Self-propagating high temperature synthesis of MoSi_2 matrix composites

MoSi2 is presently regarded as the most important material for electrical heating and as one with huge potential for high temperature structural uses. MoSi2 and MoSi2 matrix composites were prepared by self-propagating high temperature synthesis （SHS）. Pure MoSi2 was obtained and a compound of MoSi2 and WSi2was synthesized in the form of predominant solid solution （Mo,W）Si2. By adding aluminum of 5.5 at.% to Mo-Si, the crystal structure of MoSi2 changed into a mixture of tetragonal Cllb MoSi2and hexagonal C40 Mo（Si,Al）2. The （Mo,W）Si2-Mo（Si,Al）2-W（Si,Al）2 composite materials were synthesized by adding aluminum of 5.5 at.% to Mo-W-Si. However, if the amount of the added aluminum was not larger than 2.5 at.%, it did not have any significant effect. SHS is an effective technology for synthesis of MoSi2 and MoSi2 matrix composites.

Preparation of low-oxygen Ti powder from TiO_(2) through combining self-propagating high temperature synthesis and electrodeoxidation

An effective method was reported to prepare low-oxygen Ti powder,which included two experimental steps:the fast conversion of TiO_(2) to TiO_(x<1) powder by self-propagating high-temperature synthesis(SHS)process and the generation of low-oxygen Ti powder by electrodeoxidizing TiO_(x<1) powder at the cathode in molten CaCl_(2).The key intermediate steps were analyzed by XRD,SEM and electrochemical testing techniques.The results demonstrated that TiO_(x<1) powder(TiO_(0.325) and TiO_(0.97))was generated after acid leaching MgO in SHS products with TiO_(2)/Mg molar ratio of 1:2,and the TiO_(x<1) powder with 16.3 wt.%oxygen could be transformed into pure titanium powder with 0.121 wt.%oxygen by electrodeoxidation at a constant potential of−3.3 V for 10 h.The electrodeoxidation of TiO_(x<1) powder in CaCl_(2) molten salt follows the step-by-step deoxidation mode,and the lattice of TiO_(x<1) powder after electrodeoxidation shrinks.

A Self-propagating high-temperature synthesis process for the fabrication of Fe（Cr）–Al2O3 nanocomposite

Self-propagating high-temperature synthesis(SHS)was used to fabricate a Fe(Cr)–Al2O3 nanocomposite.The composite was fabricated by the reactions between the powders of Fe,Fe2O3,Cr2O3,and Al.The effect of blending ratio and mechanical activation of the initial powders and the precursor compressing pressure on the microstructure of the final product was studied by optical microscopy,scanning electron microscopy,transmission electron microscopy,and X-ray diffraction.The significance of the effect of each of the aforementioned parameters on the quality of the composite(assessed by measuring the compressive strength and wear resistance)was determined using a full-factorial design of experiments method.The results showed that the best molar powder ratio that produced the most homogeneous product through a sustainable SHS reaction was Fe:Fe2O3:Cr2O3:Al=10:1:1:4.A lower Fe content caused the Fe(Cr)phase to melt and separate from the rest of the materials.

Synthesis gas production on glass cloth catalysts modified by Ni and Co oxides

The catalytic activity of nanostructured low percent (1%) Co-Ni catalysts on the basis of glass fiber (GF) prepared by a"solution combustion" (SC) method was studied.The catalytic activity of the prepared samples was studied in the reaction of dry reforming of methane (DRM) with CO2.The obtained samples were characterized by a number of physico-chemical methods,including XRD,SEM,TEM,TGA and AFM.The active component was shown to be dispersed in the near-surface layer of the support as nanoparticles of 10—20 nm in size.The active component showed a Co3O4 or(Co,Ni)Co2O4 spinel structure,depending on the catalyst composition.The spinel structure of the active component interacted strongly with the carrier,providing resistance to carbonization,high catalytic activity toward DRM,and high activity and stability in oxidation reactions.

Optimal design of self-propagating high temperature one-dimensional nano-SnO_2 synthesis

The success in synthesizing high purity SnO2 nanobelts via self-propagating high tem- perature synthesis was achieved. According to the experimental results, a relationship between the residual heat of the reaction system at 2848 K and SnO2 nanobelts yield was identified. The most appropriate formula for this self-propagating high tempera- ture synthesis method is turned out to be composed of Sn powder and thermite with weight ratio of 1：1.

High-temperature synthesis of SAPO-34 molecular sieve using a dry gel method

SAPO-34 is one of the main catalysts used in the petrochemical industry. Various effective methods have been developed to synthesize SAPO-34 with optimal size and characteristics for such application, In the present study, SAPO-34 was synthesized using a dry gel method at high temperatures. Morpholine was used as an organic template. The products were characterized by X-ray diffraction, field-emission scan- ning electron microscopy, energy-dispersive X-ray spectroscopy, and gas sorption analysis, The results showed that application of the dry gel method at high temperatures successfully afforded a pure catalyst with high crystallinity, Small particles of less than 500 nm could be obtained within a short reaction time of 30 min.

Influences of NiCO_3 content on the microstructure and magnetic properties of Ni_(0.5)Zn_(0.5)Fe_2O_4 powders prepared by SHS

Stoichiometric Ni0.5Zn0.5Fe2O4 powders were produced by self-propagating high temperature synthesis （SHS）. The effects of NiCO3 content in the raw materials on the microstructure and magnetic properties of Ni-Zn ferrite powders were systematically studied. The Ni0.5Zn0.5Fe2O4 powders were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The magnetic properties of the powders were evaluated by vibrating sample magnetometry （VSM）. The results show that the introduction of NiCO3 into reactants improves the con- version percentage and refines the Ni0.5Zn0.5Fe2O4 particles. The increase of NiCO3 content enhances the magnetic properties of Ni0.5Zn0.5Fe2O4. Particularly, the saturation magnetization reaches the maximum when the NiCO3 content is 3 at.%.

Microstructures and Properties of FeAl-Fe_3AlC_(0.5) Composites Prepared by SHS Casting

FeAl composites with 21, 37 and 50 wt pct Fe3AlC0.5 were fabricated by a self-propagating high temperature synthesis （SHS） casting. Phases and microstructures were analyzed by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. Microhardness and bending strength of the composites were measured. The composites with 21 and 50 wt pct Fe3AlC0.5 mainly consisted of FeAl and FesAlC0.5 phases, whereas the composite with 37 wt pct Fe3AlC0.5 was composed of FeAl, Fe3AlC0.5 and graphite phases. The bonding of the reinforcement and the matrix was good. Hardness and bending strength of the composite with 37 wt pct Fe3AlC0.5 was lower than those of the 21 and 50 wt pct composites owing to the presence of the soft graphite phase.

Preparation of an ultrafine-grained Fe-40Al intermetallic compound

An ultrafine grained Fe-40Al intermetallic compound is fabricated by a self- propagating high temperature synthesis （SHS） casting. The XRD result shows that the Fe-40Al intermetallic compound consists of the B2 FeAl phase. The Fe-40Al intermetallic compound presents ultrafine grain size in the range of 100-600 rim, leading from the high nucleation rate and the low growth rate. The Fe-40Al intermetallic compound exhibits high hardness （3.4 GPa） and high bending strength （830 MPa） and high compressive strength （2700 MPa）, which originate from the ultrafine-structure in the material. The effect of the load on dry-sliding wear rate of the material against AISI52100 steel was investigated. The wear rate increases with the increase of normal load. The dominated weax mechanism is microfracture.