Articoli di riviste: "Precipitate dissolution"

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Solis-Bravo, Gregorio, Matthew Merwin e C. Isaac Garcia. "Impact of Precipitate Morphology on the Dissolution and Grain-Coarsening Behavior of a Ti-Nb Microalloyed Linepipe Steel". Metals 10, n. 1 (4 gennaio 2020): 89. http://dx.doi.org/10.3390/met10010089.

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The relationship between precipitate morphology and dissolution on grain coarsening behavior was studied in two Ti-Nb microalloyed Linepipe (LP) Steels. The developed understanding highlights the importance of the complex relationship between precipitate constitutive make-up, dissolution mechanism and grain boundary (GB) pinning force. Equilibrium-based empirical solubility products were used to calculate precipitate volume fractions and compared to experimental measurements. Scanning Electron Microscopy (SEM), Electron Backscatter Diffraction (EBSD) and Electron Probe Micro-Analysis (EPMA) were conducted on bulk samples. Transmission Electron Microscopy (TEM)-based techniques were used on C-replica extractions and thin-foils. A retardation in the grain-coarsening temperature compared to the predicted coarsening temperature based on equilibrium calculations was noticed. In addition, a consistent NbC epitaxial formation over pre-existing TiN was observed. The resulting reduction in total precipitate/matrix interface area and the low energy of the TiN/NbC interface are pointed to as responsible mechanisms for the retardation in the kinetics of precipitates’ dissolution. This dissolution retardation mechanism suggests that a lower Nb content might be effective in controlling the grain coarsening behavior of austenite.

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Mineta, S., Shigenobu Namba, Takashi Yoneda, Kyosuke Ueda e Takayuki Narushima. "Changes in Microstructure of Biomedical Co-Cr-Mo-C Alloys with Solution Treating and Aging". Advanced Materials Research 89-91 (gennaio 2010): 377–82. http://dx.doi.org/10.4028/www.scientific.net/amr.89-91.377.

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Microstructural changes occurring in biomedical Co-Cr-Mo alloys with three carbon levels due to solution treatment and aging were investigated. Ingots of Co-Cr-Mo alloys with three different carbon levels were prepared by vacuum furnace melting; their chemical composition was Co-28Cr-6Mo-xC (x = 0.12, 0.25 and 0.35 mass%). Precipitates were electrolytically extracted from as-cast and heat-treated alloys. An M23C6 type carbide and a phase were detected as precipitates in as-cast Co-28Cr-6Mo-0.12C alloy, and an M23C6 type carbide and an  phase (M6C-M12C type carbide) were detected in as-cast Co-28Cr-6Mo-0.25C and Co-28Cr-6Mo-0.35C alloys. Only the M23C6 type carbide was detected during solution treatment. Complete precipitate dissolution occurred in all the three alloys after solution treatment. The holding time required for complete precipitate dissolution increased with increasing carbon content and decreasing solution treatment temperature. Complete precipitate dissolution occurred in the Co-Cr-Mo-C alloys solution treated at 1523 K for 43.2 ks; they were then subjected to aging from 873 to 1473 K for a heating time up to 44.1 ks after complete precipitate dissolution in solution treatment at 1523 K for 43.2 ks. The M23C6 type carbide with a grain size of 0.1–3 m was observed after aging. A time-temperature-precipitation diagram of the M23C6 type carbide formed in the Co-28Cr-6Mo-0.25C alloy was plotted.

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Mineta, Shingo, Alfirano, Shigenobu Namba, Takashi Yoneda, Kyosuke Ueda e Takayuki Narushima. "Phase and Morphology of Carbides in ASTM F75 Co-Cr-Mo-C Alloys Formed at 1473 to 1623 K". Materials Science Forum 654-656 (giugno 2010): 2176–79. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2176.

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The phase and morphology of precipitates in heat-treated Co-28Cr-6Mo-xC (x = 0.12, 0.15, 0.25, and 0.35mass%) alloys were investigated. The as-cast alloys were solution-treated in the temperature range of 1473 to 1623 K for 0 to 43.2 ks. Complete precipitate dissolution was observed in all four alloys, each of which had different carbon contents. The holding time for complete dissolution was greater for alloys with greater carbon content. The curve representing the boundary between the complete- and incomplete-dissolution conditions for each alloy is C shaped. Under the incomplete precipitate dissolution conditions of the Co-28Cr-6Mo-0.25C alloy, an M23C6 type carbide and a π-phase (M2T3X type carbide with β-Mn structure) were observed at 1548 to 1623 K, and starlike precipitates with a stripe pattern and with a dense appearance were both observed; the former comprised the M23C6 type carbide + γ-phase, and the latter was the π-phase. In contrast, only a blocky-dense M23C6 type carbide was observed at 1473 to 1523 K.

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Chemezova, K. S., e N. M. Khlynova. "FORMATION OF ANODE ARSENATE FILM ON SILVER ELECTRODE". IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENIY KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 59, n. 1 (7 giugno 2018): 63. http://dx.doi.org/10.6060/tcct.20165901.5174.

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The single current peak is registrated on voltammograms of electro dissolution of precipitates forming on silver electrode into solutions containing arsenate ions. The precipitate amount is proportional to a concentration of arsenate ions in a solution. This amount can be used for ions determination. Optimal conditions for electro deposition and electro dissolution are recommended.

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Liu, Yong, Dongyu Fang, Bin Zhu, Yilin Wang, Shiqi Li e Yisheng Zhang. "Modeling of Isothermal Dissolution of Precipitates in a 6061 Aluminum Alloy Sheet during Solution Heat Treatment". Metals 11, n. 8 (3 agosto 2021): 1234. http://dx.doi.org/10.3390/met11081234.

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During the solution heat treatment (SHT) process of aluminum alloys, precipitates dissolve into the matrix. To predict the dissolution time, modeling of isothermal dissolution of precipitates in 6061 aluminum alloy during SHT was conducted. A precipitate dissolution model was established, and the flowchart of the modeling was designed as well. Then the explicit finite-difference method was employed to solve the dissolution model, and the mobile nodes method was used to deal with the moving interface. The simulation was based on real precipitates in 6061, and SHT experiments were conducted to validate the numerical model. The simulation results showed that the isothermal dissolution time of precipitates in 6061-T6 aluminum alloy at 560 °C is 11.6856 s. The dissolution time in the simulation was close to the experimental results, with an error of 16.7%, indicating that the modeling in this study was fairly reasonable and accurate. The error was caused by many factors, and the model should be improved.

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Ueki, Kosuke, Motoka Kasamatsu, Kyosuke Ueda, Yuichiro Koizumi, Daixiu Wei, Akihiko Chiba e Takayuki Narushima. "Precipitation during γ-ε Phase Transformation in Biomedical Co-Cr-Mo Alloys Fabricated by Electron Beam Melting". Metals 10, n. 1 (2 gennaio 2020): 71. http://dx.doi.org/10.3390/met10010071.

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We studied the precipitates that were induced during γ-ε phase transformation in biomedical Co-28Cr-6Mo (mass%) alloys that were fabricated by electron beam melting with carbon contents of 0.184 and 0.018 mass%. In the high-C as-built alloy, M23X6-type, π-phase (M3T2X-type), and η-phase (M6X-M12X-type) precipitates were observed (M and T: metallic elements, X: C and/or N). σ-phase (Co(Cr,Mo)), π-phase, and Co3Mo2Si-type precipitates were observed in the low-C as-built alloy. This is the first report that shows the presence and chemical composition of this precipitate, as the Co3Mo2Si-type precipitate has not been detected in biomedical Co-Cr-Mo alloys before. After aging in the ε-phase stability region, the high-C and low-C alloys both contained a single ε-phase matrix, and the amount of π-phase precipitates increased. Conversely, the amount of π-phase precipitates in both alloys decreased when a reverse transformation treatment was applied in the γ-phase stability region after aging. In the low-C alloy, the amount of Co3Mo2Si-type precipitates increased after reverse transformation treatment. These results indicate that the dissolution of π-phase precipitates and the formation of Co3Mo2Si-type precipitates during reverse transformation promote the formation of fine γ-phase grains at the precipitate/ε-phase matrix interface, because the formation and dissolution of these precipitates affect the γ-phase stability of the matrix.

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Katsman, A., Anton Gorny, D. Shepelev e Menachem Bamberger. "Evolution of Precipitate Depleted Zones in Mg-Based Alloys Strengthened by Precipitation Hardening". Defect and Diffusion Forum 289-292 (aprile 2009): 153–59. http://dx.doi.org/10.4028/www.scientific.net/ddf.289-292.153.

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Extensive research work has been devoted to Mg-based alloys strengthened by precipitation hardening. Increasing the aging time leads to the appearance of zones depleted of precipitates near grain boundaries. The formation of precipitate depleted zones (PDZ's) is explained by near-grain boundary (NGB) coarsening. The evolution of PDZ's was considered on the basis of the model taking into account diffusional fluxes between adjacent precipitates. The set of equations was solved numerically by using a fourth-order Runge-Kutta method for different initial sizes of precipitates and densities of precipitate layers near grain boundaries. The dissolution of precipitates in the NGB-zones is initially provided by diffusion from them to large precipitates at the grain boundary, and then also by diffusion from these decreased precipitates to the larger precipitates at the outer border of the PDZ. As a result, the outer borders of the depleted zones are adjoined by bands of enlarged precipitates forming a PDZ "crust". Being a diffusion controlled process, the depleted zones are widened with temperature and aging time. Experimental investigation of PDZ evolution was conducted by SEM and TEM on Mg-Zn-Sn-alloys aged at different temperatures for different times. Comparison of the calculated results with experimental data allowed the evaluation of the model parameters and physical parameters of the system (diffusion coefficients and interface energy of the precipitated phases).

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Danielsen, Hilmar Kjartansson. "Atomic Resolution Microscopy of Nitrides in Steel". Materials Science Forum 783-786 (maggio 2014): 1617–22. http://dx.doi.org/10.4028/www.scientific.net/msf.783-786.1617.

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MN and CrMN type nitride precipitates in 12%Cr steels have been investigated using atomic resolution microscopy. The MN type nitrides were observed to transform into CrMN both by composition and crystallography as Cr diffuses from the matrix into the MN precipitates. Thus a change from one precipitate type to another does not necessarily involve nucleation of the new precipitate type followed by dissolution of the old precipitates. By studying the interface between these nitrides and the matrix, it could be observed that the MN and CrMN type precipitates had a few nanometers thick amorphous layer between the crystalline nitride and ferrite matrix. Usually precipitates are described as having (semi) coherent or incoherent interfaces, but in this case it is more energetically favourable to create an amorphous layer instead of the incoherent interface.

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Narushima, T., Alfirano, S. Mineta, Shigenobu Namba, Takashi Yoneda e Kyosuke Ueda. "Precipitates in Biomedical Co-Cr-Mo-C-Si-Mn Alloys". Advanced Materials Research 277 (luglio 2011): 51–58. http://dx.doi.org/10.4028/www.scientific.net/amr.277.51.

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The phase and dissolution behavior of precipitates in biomedical ASTM F75 Co-Cr-Mo-C-Si-Mn alloys were investigated. Alloys of five different compositions, Co-28Cr-6Mo-0.25C-1Si, Co-28Cr-6Mo-0.25C-1Mn, Co-28Cr-6Mo-0.25C-1Si-1Mn, Co-28Cr-6Mo-0.15C-1Si, and Co-28Cr-6Mo-0.35C-1Si, were heat-treated from 1448 to 1548 K. The precipitates observed in the as-cast and heat-treated alloys were carbides (M23C6type, h-phase, and p-phase) and an intermetallic compound (c-phase). The main precipitates observed after heat treatment at high temperatures such as 1548 K were p-phase and M23C6type carbide. At these high temperatures, two types of starlike precipitates—dense and stripe-patterned—were observed. The starlike-dense precipitate was the p-phase, and the starlike precipitate with a stripe pattern was identified as the M23C6type carbide and metallic fcc g-phase. In the alloys heat-treated at 1448 to 1498 K, blocky-dense M23C6type carbide was primarily observed. c-phase was detected in the Co-28Cr-6Mo-0.15C-1Si alloy under as-cast condition and after heat treatment at 1448–1523 K for a short holding time. The addition of Si seemed to increase the holding time for complete precipitate dissolution because of the effects of Si on the promotion of p-phase formation at high temperatures and the increased carbon activity in the metallic matrix.

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Sharma, Chaitanya, e Vikas Upadhyay. "Investigating the Effect of Friction Stir Welding on Microstructure and Corrosion Behaviour of Al-Zn-Mg Alloy". Materials Science Forum 969 (agosto 2019): 517–23. http://dx.doi.org/10.4028/www.scientific.net/msf.969.517.

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In this work, Friction Stir Welding (FSW) of alloy 7039 was carried out in T4 temper and resulting microstructure and corrosion behaviour of developed weld were studied. FSW transformed the starting microstructure of base metal and formed stirred zone (SZ) and heat affected zone (HAZ) with varying microstructure and precipitate morphology. The observed zones in welded joints exhibited decreased protection to corrosion resistance than base metal. Dissolution of secondary precipitates in SZ and occurrence of precipitate free zones (PFZs) in HAZ enhanced susceptibility to corrosion of HAZ and weld nugget zone (WNZ) than base metal.

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Li, Dongfan, Hangshan Gao, Zhixun Wen, Zhenwei Li e Zhufeng Yue. "The Effect of Post-heat Treatment on the Microstructures of Single Crystal DD6 Superalloy". High Temperature Materials and Processes 35, n. 8 (1 settembre 2016): 751–60. http://dx.doi.org/10.1515/htmp-2015-0037.

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AbstractVarious thermal cycles at the end of solution heat treatment and their influences on microstructure of single crystal superalloy DD6 were studied by experiments. During various thermal cycles, the qualitative and quantitative microstructure of samples quenched of the transformations is microscopically characterized. This completely includes the large changes in volume fraction, size distribution and morphology of gamma prime precipitate experienced in the upper temperature transformation. Noticeable deviation from the equilibrium volume fraction of γ’ phase is detected in both the dissolution and precipitation processes above 1,120°C for both moderate cooling and heating rate; differences were mainly attributed to the unsteady nature of the turbulent flow. The growth and alignment of the γ’ precipitates are deeply influenced by several factors, e.g. ageing time, cooling rate and quenching temperature. In addition, interesting findings such as “labyrinth” and “cluster” morphologies were observed by scanning electron microscope. During precipitation processes, the complicated microstructure evolution is illustrated by considering the consecutive equilibrium shapes of a coherent precipitate, which grows under the interaction with its neighbors and the coherency of the precipitates improves their potential to resist dissolution.

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Couperthwaite, Sara J., Sujung Han, Talitha Santini, Gurkiran Kaur, Dean W. Johnstone, Graeme J. Millar e Ray L. Frost. "Bauxite residue neutralisation precipitate stability in acidic environments". Environmental Chemistry 10, n. 6 (2013): 455. http://dx.doi.org/10.1071/en13048.

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Environmental context Although land remediation programs for bauxite residues aim at vegetation coverage, the stability of compounds in the residues with acids produced by the vegetation has not been investigated. We show that, despite the instability of caustic components in the residues (negative effects on plant development), this instability actually assists in neutralising acidic soils. These results further affirm the suitability and sustainability of current land remediation programs for bauxite residues in terms of minimising acidic soil formation. Abstract This investigation used a combination of techniques, such as X-ray diffraction, inductively coupled plasma optical emission spectroscopy and infrared spectroscopy, to determine the dissolution mechanisms of the Bayer precipitate and the associated rate of dissolution in acetic, citric and oxalic acid environments. The Bayer precipitate is a mixture of hydrotalcite, calcium carbonate and sodium chloride that forms during the seawater neutralisation of Bayer liquors (waste residue of the alumina industry). The dissolution rate of a Bayer precipitate is found to be dependent on (1) the strength of the organic acid and (2) the number of donating H+ ions. The dissolution mechanism for a Bayer precipitate consists of several steps involving: (1) the dissolution of CaCO3, (2) formation of whewellite (calcium oxalate) when oxalic acid is used and (3) multiple dissolution steps for hydrotalcite that are highly dependent on the pH of solution. The decomposition of the Al–OH hydrotalcite layers resulted in the immediate formation of Al(OH)3, which is stable until the pH decreases below 5.5. This investigation has found that the Bayer precipitate is stable across a wide pH range in the presence of common organic acids found in the rhizosphere, and that initial decomposition steps are likely to be beneficial in supporting plant growth through the release of nutrients such as Ca2+ and Mg2+.

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Naseri, Larouche, Martinez, Breton e Massinon. "Analytical Modeling of the Mixed-Mode Growth and Dissolution of Precipitates in a Finite System". Metals 9, n. 8 (14 agosto 2019): 889. http://dx.doi.org/10.3390/met9080889.

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In this paper, a novel analytical modeling of the growth and dissolution of precipitates in substitutional alloys is presented. This model uses an existing solution for the shape-preserved growth of ellipsoidal precipitates in the mixed-mode regime, which takes into account the interfacial mobility of the precipitate. The dissolution model is developed by neglecting the transient term in the mass conservation equation, keeping the convective term. It is shown that such an approach yields the so-called reversed-growth approximation. A time discretization procedure is proposed to take into account the evolution of the solute concentration in the matrix as the phase transformation progresses. The model is applied to calculate the evolution of the radius of spherical -Al2Cu precipitates in an Al rich matrix at two different temperatures, for which growth or dissolution occurs. A comparison of the model is made, with the results obtained using the numerical solver DICTRA. The very good agreement obtained for cases where the interfacial mobility is very high indicates that the time discretization procedure is accurate.

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Borggren, Ulrika, Göran Engberg e Tadeusz Siwecki. "A Model for Particle Dissolution and Precipitation in HSLA Steels". Advanced Materials Research 15-17 (febbraio 2006): 714–19. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.714.

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Precipitation of carbonitrides has been studied in as-cast slabs of one Nb and one Nb and Ti containing HSLA steel. The precipitates have been quantified using LOM and TEM. The measured size and number distributions was then compared to model calculations of precipitate nucleation and growth using estimates of the cooling rates in the austenitic range (1490oC to 800oC) during casting. Both average size and number distributions could be modelled with good agreement using identical model parameters (except for individual diffusion coefficients for the participating species). The model is based on classic nucleation rate theory and a quasistationary approximation for growth of spherical particles. Local equilibrium is assumed at the phase boundary.

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Alfirano, Shingo Mineta, Shigenobu Namba, Takashi Yoneda, Kyosuke Ueda e Takayuki Narushima. "Heat Treatment of ASTM F75 Co-Cr-Mo-C-Si-Mn Alloys". Materials Science Forum 654-656 (giugno 2010): 2180–83. http://dx.doi.org/10.4028/www.scientific.net/msf.654-656.2180.

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In this study, the carbide dissolution and formation of biomedical Co-28Cr-6Mo-0.25C-1Si (1Si) and Co-28Cr-6Mo-0.25C-1Mn (1Mn) alloys occurring during solution treatment and aging were investigated. The addition of Si or Mn markedly affected the behavior of precipitates during heat treatment. The alloy with added Si required a longer solution treatment time for complete precipitate dissolution as compared to the alloy with added Mn. Blocky M23C6-type carbide was observed during solution treatment at 1448–1523 K. Starlike precipitates were observed in the 1Si and 1Mn alloys at 1523–1548 K and 1523 K, respectively. The starlike precipitates exhibited two types of morphologies: dense and stripe patterned. The starlike precipitates with dense and stripe-patterned appearances were a -phase and M23C6¬-type carbide + metallic -phase, respectively. An M23C6-type carbide and an -phase were formed during the aging of both the 1Si and the 1Mn alloys. In addition, an intermetallic -phase was detected during the aging of the 1Si alloy at 1373 K.

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Akinwande, Kayode I., e Diane M. Keehn. "Dissolution of Phenytoin Precipitate with Sodium Bicarbonate in an Occluded Central Venous Access Device". Annals of Pharmacotherapy 29, n. 7-8 (luglio 1995): 707–9. http://dx.doi.org/10.1177/106002809502907-811.

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Objective: To report a case of restored patency of a central venous access device occluded by precipitate of phenytoin sodium injection. Case Summary: A patient experienced total occlusion of an implanted subcutaneous port caused by precipitation of phenytoin. Phenytoin sodium injection was mixed inadvertently with dextrose 5% in NaCl 0.45% injection during intravenous administration. Dextrose 5% in NaCl 0.45% injection, which is acidic (pH 4.0), caused the phenytoin sodium injection, a basic solution (pH 12.0), to precipitate. Local instillation of sodium bicarbonate 8.4% injection to decrease the pH of the medium restored patency of the occluded port. Discussion: There are reports of local instillation of solvent restoring central ports occluded by lipid-containing parenteral nutrient admixture, calcium phosphate salt precipitate, and coagulated blood. No report of local instillation into an occluded port to dissolve precipitate of phenytoin could be found. Several factors are involved in the precipitation and dissolution of phenytoin. The key factor in this case was the hydrogen ion concentration (pH) of the solution. Decreased pH caused the precipitation, but increased pH caused the dissolution of the precipitate of phenytoin. Conclusions: Sodium bicarbonate injection was a suitable agent for clearing precipitate of phenytoin in this case of an occluded implanted central venous access device.

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Dhumal, Ravindra, Shamkant Shimpi e Anant Paradkar. "Development of spray-dried co-precipitate of amorphous celecoxib containing storage and compression stabilizers". Acta Pharmaceutica 57, n. 3 (1 settembre 2007): 287–300. http://dx.doi.org/10.2478/v10007-007-0023-7.

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Development of spray-dried co-precipitate of amorphous celecoxib containing storage and compression stabilizersThe purpose of this study was to obtain an amorphous system with minimum unit operations that will prevent recrystallization of amorphous drugs since preparation, during processing (compression) and further storage. Amorphous celecoxib, solid dispersion (SD) of celecoxib with polyvinyl pyrrollidone (PVP) and co-precipitate with PVP and carrageenan (CAR) in different ratios were prepared by the spray drying technique and compressed into tablets. Saturation solubility and dissolution studies were performed to differentiate performance after processing. Differential scanning calorimetry and X-ray powder difraction revealed the amorphous form of celecoxib, whereas infrared spectroscopy revealed hydrogen bonding between celecoxib and PVP. The dissolution profile of the solid dispersion and co-precipitate improved compared to celecoxib and amorphous celecoxib. Amorphous celecoxib was not stable on storage whereas the solid dispersion and co-precipitate powders were stable for 3 months. Tablets of the solid dispersion of celecoxib with PVP and physical mixture with PVP and carrageenan showed better resistance to recrystallization than amorphous celecoxib during compression but recrystallized on storage. However, tablets of co-precipitate with PVP and carageenan showed no evidence of crystallinity during stability studies with comparable dissolution profiles. This extraordinary stability of spray-dried co-precipitate tablets may be attributed to the cushioning action provided by the viscoelastic polymer CAR and hydrogen bonding interaction between celecoxib and PVP. The present study demonstrates the synergistic effect of combining two types of stabilizers, PVP and CAR, on the stability of amorphous drug during compression and storage as compared to their effect when used alone.

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Jiao, Z., M. D. McMurtrey e G. S. Was. "Strain-induced precipitate dissolution in an irradiated austenitic alloy". Scripta Materialia 65, n. 2 (luglio 2011): 159–62. http://dx.doi.org/10.1016/j.scriptamat.2011.04.003.

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Wu, Gang, e M. M. Sharma. "Model for precipitation and dissolution processes with precipitate migration". AIChE Journal 35, n. 8 (agosto 1989): 1385–90. http://dx.doi.org/10.1002/aic.690350819.

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Solórzano, I. G., e G. C. Weatherly. "Dislocation structures produced by dissolution of discontinuous precipitate products". Materials Science and Engineering 81 (agosto 1986): 101–5. http://dx.doi.org/10.1016/0025-5416(86)90255-7.

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Chou, S. P., e N. M. Ghoniem. "On precipitate dissolution using the cascade slowing-down theory". Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 42, n. 1 (maggio 1989): 145–48. http://dx.doi.org/10.1016/0168-583x(89)90022-0.

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Brossard, R. L., e G. M. Raynaud. "Influence of temperature on copper bromide formation and dissolution". Canadian Journal of Chemistry 63, n. 3 (1 marzo 1985): 720–24. http://dx.doi.org/10.1139/v85-119.

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The influence of temperature on copper bromide formation and dissolution has been investigated in deaerated aqueous solutions of 0.2 M NaBr at pH 4. The morphology of CuBr accumulated on the copper anode supports the idea that CuBr precipitates in the vicinity of the electrode. Under a constant potential of −70 mVsec very large flat platelets of CuBr are observed at 71 °C compared to grains at 22 °C. In addition, irregular current variations are noted on the current time curves at 71 °C when large cracks are present in the film. It is deduced that the irregular current variations are due to the formation and repair of the cracks in the film. The current of the anode eventually reaches a steady value equal to the dissolution rate of the copper bromide precipitate formed on the electrode.The influence of the temperature on the dissolution rate of CuBr may be entirely predicted assuming that the rate-determining step for the dissolution of this compound is the mass transfer of intermediates, e.g., CuBr2− from the electrode surface to the bulk electrolyte.

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Rath, Markus, e Ernst Kozeschnik. "Coupled Grain Growth and Precipitation Modeling in Multi-Phase Systems". Materials Science Forum 753 (marzo 2013): 357–60. http://dx.doi.org/10.4028/www.scientific.net/msf.753.357.

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In this work, we utilize recent software for precipitation kinetics simulation and couple it with models for grain growth. Basis of our studies is the thermo-kinetic software MatCalc, which has been designed for simulation of the evolution of precipitates in general multi-component multi-phase alloy systems. Grain growth approaches of different complexity are incorporated into the precipitation kinetics framework, investigated with respect to their coupling behavior with precipitation and precipitate dissolution and, finally, benchmarked on typical grain growth problems of industrial practice. The example presented in this work comprises austenite grain growth studies accompanying TiN and NbC precipitation/dissolution during austenitization of a Ti/Nb microalloyed steel. It is demonstrated that the present approach represents a versatile tool for analysis of simultaneous grain growth and precipitation in industrially important alloy systems.

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Cuesta Mayorga, Iris, José Manuel Astilleros e Lurdes Fernández-Díaz. "Precipitation of CaCO3 Polymorphs from Aqueous Solutions: The Role of pH and Sulphate Groups". Minerals 9, n. 3 (13 marzo 2019): 178. http://dx.doi.org/10.3390/min9030178.

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In this work, we aimed to experimentally study the nucleation and growth of CaCO3 phases precipitated from supersaturated aqueous solutions in the presence of varying concentrations of sulphate oxyanion. The experiments were conducted under pH conditions close to neutral (7.6) and by considering a wide range of initial (SO42−)/(CO32−) ratios (0 to approx. 68) in the aqueous solution. We paid special attention to the evolution of the precipitates during ageing within a time framework of 14 days. The mineralogy, morphology, and composition of the precipitates were studied by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy, and EDX microanalysis. The concentration of sulphate ions in the reacted aqueous solution was studied by ICPs. The experimental results showed that the mineral composition of the precipitate recovered in each run varied with the (SO42−)/(CO32−) ratio in the parental solution, which influenced the mineral evolution of the precipitates during ageing. We observed that high concentrations of sulphate in the aqueous solution stabilized the vaterite precipitates and inhibited calcite formation. Furthermore, aragonite never precipitated directly from the solution, and it was only formed via a dissolution-precipitation process in solutions with a high (SO42−)/(CO32−) ratio after long reaction times. Finally, gypsum only precipitated after long ageing in those aqueous solutions with the highest concentration of sulphate. The reaction pathways during ageing, the morphology of the calcite crystals, and the composition of vaterite and calcite were discussed considering both kinetic and thermodynamic factors. These results showed a considerably more complex behavior of the system than that observed in experiments conducted under higher pHs and supersaturation levels and lower (SO42−)/(CO32−) ratios in the aqueous phase.

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Geng, Xinglian, e Wesley A. Henderson. "Impact of non-solvents on the structural features and enzymatic digestibility of cellulose regenerated from an ionic liquid". RSC Adv. 4, n. 59 (2014): 31226–29. http://dx.doi.org/10.1039/c4ra05019c.

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26

Kamp, Nicolas, A. Sullivan, R. Tomasi e Joseph D. Robson. "Modelling Heterogeneous Precipitation in 7xxx Aluminium Alloys during Complex Processing". Materials Science Forum 519-521 (luglio 2006): 1435–40. http://dx.doi.org/10.4028/www.scientific.net/msf.519-521.1435.

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Abstract (sommario):

A numerical model based on the Kampmann and Wagner method was developed to predict the evolution of precipitate distribution in 7xxx aluminium alloy during non-isothermal heat treatments. The model considers the nucleation, growth and coarsening/dissolution of the metastable and equilibrium precipitate phases, η' and η with their stochiometric composition, MgZn2. Constitutive model equations for nucleation were based on the classical theory of nucleation whilst growth and coarsening were treated using classical phase transformation theory. The transition between η' and η, where η' acts as a precursor for η was also accounted for in the model. Differential scanning calorimetry was used to calibrate the homogeneous precipitation kinetics. The model also predicts the evolution of grain boundary precipitates and their effect on precipitate free zone size. Jominy end quench tests were performed to calibrate grain boundary precipitation kinetics. Precipitation on dislocations and dispersoids was considered. The dislocation and dispersoid densities were varied to represent different regions of a grain and therefore account for the spatial distribution of preferential heterogeneous precipitation sites. Comparison between the model prediction and experimental characterisation of the microstructure evolution of a friction stir welded 7449 aluminium alloy was found to be reasonably consistent.

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27

Alfirano. "Effect of Alloying Elements on Microstructure of Biomedical Co-Cr-Mo F75 Alloy". Advanced Materials Research 1112 (luglio 2015): 421–24. http://dx.doi.org/10.4028/www.scientific.net/amr.1112.421.

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Precipitates in biomedical Co-Cr-Mo cast alloys are closely related to their wear and mechanical properties. It is important to elucidate the effects of addition of alloying elements listed in ASTM F75 on precipitation and dissolution in order to control microstructural changes in fabricating biomedical Co-Cr-Mo alloy implants. In this study, Si and Mn were selected as the alloying elements. The chemical compositions of two cast alloys were Co-28Cr-6Mo-0.25C with containing 1mass% Si dan Mn. The alloys were solution treated at temperatures at 1448 to 1548 K for holding time of 1.8-43.2 ks, followed by water quenching. The precipitates in the as-cast alloy with Si addition were M23C6 carbide, h-phase (M6C-M12C type carbide) and p-phase (M2T3X type carbide with a b-Mn structure), while M23C6 carbide and h-phase were detected in the as-cast alloy with Mn addition. The alloy with Si addition required longer solution treatment time for complete precipitate dissolution as compared with the alloy with Mn addition. The phase and morphology of precipitates observed during solution treatment depended on the heat treatment temperature and holding time and alloy composition.

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28

Olsson, J., S. L. S. Stipp e S. R. Gislason. "Element scavenging by recently formed travertine deposits in the alkaline springs from the Oman Semail Ophiolite". Mineralogical Magazine 78, n. 6 (novembre 2014): 1479–90. http://dx.doi.org/10.1180/minmag.2014.078.6.15.

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Ultramafic rocks, such as the Semail Ophiolite in the Sultanate of Oman, are considered to be a potential storage site for CO2. This type of rock is rich in divalent cations that can react with dissolved CO2 and form carbonate minerals, which remain stable over geological periods of time. Dissolution of the ophiolite mobilizes heavy metals, which can threaten the safety of surface and groundwater supplies but secondary phases, such as iron oxides, clays and carbonate minerals, can take up significant quantities of trace elements both in their structure and adsorbed on their surfaces.Hyperalkaline spring waters issuing from the Semail Ophiolites can have pH as high as 12. This water absorbs CO2 from air, forming carbonate mineral precipitates either as thin crusts on the surface of placid water pools or bottom precipitates in turbulent waters. We investigated the composition of the spring water and the precipitates to determine the extent of trace element uptake. We collected water and travertine samples from two alkaline springs of the Semail Ophiolite. Twenty seven elements were detected in the spring waters. The bulk of the precipitate was CaCO3 in aragonite, as needles, and rhombohedral calcite crystals. Traces of dypingite (Mg5(CO3)4(OH)2·5H2O) and antigorite ((Mg,Fe)3Si2O5(OH)4) were also detected. The bulk precipitate contained rare earth elements and toxic metals, such as As, Ba, Cd, Sr and Pb, which indicated scavenging by the carbonate minerals. Boron and mercury were detected in the spring water but not in the carbonate phases. The results provide confidence that many of the toxic metals released by ophiolite dissolution in an engineered CO2 injection project would be taken up by secondary phases, minimizing risk to water quality.

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29

Lopez, R., B. Ducoeur, M. Chiumenti, B. de Meester e C. Agelet de Saracibar. "Modeling Precipitate Dissolution in Hardened Aluminium Alloys using Neural Networks". International Journal of Material Forming 1, S1 (aprile 2008): 1291–94. http://dx.doi.org/10.1007/s12289-008-0139-4.

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30

Shahriari, D., M. H. Sadeghi e A. Akbarzadeh. "γ' Precipitate Dissolution during Heat Treatment of Nimonic 115 Superalloy". Materials and Manufacturing Processes 24, n. 5 (maggio 2009): 559–63. http://dx.doi.org/10.1080/10426910902746820.

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31

Semiatin, S. L., N. C. Levkulich, A. E. Saurber, D. W. Mahaffey, E. J. Payton e O. N. Senkov. "The Kinetics of Precipitate Dissolution in a Nickel-Base Superalloy". Metallurgical and Materials Transactions A 48, n. 11 (25 settembre 2017): 5567–78. http://dx.doi.org/10.1007/s11661-017-4322-4.

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32

Posthill, J. B., Darrel Frear e J. W. Morris. "In situ HREM observation of interphase boundary motion in 95Pb-5Sn solder". Proceedings, annual meeting, Electron Microscopy Society of America 44 (agosto 1986): 410–11. http://dx.doi.org/10.1017/s042482010014364x.

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Abstract (sommario):

The use of solder to provide mechanical attachment and electrical interconnection for electronic packaging is widespread throughout the industry. One application for a lead-rich solder is in the IC chip/ceramic carrier connection. It is well-established that this joint is susceptible to thermal-fatigue failure and, hence, a thorough microstructural study is warranted. Previous work has shown that 95Pb-5Sn contains β-Sn precipitates that have formed upon solidification and subsequent aging at ambient temperature. Diffraction contrast TEM demonstrated that the precipitates lie on {111}pb habit planes. High-resolution electron microscopy was undertaken to establish whether or not the habit plane was faceted on the atomic level. This contribution reports on an observation of beam-induced precipitate dissolution.

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33

Lee, Won Bae, Hyung Sun Jang, Yun Mo Yeon e Seung Boo Jung. "Effect of PWHT on Behaviors of Precipitates and Hardness Distribution of 6061 Al Alloy Joints by Friction Stir Welding Method". Materials Science Forum 449-452 (marzo 2004): 601–4. http://dx.doi.org/10.4028/www.scientific.net/msf.449-452.601.

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Abstract (sommario):

The hardness distribution related to the precipitates behaviors as friction stir welded and PWHT (post weld heat treated) 6061 Al alloy have been investigated. Frictional heat and plastic flow during friction stir welding created a fine, eqiuaxed and elongated microstructure near the weld zone due to dynamic recovery and recrystallization. A softened region which had been formed near the weld zone couldn't be avoidable due to the dissolution and coarsening of the strengthening precipitates. PWHT (SHT+ Aging) homogeneously recovered the hardness distribution over that of the base metal without softening region, resulted from non-homogeneously distributed hardness only aging treated. 36ks aging followed by SHT gave a higher hardness overall weld than that of the base metal due to a higher density of the spherical shaped precipitate.;

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34

Wen Chen, Roa, e Kenneth S. Vecchio. "δ’ (Al3Li) dissolution as a thermal probe in shear-banding studies". Proceedings, annual meeting, Electron Microscopy Society of America 51 (1 agosto 1993): 1178–79. http://dx.doi.org/10.1017/s0424820100151726.

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Abstract (sommario):

The Al-Li alloy system can provide a unique opportunity to study the thermal history of shear-band formation by following the thermal dissolution of the precipitate phase δ’ (Al3Li) as a function of Li concentration and δ’ solvus temperature. The Al-Li system was chosen primarily for the rather rapid precipitation and dissolution kinetics resulting from the high diffusivity of Li in the Al lattice. δ’ is a spherical, coherent and metastable precipitate which is the main strengthening phase in dilute Al-Li alloys. Although δ’ is metastable, the location of the δ’ solvus in the Al-Li phase diagram has been well documented for dilute Li additions (<5 wt.% Li).e.g.1 The metastable δ’ solvus increases in temperature with increasing Li concentration. As such, the dissolution of δ’ within the shear bands, as a function of Li alloy concentration, can provide an internal temperature probe to study the thermal history of the shear band.

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35

Kursunoglu, Sait. "Synergistic effect of organic acid on the dissolution of mixed nickel-cobalt hydroxide precipitate in sulphuric acid solution". Metallurgical Research & Technology 116, n. 3 (2019): 319. http://dx.doi.org/10.1051/metal/2018107.

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Abstract (sommario):

The synergistic effect of an organic acid on the dissolution of nickel and cobalt from a mixed nickel-cobalt hydroxide precipitate (MHP) in sulphuric acid solution was studied. The effects of sulphuric acid concentration, the type of organic acid, leaching time, leaching temperature and stirring speed on the dissolution of the metals were experimentally investigated. It was observed that there is no beneficial effect of leaching temperature and stirring speed on the dissolution of the metals from the used MHP product which contains 37.7% Ni, 2.1% Co and 5.6% Mn. It was found that citric acid was more effective than oxalic acid for the dissolution of nickel and manganese, whereas oxalic acid was more effective than citric acid for the dissolution of cobalt. The addition of oxalic acid into the leaching system, however, affected the dissolution of nickel negatively because nickel precipitate as nickel oxalate. Therefore, the use of citric acid as synergist for sulphuric acid leaching of MHP product is more promising. After 60 min of leaching, 90.9% Ni, 84.2% Co and 98.1% Mn were dissolved under the following conditions: 0.75 M sulphuric acid, 2 g citric acid, 1/10 solid-to-liquid ratio, 400 rpm stirring speed and 30 °C temperature. The experimental results demonstrate that the addition of citric acid as a synergist for sulphuric acid leaching of a MHP product provides beneficial effect for the dissolution of nickel, cobalt and manganese.

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36

Tian, Qing Chao, Xiao Ming Dong e Qing An Zhang. "Electrochemical Behavior of Cu-Bearing CrMo Steel in H₂S Saturated Aqueous Brine Solution". Key Engineering Materials 385-387 (luglio 2008): 121–24. http://dx.doi.org/10.4028/www.scientific.net/kem.385-387.121.

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Electrochemical measurement techniques were applied to investigate the polarization and hydrogen permeation behavior of Cu-bearing CrMo steel in a H2S saturated aqueous brine solution. The observation on microstructure and precipitate phases of the steel was conducted by transmission electron microscopy (TEM), and the corrosion product was investigated by using X-ray diffractometer (XRD), X-ray photoelectron spectroscopy (XPS), and scanning electron microscopy (SEM). It is disclosed that copper addition could effectively influence the electrochemical behavior of the investigated steel, and the dissolution behavior of iron matrix and carbide precipitates in the H2S solution acts as a key role for the steel resistance to hydrogen sulfide corrosion.

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37

Gorbachev, I. I., Vladimir V. Popov e A. Yu Pasynkov. "Simulation of Precipitates Evolution in Steels with V and Nb at Annealing". Diffusion Foundations 3 (febbraio 2015): 167–80. http://dx.doi.org/10.4028/www.scientific.net/df.3.167.

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Based on the mean field approximation, a model has been worked out for the description of evolution of carbonitride precipitate ensemble with various composition in steels at the stages of their growth, dissolution and coarsening. Based on the numerical realization of this model, the calculations of growth and dissolution kinetics of carbonitrides in a Fe-Nb-V-C-N system have been carried out.

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38

Kundu, Amrita, Claire L. Davis e Martin Strangwood. "Pinning of Austenite Grain Boundaries by Mixed AlN and Nb(C,N) Precipitates". Solid State Phenomena 172-174 (giugno 2011): 458–63. http://dx.doi.org/10.4028/www.scientific.net/ssp.172-174.458.

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The use of Nb(C,N) to pin prior austenite grains during thermomechanical processing can give rise to bimodal structures linked to Nb segregation and subsequent variation in precipitate distribution and stability on reheating and deformation. The segregation tendency of Al is much less compared with Nb so that AlN may provide grain boundary pinning in regions of reduced Nb(C,N) volume fraction and stability. Quantification of precipitate and prior austenite grain size distributions after reheating has confirmed the governing mechanisms of precipitate dissolution / coarsening whilst identifying grain boundary pinning by AlN at temperature below 1125 °C, but controlled by Nb(C,N) at higher temperatures.

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39

Zheng, Kailun, Yong Li, Song Yang, Kunning Fu, Jinghua Zheng, Zhubin He e Shijian Yuan. "Investigation and Modeling of the Preheating Effects on Precipitation and Hot Flow Behavior for Forming High Strength AA7075 at Elevated Temperatures". Journal of Manufacturing and Materials Processing 4, n. 3 (23 luglio 2020): 76. http://dx.doi.org/10.3390/jmmp4030076.

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Abstract (sommario):

Preheating is the first but critical step for hot stamping high strength precipitate hardened aluminum alloys. To thoroughly understand the effects of preheating conditions—i.e., preheating rate and heating temperature—on the strength and hot deformation of aluminum alloys, a series of thermal–mechanical tests was performed to determine the post-hardness evolution and hot flow behaviors. Typical microstructures with different preheating conditions were also observed through transmission electron microscopy (TEM), with which a unified model of both hot flow and strength based on key microstructural variables was developed, enabling the successful prediction of macroscopic properties using different preheating strategies. The results have shown that for high strength AA7075 at the T6 condition, the dominant mechanism of precipitate evolution with increasing temperature is the coarsening of precipitates first, followed by dissolution when they exceed a critical temperature. A higher heating rate results in a slower coarsening and a relatively higher strength level. In addition, the flow stress of hot deformation is also higher using a quick heating rate, with more significant softening and reduced ductility.

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40

Looney, E. E., H. S. Laine, A. Youssef, M. A. Jensen, V. LaSalvia, P. Stradins e T. Buonassisi. "Oxygen migration enthalpy likely limits oxide precipitate dissolution during tabula rasa". Applied Physics Letters 111, n. 13 (25 settembre 2017): 132102. http://dx.doi.org/10.1063/1.4987144.

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41

Kamal Babu, Karupannan, Kavan Panneerselvam, Paulraj Sathiya, Abdul Haq Noorul Haq, Srinivasan Sundarrajan, Potta Mastanaiah e Chunduri Venkata Srinivasa Murthy. "Effects of various tool pin profiles on mechanical and metallurgical properties of friction stir welded joints of cryorolled AA2219 aluminium alloy". Metallurgical Research & Technology 115, n. 2 (2018): 212. http://dx.doi.org/10.1051/metal/2017100.

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Abstract (sommario):

Friction stir welding (FSW) process was conducted on cryorolled (CR) AA2219 plate using different tool pin profiles such as cylindrical pin, threaded cylindrical pin, square pin and hexagonal pin profiles. The FSW was carried out with pairs of 6 mm thick CR aluminium plates with different tool pin profiles. The different tool pin profile weld portions' behaviors like mechanical (tensile strength, impact and hardness) and metallurgical characteristics were analyzed. The results of the mechanical analysis revealed that the joint made by the hexagonal pin tool had good strength compared to other pin profiles. This was due to the pulsating action and material flow of the tool resulting in dynamic recrystallization in the weld zone. This was confirmed by the ultra fine grain structure formation in Weld Nugget (WN) of hexagonal pin tool joint with a higher percentage of precipitate dissolution. The fractograph of the hexagonal tool pin weld portion confirmed the finer dimple structure morphology without having any interior defect compared to other tool pin profiles. The lowest weld joint strength was obtained from cylindrical pin profile weld joint due to insufficient material flow during welding. The Transmission Electron Microscope and EDX analysis showed the dissolution of the metastable θ″, θ′ (Al2Cu) partial precipitates in the WN and proved the influence of metastable precipitates on enhancement of mechanical behavior of weld. The XRD results also confirmed the Al2Cu precipitation dissolution in the weld zone.

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42

Lv, Ningning, Chang Su, Hui Kong, Jinxing Yang, Weiming Liu e Haichuan Wang. "Dissolution mechanism of various elements from steelmaking slag into citric acid solution". Metallurgical Research & Technology 116, n. 3 (2019): 321. http://dx.doi.org/10.1051/metal/2018125.

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Abstract (sommario):

To recycle valuable elements from steelmaking slag, their dissolution mechanism into citric acid solution has been investigated. First, the relationship between dissolution ratio of each element and initial concentration of citric acid (ci) was studied. Then, the concentrations of each species in solution were calculated through mass balance. Based on these results, it can been seen that whenci = 0.00104 mol/L, Ca2+, CaCit−, MgCit−, FeH2PO42+and CaHPO4are the predominant species in solution, and Ca5(PO4)3(OH)(s) precipitate can form easily, which may suppress the dissolution of elements. Whenciincreases to 0.0104 mol/L, dissolution ratio of each element increases significantly, except for iron. And the predominant species correspondingly change to Ca2+, Mg2+, CaCit−, MgCit−, H2Cit−, H3Cit and FeH2PO42+.

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43

Ye, Tie, Cheng Zhou e Zhen Yu Gao. "Evolution of Microstructure, Precipitate and Magnetic Properties with the Different Annealing Temperature in High Grade Nonoriented Electrical Steels". Applied Mechanics and Materials 416-417 (settembre 2013): 1645–51. http://dx.doi.org/10.4028/www.scientific.net/amm.416-417.1645.

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The evolution of microstructure, precipitate and magnetic properties in nonoriented electrical steels with different annealing temperature was studied. The iron loss of steel decreases with an increase in the final annealing temperature ranging from 800~900°C. This phenomenon is associated with grains recovery; recrystallization and grains grow up with the temperature increasing. Grain size continues to increase, but the average particle size decreases and particle density increases at 880~900°C which show precipitates have dissolved. It approved that the dissolution process of a lot of precipitates occurred after grains growing up. Precipitates are mainly of the second phase particles MnS and AlN. The magnetic induction increased firstly at 800~880°C and then increasing at 880~900°C.It can be found that the proportion of the texture for [{100} +Gos/ {111} at 900°C is higher than that at 880°C and the proportion of Gauss texture is higher at 900°C than that at 880°C. Gauss texture in high grade silicon steel plays an important role which promotes magnetic induction to increase.

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44

Wolke, Joop G. C., E. Vandenbulcke, B. van Oirschot e John A. Jansen. "A Study to the Surface Characteristics of RF Magnetron Sputtered Bioglass - and Calcium Phosphate Coatings". Key Engineering Materials 284-286 (aprile 2005): 187–90. http://dx.doi.org/10.4028/www.scientific.net/kem.284-286.187.

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The RF magnetron sputter technique was used to deposit Bioglass (BG) and hydroxyapatite (HA) coatings onto titanium substrates. In the current study, the physico-chemical and dissolution properties of various deposited coatings were investigated. X-ray diffraction demonstrated that the as-sputtered coatings had an amorphous structure, a heattreatment for 2 hours at 600°C changed only the HA coating into a crystalline apatite structure. Dissolution experiments demonstrated that all the amorphous coatings dissolved during the incubation for 4 weeks in simulated body fluid, while all the heattreated sputter coatings were still maintained. In contrast with the HA heattreated sputter coatings all the bioglass containing sputter coatings showed the formation of a crystalline apatite phase. Scanning electron microscopical examination of the sputtered coatings demonstrated that on all the heattreated BG/HG sputter coating a thick CaP precipitate was formed, while on the BG sputter coating occasionally a globular precipitate was observed.

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45

Jakobsen, F., H. Lindgreen e N. Springer. "Precipitation and flocculation of spherical nano-silica in North Sea chalk". Clay Minerals 35, n. 1 (marzo 2000): 175–84. http://dx.doi.org/10.1180/000985500546567.

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AbstractIn the Maastrichtian-Danian chalk in the North Sea, discrete intervals, appearing as normal white chalk, contain up to 60% α-quartz <2 μm in size. Atomic force microscopy (AFM) reveals that the particles are of nm size, appearing as spherical particles and aggregates. Similar particles consisting of opal-CT were found in surface exposures of chalk in Denmark. Two new abiogenic pathways of silica formation in chalk are proposed. The first model proposes that SiO2 nano-size particles and aggregates precipitated and flocculated in the free-water phase as opal and were diagenetically transformed from opal-CT at low temperature to α-quartz at elevated temperature. In the second model, the dominance of radiolarians in the deep-water environment of the North Sea resulted in low dissolution supply with subsequent precipitation and flocculation of nano-size α-quartz particles. In the shallower water of the shelf environment of the present onshore chalk, the abundance of sponges and their dissolution supplied enough Si to precipitate opal-CT in the free-water phase.

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46

Xiao, Na Min, Ai Xue Sha e Xing Wu Li. "A Mesoscopic Modelling Framework of Microstructure Evolution and its Application on Thermo-Mechanical Processes". Materials Science Forum 1035 (22 giugno 2021): 792–800. http://dx.doi.org/10.4028/www.scientific.net/msf.1035.792.

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In present study a quantitative modelling framework based on phase-field method is developed to simulate the microstructure evolution during thermomechanical process, e. g. grain growth, recrystallization, solid phase transformations and their interactions. Two application cases of microstructure evolution are introduced. The first one is the dynamic recrystallization behavior during the hot deformation of stainless steel. The effect of thermo-mechanical parameters including strain, strain rate, and temperature on DRX have been investigated quantitatively. Moreover, the present simulation provided an explanation of the dependence of final recrystallized grain size on initial grain size when it is decreased to a critically small value. This modelling framework is also used to simulate the interaction between the dissolution of precipitates and grain coarsening of matrix in the nickel alloys. The simulation results show that the decreasing dissolution temperature of precipitate slow down the matrix coarsening kinetics obviously. This provides an quantitative tool to predict and control the local microstructure of nickel alloy disk. In summary, the mesoscopic modelling can be used to investigate more kinetic details of microstructure evolution and engineering optimization for thermo-mechanical process.

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47

Lundin, C. D., e C. Y. P. Qiao. "Microstructural Investigation of the Weld HAZ in a Modified 800H Alloy". Journal of Engineering for Gas Turbines and Power 116, n. 3 (1 luglio 1994): 629–34. http://dx.doi.org/10.1115/1.2906866.

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Abstract (sommario):

Detailed metallographic investigations of Gleeble simulated HAZ samples in modified 800H were performed. Precipitate dissolution, gain growth, HAZ liquation and the hardness degradation behavior in modified 800H were also addressed. Results of this study agree with previous HAZ hot cracking and softening behavior evaluations.

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48

González-Pociño, Alejandro, Florentino Alvarez-Antolin, Juan Asensio-Lozano e Hugo Alvarez-Perez. "Influence of Thermal Processing Factors, Linked to the Destabilisation of Austenite, on the Microstructural Variation of a White Cast Iron Containing 25% Cr and 0.6% Mo". Metals 10, n. 6 (23 giugno 2020): 832. http://dx.doi.org/10.3390/met10060832.

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Hypoeutectic white cast irons containing 25% Cr are used in ore-processing industries due to their high resistance to erosive wear. Applying a Design of Experiments (DoE), the aim of this study is to analyse the influence of thermal processing factors on the microstructural variation of a white cast iron containing 25% Cr and 0.6% Mo. The carbides present in the as-cast state are of the M7C3, M2C, and M3C types. M2C carbides precipitate on the eutectic M7C3 carbides favoured by heterogeneous nucleation conditions. Two kinetics compete during the destabilisation of austenite. One dissolves those eutectic carbides precipitated as a result of non-equilibrium solidification (M7C3 and M2C), while the other enables the precipitation of secondary M7C3 and M23C6 carbides. The M7C3 carbides begin to precipitate first. Low destabilisation temperatures and short dwell times are insufficient to dissolve the precipitated eutectic carbides from non-equilibrium conditions, thus favouring the presence of M2C carbides, which are associated with Mo. The factor that has the greatest influence on hardness is the tempering temperature. The optimal tempering temperature is found to be 500 °C. Short tempering times maintain the distortion of the ferrite unit cell. The precipitation of Cr carbides during tempering requires a temperature of 500 °C and the prior dissolution of the carbon precipitated during the initial stages of said tempering. With short tempering times, the Cr atoms still remain dissolved in the ferrite, distorting its unit cell and increasing the hardness of the matrix constituent of the alloy.

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49

Carter, P., B. Gleeson e D. J. Young. "Calculation of precipitate dissolution zone kinetics in oxidising binary two-phase alloys". Acta Materialia 44, n. 10 (ottobre 1996): 4033–38. http://dx.doi.org/10.1016/s1359-6454(96)00054-7.

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50

Camus, Eric, Christian Abromeit, Françoise Bourdeau, Nelja Wanderka e Heinrich Wollenberger. "Evolution of long-range order and composition for radiation-induced precipitate dissolution". Physical Review B 54, n. 5 (1 agosto 1996): 3142–50. http://dx.doi.org/10.1103/physrevb.54.3142.

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