.49(2), c=1815.16(3) pm; α=104.149(1), β=95.220(1), γ=102.617(1)°, Z=2). Its crystal structure comprises six crystallographically independent Pr3+ cations, eight tetrahedral [MoO4]2− units, and one [Mo2O7]2− entity. The cations display coordination numbers of seven (1×) and eight (5×), while the [MoO4]2− tetrahedra are surrounded by five Pr3+ cations each. The [Mo2O7]2− anions exhibit a coordination environment of seven Pr3+ cations. The attempt to synthesize PrF[MoO4] using PrOF (from in situ thermal decomposition of PrF[CO3]) as reagent did not lead to the desired product but to monoclinic B-type Pr6Mo10O39. This slightly less dense modification compared to its triclinic analogue crystallizes in space group C2/c (a=1247.93(3), b=1989.68(6), c=1392.52 (4) pm, β=100.505(2)°, Z=4) with three crystallographically independent Pr3+ cations, four [MoO4]2− tetrahedra, and again one [Mo2O7]2− unit in the crystal structure. Thus, both Pr6Mo10O39 modifications are better described with the structured formula Pr6[MoO4]8[Mo2O7]. The coordination numbers around the Pr3+ cations are seven (1×) and eight (2×) while all four [MoO4]2− anions are again surrounded by five Pr3+ cations each. Six of the latter represent the coordination environment around the [Mo2O7]2− entities. Besides the thorough comparison of the crystal structures single crystal Raman spectra were recorded for both Pr6Mo10O39 phases.

scholarly journals Characterization of Ti/SnO2 Interface by X-ray Photoelectron Spectroscopy

Nanomaterials ◽  
2022 ◽  
Vol 12 (2) ◽  
pp. 202
Author(s):  
Miranda Martinez ◽  
Anil R. Chourasia
Keyword(s):  
Photoelectron Spectroscopy ◽  
Room Temperature ◽  
Chemical Interaction ◽  
Photoelectron Spectra ◽  
X Ray ◽  
Increasing Trend ◽  
Substrate Temperatures ◽  
Beam Technique

The Ti/SnO2 interface has been investigated in situ via the technique of x-ray photoelectron spectroscopy. Thin films (in the range from 0.3 to 1.1 nm) of titanium were deposited on SnO2 substrates via the e-beam technique. The deposition was carried out at two different substrate temperatures, namely room temperature and 200 °C. The photoelectron spectra of tin and titanium in the samples were found to exhibit significant differences upon comparison with the corresponding elemental and the oxide spectra. These changes result from chemical interaction between SnO2 and the titanium overlayer at the interface. The SnO2 was observed to be reduced to elemental tin while the titanium overlayer was observed to become oxidized. Complete reduction of SnO2 to elemental tin did not occur even for the lowest thickness of the titanium overlayer. The interfaces in both the types of the samples were observed to consist of elemental Sn, SnO2, elemental titanium, TiO2, and Ti-suboxide. The relative percentages of the constituents at the interface have been estimated by curve fitting the spectral data with the corresponding elemental and the oxide spectra. In the 200 °C samples, thermal diffusion of the titanium overlayer was observed. This resulted in the complete oxidation of the titanium overlayer to TiO2 upto a thickness of 0.9 nm of the overlayer. Elemental titanium resulting from the unreacted overlayer was observed to be more in the room temperature samples. The room temperature samples showed variation around 20% for the Ti-suboxide while an increasing trend was observed in the 200 °C samples.

Preparation and Microwave Permittivity of SiC-AlN Solid Solution Powders

2007 ◽  
Vol 336-338 ◽  
pp. 310-312
Author(s):  
Xiao Kui Liu ◽  
Wan Cheng Zhou ◽  
Fa Luo ◽  
Dong Mei Zhu
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Carbon Black ◽  
Atomic Ratio ◽  
Nitrogen Atmosphere ◽  
Argon Atmosphere ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Microwave Permittivity ◽  
Shs Method

SiC-AlN solid solution powders were prepared from the mixtures of aluminum, silicon and carbon black in a nitrogen atmosphere with preheating self-propagating high temperature synthesis (SHS) method. The powders synthesized with different ratios of Al/Si were mixed with paraffin wax and the microwave permittivity of the mixtures was measured at the frequency of 8.2~12.4GHz. The results were contrasted with that of SiC powders synthesized by preheating SHS in argon and nitrogen atmosphere respectively. The ε′, ε″, and the tgδ (ε″/ε′) of the mixture of SiC prepared in a nitrogen atmosphere are highest, followed with those of the SiC-AlN solid solution powders and the SiC powders prepared in an argon atmosphere. Along with the increase of atomic ratio of Al/Si, the ε′, ε″, and tgδ of SiC-AlN solid solution decrease. We believe that, with the increase of AlN dissolved, the concentration of carriers and the effect of dielectric relaxation will decrease because of the two contrary dopants.

Immobilization of Radioactive Wastes into Perovskite Synrock by the SHS Method

2005 ◽  
Vol 475-479 ◽  
pp. 1627-1630 ◽  
Author(s):  
Rui Zhu Zhang ◽  
Zhi Meng Guo ◽  
Cheng Chang Jia ◽  
Guangfeng Lu
Keyword(s):  
High Temperature ◽  
Synthesis Process ◽  
Temperature Synthesis ◽  
Geological Disposal ◽  
Major Phase ◽  
Leach Rate ◽  
High Temperature Synthesis ◽  
Waste Loading ◽  
Shs Method

This paper researched the fabrication of perovskite synrock by self-propagating high temperature synthesis (SHS) and the characterization of the products. This synthesis process is simpler, the fabricated synrock can immobilize waste loading up to 35wt% SrO with satisfied physical properties (density>4.2g•cm-3, open porosity<0.2%, Leach rate<1.0 g•m-2•d-1). The structure analyses by XRD and SEM/EDS show that the major phase is perovskite which well agrees with the design. It proves that SHS offer a suitable Sr-waste synroc which is favorable for geological disposal.

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