Combustion-synthesized functionally gradient refractory materials

1993 ◽  
Vol 8 (8) ◽  
pp. 2026-2034 ◽  
Author(s):  
Scott E. Niedzialek ◽  
Gregory C. Stangle ◽  
Yoshinari Kaieda
Keyword(s):  
Temperature Control ◽  
Reaction Temperature ◽  
Applied Pressure ◽  
External Pressure ◽  
Powder Size ◽  
Starting Mixture ◽  
Functionally Gradient ◽  
High Temperature Synthesis ◽  
One Step ◽  
Commercial Applications

Functionally Gradient Materials (FGM's) are soon to be used in a variety of important commercial applications; joining and thermal barrier coatings are two of the most widely studied. FGM's of the TiC/NiAl and the TiC/Ni3Al systems were fabricated using a one-step, self-propagating high-temperature synthesis (SHS) and densification method. It was observed that ignition of the starting mixture for these two systems was affected by the initial sample temperature and the external pressure that was applied to the sample during the ignition stage. Quality of the final product (e.g., porosity, grain size, cracking and microcracking, etc.) depends on a number of factors during this one-step operation. Reaction temperature control is important and is necessary to minimize residual porosity of the final product. Particle size of reactant powders, as well as applied pressure, also has an effect on the resulting microstructure. If careful reaction temperature control is achieved, along with optimum reactant powder size and applied pressure, an FGM of minimal porosity is obtained without residual macrocracks. Further, this method can easily be used to fabricate an FGM with a highly precise composition and material properties gradient. Finally, this process results in FGM's of similar quality when compared to those prepared by existing fabrication methods at only a fraction of the cost. Most importantly, it is expected that this process can be scaled up with relative ease.

Fundamentals of The Shs Joining Process

1993 ◽  
Vol 314 ◽  
Author(s):  
Robert W. Messler ◽  
Timothy T. Orling
Keyword(s):  
Applied Pressure ◽  
Dissimilar Materials ◽  
Gradient Material ◽  
Functionally Gradient ◽  
High Temperature Synthesis ◽  
Joint Properties ◽  
Mechanical And Physical Properties ◽  
Nonoxide Ceramics ◽  
Joining Process

AbstractThe process of self-propagating high-temperature synthesis offers potential for joining similar or dissimilar combinations of heat-resisting or refractory metals and refractory or corrosion resistant oxide or nonoxide ceramics or intermetallics by using the exothermy inherent in the synthesis reaction. The process offers unique capability for producing functionally gradient material joints between dissimilar materials to overcome mismatches in chemical, mechanical and physical properties, facility for incorporating reinforcing phases in the filler, and exceptional efficiency given that the energy for joining is largely internally generated. A systematic study of the fundamentals of the process critical for joining in either a primary or a secondary mode is being undertaken. Specialized fixtures are being employed to study the role of substrate temperature in bond formation and strength, and the role of precompaction density and applied pressure on joint density. A Gleeble thermomechanical simulator is being used to study the role of reactant composition, reactant particle size, heating rate and reaction mode, precompaction and applied pressure, and atmosphere. Ultimately, a model of the SHS process for joining will be developed to facilitate joint design, predict joint properties, and enable intelligent control.

Self-propagating high-temperature synthesis microalloying of MoSi2 with Nb and V

2003 ◽  
Vol 18 (8) ◽  
pp. 1842-1848 ◽  
Author(s):  
F. Maglia ◽  
C. Milanese ◽  
U. Anselmi-Tamburini ◽  
Z. A. Munir
Keyword(s):  
Solid Solution ◽  
High Temperature ◽  
Tetragonal Phase ◽  
Synthesis Method ◽  
The Self ◽  
Alloying Elements ◽  
Alloying Element ◽  
Temperature Synthesis ◽  
Starting Mixture ◽  
High Temperature Synthesis

Microalloying of MoSi2 to form Mo(1−x)MexSi2 (Me = Nb or V) was investigated by the self-propagating high-temperature synthesis method. With alloying element contents up to 5 at.%, a homogeneous C11b solid solution was obtained. For higher contents of alloying elements, the product contained both the C11b and the hexagonal C40 phases. The relative amount of the C40 phase increases with an increase in the content of alloying metals in the starting mixture. The alloying element content in the hexagonal C40 Mo(1−x)MexSi2 phase was nearly constant at a level of about 12 at.% for all starting compositions. In contrast, the content of the alloying elements in the tetragonal phase is considerably lower (around 4 at.%) and increases slightly as the Me content in the starting mixture is increased.

Effect of C/Ti Ratio and Al Powder Size on Microstructure and Performance of Al-Ti-C Grain Refiner

2007 ◽  
Vol 353-358 ◽  
pp. 2981-2984
Author(s):  
Chun Xiang Xu ◽  
Li Ping Liang ◽  
Bin Feng Lu ◽  
Jin Shan Zhang ◽  
Wei Liang
Keyword(s):  
Powder Size ◽  
Grain Refining ◽  
Grain Refiner ◽  
Casting Method ◽  
High Temperature Synthesis ◽  
Method Effects ◽  
Refining Performance ◽  
Al Powder ◽  
And Performance ◽  
Microstructure And Performance

Al-Ti-C grain refiners have been prepared by combining self-propagating high-temperature synthesis (SHS) technique and melting-casting method. Effects of Al powder size and C/Ti ratio on the microstructures and grain-refining efficiency of Al-Ti-C grain refiners were studied by OM, XRD, SEM and EDS. The results show that when Al powder size is fine, and C/Ti ratio is 1: 8, SHS reaction among the mixed powders can easily carry on in the melt. As a result, the prepared grain refiner consists of blocky Al3Ti and fine TiC particles distributed in Al matrix, and exhibits excellent grain refining performance on commercially pure Al.

scholarly journals Esterification of Crude Palm Oil Using H2SO4 and Transesterification Using CaO Catalyst Derived from Anadara granosa

2017 ◽  
Vol 17 (2) ◽  
pp. 309 ◽  
Author(s):  
Nurhayati Nurhayati ◽  
Sofia Anita ◽  
Tengku Ariful Amri ◽  
Amilia Linggawati
Keyword(s):  
Reaction Time ◽  
Reaction Temperature ◽  
Palm Oil ◽  
Reaction Times ◽  
Crude Palm Oil ◽  
Process Step ◽  
Molar Ratios ◽  
One Step ◽  
Esterification Reactions ◽  
Anadara Granosa

In this study biodiesel was produced from crude palm oil through two-step processes, namely esterification reactions using homogeneous H2SO4 catalyst and transesterification using the heterogeneous base CaO catalyst derived from Anadara granosa shell. Several parameters affecting to the yields of biodiesel were investigated including the amount of the catalysts, the molar ratios of oil to methanol, reaction times and reaction temperatures. The CaO catalyst was prepared by calcining the A. granosa shells at the temperatures of 800 and 900 °C for 10 h. The as-synthesized biodiesel was analyzed using GC and its characteristics were determined and the results were compared to Standard National for Biodiesel (SNI 04-7183-2006). The optimum condition for the esterification process (step 1) was as follows: reaction temperature of 65 °C, reaction time of 3 h and mol ratio of oil to methanol 1:24. For the transesterification (step 2) the optimum conditions were attained using the catalyst weight 3%, reaction temperature of 60 °C, reaction time of 3 h, mole ratio of oil/methanol 1:6 and the catalyst calcination time of 10 h with the conversion of 87.17%. This biodiesel yield by the two-step processes was higher (2.7%) than that using only one-step process (transesterification).

scholarly journals Carbon Nanotube Sheet-Synthesis and Applications

Nanomaterials ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 2023
Author(s):  
Megha Chitranshi ◽  
Anuptha Pujari ◽  
Vianessa Ng ◽  
Daniel Chen ◽  
Devika Chauhan ◽  
...  
Keyword(s):  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Large Scale ◽  
Hydrogen Gas ◽  
Synthesis Process ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Metal Ceramic ◽  
Commercial Applications ◽  
Manufacturing Problems

Decades of extensive research have matured the development of carbon nanotubes (CNTs). Still, the properties of macroscale assemblages, such as sheets of carbon nanotubes, are not good enough to satisfy many applications. This paper gives an overview of different approaches to synthesize CNTs and then focuses on the floating catalyst method to form CNT sheets. A method is also described in this paper to modify the properties of macroscale carbon nanotube sheets produced by the floating catalyst method. The CNT sheet is modified to form a carbon nanotube hybrid (CNTH) sheet by incorporating metal, ceramic, or other types of nanoparticles into the high-temperature synthesis process to improve and customize the properties of the traditional nanotube sheet. This paper also discusses manufacturing obstacles and the possible commercial applications of the CNT sheet and CNTH sheet. Manufacturing problems include the difficulty of injecting dry nanoparticles uniformly, increasing the output of the process to reduce cost, and safely handling the hydrogen gas generated in the process. Applications for CNT sheet include air and water filtering, energy storage applications, and compositing CNTH sheets to produce apparel with anti-microbial properties to protect the population from infectious diseases. The paper also provides an outlook towards large scale commercialization of CNT material.

scholarly journals One-step ultra-rapid fabrication and thermoelectric properties of Cu2Se bulk thermoelectric material

RSC Advances ◽  
2019 ◽  
Vol 9 (19) ◽  
pp. 10508-10519 ◽  
Author(s):  
Tiezheng Hu ◽  
Yonggao Yan ◽  
Si Wang ◽  
Xianli Su ◽  
Wei Liu ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermoelectric Properties ◽  
Single Phase ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Thermoelectric Energy ◽  
Rapid Fabrication ◽  
One Step ◽  
First Time

Cu2Se is a promising material for thermoelectric energy conversion. Fully dense single-phase bulk Cu2Se was prepared by the combination of self-propagating high-temperature synthesis with in situ quick pressing for the first time.

scholarly journals Stability-Ranking of Crystalline Ice Polymorphs Using Density-Functional Theory

Crystals ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 40
Author(s):  
Pralok K. Samanta ◽  
Christian J. Burnham ◽  
Niall J. English
Keyword(s):  
Density Functional Theory ◽  
Structure Prediction ◽  
Density Functional ◽  
Applied Pressure ◽  
External Pressure ◽  
Crystal Structure Prediction ◽  
Functional Theory ◽  
Stability Ranking ◽  
High Level ◽  
Basin Hopping

In this work, we consider low-enthalpy polymorphs of ice, predicted previously using a modified basin-hopping algorithm for crystal-structure prediction with the TIP4P empirical potential at three pressures (0, 4 and 8 kbar). We compare and (re)-rank the reported ice polymorphs in order of energetic stability, using high-level quantum-chemical calculations, primarily in the guise of sophisticated Density-Functional Theory (DFT) approaches. In the absence of applied pressure, ice Ih is predicted to be energetically more stable than ice Ic, and TIP4P-predicted results and ranking compare well with the results obtained from DFT calculations. However, perhaps not unexpectedly, the deviation between TIP4P- and DFT-calculated results increases with applied external pressure.

Preparation of Alkyl Polyglucoside Surfactants by One-Step

2012 ◽  
Vol 550-553 ◽  
pp. 75-79 ◽  
Author(s):  
Jia Yin Li ◽  
Yan Jun Liu ◽  
Guo Zheng ◽  
Yu Sun ◽  
Ya Ning Hao ◽  
...  
Keyword(s):  
Reaction Temperature ◽  
Reaction Conditions ◽  
Reaction Pressure ◽  
Toluenesulfonic Acid ◽  
Catalyst Type ◽  
One Step ◽  
Temperature And Pressure ◽  
Alkyl Polyglucoside

Dodecyl polyglucoside was synthesized by glucose and dodecanol using P-toluenesulfonic acid as catalyst. The effects catalyst type, proportion of material, reaction temperature and pressure were discussed in this paper. The most appropriate reaction conditions: mole ratio of laurel alcohol and glucose 6:1, mass of ratio of P-toluenesulfonic and glucose 0.008:1, reaction temperature 120°C and reaction pressure 5.0kPa.

Superfast Sintering of Nanocrystalline Y2O3 Ceramics

2009 ◽  
Vol 66 ◽  
pp. 100-103 ◽  
Author(s):  
Xia Zheng ◽  
Zheng Yi Fu ◽  
Jin Yong Zhang ◽  
Wei Min Wang ◽  
Hao Wang ◽  
...  
Keyword(s):  
High Temperature ◽  
Heating Rate ◽  
Grain Growth ◽  
Combustion Temperature ◽  
Applied Pressure ◽  
The Self ◽  
Temperature Synthesis ◽  
High Temperature Synthesis ◽  
Chemical Furnace ◽  
Maximum Combustion Temperature

Dense nanocrystalline Y2O3 ceramics without grain growth have been successfully obtained by a new method, which is based on the self-propagating high temperature synthesis and quick pressing. A suitable self-propagating system with a maximum combustion temperature of 1350 °C and a heating rate of 1300 °C/min was chosen as a chemical furnace to supply the heat to densify nanocrystalline Y2O3. Dense samples without grain growth were obtained when the applied pressure was 120 MPa.

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