scholarly journals Microstructures of a SiC–ZrC Ceramic Fiber Derived from a Polymeric Precursor

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2142 ◽  
Author(s):  
Min Ge ◽  
Xiaoxu Lv ◽  
Hao Zhang ◽  
Shouquan Yu ◽  
Zhenxi Lu ◽  
...  
Keyword(s):  
Heat Treatment ◽  
Melt Spinning ◽  
Zirconium Carbide ◽  
Temperature Treatment ◽  
Free Carbon ◽  
Ceramic Fiber ◽  
High Temperature Treatment ◽  
Average Grain Size ◽  
Electron Beam Curing ◽  
20 Nm

Continuous ceramic fiber comprising silicon carbide–zirconium carbide (SiC–ZrC) binary phases was obtained through melt spinning, electron-beam curing and pyrolysis of a pre-ceramic precursor of polyzirconocenecarbosilanes (PZCS). After pyrolysis and heat treatment, ZrC particles with mean diameters of 15–20 nm were formed and homogeneously dispersed in a matrix of fine crystalline β-SiC with an average grain size of 6–10 nm. Concentration of Zr in the fiber varies from 14.88% to 17.45% by mass. Fibers consisting of near-stoichiometric ZrC and SiC with little free carbon can be obtained through pyrolysis decarbonization of the as-cured fiber in hydrogen from room temperature to 1000 °C, and subsequently heat treatment in argon up to 1600 °C for 1 h. High-temperature treatment of these amorphous inorganic fibers leads to crystallization of the binary phases of β-SiC and ZrC. The removal of free carbon under hydrogen results in more rapid growth of β-SiC and ZrC crystals, in which obvious aggregation of the dispersed ZrC particles among the continuous β-SiC matrix can be ascribed to a fast migration of Zr cation.

Microstructure in Rapidly Quenched Al-Ti,Al-B and Al-Ti-B Alloys

1986 ◽  
Vol 80 ◽  
Author(s):  
A. Majumdar ◽  
R. H. Mair ◽  
B. C. Muddle
Keyword(s):  
Heat Treatment ◽  
Solid Solution ◽  
Melt Spinning ◽  
Analytical Electron Microscopy ◽  
Primary Phase ◽  
Nucleation Sites ◽  
Uniform Dispersion ◽  
Average Grain Size ◽  
Melt Spun ◽  
Chill Cast

AbstractRapidly quenched ribbons (˜50m thickness) of Al-5wt.%Ti, Al-lwt.%B and a range of Al-Ti-B alloys have been produced by melt spinning under He atmosphere and the microstructures of the ribbons, following solidification and post-solidification heat treatment, characterized using analytical electron microscopy. In the Al-5Ti alloy, the coarse equilibrium primary phase (b.c.t. Al3 Ti) that is observed following conventional casting is replaced by fine (0.1–0. 2μm), cuboidal particles of a metastable cubic (Ll2) Al3Ti in melt-spun ribbon. These metastable particles form directly from the melt and act as nucleation sites for the solid solution which subsequently forms. A refined microstructure with an average grain size of 1–2μm results. A supersaturation of Ti is retained in matrix solid solution following solidification and a variety of solid state precipitate forms, including fine dispersions of coherent, metastable Al3 Ti particles, is observed to emerge during post-solidification heat treatment. For the Al-1B alloy, the coarse distribution of primary AlB2 particles in a chill-cast ingot is replaced by a fine, uniform dispersion of the metastable boride, α-AlB12, in the melt-spun ribbon. Attempts to induce a refined boride dispersion in melt-spun Al-Ti-B alloys have proved largely unsuccessful.

Reduction of hardseededness in mungbean by short duration high temperature treatment

1992 ◽  
Vol 32 (4) ◽  
pp. 483 ◽  
Author(s):  
BC Imrie
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Short Duration ◽  
Vigna Radiata ◽  
Pilot Trial ◽  
Rotating Cylinder ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Hot Plate ◽  
Hard Seeds

Seeds of 2 lines of mungbean (Vigna radiata), soft-seeded cv. Berken and HS23 with 34% hard seeds, were agitated on a hot plate to determine the effects of temperatures up to 200�C on hardseededness, germination and seed variability. The results of this experiment, combined with a pilot trial using a heated rotating cylinder, showed that the temperature of 175�C for 30 s was the optimum treatment to produce seeds suitable for sprouting. This heat treatment reduced hardseededness from 34 to 1%, increased germination from 64 to 96%, and did not increase the percentage of dead seeds.

Processing and Tensile Property of Nano Dispersed Al-Fe-(Mo, V, Zr) Bulk Alloy

2007 ◽  
Vol 26-28 ◽  
pp. 87-90
Author(s):  
Taek Kyun Jung ◽  
Mok Soon Kim ◽  
W.Y. Kim ◽  
Hyouk Chon Kwon ◽  
S. Yi
Keyword(s):  
Melt Spinning ◽  
Hot Extrusion ◽  
Grain Structure ◽  
Bulk Alloy ◽  
Average Grain Size ◽  
Spinning Process ◽  
20 Nm ◽  
Equiaxed Grain ◽  
Very High ◽  
Zr Alloy

The microstructures and mechanical properties of the bulk Al-Fe-(Mo, V, Zr) alloy produced by melt spinning process and subsequent hot extrusion at 693K in the extrusion ratio of 25 to 1 were investigated. TEM observation revealed an equiaxed grain structure with the average grain size of 200 nm for the extruded bulk alloy. Extremely fine dispersoids based on Al-Fe phases, Al-Fe-(Mo, V) phases and Al-Zr phases were observed to be distributed uniformly within grains and at grain boundaries. The size distribution of the binary Al-Fe and the Al-Fe-(Mo, V) phases were ranged from 20 nm to 50 nm, whereas the Al-Zr phase was less than 10 nm. The very high tensile strength of about 800MPa was achieved at room temperature for the extruded bulk alloy.

A modified ultra high temperature treatment for reducing microbial lipolysis in stored milk

1987 ◽  
Vol 54 (2) ◽  
pp. 275-282 ◽  
Author(s):  
Anthony R. Bucky ◽  
Patrick R. Hayes ◽  
David S. Robinson
Keyword(s):  
Heat Treatment ◽  
Fatty Acids ◽  
High Temperature ◽  
Free Fatty Acids ◽  
Storage Period ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Viable Cells ◽  
Whole Milk ◽  
Ultra High Temperature

SummaryCultures ofPseudomonasP46 grown in whole milk to contain ∼ 2 × 107or 1 × 108viable cells ml−1before ultra high temperature (UHT) treatment (140°C for 5 s) demonstrated near linear increases in the concentration of short-chain free fatty acids (FFA) during storage at 20°C. However with 5 × 106cells ml−1before UHT heat treatment there was no detectable increase in these FFA levels over a 6-month storage period. A novel heat treatment (140°C for 5 s followed by 60°C for 5 min) reduced the rate of production of volatile FFA to < 10% of the rates achieved after the normal UHT treatment.

Effect of Structure on the Mechanical Properties of PAN-Based Carbon Fibers during Graphitization

2011 ◽  
Vol 686 ◽  
pp. 770-777 ◽  
Author(s):  
Hao Xiao ◽  
Yong Gen Lu ◽  
Xian Ying Qin ◽  
Ya Wen
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Fiber Surface ◽  
Total Porosity ◽  
Interlayer Spacing ◽  
Temperature Treatment ◽  
Treatment Temperature ◽  
High Temperature Treatment ◽  
X Ray Diffraction ◽  
Crystallite Sizes

An investigation was conducted to determine the influence of high temperature treatment from 1600°C to 2800°C under stretching stress of 10MPa on PAN-based carbon fiber structure and physical properties. The tensile strength of fibers decreased from 4.5GPa to 2.97GPa with increasing treatment temperature up to 2800°C，while the modulus of fibers increased from 230GPa to 375GPa The texture in the longitudinal surface of fibers through heat treatment was characterized using a scanning electron microscopy. The contours of fiber surface became accidented with gaps becoming deeper as temperature increased. It has been observed that both the crystallite sizes (La, Lc) and the degree of preferred orientation increasd, while the crystallite interlayer spacing (d002) decreased by X-ray diffraction analysis with increasing heat-treatment temperature. The total porosity of fibers decreased from 21.01% to 15.09% and while the density of fibers increased from 1.720g/cm-3to1.886 g/cm-3with increasing heat-treatment. In addition, the relationship between mechanical properties and structure of variants was also explored in detail.

Computer Modeling of the Process of Synthesis of Porous Glass-Composite Materials

2019 ◽  
Vol 945 ◽  
pp. 975-980
Author(s):  
L.A. Yatsenko ◽  
Elena A. Yatsenko ◽  
B.M. Goltsman
Keyword(s):  
Experimental Data ◽  
Heat Treatment ◽  
Computer Simulation ◽  
Pore Formation ◽  
Laboratory Experiments ◽  
Foam Glass ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Glass Composite ◽  
Computer Simulation Program

The operational properties of thermal insulation materials directly depend on their structure. The processes of pore formation occur inside the material after high-temperature treatment, which makes their studying more expensive and complicated. On the basis of experimental data, a computer simulation program for the process of pore formation has been developed, which makes it possible to simulate the processes of changing the structure of foam glass during heat treatment without repeated laboratory experiments.

scholarly journals Role of acid-base interactions in synthesis of cordierite from talc and sillimanite group minerals

2013 ◽  
Vol 45 (3) ◽  
pp. 273-279 ◽  
Author(s):  
E.G. Avvakumov ◽  
G.G. Lepezin ◽  
A.A. Gusev ◽  
O.B. Vinokourova
Keyword(s):  
Heat Treatment ◽  
Temperature Treatment ◽  
High Temperature Treatment ◽  
Acid Base ◽  
Oxygen Ions ◽  
Limiting Step ◽  
Significant Acceleration ◽  
Rate Of Reaction ◽  
The Difference

It has been found that the mechanical activation of mixtures of sillimanite group minerals with talc and silica additives in grinding-activating devices with periodic and flow action provides significant acceleration of their interaction with formation of cordierite at the subsequent high-temperature treatment. It is shown that the output of cordierite depends on nature of mineral: in mixture with a sillimanite it is considerably higher, than with an andalusite and kyanite, while the rate of mullitization of these minerals has opposite character. It means that the formation of mullite during heat treatment is not a limiting step in synthesis of cordierite. It is shown that the rate of reaction is determined by the difference in the acid-base properties of these minerals, which depend on the coordination of aluminum cations by oxygen ions, different for each of the modifications.

scholarly journals Microstructure Characterization of Ni-Based Alloys for Packaging Application upon Long-Term Heat Treatment

Coatings ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1159
Author(s):  
Jianbing Ren ◽  
Yilong Ma ◽  
Kejian Li
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Grain Size ◽  
Temperature Treatment ◽  
Working Environment ◽  
High Temperature Treatment ◽  
Surface Corrosion ◽  
Two Samples ◽  
Mo Content

In this study, an investigation was conducted to examine two types of Ni-based alloys upon long-term heat treatment and compare their grains, surface corrosion layers and microhardness values. The working environment of the tested samples was a temperature of 1000 °C for 5000 h. Two samples, respectively, contained low (~8 wt.%) and high (~16 wt.%) contents of Mo, and the low-Mo-content sample contained Nb (~4 wt.%) and other elements. The grains, precipitates, corrosion layers and microhardness values of the samples before and after heat treatment were determined by scanning electron microscopy, electron back-scattered diffraction, transmission electron microscopy, X-ray diffraction analysis and Vickers hardness tests. The results revealed that the grain was surprisingly stable in the sample with the higher Mo content; after heat treatment, the grain size was ~35 μm, which was similar to the grain size before heat treatment. Moreover, for the sample with the higher Mo content, the microhardness was found to be higher, especially after long-term high-temperature treatment, which is of great significance for the long service life of materials.

Effects of High Temperature Treatment on Thermal Cyclic Behavior of Thermal Barrier Coatings

2013 ◽  
Vol 591 ◽  
pp. 185-189
Author(s):  
Dong Bo Zhang
Keyword(s):  
Heat Treatment ◽  
High Temperature ◽  
Thermal Barrier Coatings ◽  
Turbine Blades ◽  
Temperature Treatment ◽  
Cyclic Behavior ◽  
High Temperature Treatment ◽  
Thermal Barrier ◽  
Air Cooling ◽  
Barrier Coatings

Ni3Al based alloy IC10 has been developed for turbine blades and vanes of advanced aero-engines and other high temperature structural components. Conventional two-layered structure thermal barrier coatings (TBCs) were produced by EB-PVD onto Ni-based superalloy. The thickness of bond coat and top coat was approximately 60μm and 120μm, respectively. After thermal barrier coatings were produced, it was heated at 1523K for 2hs, 6hs, 14hs and 20hs under 1×10-2Pa, respectively. After heat treatment was done, the thermal cyclic test was carried out by exposure to air at 1373K for 0.5h, and then cooled to room temperature within 5 minutes by forced air cooling. Scanning electron microscopy (SEM) was employed to study the microstructure of the coatings. After thermal cycled in air at 1373K for TBCs without heat treatment at 1523K, its lifetime is about 810 hours. After 760hs thermal cycles, the spallation occurred on the TBCs that the heat treatment was treated at 1523K for 2hs. The lifetime of TBCs, which the heat treatment was treated at 1523K for 6hs, was 710hs. The lifetime of TBCs, which the heat treatment was treated at 1523K for 14hs and 20hs, was 600hs and 560hs, respectively. The results showed that, with the increasing of the time of heat treatment, the weight gain increased evidently during thermal cycled. The results showed that heat treatment at 1523K affect the lifetime of TBCs during thermal cyclic evidently.

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