Effect Of Heat Treatment Atmosphere Research Articles

Effect of heat treatment atmospheres on microstructure evolution and corrosion resistance of 2205 duplex stainless steel weldments

The effects of post heat treatment atmosphere on microstructure and corrosion resistance of duplex stainless steel welded joints were investigated. Post weld heat treatment (PWHT) was carried out with and without protective atmospheres. Nitrogen and argon are used as protective gases individually. Detailed microstructure examination (optical and SEM) demonstrates that nitrides precipitates are highly observed in the welded zones for nitrogen protected samples. An observed drop of ferrite volume fraction in post weld heat treated samples compared with welded samples without heat treatment leading to corrosion resistance enhancement of heat treated welded joints. An exception for using nitrogen as heat treatment atmosphere a decreased corrosion resistance of weldments is investigated due to nitride precipitates. An increase in the weld zone hardness for post weld heat treated samples compared with base alloy. The initial hardness of duplex stainless steel was 286 Hv while average hardness of weld zone was 340, 411, 343, and 391 Hv for as welded, PWHT using air, argon, and nitrogen atmospheres, respectively. Weld zone hardness increased to 33, 44, 20, and 37%. A significant decrease in the ultimate tensile strength and elongation after PWHT. The initial Ultimate tensile strength duplex stainless steel base material was 734.9 MPa while Ultimate tensile strength of the welded joints was 769.3, 628.4, 737.8, and 681.4 MPa for the following conditions: as welded, PWHT using air, argon, and nitrogen atmospheres, respectively.

Effects of Heat Treatment Atmosphere and Temperature on the Properties of Carbon Fibers.

In this study, carbon fibers were heat-treated in a nitrogen and oxygen atmosphere according to temperature to elucidate the mechanism of chemical state changes and oxygen functional group changes on the carbon fiber surface by analyzing the mechanical and chemical properties of carbon fibers. Carbon fibers before and after heat treatment were analyzed using FE-SEM (Field Emission Scanning), UTM (Universal Tensile Testers), XPS (X-ray Photoelectron Spectroscopy), and surface-free energy. In the nitrogen atmosphere, which is an inert gas, the tensile strength was equivalent to that of the virgin up to 500 °C but decreased to 71% with respect to the virgin at 1000 °C. Furthermore, as the temperature increased from room temperature to 1000 °C, the oxygen functional group and the polar free energy gradually decreased compared with the virgin. On the other hand, in the oxygen atmosphere, which is an active gas, the tensile properties were not significantly different from those of the virgin up to 300 °C but gradually decreased at 500 °C. Above 600 °C, the carbon fibers deteriorated, and measurement was impossible. The oxygen functional group decreased at 300 °C, but above 300 °C, among the oxygen functional groups, the hydroxyl group and the carbonyl group increased. Furthermore, the lactone group formed and rapidly increased compared with the virgin, and the polar free energy increased as the temperature increased.

Effects of heat-treatment atmosphere and temperature on cobalt species in Co/Al2O3 catalyst for propane dehydrogenation

Co-based catalysts have attracted increasing attention as promising catalysts for propane dehydrogenation (PDH) because of their C–H bond activation ability. Co species in Co/Al2O3 are present in various forms, such as Co3O4, CoAl2O4, CoO, and metallic Co. However, the catalytic properties of the various Co species in PDH are unclear. In this work, we prepare Co/Al2O3 with different compositional distribution of Co species by heat-treating the supported Co precursor under O2, Ar, and H2 atmospheres at temperatures between 500 and 600 °C. H2-treated Co/Al2O3 results in superior performance compared to O2- and Ar-treated catalysts. This is attributed to the relatively high Co surface concentration and relatively high ratio of tetrahedral Co2+ stabilized in CoAl2O4 to the total Co species. A detailed study shows that both tetrahedral Co2+ and metallic Co in Co/Al2O3 are active for PDH, but the former is more selective.

Effect of Heat Treatment Atmosphere on Carbon Flux in Ultra-Rapid Carburizing

Effect of Heat Treatment Atmosphere on Carbon Flux in Ultra-Rapid Carburizing

Effect of heat treatment atmosphere on the piezoresistivity of indium tin oxide ceramic strain sensor

Abstract Indium tin oxide (ITO) strain sensors were prepared by RF magnetron sputtering, and then heat treated in nitrogen and air atmosphere, respectively. The effect of air and N2 heat treatment on the piezoresistivity of ITO ceramic strain sensors were investigated at 1200 °C. It was found that although both the ITO ceramic strain sensors heat treated in N2 and air had similar temperature coefficient of resistance (TCR), the ITO strain sensor heat treated in N2 had better resistance stability. In addition, the ITO strain sensor heat treated in N2 had a smaller but more stable gage factor, compared to that in air. These observations were attributed to the increased content of Sn4+ donors and the enhanced photon scattering due to smaller grain sizes after the incorporation of nitrogen into ITO lattice.

Effects of heat treatment atmosphere on the structure and activity of Pt3Sn nanoparticle electrocatalysts: a characterisation case study.

Comprehensive identification of the phases and atomic configurations of bimetallic nanoparticle catalysts are critical in understanding structure-property relationships in catalysis. However, control of the structure, whilst retaining the same composition, is challenging. Here, the same carbon supported Pt3Sn catalyst is annealed under air, Ar and H2 resulting in variation of the extent of alloying of the two components. The atmosphere-induced extent of alloying is characterised using a variety of methods including TEM, XRD, XPS, XANES and EXAFS and is defined as the fraction of Sn present as Sn0 (XPS and XANES) or the ratio of the calculated composition of the bimetallic particle to the nominal composition according to the stoichiometric ratio of the preparation (TEM, XRD and EXAFS). The values obtained depend on the structural method used, but the trend air < Ar < H2 annealed samples is consistent. These results are then used to provide insights regarding the electrocatalytic activity of Pt3Sn catalysts for CO, methanol, ethanol and 1-butanol oxidation and the roles of alloyed Sn and SnO2.

NaVPO4F prepared under air as a cathode material for sodium-ion batteries

NaVPO4F with trivalent vanadium was successfully synthesized under air through controlling the appropriate heating/cooling rate and holding temperature after a hydrothermal process. The vanadium (III) in NaVPO4F can be facilely and successfully maintained even under air. As produced NaVPO4F has similar structure and cycle performance as the one prepared under argon protection. Even more excellent capability was exhibited when operating at high rate currents as cathode material for sodium-ion batteries. The effects of heat treatment atmosphere on electrochemical performances were evaluated by cycle performance, rate capability, and electrochemical impedance spectroscopy. NaVPO4F heated under air could offer a wider range of applications for sodium-ion batteries due to its facile synthesis and low cost.

Effect of heat treatment atmosphere on the structure and apatite-inducing ability of Ca, P, Si and Na incorporated microarc oxidation coating on titanium

Amorphous microarc oxidation (MAO) coating containing Ca, P, Si and Na elements on Ti substrate has been heat treated in different atmospheres (air or argon) to adjust the phase composition, surface structure and bioactivity. After heat treatment in air at 800°C for 1h, the coating consists of anatase, rutile and CaTi4(PO4)6, with almost unchanged microporous surface structure. As for the one treated in argon at 800°C for 1h, anatase and rutile are formed on the coating, and the coating surface is covered by flower-like rutile particles. The formation of rutile particles could be attributed to the prior growth of the oxidized β-Ti along the discharge channel caused by the diffusion of incorporated elements. Thanks to the crystallization of TiO2 and the rise of surface roughness, which provides good sites for apatite nucleation, the MAO coated Ti after heat treatment in argon at 800°C exhibits good apatite-inducing ability.

Effect of Heat Treatment Atmosphere on the Microstructure of TiH2-MoO3 Powder Mixtures

Effect of Heat Treatment Atmosphere on the Microstructure of TiH2-MoO3 Powder Mixtures

Effects of heat-treatment atmosphere on electrochemical performances of Ni-rich mixed-metal oxide (LiNi0.80Co0.15Mn0.05O2) as a cathode material for lithium ion battery

Ni-rich mixed metal oxides (LiNi0.80Co0.15Mn0.05O2) as a high capacity cathode material for lithium ion battery are synthesized in two different heat-treatment atmospheres of air and oxygen, respectively. A cell with LiNi0.80Co0.15Mn0.05O2 heat-treated in the oxygen atmosphere shows better electrochemical performance of initial (193.7 mAh/g) and retention (185.2 mAh/g) capacities than a cell with the cathode material heat-treated in the air atmosphere (initial capacity: 185.2 mAh/g and retention capacity: 172.0 mAh/g). In order to find the reasons of the different electrochemical performance, the samples have been characterized in detail by X-ray diffraction and scanning electron microscopy. The structural differences are revealed at the nanometer scale from the experimental works of scanning transmission electron microscopy images mapped with orientation and reliability indices and electron energy loss spectroscopy. The NiO phase of the rock salt structure is considerably developed on the surfaces of the materials in the less oxidative environment of the air atmosphere; this is related to the poor electrochemical performances.

Effect of Heat-treatment Atmosphere on Photoluminescence of Eu-doped Li-Al-O System

Effect of Heat-treatment Atmosphere on Photoluminescence of Eu-doped Li-Al-O System

The Effect of Heat Treatment Atmosphere on Hardening of Surface Region of H13 Tool Steel

The main objective of the die heat treatment is to enhance the surface hardness and wear properties to extend the die service life. In this paper, a series of heat treatment experiments were conducted under different atmospheric conditions and length of treatment. Four austenitization atmospheric conditions were studied and although each heat treatment condition resulted in a different hardness profile, it did not affect the results for gas nitriding. All samples subjected to the nitriding process produced similar thicknesses of hardened case layer with average hardness of 70 - 72 HRC if the initial carbon content is not too low. It was shown that heat treatment without atmospheric control results in a lower hardness on the surface since the material was subjected to decarburization effect. The stainless steel foil wrapping around the sample and heat treatment in a vacuum furnace could restrict the decarburization process, while pack carburization heat treatment resulted in a carburization effect on the material.

Chemical Change of Copper Species in Liquid Paraffin

To reveal the chemical species of copper,typically the low-valence speices,in Cu-Zn-Al catalyst prepared by complete liquid-phase method before reduction,the effects of heat-treatment atmosphere,interactions among all components and copper precursor on heat-treatment have been systematically studied during the heat treatment of several different kind of copper precursor in liquid paraffin.The results showed that Cu2+ could be reduced by liquid paraffin under heating condition.The Cu+ is formed before the formation of Cu.The reductive degree of Cu2+ was related with the category of copper salts and heat-treatment temperature.CuO can be reduced to Cu2O by liquid paraffin at 240 ℃,and then to Cu at 300 ℃.The copper nitrate could be easily reduced by liquid paraffin than copper acetate at the same temperature.The reason of the low-valent copper appearing in Cu-base catalyst prepared by complete liquid-phase method before reduction could be attributed to the presence of liquid paraffin.

The Effects of Heat Treatment Atmosphere on the Bone-Like Apatite Inducement on the Alkali Treated Ti-6Al-4 V Surfaces

The purpose of this study is to investigate the bone-like apatite inducement ability on the 5M NaOH, deionized water and 600°C atmospheric or vacuum heat treated Ti-6Al-4V surfaces in the modified simulated body fluid (m-SBF) solutions. The alkali-heat treated specimens were soaked in m-SBF up to 7 days for their bioactivity evaluation and induced bone-like apatite layer investigation. All the samples were characterized their surface morphology, chemical and bioactivity by SEM, EDX, XRD and contact angle analysis, respectively. The experimental results show that a thin HA-rich bone-like apatite layer was formed along all the alkali-heat treated Ti-6Al-4V surfaces within 5 days after soaking in the m-SBF. It is also found the alkali-atmospheric heat treated Ti-6Al-4V samples have more favourable bioactivity than alkali-vacuum heat treated counterparts.

Liquid-phase preparation of catalysts used in slurry reactors to synthesize dimethyl ether from syngas: Effect of heat-treatment atmosphere

A CuZnAl slurry catalyst was prepared directly from a solution of metal salts by an entirely liquid-phase method. The influence of heat-treatment atmospheres with different proportions of CO 2 on the single-step synthesis of dimethyl ether (DME) from syngas was investigated and the catalysts were characterized by powder X-ray diffraction (XRD), H 2 temperature-programmed reduction (H 2-TPR), temperature-programmed desorption of ammonia (NH 3-TPD), X-ray photoelectron spectrometry (XPS) and thermogravimetry-mass spectrometry (TG-MS). Results showed that the introduction of CO 2 into the heat-treatment atmosphere made it easier to reduce the catalyst. It also adjusted the Cu 0/Cu + ratio on the catalyst surface, the CO 2 reacting with the metallic carbide there to form CO, which then reduced part of the Cu 2O to Cu. Moreover, it was concluded that the final phase structure of the catalyst and the Cu/Zn ratio on its surface depended mainly on its composition and the reaction environment and less so on the heat-treatment atmosphere. In the DME synthesis reaction, it was found that the introduction of CO 2 into the heat-treatment atmosphere restrained the water–gas shift reaction and raised the DME selectivity. An optimal amount of CO 2 in the heat-treatment atmosphere favored the increase of the DME space–time yield. The catalysts performed best when the heat-treatment atmosphere contained 50% CO 2.

Effect of heat treatment atmosphere on surface recrystallization of a directionally solidified Ni-base superalloy

The effect of heat treatment atmosphere on surface recrystallization (RX) induced by shot-peening in a directionally solidified (DS) superalloy was investigated. The evolution of surface RX and oxidation during heat treatment at 1220 °C in air was revealed by quenching experiments. The RX depth of samples heat treated in air was apparently larger than those heat treated in vacuum. The mechanism was discussed based on the observation of kinetics of oxidation and RX and interactions between them.

Effect of heat-treatment atmosphere on the bond strength of apatite layer on Ti substrate

Objectives The purpose of this study was to investigate the bond strength of apatite layer on titanium (Ti) substrate coated by biomimetic method and to improve the bonding of apatite layer to Ti substrate by optimizing the alkali heat-treatment process. Methods Ti plates pre-treated with an alkali solution of 10 M sodium hydroxide (NaOH) were heat-treated at 600 °C for 1 h at different atmospheres: in air and in vacuum. A dense apatite layer formed on top of the sodium titanate layer after soaking the alkali and heat-treated Ti samples in simulated body fluid (SBF) for up to 3 weeks. The bond strengths of the sodium titanate layer on Ti substrate, and apatite layer on the sodium titanate layer, were measured, respectively, by applying a tensile load. The fracture sites were observed with a scanning electron microscope (SEM). Results The apatite layer on the substrate after alkali heat-treatment in air achieved higher bond strength than that on the substrate after alkali heat-treatment in vacuum. It was found that the interfacial structure between the sodium titanate and Ti substrate has a significant influence on the bond strength of the apatite layer. Significance It is advised that titanium implants can achieve better osseointegration under load-bearing conditions by depositing an apatite layer in vivo on a Ti surface subjected to alkali and heat-treated in air.

Effect of heat treatment atmosphere on the multistage martensitic transformation in aged Ni-rich Ti–Ni alloys

We demonstrated by systematic experiments that the appearance and disappearance of a multistage martensitic transformation in aged Ni-rich Ti–Ni alloys depends on the heat treatment atmosphere. No multistage transformation occurs when the evaporation of Ti and/or Ni and the preferential oxidation of Ti are prevented by the purification of the heat treatment atmosphere in an evacuated quartz tube by a Ti-getter. The heterogeneity in precipitation morphology of the Ti 3Ni 4 phase, which is responsible for the multistage transformation, can thus be suppressed. The influence of changes in the Ni concentration and specimen size on the multistage transformation is also discussed. The multistage transformation is not detected in the concentrated Ni alloy such as Ti–51.4 at.% Ni. All the results obtained in the present study are consistently explained by assuming the formation of zones I and II. The zone I is considered to be a contamination region with interstitial impurity elements, which is responsible for the multistage transformation. The zone II is considered to be a zone of relatively higher Ni concentration as compared to the original alloy composition at the surface.

Effect of Heat Treatment Atmosphere on Multistage R-Phase Transformation in an Aged Ti&amp;ndash;51.0 at%Ni Alloy

The present study systematically investigates the effect of heat treatment atmosphere on the multistage R-phase transformation (MRT) in an aged Ti–51.0 at%Ni alloy. No MRT occurs when the heat treatments were completed under the regulated atmosphere. On the other hand, the MRT is observed in the specimen heat treated under the unregulated atmosphere. It is apparent from transmission electron microscope observations that the first and the second transformations take place around the grain boundary and at the grain interior, respectively. We conclude that the MRT is extrinsic, and is an artifact during the heat treatment, rather than intrinsic in nature.

Effect of Heat-Treatment Atmosphere on Transfer of Alumina Additive in Silicon Carbide

Effect of Heat-Treatment Atmosphere on Transfer of Alumina Additive in Silicon Carbide