Heat Treatment In Temperature Range Research Articles

Effect of Heat-Treatment in Ar Atmosphere on Pore Structure of Carbonaceous Materials from Polysiloxane

Nanoporous carbonaceous materials derived from polysiloxane were first prepared by pyrolysis at 1300°C followed with hydrofluoric acid (HF) etching treatment. Their thermal stability of pore structure in inert condition was investigated in this paper by nitrogen adsorption technique in detail. The specific surface area (SSA) and pore volume (total pore volume, micropore volume, mesopore volume) decreased continually in the heat-treatment temperature range of 1000~1400°C. The average pore size almost kept the same with the raw sample. However, when the temperature exceeded 1400°C, the micropore interconnection began transforming to mesopore structure, which led to the decline of SSA and the increase of average pore size. Furthermore, the pore size distributions (PSDs) curves showed that heat-treatment had an advantage on the transition process of pore structure from disorder to regularity to some extent when heat-treated in the range 1000~1400°C for the most possible reason of relief of residue strain in the carbonaceous materials.

General features of mineral substance high-temperature conversion

Functional areas (stages): low-, medium-, and high-temperature, are established in accordance with cyclic changes of composition, structure, and physicochemical properties of minerals (inorganic compounds) over a wide heat treatment temperature range. In the low-temperature region (<0.3T m) pyrogenetic processes are of governing importance causing dissociation of thermally active compounds and formation of pseudomorphic minerals (phases) and nanostructures with high specific surface, porosity, and physicochemical activity. At moderate temperatures (normally 0.3 – 0.8T m) a ceramic structure is formed, providing sintered products with the maximum level of physicochemical properties. The high-temperature region (>0.8T m) has thermal aging, discriminatory pyroselection of components, and thermal breakdown of ceramic material structure.

Thermomechanical modelling of microstructurally graded shape memory alloys

For better controllability in actuation applications, it is desirable to create functionally graded shape memory alloys in the actuation direction. This is achieved by applying designed heat treatment gradient along the length of a shape memory alloy wire, creating transformation stress and strain gradients. This study presents analytical solutions to predict the deformation behaviour of such functionally graded shape memory alloy wires. General polynomials are used to describe the transformation stress and strain variations with respect to the length variable. Closed-form solutions are derived for nominal stress–strain variations that are closely validated by experimental data for shape memory effect and pseudoelastic behaviour of NiTi wires. These materials exhibit distinctive inclined stress plateaus with positive slopes, corresponding to the property gradient within the sample. The average slope of the stress plateau is found to increase with increasing temperature range of the gradient heat treatment.

Selected problems of formability of aluminised steel plates

The paper presents the results testing of the influence of heat treatment on formability of aluminised steel sheets. Tests have been conducted on samples of DX52D+AS120 aluminised steel sheet with the surface coating thickness of ca. 20μm, before and after heat treatment in temperature range 300–1000°C within 3–150min and after deep drawing. Tests of thickness, roughness, structure and plasticity of coating before and after heat treatment and deep drawing have been conducted. Special equipment for non-destructive and destructive measurements has been used in these tests. A digital camera, an optical microscope and a scanning electron microscope have been used to show changes of coating surface and structure at the cross-section after tests.

Gas Diffusion Media for Proton Exchange Membrane Fuel Cells Made from Carbon Fibers with Controlled Conductivity

ABSTRACTSamples of carbon fiber were prepared from polyacrylonitrile (PAN)-based precursors, covering a range of electrical resistivity from 0.9 to 1,000 mΩ cm corresponding to a range of carbonization heat treatment temperatures (HTT) estimated to be between 700 and 2600°C. Experimental gas diffusion media (GDM) were made from these fibers using conventional phenolic resin/carbon fiber construction, prepared at two different carbonization temperatures (950 and 2150°C). GDM thermal and electrical properties displayed similar trends with respect to fiber and paper HTT. Unexpectedly, GDM bending and shear moduli increased with fiber resistivity, possibly due to shortening of the lower resistivity fiber types during GDM production. Results showed that high HTT of either the carbon fiber or the paper was sufficient to enable average (“wet” and “dry”) 5-cm2 fuel cell performance comparable to current state-of-the-art GDM. A proprietary GDM wet-laid production model predicts a potential cost reduction of about 2% at 20 million m2 annual production by reducing the paper HTT.

Densification mechanism of polyacrylonitrile-based carbon fiber during heat treatment

Polyacrylonitrile (PAN)-based carbon fibers were heat treated at various temperatures for varying durations to simulate the graphitization process in the manufacture of C/C composites. Densification of the resulting fibers was confirmed by density measurement. The composition and structure of the fibers were investigated by means of elemental analysis, X-ray diffraction and Raman spectroscopy. For specified isothermal heat treatment time, the structural parameters depended strongly on heat treatment temperature. The nitrogen content decreased with increased heat treatment temperature and extended time at constant temperature. Nitrogen loss was complete at temperatures above 1900 °C. The graphite crystallite size increased rapidly with increasing heat treatment temperature, and slowly with extended isothermal heat treatment time. At 2100 °C a more ordered graphitic structure appeared. Denitrogenation induced “puffing”, which made the fibers expand. Decrease in density in the heat treatment temperature range 1500–1900 °C originated from the abrupt evolution of nitrogen, and above 1900 °C the graphitization transition induced steadily increasing density. Densification of the carbon fibers was determined both by the rate of denitrogenation and the rearrangement of carbon atoms.

Ti/STS409L/Ti 냉연 클래드재의 접합계면특성에 미치는 후열처리의 영향

Abstract The aim of the present study is to derive optimized post heat treatment temperatures to get a proper formability for Ti/STS409L/Ti clad materials. These clad materials were fabricated by cold rolling followed by a post heat treatment process for 10 minutes at temperatures ranging from 500℃ to 850℃. The microstructure of the interface was observed using a Scanning Electron Microscope(SEM) and an Energy Dispersive X-ray Analyser(EDX) in order to investigate the effects of post heat treatment on the bonding properties of the Ti/STS409L/Ti clad materials. Diffusion bonding was observed at the interfaces with a diffusion layer thickness increasing with the post heat treatment temperature. The diffusion layer was composed of a type of(e + ζ) intermetallic compound containing additional elements, namely, Fe, Ti and Ni. The micro Knoop hardness of the Ti/STS409L interfaces was found to increase with heat treatment up to 800℃ and then decrease for temperatures rising up to 850℃. The tensile strength was shown to decrease for heat treatment temperature increasing to 750℃ and then increase rapidly for temperature rising up to 850℃. A post heat treatment temperature range of 700~750℃ was found to optimize the formability of Ti/STS409L/Ti clad materials.

Effect of heat treatment on 7Na 2O–23B 2O 3–70SiO 2 glass

Porous 7Na 2O–23B 2O 3–70SiO 2 glass was successfully fabricated by acid leaching treatment and phase-separation. The 2 mol/l hydrochloric acid (HCl) solution treatment was used for 24 h. Thermal analysis and X-ray diffraction were used to identify the temperature range of heat-treatment. The average pore size and the pore volume were investigated by a nitrogen adsorption instrument, and SEM was used to characterize the appearance of the porous glass. The results show that the average size of pores changed from 3.75 nm to 3.03 nm when heat treated at 640–680 °C for 6 h. In addition, when heat treated at 640 °C for 6–24 h, the pore size fell from 3.75 nm to 3.66 nm. The surface area and pore volume become larger with the increase in both temperature and heat treatment time.

Improved Photoluminescence of MnS/ZnS Core/Shell Nanocrystals by Controlling Diffusion of Mn Ions into the ZnS Shell

We studied the diffusion of Mn ions in MnS/ZnS core/shell nanocrystals (NCs) from the MnS core to the ZnS shell by steady-state and time-resolved photoluminescence (PL) spectroscopy. The colloidal MnS/ZnS core/shell NCs with different thicknesses of the ZnS shell synthesized in octadecene with nucleation doping strategy were annealed at different temperatures. It was found that the PL intensity and lifetime of the MnS/ZnS NCs with a thin ZnS shell significantly decreased with increasing annealing time in the heat treatment temperature range of 220−300 °C, resulting from the diffusion of Mn ions in the MnS/ZnS core/shell NCs to the surface of the ZnS shell, while the PL intensity and lifetime of the NCs with a thick ZnS shell remained almost constant in the temperature range. Furthermore, it was noted that the MnS/ZnS NCs with a small MnS core of about 2.0 nm in diameter exhibited high PL quantum yield of greater than 40%. The experimental results indicated that highly efficient luminescent Mn-doped ZnS NC...

Effect of heat treatment on the properties of nanostructured magnetically hard Pr-Dy-Fe-Co-B materials

Effect of heat treatment (HT) in the temperature range from 400 to 1000°C on the properties of sintered (Pr1 − x Dy x )12 − 17(Fe1 − y Co y )balB5 − 15 (x = 0−0.73 and y = 0.15−0.87) magnets is studied. It is shown that, depending on the cobalt and boron contents in the material, its composition and the dependence of H cI on heat treatment conditions change. In the HT temperature range 700–900°C, an H cI minimum is found: the “depth” of the minimum increases with increasing cobalt content. The minimum of H cI is reversible; i.e., after HT at 1000°C, the coercive force increases to the value corresponding to the composition of the material whatever the temperature of preliminary HT. A model that explains the dependence of H cI of the material on the HT conditions by a diffusion redistribution of boron between the basic R 2F14B (2-14-1 intermetallic) and RF 2, RF 4B, RF 3B2, and RF 2B2 phases (with R = Pr + Dy, F = Fe + Co) is suggested.

Evolution of the Char Structure of Lignite under Heat Treatment and Its Influences on Combustion Reactivity†

A lignite and its demineralized sample were pyrolyzed in a tube furnace under various temperatures from 773 to 1673 K. The resulting chars were systematically characterized with Raman spectroscopy for carbon microstructure, Fourier transform infrared spectroscopy for functional groups, and N2 adsorption isotherm for pore structure. The reactivity of char combustion was measured with thermogravimetric analysis based on a non-isothermal approach to derive the reactivity index and kinetic data. Over the range of heat-treatment temperatures studied, char structure evolution had different behaviors before and after 1073 K. Increasing the treatment temperature from 773 to 1073 K led to the increases in the concentrations and the growth of aromatic ring sizes indicated by the evolutions of Raman parameters, the decreases in functional groups, and the increase of smaller pores. When the treatment temperature was increased from 1073 to 1673 K, the evolutions of Raman band area ratios and pore structure indicated that the main change was the microstructure ordering. Mineral matter was found to have little impact on the structure evolution of the lignite char. Combustion reactivity index and activation energy were observed to increase with the treatment temperature because of char structure evolution and ordering. Mineral matter was found to have a catalytic effect on the reactivity but no influence on the activation energy. Fairly good linear correlations were found between the reactivity index and band area ratios of ID1/IG and IG/IALL when considering the structure evolution behaviors at lower and higher temperature regions, respectively.

The Effect of Co–N Addition on Mechanical Properties, Microstructure and Erosion of 17Cr Steels

The effect of Co–N addition on mechanical properties, microstructure and water-jet erosion of heat-treated 17Cr steels was examined focusing on hardness, grain size, phase volume fraction and erosion damage. In the heat-treatment temperature range, the hardness and strength of Co–N added 17Cr steels are somewhat higher than those of non-added 17Cr steel. In the 950 to 1100°C quenching temperature range, grain size, hardness and volume fraction of retained γ and δ-ferrite increased with increasing quenching temperature. The grain size in Co–N added 17Cr steels was finer than that in non-added 17Cr steel and the volume fraction of retained γ and δ-ferrite in Co–N added 17Cr steels was smaller than that in non-added 17Cr steel. The Co and N content measured by EDAX and Auger analysis were mostly contained in the matrix; therefore, Co–N added 17Cr steels probably contributed to solid solution strengthening and restraint of δ-ferrite formation in the matrix. Under the tempering treated conditions, hardness patterns are divided into three regions (maximum softening region in 250 to 350°C, secondary hardening and temper brittleness region in 400 to 500°C, maximum softening and precipitation region in 550 to 700°C). All of the Co–N added and non-added 17Cr steels had similar hardness patterns when plotted against tempering temperatures; however erosion damage depth of the Co–N added 17Cr steels in high-pressure water-jet tests was somewhat less than that in Co–N non-added 17Cr steel.

Phase Composition and Magnetic Properties of Multiphase Melt-Spun Nd&lt;sub&gt;4.3&lt;/sub&gt;Fe&lt;sub&gt;76.2&lt;/sub&gt;B&lt;sub&gt;19.5&lt;/sub&gt; Alloy

Phase transformations and magnetic properties of multiphase Nd4.3Fe76.2B19.5 alloy were investigated in the temperature range of heat treatment 600-700°C. The influence of different heat treatment regimes was observed by correlation of phase composition and measured magnetic properties. The heat treatment regime, which provided the microstructure that improves exchange interactions between grains of soft and hard magnetic phases and consequently enhances magnetic properties, was defined and discussed. For optimized magnetic alloy grain size of the present phases Fe3B, Nd2Fe14B and α-Fe was calculated by size-strain analysis of X-ray powder diffraction data. Calculated mean grain size was on a nanoscale, below 30 nm.

The study of removing hydroxyl from silica glass

The removal of hydroxyl from silica glass produced by melting quartz powder under an atmosphere containing hydrogen was investigated. After heat-treatment at the temperature range (700–1200 °C) in nitrogen atmosphere, the effective hydrogen diffusion coefficients were evaluated based on the law of nonsteady-state diffusion. The activation energy obtained is 254 kJ mol −1 for the dehydroxylation process in the heat-treatment temperature range of 700–900 °C, and a different activation energy calculated is 32 kJ mol −1 in the temperature range of 900–1200 °C. The activation energies for the dehydroxylation process at the temperature (700–900 °C) and the higher temperature (900–1200 °C) correspond to the binding energy of SiO–H bond and the activation energy for the diffusion of hydrogen in silica glass respectively, which indicate there is a change of mechanism for dehydroxylation with heat-treatment temperature.

Waste glass and fly ash derived glass-ceramic

Crystallization behavior of a waste-based glass-ceramic was studied by means of X-ray diffraction analysis, and the surface morphological observations and chemical compositions were evaluated by field emission-scanning electron microscopy and energy dispersive X-ray spectrometry. Applying the mechanical milling method, the glass-ceramic was prepared by using fly ash from a thermal power plant mixed with waste glass cullet. Powder mixtures consisting of waste glass powder (70 wt%) and fly ash (30 wt%) were used to make glass-ceramic. Various heat treatment temperatures [900, 925, 950, 975, 1000 and 1025°C] were used to obtain a glass-ceramic of the optimum crystal phase, mechanical properties and chemical durability. The X-ray diffraction analysis showed that the crystalline phases in the glass-ceramic were diopside [Ca(Mg, Al)(Si, Al)2O6], augite [Ca(Mg, Fe)Si2O6] and wollastonite [CaSiO3]. The crystallization of an acicular phase in the matrix was achieved in the heat treatment temperature range of 1000–1025°C, and the acicular type main crystal phase in the glass-ceramic was wollastonite [CaSiO3]. The heat treatment temperature range [1000–1025°C] also showed much better mechanical properties.

Dynamics of defects and surface structure formation in reticulated vitreous carbon

Morphological and microstructure properties of reticulated vitreous carbon (RVC) were analyzed by scanning electron microscopy (SEM), micro-Raman spectroscopy and x-ray diffraction (XRD) techniques as a function of heat treatment temperature (HTT). Samples produced in the HTT range of 1000 to 2400 K have demonstrated a strong dependence of HTT in their structural order mainly attributed to the presence of hydrogen and oxygen (heteroatoms), originated from precursor. In this range, the material is changed from pyropolymer to carbon. The polyfurfuryl alcohol precursor has furanic groups and its cure originates methylenical bonds and sulphur atoms. At HTT higher than 1300 K, these atoms are gradually liberated from the material generating a discrete structure ordering.

Austenite stability in Fe–Mn–Si-based shape memory alloys

The stability of austenite in a number of Fe–Mn–Si-based shape memory alloys has been investigated. It was found that a grain boundary precipitate of BCC structure is formed over a wide range of alloy compositions and heat treatment temperatures. This grain boundary phase has been identified as the chi ( χ) phase. Although up to 3 vol.% of the grain boundary precipitate was generated by isothermal aging in the range 500–800 °C, it was found not to markedly affect the mechanical properties or the shape memory effect. Nano-indentation indicated that the hardness and strength of the parent and precipitate phase are very similar, as are their compositions.

Carbon structure of coke at high temperatures and its influence on coke fines in blast furnace dust

A thermal annealing study of three industrial cokes was carried out in a horizontal tube furnace at a range of temperatures up to 1600 °C under N2. Evolution of the carbon structure of cokes was established by determining the stack height (L002) of aromatic carbon layers on the basis of the 002 carbon peak in their X-ray diffraction (XRD) spectra by using the classical Scherrer’s approach. The heat-treatment temperature is shown to have a strong impact on the growth of crystalline order of coke carbon by demonstrating a linear correlation between the carbon crystallite height (L002) and the annealing temperature. The intensity of the thermal effects on the growth of the crystalline order of coke carbon is influenced by the coke ash chemistry, particularly with the iron content of the coke. The carbon structure of blast furnace (BF) dust samples was also analyzed by using XRD and scanning electron microscopy (SEM). Under a similar range of heat-treatment temperatures, growth of the carbon crystallite (L002) of coke, in both the laboratory and the industrial BF, was found to be of the same order of magnitude. The correlation between the carbon structure (L002) of coke and the annealing temperature is used to ascertain the temperature of the origin of coke fines in a BF. The carbon structure of coke is shown to have a significant influence on the coke behavior in a BF such that highly ordered coke displayed lower reactivity as well as higher proportion of coke fines in the dust. The carbon structure of coke fines in BF dust has been shown as an indicator of the crystallite dimension (L002) of the coke in a BF, and has a potential to assess coke performance, particularly of the coke fine generations from different thermal regimes of a BF and also their subsequent consumption.

Influence of heat treatment on the microstructure and mechanical properties of 6005 and 6082 aluminium alloys

The main task of this work was to study the influence of the cooling conditions after homogenization of the 6082 aluminium alloys. The effect of the solution heat treatment temperature on the mechanism and ageing kinetics of the two commercial wrought aluminum alloys 6005 and 6082 was also analyzed. The alloys were heat treated—T4 with a wide range of solution heat treatment temperature from 510 to 580 °C and then natural ageing in the room temperature. Then, Brinell hardness measurements were conducted on both alloys in order to examine the influence of ageing time on the precipitation hardening behavior. The microstructure changes of the aluminium alloys following ageing for 120 h has been investigated by metallographic and transmission electron microscopy (TEM). The minor objective of the present study was to determine how extrusion processing affected the microstructure and mechanical properties of both aluminium alloys. For this purpose tensile tests were performed.

STRUCTURE AND PROPERTIES OF (La2-xSrx)MnO4 COMPOUNDS

Polycrystalline single phase ( La 2-x Sr x) MnO 4 (1.10≤ x ≤1.40) samples were prepared by a citrate precursor method. They have tetragonal K 2 NiF 4 structure with a space group of 14/mmm, increasing x, unit-cell a-axis increases and c-axis decreases, which is a result of decreasing of the Jahn-Teller effect due to the increase of the Mn ( IV ) ion. Spin glass state exists at low temperature and a hump observed from the susceptibility (χ) measurement is probably caused by the interactions of several magnetic phases. Among them, ( La 0.6 Sr 1.4) MnO 4 has the largest magnetoresistance ratio ([ρ(H)-ρ(0)]/ρ(0)), which reaches to 78.4% at 48 K. It is not possible to obtain single phase materials with 0.60≤ x ≤1.00 in the heat treatment temperature range of 1000-1600°C. Impurities were easily observed under SEM and X-ray diffraction patterns. Increasing the heating period and decreasing the temperature, the amount of ABO3 perovskite phase increases. In order to extend the solubility range, of the SrO in the ( La 2-x Sr x) MnO 4, it probably needs a higher temperature (&gt;1600°C) and a shorter heat treatment period (&lt;1 h).