Quick Spherodizing in GCr15 Steel by Mechanism of Divorced Eutectoid

A novel processing of quick spheroidizing annealing based on DET(divorced eutectoid transformation) mechanism has been presented in this paper. Spheroidized carbide microstructure could be achieved directly by austenite through phase transformation during cooling processing, which is different from the conventional spheroidization annealing where carbide was spheroidized by carbide lamellar gradually resolved and coarsened.The novel processing of spheroidizing annealing presented here will decrease the annealing time from 10-16 hours in conventional processing to around 2-3 hours, which could save about 50% of the energy consumption, comparing to the conventional annealing processing.

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Single-crystalline hierarchically-porous TS-1 zeolite catalysts via a solid-phase transformation mechanism

Microporous and Mesoporous Materials ◽

10.1016/j.micromeso.2020.110828 ◽

2021 ◽

Vol 313 ◽

pp. 110828

Author(s):

Yuanchao Shao ◽

Hongjuan Wang ◽

Xuefei Liu ◽

Philip Ryan Haydel ◽

Tianduo Li ◽

...

Keyword(s):

Phase Transformation ◽

Solid Phase ◽

Zeolite Catalysts ◽

Transformation Mechanism ◽

Single Crystalline ◽

Hierarchically Porous ◽

Solid Phase Transformation

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An Alternative Approach to Analyzing the Interstitial Decay from the End of Range Damage During Millisecond Annealing

MRS Proceedings ◽

10.1557/proc-1070-e06-09 ◽

2008 ◽

Vol 1070 ◽

Cited By ~ 1

Author(s):

Renata Camillo-Castillo ◽

Mark E Law ◽

Kevin S Jones

Keyword(s):

Annealing Time ◽

Dwell Time ◽

Extended Defects ◽

Temperature Dependent ◽

Temperature Regimes ◽

Alternative Approach ◽

Small Times ◽

Conventional Annealing ◽

Kinetics Of ◽

Anneal Temperature

ABSTRACTFlash-assist Rapid Thermal Processing (RTP) presents an opportunity to investigate annealing time and temperature regimes which were previously not accessible with conventional annealing techniques such as Rapid Thermal Annealing. This provides a unique opportunity to explore the early stages of the End of Range (EOR) damage evolution and also to examine how the damage evolves during the high temperature portion of the temperature profile. However, the nature of the Flash-assist RTP makes it is extremely difficult to reasonably compare it to alternative annealing techniques, largely because the annealing time at a given temperature is dictated by the FWHM of the radiation pulse. The FWHM for current flash tools vary between 0.85 and 1.38 milliseconds, which is three orders of magnitude smaller to that required for a RTA to achieve similar temperatures. Traditionally, the kinetics of the extended defects has been studied by time dependent studies utilizing isothermal anneals; in which specific defect structures could be isolated. The characteristics of Flash-assist RTP do not allow for such investigations in which the EOR defect evolution could be closely tracked with time. Since the annealing time at the target temperature for the Flash-assist RTP is essentially fixed to very small times on the order of milliseconds, isochronal anneals are a logical experimental approach to temperature dependent studies. This fact presents a challenge in the data analysis and comparison. Another feature of Flash-assist RTP which makes the analysis complex is the ramp time relative to the dwell time spent at the peak fRTP temperature. As the flash anneal temperature is increased the total ramp time can exceed the dwell time at the peak temperature, which may play a significantly larger role in dictating the final material properties. The inherent characteristics of Flash-assist RTP have consequently required the development of another approach to analyzing the attainable experimental data, such that a meaningful comparison could be made to past studies. The adopted analysis entails the selection of a reference anneal, from which the decay in the trapped interstitial density can be tracked with the flash anneal temperature, allowing for the kinetics of the interstitial decay to be extracted.

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Synthesis and Structural Transformation of Luminescent Nanostructured Gd2O3:Eu Produced by Solution Combustion Synthesis

MRS Proceedings ◽

10.1557/proc-1056-hh08-06 ◽

2007 ◽

Vol 1056 ◽

Author(s):

Luiz G. Jacobsohn ◽

Bryan L. Bennett ◽

Stephanie C. Sitarz ◽

Ozan Ugurlu ◽

Ana L. Lima Sharma ◽

...

Keyword(s):

Phase Transformation ◽

Combustion Synthesis ◽

Structural Transformation ◽

Annealing Time ◽

Solution Combustion Synthesis ◽

Nanocrystal Size ◽

Cubic Phase ◽

Temperature Phase ◽

Solution Combustion ◽

Cubic Structure

ABSTRACTIn this work we explore the uniqueness of solution combustion synthesis (SCS) technique to produce luminescent nanostructured materials with metastable phases. We synthesized Gd2O3:Eu with the high-temperature phase and induced phase transformation toward the room temperature phase to investigate the effects of structural transformation on the luminescent properties. SCS is based on exothermic redox reactions that undergo self-sustaining combustion, yielding powders composed of agglomerates of nanocrystals with typical dimensions of tens of nanometers. Synthesis of materials through SCS occurs in conditions far from thermodynamic equilibrium and, due to the high temperatures achieved during combustion, metastable crystallographic phases can be formed. Eu-doped Gd2O3 was obtained with base-centered monoclinic structure and average nanocrystal size of 35 nm as determined by Debye-Scherre analysis. Phase transformation to the cubic structure was induced by isothermal annealing at 1000 oC for up to 152 hrs and followed by x-ray diffraction (XRD). Luminescence excitation and emission spectra were obtained as a function of annealing time. The transformation from monoclinic to cubic structure was followed by the behavior of the (111) monoclinic/(222) cubic intensity ratio. The ratio value for the as-prepared material is 6, decreasing fast to 3 after 5 hrs. annealing, and reaching a value of 0.1 after 152 hrs. Concomitant to the structural transformation, nanocrystal size was followed for both crystalline phases. The average nanocrystal size for the cubic phase increases from 27 to 47 nm from 1 to 152 hrs., respectively. On the other hand, nanocrystals with the monoclinic phase remained with a constant size around 38 nm. Overall, variation in size is small due to the low connectivity among nanocrystals resulting from the low isostatic pressure employed to prepare the pellets, together with the non-uniform shape of the agglomerates. Photoluminescence excitation spectra are dominated by a broad centered near 278 nm and assigned to the O2-Eu3+ charge transfer band. Photoluminescence emission results present the 5D0-7FJ (with J = 0-4) transitions of Eu3+ ions. The behavior of these bands was investigated as a function of annealing time and subsequently related to the structural changes.

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Hydrothermal Synthesis and Phase Formation Mechanism of TiO2(B) Nanorods via Alkali Metal Titanate Phase Transformation

Solid State Phenomena ◽

10.4028/www.scientific.net/ssp.283.23 ◽

2018 ◽

Vol 283 ◽

pp. 23-36 ◽

Cited By ~ 2

Author(s):

Yothin Chimupala ◽

Rik Drummond-Brydson

Keyword(s):

Phase Transformation ◽

Intermediate Product ◽

Intermediate Phase ◽

Metastable Phase ◽

Exchange Process ◽

Titanium Isopropoxide ◽

Growth Direction ◽

Proton Exchange ◽

Transformation Mechanism ◽

Synthesis Conditions

Titanium dioxide (B phase) with 1-D structures was successfully fabricated via a hydrothermal method with a subsequent ion-exchange process and calcination. P25, titanium isopropoxide (TTIP), rutile and also anatase were used as Ti precursors in the alkali hydrothermal system. TTIP promoted an elongation of nanorod morphology whereas the other precursors produced short nanorod structures. The different types of titanium precursors did not have any influence on the phase transformation during the fabrication process. Na2Ti6O13 was the primary intermediate product after washing the hydrothermal sample. H2Ti3O7 was the secondary intermediate phase obtained following proton-exchange of Na2Ti6O13 in HNO3 solution. Finally, the TiO2(B) phase was the product of calcination of the secondary intermediate product at 400°C for 5 hr. A phase transformation mechanism is presented based on an investigation of products at each of the steps. The effects of the synthesis conditions on tailoring of the crystal morphology are discussed. The growth direction of the TiO2(B) nanorods was investigated by HR-TEM and SADP. Finally, the metastable phase of TiO2(B) was shown to be transformed to anatase during thermal treatment at temperatures higher than 400°C.

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