Articles de revues : « Synthesis of precursor »

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Gianvittorio, Stefano, Domenica Tonelli et Andreas Lesch. « Print-Light-Synthesis for Single-Step Metal Nanoparticle Synthesis and Patterned Electrode Production ». Nanomaterials 13, n^o 13 (23 juin 2023) : 1915. http://dx.doi.org/10.3390/nano13131915.

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The fabrication of thin-film electrodes, which contain metal nanoparticles and nanostructures for applications in electrochemical sensing as well as energy conversion and storage, is often based on multi-step procedures that include two main passages: (i) the synthesis and purification of nanomaterials and (ii) the fabrication of thin films by coating electrode supports with these nanomaterials. The patterning and miniaturization of thin film electrodes generally require masks or advanced patterning instrumentation. In recent years, various approaches have been presented to integrate the spatially resolved deposition of metal precursor solutions and the rapid conversion of the precursors into metal nanoparticles. To achieve the latter, high intensity light irradiation has, in particular, become suitable as it enables the photochemical, photocatalytical, and photothermal conversion of the precursors during or slightly after the precursor deposition. The conversion of the metal precursors directly on the target substrates can make the use of capping and stabilizing agents obsolete. This review focuses on hybrid platforms that comprise digital metal precursor ink printing and high intensity light irradiation for inducing metal precursor conversions into patterned metal and alloy nanoparticles. The combination of the two methods has recently been named Print-Light-Synthesis by a group of collaborators and is characterized by its sustainability in terms of low material consumption, low material waste, and reduced synthesis steps. It provides high control of precursor loading and light irradiation, both affecting and improving the fabrication of thin film electrodes.

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Chauhan, Preeti, Dr Priyanka Mathur et Dr Anil Kumar Sharma. « Study on Sustainable Resource Utilization as Ligand Precursors in Coordination Chemistry ». International Journal for Research in Applied Science and Engineering Technology 12, n^o 5 (31 mai 2024) : 757–62. http://dx.doi.org/10.22214/ijraset.2024.60427.

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Ligand Precursors in Coordination Chemistry.” Sustainable resource utilization in ligand precursor synthesis is crucial for advancing green chemistry principles and addressing environmental concerns in coordination chemistry. This study investigates the feasibility and efficacy of utilizing renewable resources as precursor materials for ligand synthesis, aiming to reduce environmental impact while maintaining the efficacy and versatility required in coordination chemistry applications. Through a combination of synthetic organic chemistry and coordination chemistry techniques, novel ligand precursors derived from sustainable sources were synthesized and characterized. Various renewable feedstocks, including biomass-derived compounds and waste materials, were explored as potential starting materials for ligand precursor synthesis. Optimization of synthetic routes and reaction conditions led to the development of efficient protocols for the synthesis of sustainable ligand precursors. Characterization techniques such as nuclear magnetic resonance spectroscopy, mass spectrometry, and infrared spectroscopy were employed to confirm the structures and purities of synthesized ligand precursors. Evaluation of the performance of sustainable ligand precursors in coordination chemistry reactions demonstrated their ability to form stable complexes with metal ions and exhibit catalytic activity in relevant reactions. Comparative studies with traditional ligands revealed the environmental advantages of sustainable ligand precursors, including reduced energy consumption, greenhouse gas emissions, and solvent usage. Overall, this study highlights the importance of sustainable resource utilization in ligand precursor synthesis for promoting environmentally friendly practices in coordination chemistry and advancing the principles of green chemistry.

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Jalalian-Khakshour, A., C. O. Phillips, L. Jackson, T. O. Dunlop, S. Margadonna et D. Deganello. « Solid-state synthesis of NASICON (Na3Zr2Si2PO12) using nanoparticle precursors for optimisation of ionic conductivity ». Journal of Materials Science 55, n^o 6 (11 novembre 2019) : 2291–302. http://dx.doi.org/10.1007/s10853-019-04162-8.

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Abstract In this work, the effect of varying the size of the precursor raw materials SiO2 and ZrO2 in the solid-state synthesis of NASICON in the form Na3Zr2Si2PO12 was studied. Nanoscale and macro-scale precursor materials were selected for comparison purposes, and a range of sintering times were examined (10, 24 and 40 h) at a temperature of 1230 °C. Na3Zr2Si2PO12 pellets produced from nanopowder precursors were found to produce substantially higher ionic conductivities, with improved morphology and higher density than those produced from larger micron-scaled precursors. The nanoparticle precursors were shown to give a maximum ionic conductivity of 1.16 × 10−3 S cm−1 when sintered at 1230 °C for 40 h, in the higher range of published solid-state Na3Zr2Si2PO12 conductivities. The macro-precursors gave lower ionic conductivity of 0.62 × 10−3 S cm−1 under the same processing conditions. Most current authors do not quote or consider the precursor particle size for solid-state synthesis of Na3Zr2Si2PO12. This study shows the importance of precursor powder particle size in the microstructure and performance of Na3Zr2Si2PO12 during solid-state synthesis and offers a route to improved predictability and consistency of the manufacturing process.

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Tetrick, Mark A., et Jack Odle. « What Constitutes a Gluconeogenic Precursor ? » Journal of Nutrition 150, n^o 9 (11 juillet 2020) : 2239–41. http://dx.doi.org/10.1093/jn/nxaa166.

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ABSTRACT A gluconeogenic precursor is a biochemical compound acted on by a gluconeogenic pathway enabling the net synthesis of glucose. Recognized gluconeogenic precursors in fasting placental mammals include glycerol, lactate/pyruvate, certain amino acids, and odd-chain length fatty acids. Each of these precursors is capable of contributing net amounts of carbon to glucose synthesis via the tricarboxylic acid cycle (TCA cycle) because they are anaplerotic, that is, they are able to increase the pools of TCA cycle intermediates by the contribution of more carbon than is lost via carbon dioxide. The net synthesis of glucose from even-chain length fatty acids (ECFAs) in fasting placental mammals, via the TCA cycle alone, is not possible because equal amounts of carbon are lost via carbon dioxide as is contributed from fatty acid oxidation via acetyl-CoA. Therefore, ECFAs do not meet the criteria to be recognized as a gluconeogenic precursor via the TCA cycle alone. ECFAs are gluconeogenic precursors in organisms with a functioning glyoxylate cycle, which enables the net contribution of carbon to the intermediates of the TCA cycle from ECFAs and the net synthesis of glucose. The net conversion of ECFAs to glucose in fasting placental mammals via C3 metabolism of acetone may be a competent though inefficient metabolic path by which ECFA could be considered a gluconeogenic precursor. Defining a substrate as a gluconeogenic precursor requires careful articulation of the definition, organism, and physiologic conditions under consideration.

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Cai, Binxiang, Huazhang Liu et Wenfeng Han. « Solution Combustion Synthesis of Fe2O3-Based Catalyst for Ammonia Synthesis ». Catalysts 10, n^o 9 (7 septembre 2020) : 1027. http://dx.doi.org/10.3390/catal10091027.

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Fe2O3-based catalysts were prepared by solution combustion synthesis (SCS) with metal nitrates (Fe, K, Al, Ca) as the precursors and glycine as the fuel. The activities of catalysts were evaluated in terms of ammonia synthesis reaction rate in a fixed bed reactor similar to the industrial reactors. The results indicate that the precursor of catalyst prepared by SCS is Fe2O3 which facilitates the high dispersion of promoters to provide high activity. The catalysts exhibit higher activity for ammonia synthesis than that of traditional catalysts, and the reaction rate reaches 138.5 mmol g−1 h−1. Fe2O3 prepared by SCS could be favorable precursor for ammonia synthesis catalyst. The present study provides a pathway to prepare catalyst for ammonia synthesis.

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Novembre, Daniela, Domingo Gimeno et Brent Poe. « Diatomite as natural precursor for the synthesis of KAlSiO4-O1 ». European Journal of Mineralogy 30, n^o 6 (20 décembre 2018) : 1127–32. http://dx.doi.org/10.1127/ejm/2018/0030-2782.

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Şahin Ün, Şule, Ramazan Altundaş et Ahmet C. Gören. « Synthesis of ɣ-glutamyl β-cyanoalanine precursor ». Organic Communications 13, n^o 4 (26 décembre 2020) : 202–6. http://dx.doi.org/10.25135/acg.oc.89.20.05.1660.

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The synthesis of precursors of neurotoxic ɣ-glutamyl β-cyanoalanine was developed starting from L-Serine via through the preparation of b-cyanoalanine and glutamyl units. Coupling of these two intermediates gave methyl ester of ɣ-glutamyl β-cyanoalanine precursor.

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Gants, Oksana Y., Angelina D. Yudina, Valentina O. Zhirnova, Anna S. Timonina, Yulia I. Lyukshina et Anna A. Akhmatova. « SYNTHESIS OF RUTHENIUM (IV) OXIDE ON TANTALUM BY ATOMIC LAYER DEPOSITION ». IZVESTIYA VYSSHIKH UCHEBNYKH ZAVEDENII KHIMIYA KHIMICHESKAYA TEKHNOLOGIYA 63, n^o 7 (21 mai 2020) : 26–30. http://dx.doi.org/10.6060/ivkkt.20206307.6190.

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The results of synthesis of nanoscale films of ruthenium dioxide on tantalum are presented. The films were obtained by atomic layer deposition at the TFS 200 Beneq setup (production Finland). As precursors bis(ateltico-pentadienyl) ruthenium and oxygen were used. Nitrogen acted as an inert gas to purge the reaction chamber of precursor residues and reaction products. The synthesis was carried out in two stages: activation of the tantalum surface by hydroxyl groups and alternate supply of ruthenium and oxygen precursors to the reaction chamber under certain conditions. The main regularities of the process were revealed and the method of synthesis realization was proposed. It is shown that the synthesis result is influenced by the process parameters of the atomic layer deposition method. The main parameters affecting the process are the temperature in the reaction chamber and the precursor requiring heating, the time of the precursor intake and the time of nitrogen purging. Also, in the process of synthesis, such a parameter as "pause" is used-the temporary cessation of the supply of any reagents to the reaction chamber to increase the ratio of reacting molecules. The influence of each process parameter on the synthesis of thin films of ruthenium dioxide is substantiated and experimentally confirmed. It was concluded that the optimal deposition temperature of ruthenium dioxide is 220 °C. The optimum temperature of the heated precursor is 80 °C. The optimal time of the ruthenium precursor is 1 s, the time of the oxidizing agent is 10 s under the stated conditions. The optimal "pause" time is 3 s after the intake of bis (ethylcyclopentadienyl) ruthenium, and 5 s after the intake of oxygen. The presented method of synthesis of ruthenium dioxide will allow to obtain high-quality, uniform throughout the thickness of nanoscale films that can be used as an electrode in capacitors.

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Cademartiri, Ludovico, et Geoffrey A. Ozin. « Emerging strategies for the synthesis of highly monodisperse colloidal nanostructures ». Philosophical Transactions of the Royal Society A : Mathematical, Physical and Engineering Sciences 368, n^o 1927 (28 septembre 2010) : 4229–48. http://dx.doi.org/10.1098/rsta.2010.0126.

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This short perspective describes recent developments in the synthesis of nanoscale colloids from sparingly soluble precursors. These strategies, which we dubbed ‘heterogeneous nanocrystal syntheses’ owing to the presence of a precursor in a non-colloidal solid state, have demonstrated the ability to generate new colloidal shapes, a superior monodispersity and a remarkable ability to delay the onset of Ostwald ripening, when compared with more traditional and purely colloidal strategies. We review the key contributions to this emerging area of research and discuss in detail the remarkable number of differences between these syntheses and the widely used homogeneous organometallic syntheses for making nanoscale colloids.

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Huang, Jian-Zhi, I.-Chih Ni, Yun-Hsuan Hsu, Shu-Wei Li, Yu-Chen Chan, Shin-Yi Yang, Ming-Han Lee, Shau-Lin Shue, Mei-Hsin Chen et Chih-I. Wu. « Low-temperature synthesis of high-quality graphene by controlling the carbon-hydrogen ratio of the precursor ». Nano Express 3, n^o 1 (1 mars 2022) : 015003. http://dx.doi.org/10.1088/2632-959x/ac3388.

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Abstract A furnace-free inductively coupled plasma chemical vapor deposition (ICP-PECVD) system, which does not require sample heating, was used to grow graphene at a temperature below 300 °C. This studies have found that under low-temperature PECVD growth conditions, liquid precursors are more suitable for preparing low-temperature graphene precursors than gaseous precursors. Hence, benzene is used as a carbon precursor to obtain a sheet resistance of approximately 1.24 kΩ sq−1. In this research, it was discovered that the carbon-hydrogen ratio of the precursor molecule is an important factor while using PECVD to grow graphene. This factor affects the quality of graphene and the sheet resistance value —when the carbon–hydrogen ratio for the precursor molecule is 1:1, graphene has the high quality and lowest sheet resistance; when it is less than 1:2, the graphene that cannot be deposited has the worst quality and sheet resistance. Furthermore, we found that methane, a precursor often used to deposit graphene, will etch graphene under low-temperature conditions, and that acetylene can be used as a precursor to deposit graphene. It was further proven that the carbon–hydrogen ratio of the precursor molecules in the PECVD process caused the reduction in the graphene temperature.

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Yan, Yuxin, Fathima Zahra Nashath, Sharon Chen, Sivakumar Manickam, Siew Shee Lim, Haitao Zhao, Edward Lester, Tao Wu et Cheng Heng Pang. « Synthesis of graphene : Potential carbon precursors and approaches ». Nanotechnology Reviews 9, n^o 1 (1 janvier 2020) : 1284–314. http://dx.doi.org/10.1515/ntrev-2020-0100.

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Abstract Graphene is an advanced carbon functional material with inherent unique properties that make it suitable for a wide range of applications. It can be synthesized through either the top–down approach involving delamination of graphitic materials or the bottom–up approach involving graphene assembly from smaller building units. Common top–down approaches are exfoliation and reduction while bottom–up approaches include chemical vapour deposition, epitaxial growth, and pyrolysis. A range of materials have been successfully used as precursors in various synthesis methods to derive graphene. This review analyses and discusses the suitability of conventional, plant- and animal-derived, chemical, and fossil precursors for graphene synthesis. Together with its associated technical feasibility and economic and environmental impacts, the quality of resultant graphene is critically assessed and discussed. After evaluating the parameters mentioned above, the most appropriate synthesis method for each precursor is identified. While graphite is currently the most common precursor for graphene synthesis, several other precursors have the potential to synthesize graphene of comparable, if not better, quality and yield. Thus, this review provides an overview and insights into identifying the potential of various carbon precursors for large-scale and commercial production of fit-for-purpose graphene for specific applications.

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Yan, Xu, Yao Dong, Yawen Gu et Hao Cui. « Effect of Precursors and Their Regulators on the Biosynthesis of Antibiotics in Actinomycetes ». Molecules 29, n^o 5 (3 mars 2024) : 1132. http://dx.doi.org/10.3390/molecules29051132.

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During the life activities of microorganisms, a variety of secondary metabolites are produced, including antimicrobials and antitumor drugs, which are widely used in clinical practice. In addition to exploring new antibiotics, this makes it one of the research priorities of Actinomycetes to effectively increase the yield of antibiotics in production strains by various means. Most antibiotic-producing strains have a variety of functional regulatory factors that regulate their growth, development, and secondary metabolite biosynthesis processes. Through the study of precursor substances in antibiotic biosynthesis, researchers have revealed the precursor biosynthesis process and the mechanism by which precursor synthesis regulators affect the biosynthesis of secondary metabolites, which can be used to obtain engineered strains with high antibiotic production. This paper summarizes the supply of antibiotic biosynthesis precursors and the progress of research on the role of regulators in the process of precursors in biosynthesis. This lays the foundation for the establishment of effective breeding methods to improve antibiotic yields through the manipulation of precursor synthesis genes and related regulators.

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Zhang, Guanhua, Hao Wang, Zihan Yang, Haoyang Xie, Zhenggang Jia et Yueping Xiong. « Enhancing the Electrochemical Stability of LiNi0.8Co0.1Mn0.1O2 Compounds for Lithium-Ion Batteries via Tailoring Precursors Synthesis Temperatures ». Materials 16, n^o 15 (1 août 2023) : 5398. http://dx.doi.org/10.3390/ma16155398.

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LiNi0.8Co0.1Mn0.1O2 (LNCMO) cathode materials for lithium-ion batteries (LIBs) were prepared by the hydrothermal synthesis of precursors and high-temperature calcination. The effect of precursor hydrothermal synthesis temperature on the microstructures and electrochemical cycling performances of the Ni-rich LNCMO cathode materials were investigated by SEM, XRD, XPS and electrochemical tests. The results showed that the cathode material prepared using the precursor synthesized at a hydrothermal temperature of 220 °C exhibited the best charge/discharge cycle stability, whose specific capacity retention rate reached 81.94% after 50 cycles. Such enhanced cyclic stability of LNCMO was directly related to the small grain size, high crystallinity and structural stability inherited from the precursor obtained at 220 °C.

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Nymann Petersen, Ida, Jacob Madsen, Christian Bernard Matthijs Poulie, Andreas Kjær et Matthias Manfred Herth. « One-Step Synthesis of N-Succinimidyl-4-[18F]Fluorobenzoate ([18F]SFB) ». Molecules 24, n^o 19 (22 septembre 2019) : 3436. http://dx.doi.org/10.3390/molecules24193436.

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Herein, we present a one-step labeling procedure of N-succinimidyl-4-[18F]-fluorobenzoate ([18F]SFB) starting from spirocyclic iodonium ylide precursors. Precursor syntheses succeeded via a simple one-pot, two-step synthesis sequence, in yields of approximately 25%. Subsequent 18F-nucleophilic aromatic labeling was performed, and radiochemical incorporations (RCCs) from 5–35% were observed. Purification could be carried out using HPLC and subsequent solid phase extraction. Radiochemical purity (RCP) of >95% was determined. The total synthesis time, including purification and formulation, was no longer than 60 min. In comparison to the established 3-step synthesis route of [18F]SFB, this one-step approach avoids formation of volatile radioactive side-products and simplifies automatization.

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Djavaheri-Mergny, M., L. Mora, C. Mazière, M. Auclair, R. Santus, L. Dubertret et J. C. Mazière. « Inhibition of diphosphatidylglycerol synthesis by u.v. A radiations in N.C.T.C. 2544 human keratinocytes ». Biochemical Journal 299, n^o 1 (1 avril 1994) : 85–90. http://dx.doi.org/10.1042/bj2990085.

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The effects of u.v. A radiations on phospholipid synthesis were studied in the N.C.T.C. 2544 human keratinocyte cell line, by using [14C]arachidonic acid, [14C]oleic acid or sodium [32P]orthophosphate as precursors. Cells were irradiated in Hanks' medium with 365 nm light at doses up to 19 J/cm2, and then phospholipid synthesis from the three precursors was studied. Under these conditions, only small alterations in the incorporation pattern of [14C]arachidonic into phospholipids [phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidylinositol (PI)] were observed, for u.v. A irradiation doses up to 19 J/cm2. In contrast, with [14C]oleic acid as precursor, two additional spots were observed, which co-migrate with pure phosphatidylglycerol (PG) and diphosphatidylglycerol (DPG) standards. The incorporation of [14C]oleic acid into PG and DPG was decreased in a dose-dependent manner after u.v. A exposure, with about 50% and 75% decreases at 9.5 J/cm2 and 19 J/cm2 respectively. As for arachidonic acid incorporation, no significant differences in the synthesis of the major phospholipids (PC, PE, PI) were noted upon u.v. A exposure. The dramatic and selective decrease in PG and DPG syntheses was confirmed with [32P]orthophosphate as precursor. As DPG is a specific component of the mitochondrial inner membrane, it appears that one of the early kinds of damage induced by u.v. A irradiation could be the impairment of mitochondrial functions.

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Perez, Henri, Virginie Jorda, Pierre Bonville, Jackie Vigneron, Mathieu Frégnaux, Arnaud Etcheberry, Axelle Quinsac, Aurélie Habert et Yann Leconte. « Synthesis and Characterization of Carbon/Nitrogen/Iron Based Nanoparticles by Laser Pyrolysis as Non-Noble Metal Electrocatalysts for Oxygen Reduction ». C 4, n^o 3 (30 juillet 2018) : 43. http://dx.doi.org/10.3390/c4030043.

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This paper reports original results on the synthesis of Carbon/Nitrogen/Iron-based Oxygen Reduction Reaction (ORR) electrocatalysts by CO2 laser pyrolysis. Precursors consisted of two different liquid mixtures containing FeOOH nanoparticles or iron III acetylacetonate as iron precursors, being fed to the reactor as an aerosol of liquid droplets. Carbon and nitrogen were brought by pyridine or a mixture of pyridine and ethanol depending on the iron precursor involved. The use of ammonia as laser energy transfer agent also provided a potential nitrogen source. For each liquid precursor mixture, several syntheses were conducted through the step-by-step modification of NH3 flow volume fraction, so-called R parameter. We found that various feature such as the synthesis production yield or the nanomaterial iron and carbon content, showed identical trends as a function of R for each liquid precursor mixture. The obtained nanomaterials consisted in composite nanostructures in which iron based nanoparticles are, to varying degrees, encapsulated by a presumably nitrogen doped carbon shell. Combining X-ray diffraction and Mossbauer spectroscopy with acid leaching treatment and extensive XPS surface analysis allowed the difficult question of the nature of the formed iron phases to be addressed. Besides metal and carbide iron phases, data suggest the formation of iron nitride phase at high R values. Interestingly, electrochemical measurements reveal that the higher R the higher the onset potential for the ORR, what suggests the need of iron-nitride phase existence for the formation of active sites towards the ORR.

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Zhao, Wei, Ruo Cai Pan et Hao Xue. « Synthesis of Plate-Like SrTiO₃ Particles ». Materials Science Forum 663-665 (novembre 2010) : 1024–27. http://dx.doi.org/10.4028/www.scientific.net/msf.663-665.1024.

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Micro-scale plake-like SrTO3 particles were synthesized by two routes of topochemical conversion. One is by growing on Sr3Ti2O7 (S3T2) core particles in molten salt condition, and the other is from the layer-structured SrBi4Ti4O15 (SBT) precursor in a KCl medium. The effects of the morphology and size of the precursor to platelet SrTiO3 crystals were studied. X-ray diffraction analysis revealed that the crystallographic {010} plane of SBT was converted into the pseudo-cubic {001} plane of SrTiO3. The polycrystalline SrTiO3 particles from BST precursor exhibited a plate-like shape with 10-15μm in length and a high aspect ratio, and were more suitable for preparing textured ceramics by templated grain growth process than the platelets from the S3T2 precursors.

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Hase, Takashi, Ryusuke Kita, Kenichi Kawaguchi, Takeshi Koga et Tadataka Morishita. « Synthesis of single phase YBa2Cu3O7−x thin films from a Y-Ba-Cu metallic precursor by a low-temperature annealing ». Journal of Materials Research 9, n^o 6 (juin 1994) : 1337–42. http://dx.doi.org/10.1557/jmr.1994.1337.

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YBa2Cu3O7−x (YBCO) superconducting thin films that show no x-ray diffraction peaks due to any other non-superconducting phases have been synthesized by annealing Y-Ba-Cu-O amorphous precursors at 750 °C. The Y-Ba-Cu-O precursors have been fabricated by oxidizing Y-Ba-Cu metallic precursors coevaporated from Y, Ba, and Cu metallic sources under ultrahigh vacuum conditions. Crystallization behavior from the Y-Ba-Cu-O precursor to YBCO films drastically depends on an oxidation temperature for the Y-Ba-Cu metallic precursor. YBCO thin film synthesized from the precursor oxidized at an optimum temperature shows a zero resistance temperature of over 80 K and a very smooth surface.

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Bequette, B. J., F. R. C. Backwell, A. G. Calder, J. A. Metcalf, D. Wray-Cahen, J. C. MacRae et G. E. Lobley. « Milk Protein Precursors in the Goat During Late Lactation ». Proceedings of the British Society of Animal Production (1972) 1993 (mars 1993) : 1. http://dx.doi.org/10.1017/s0308229600023321.

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Previously, we have reported on work in dairy goats using stable isotope kinetics to examine the precursors for milk protein synthesis (1). Contrary to a previous hypothesis (2), these results suggested that blood free amino acids (AA) are not simply transported into the mammary gland and incorporated directly into milk protein. Although the latter may still occur, a substantial amount of the AA for milk protein synthesis appears to be channelled through constitutive mammary gland protein(s) first. Moreover, the data indicated that a proportion (12-20%) of the casein protein precursor may be derived from extra-mammary sources other than blood free AA, e.g. peptides and/or proteins. It may be possible therefore to alter milk protein synthesis by the provision of different forms of precursor amino acids. Since the previous study was in goats during early lactation (day 61 ± 11), the present study reports on the precursors for milk protein synthesis in goats during late lactation, and allows a comparison between stages of lactation.

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Liu, Hui Ping. « Hydrothermal Synthesis of Mesoporous Al₂O₃ : Influences of pH Values and Aluminum Precursors ». Advanced Materials Research 581-582 (octobre 2012) : 396–400. http://dx.doi.org/10.4028/www.scientific.net/amr.581-582.396.

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The influences of pH values and aluminum precursors of “glucose-water-aluminum salt” reaction system on the hydrothermal synthesis of mesoporous Al2O3 were investigated. With the aid of scanning electron microscopy (SEM), electron diffraction spectrum (EDS) and X-ray diffraction (XRD) characterizations, we found that, under hydrothermal treatment at 180 °C for 20 h, aluminum nitrate (Al(NO3)3) could be used as the precursor to synthesize the spherical flower-like Al2O3 by using the synthesis solutions with different pH values in a certain scope; using aluminum chloride (AlCl3) as precursor, we can only get a small amount of Al2O3 composed of micro-spheres and sheets; while adopting aluminum sulfate (Al2(SO4)3) as precursor, a small amount of cubic-shape aluminum sulfate crystal can be obtained.

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Guerette, Michael, Timothy A. Strobel, Haidong Zhang, Stephen Juhl, Nasim Alem, Konstantin Lokshin, Lakshmi Krishna et P. Craig Taylor. « Advanced Synthesis of Na4Si24 ». MRS Advances 3, n^o 25 (2018) : 1427–33. http://dx.doi.org/10.1557/adv.2018.44.

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ABSTRACTThe recently discovered orthorhombic allotrope of silicon, Si24, is an exciting prospective material for the future of solar energy due to a quasi-direct bandgap near 1.3 eV, coupled with the abundance and environmental stability of silicon. Synthesized via precursor Na4Si24at high temperature and pressure (∼850 °C, 9 GPa), typical synthesis results have yielded polycrystalline samples with crystallites on the order of 20 μm. Several approaches to increase the crystal size have yielded success, including in-situ thermal spikes and refined selection of the starting materials. Microstructural analysis suggests that coherency exists between diamond silicon (d-Si) and Na4Si24. This hypothesis has led to the successful attempts at single crystal synthesis by selecting large crystals of d-Si along with metallic Na as the precursors rather than powdered and mixed precursor material. The new synthesis approach has yielded single crystals of Na4Si24greater than 100 μm. These results represent a breakthrough in synthesis that enables further characterization and utility. The promise of Si24for the future of solar energy generation and efficient electronics is strengthened through these advances in synthesis.

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Wang, Yong Gang, Hai Yan Lin, Xiao Qian Zhang, Lin Lin Yang, Yu Jiang Wang et Xiao Feng Wang. « Effect of Precursor on Sonochemical Synthesis of PbWO₄ Crystals ». Applied Mechanics and Materials 184-185 (juin 2012) : 826–29. http://dx.doi.org/10.4028/www.scientific.net/amm.184-185.826.

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A sonochemical method has been applied to prepared PbWO4 crystals by using different precursors. The as-prepared samples were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). It was found that the precursor played an important role in the synthesis of PbWO4 crystals. PbWO4 nanostructures with different morphologies, such as flower-like, rod-like, and dendrite-like, have been successfully obtained via a mild sonochemical method corresponding to the precursor PbCO3, Pb(NO3)2, and Pb(Ac)2, respectively.

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Chi, Lin, Zheng Wang, Youfang Zhou, Shuang Lu et Yan Yao. « Layered Double Hydroxides Precursor as Chloride Inhibitor : Synthesis, Characterization, Assessment of Chloride Adsorption Performance ». Materials 11, n^o 12 (13 décembre 2018) : 2537. http://dx.doi.org/10.3390/ma11122537.

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In this study, the chloride adsorption behaviors of CaAl-Cl LDH precursors with various Ca:Al ratios were investigated. The optimal chloride ion removal rate was 87.06% due to the formation of hydrocalumite. The chloride adsorption products of CaAl-Cl LDH precursors were further characterized by X-ray diffraction analysis and atomic structure analysis, the adsorption mechanism was considered to be co-precipitate process. The chloride adsorption behaviors of cementitious materials blended with CaAl-Cl LDH precursors were further investigated. Leaching test according to Test Code for Hydraulic Concrete (SL352-2006) was performed to testify the stability of chloride ions in the mortar. The results show that more than 98.3% chloride ions were immobilized in cement mortar blended with CaAl-Cl LDH precursor and cannot be easily released again. The inhibition performance of steel in the electrolytes with/without CaAl LDH precursor was investigated by using electrochemical measurements. The results indicate that CaAl LDH precursor can effectively protect the passive film on steel surface by chloride adsorption. Considering the high anion exchange capacities of the LDHs, synthesized chloride adsorbent precursor can be applied as new inhibitors blended in cementitious materials to prevent the chloride-induced deterioration. Moreover, the application of chloride adsorption on CaAl-Cl LDH could also be of interest for the application of seawater blended concrete.

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Devi, P. Sujatha, Yongjae Lee, Joshua Margolis, John B. Parise, Sanjay Sampath, Herbert Herman et Jonathan C. Hanson. « Comparison of citrate–nitrate gel combustion and precursor plasma spray processes for the synthesis of yttrium aluminum garnet ». Journal of Materials Research 17, n^o 11 (novembre 2002) : 2846–51. http://dx.doi.org/10.1557/jmr.2002.0413.

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The influence of synthesis conditions on the formation of yttrium aluminum garnet (YAG) powders starting from the same solution precursors was investigated by employing a citrate–nitrate gel combustion process and a precursor plasma spraying technique. YAG powders were formed at ≥500 °C, through the citrate–nitrate gel combustion process, without any intermediate phase formation. Time-resolved x-ray experiments were performed for the first time on these citrate–nitrate precursor materials to understand their mode of decomposition. The in situ data confirmed a single-step conversion to YAG from the precursor powder without any intermediate phase formation. Ex situ experiments also produced similar results. However, the use of the same citrate–nitrate precursor solution as a liquid feedstock material in the precursor plasma spraying technique revealed an entirely different transformation mechanism to YAG through intermediate phases like H–YalO3 and O–YalO3.

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Sharma, Vinay, Sandip K. Singh et Shaikh M. Mobin. « Bioinspired carbon dots : from rose petals to tunable emissive nanodots ». Nanoscale Advances 1, n^o 4 (2019) : 1290–96. http://dx.doi.org/10.1039/c8na00105g.

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The present study addresses the limitation of versatility in green precursors by exploring the formation of carbon dots with respect to the contents of green precursor, i.e. Rosa indica. The synthesis mechanism is elucidated by analysing the precursors and intermediates at different intervals.

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Okano, Kentaro, Ryo Nakura, Kazuki Inoue et Atsunori Mori. « Practical Synthesis of Precursors of Cyclohexyne and 1,2-Cyclohexadiene ». Synthesis 51, n^o 07 (11 janvier 2019) : 1561–64. http://dx.doi.org/10.1055/s-0037-1610356.

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This study investigated a practical method for regiocontrolled synthesis of precursors of strained cyclohexynes and 1,2-cyclohexadienes, which is a one-pot procedure consisting of a rearrangement of silyl enol ether and subsequent formation of the enol triflates. Triethylsilyl enol ether, derived from cyclohexanone, was treated with a combination of LDA and t-BuOK in n-hexane/THF to encourage the migration of the silyl group to generate an α-silyl enolate. Subsequently, the α-silyl enolate was reacted with Comins’ reagent to yield the corresponding enol triflate. Finally, the α-silylated trisubstituted lithium enolate for the synthesis of 1,2-cyclohexadiene precursor was isomerized in the presence of a stoichiometric amount of water for one hour at room temperature to exclusively provide tetrasubstituted lithium enolate for the synthesis of cyclohexyne precursor in one pot.

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Choi, Byeong-Min, Seok-Hwan Son, Chul-Wee Lee, Sun-Yeong Park et Min-Chul Chung. « Characterization and Synthesis of Molybdenum Metal Precursors for Hydrocracking Reaction of Vacuum Residues ». Journal of Nanoscience and Nanotechnology 20, n^o 9 (1 septembre 2020) : 5787–90. http://dx.doi.org/10.1166/jnn.2020.17650.

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In this study, Molybdenum precursors were synthesized with Triphenylphosphine, 1,2-Bis(diphenylphosphino)ethane, Pyridine, 2,2-Bipyridine as a ligands. The molybdenum precursors was used for Hydrocraking reaction of Vacuum Residue (VR). Hydrocracking reactions were carried out under the 430 °C and H2 pressure of 80 bar in an 100 ml high pressure reactor. New Molybdenum precursors were tested and their activities were compared with Mo-octoate. The Molybdeum-Phosphine precursor showed the best performances, high yield and low coke contents (below 0,5 wt%), in of hydrocracking for VR. To characterize the physicochemical properties of Moprecursor catalyst, various characterization techniques (NMR, XPS) were carried out. We confirmed that cokes in the reactor were contained the P atoms derived from ligand of Mo-precursor after hydrocracking of VR.

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Wang, Qiu Xiang, Qian Zhang et Li Feng Dong. « Catalytic Synthesis and Growth Mechanism of Multi-Branched Carbon Fibers by Cupric Solution Precursors ». Advanced Materials Research 645 (janvier 2013) : 24–29. http://dx.doi.org/10.4028/www.scientific.net/amr.645.24.

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Carbon fibers with different morphologies are obtained using different cupric solution precursors (e.g., cupric sulfate, cupric nitrate, and cupric chloride) at various temperatures. The morphology of carbon fibers depends on the type of catalyst precursor and reaction temperature but not the concentration of the precursor solution. For example, cupric chloride solution is a desirable catalyst precursor for the growth of carbon fibers with multi-branches at 450 °C. However, a mixture of carbon sheets and linear fibers forms at 300-350 °C. The splitting mode can be used to explain the formation of carbon fibers with different morphologies at various reaction temperatures.

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Azmina, M. S., Abu Bakar Suriani, M. Salina, A. A. Azira, A. R. Dalila, N. A. Asli, J. Rosly, Roslan Md Nor et M. Rusop. « Variety of Bio-Hydrocarbon Precursors for the Synthesis of Carbon Nanotubes ». Nano Hybrids 2 (août 2012) : 43–63. http://dx.doi.org/10.4028/www.scientific.net/nh.2.43.

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In this work, we have synthesized carbon nanotubes (CNT) using different bio-hydrocarbon precursors namely palm, olive, coconut, corn and sesame oils. Prior to the synthesis process, thermogravimetric analysis (TGA) characterization was performed on the carbon precursors to facilitate the optimization procedures of CNT and reach maximum yield and higher quality CNT. The CNT arrays were deposited on a silicon substrate by thermal catalytic decomposition of the precursor using 5.33 wt% ferrocene. The synthesis was carried out at 750 °C for 60 min under argon ambient. The samples were characterized using field emission scanning electron microscopy, micro-Raman spectroscopy and TGA analysis. The difference in oil density resulted in different quality and tube diameter of CNT produced. Among all, the CNT synthesized from coconut oil can be considered as the best bio-hydrocarbon precursor for higher quality (ID/IG ~0.62) and good purity (81.95 %) CNT.

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Fernandes, Sónia, Joaquim C. G. Esteves da Silva et Luís Pinto da Silva. « Life Cycle Assessment-Based Comparative Study between High-Yield and “Standard” Bottom-Up Procedures for the Fabrication of Carbon Dots ». Materials 15, n^o 10 (11 mai 2022) : 3446. http://dx.doi.org/10.3390/ma15103446.

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Carbon dots (CDs) are carbon-based nanomaterials with remarkable properties that can be produced from a wide variety of synthesis routes. Given that “standard” bottom-up procedures are typically associated with low synthesis yields, different authors have been trying to devise alternative high-yield fabrication strategies. However, there is a doubt if sustainability-wise, the latter should be really preferred to the former. Herein, we employed a Life Cycle Assessment (LCA) approach to compare and understand the environmental impacts of high-yield and “standard” bottom-up strategies, by applying different life cycle impact assessment (LCIA) methods. These routes were: (1) production of hydrochar, via the hydrothermal treatment of carbon precursors, and its alkaline peroxide treatment into high-yield CDs; (2) microwave treatment of carbon precursors doped with ethylenediamine; (3) and (6) thermal treatment of carbon precursor and urea; (4) hydrothermal treatment of carbon precursor and urea; (5) microwave treatment of carbon precursor and urea. For this LCA, four LCIA methods were used: ReCiPe, Greenhouse Gas Protocol, AWARE, and USEtox. Results identified CD-5 as the most sustainable synthesis in ReCiPe, Greenhouse Gas Protocol, and USEtox. On the other hand, in AWARE, the most sustainable synthesis was CD-1. It was possible to conclude that, in general, high-yield synthesis (CD-1) was not more sustainable than “standard” bottom-up synthesis, such as CD-5 and CD-6 (also with relatively high-yield). More importantly, high-yield synthesis (CD-1) did not generate much lower environmental impacts than “standard” approaches with low yields, which indicates that higher yields come with relevant environmental costs.

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Higuchi, Mai, Mizuri Yaguchi, Miru Yoshida-Hirahara, Hitoshi Ogihara et Hideki Kurokawa. « Facile synthesis of nanostructured perovskites by precursor accumulation on nanocarbons ». RSC Advances 12, n^o 10 (2022) : 6186–91. http://dx.doi.org/10.1039/d1ra08357k.

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Various nano-perovskites are synthesized by dropping a precursor solution of metal salts into nanocarbon, followed by drying and calcination in air. The accumulation of precursors on the surface of nanocarbon is the key step.

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Kassabova-Zhetcheva, Violeta. « Characterization of the citrate precursor, used for synthesis of nanosized Mg-Zn ferrites ». Open Chemistry 7, n^o 3 (1 septembre 2009) : 415–22. http://dx.doi.org/10.2478/s11532-009-0054-7.

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AbstractThe citrate precursor has been used to synthesize nanocrystalline Mg-Zn-ferrites. The nature of the prepared precursor is characterized and compared with those of the precursors studied earlier, prepared by the same process. The study has been performed by inorganic and organic elemental analyses, Fourier Transformed Infrared Spectroscopy (FTIR), Mössbauer spectroscopy, X-ray Photoelectron Spectroscopy (XPS), Electron Paramagnetic Resonance (EPR), Electronic absorption spectrometry in the UV-VIS region, Differential Thermal analysis/ Thermogravimetry (DTA-TG) analyses, and X-ray diffraction (XRD) analysis. The collected results determined the precursor as a coordination polymer with monomer unit (NH4)4{M [Fe(C6H5O7)2]2}, where M=Zn or Mg.

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Deng, Chong, Bowen Fu, Lili Li, Yanlai Wang et Lin Yang. « Influence of Sulfur Precursor Solutions on Crystallinity of CuInS2 Nanocrystals Fabricated with Hot-Injection Method ». Journal of Nanoscience and Nanotechnology 20, n^o 7 (1 juillet 2020) : 4533–36. http://dx.doi.org/10.1166/jnn.2020.17894.

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The hot-injection method was used for the synthesis of ternary metal chalcogenide nanocrystals (NCs) CuInS2 (CIS); this was achieved by using the metal precursors (copper iodide and indium acetate) and four different types of sulfur precursor solutions. It was discovered that CIS NCs synthesized with different sulfur precursor solutions exhibited the chalcopyrite structure with similar particle sizes of ~4.2 nm. As a comparison, CIS NCs synthesized using ODE-S precursor displayed an enhanced luminescence intensity and a long PL decay lifetime, which could be considered as an evidence of improved interior crystallinity.

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Bocharova, Irina V., et Galina B. Kunshina. « Study of ceramic and glass-ceramic solid electrolyte Li1,5Al0,5Ge1,5(PO4)3 properties obtained from oxalate and citrate precursors ». Transactions of the Kоla Science Centre of RAS. Series : Engineering Sciences 13, n^o 1/2022 (27 décembre 2022) : 26–32. http://dx.doi.org/10.37614/2949-1215.2022.13.1.004.

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The synthesis of lithium conducting solid electrolyte Li1.5Al0.5Ge1.5(PO4)3 (LAGP) by liquid-phase method from oxalate and citrate precursors is investigated. The samples were characterized by XRD, DSC / TG, IR, impedance spectroscopy and potentiostatic chronoamperometry. It was found that the formation of a single - phase LAGP from an oxalate precursor occurs at a lower temperature (600–650 °C) and is preferable compared to the synthesis of LAGP from a citrate precursor. The ionic conductivity of the electrolyte was 4,2 · 10-4 S / cm, the electronic conductivity did not exceed 2 · 10-10 S / cm, the decomposition potential was 3.8 V.

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Krstić, J., N. Vukelić, Zoran Nedić, A. Milutinović-Nikolić, A. Šućurović et D. Jovanović. « Nickel/Silica Precursor from Sodium Silicate Solution - Synthesis and Characterization ». Materials Science Forum 494 (septembre 2005) : 333–38. http://dx.doi.org/10.4028/www.scientific.net/msf.494.333.

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The aim of this paper was the investigation of the influence of synthesis parameters, as well as the order of synthesis steps, in procedure of chemical precipitation, on the properties of synthesized nickel precursor. The starting materials were always the same aqueous solutions of Ni(NO3)2×6H2O and Mg(NO3)2×6H2O of constant molar ratio, 2% solution of SiO2 in the form of sodium silicate solution (module SiO2/Na2O = 3.0) and 10% solution of Na2CO3, while synthesis steps and addition modes were varied. Complete pH and temperature monitoring was performed during entire synthesis at 90°C. The formed precipitate aged 30 minutes at synthesis temperature. By changing the order and conditions of adding SiO2 and Na2CO3 solutions and keeping the treatment of precipitates the same (rinsing with hot distilled water followed by drying at 110°C for 24 hours) six different precursors were obtained. Samples characterizations were performed using different experimental techniques: XRD analysis, IR spectroscopy, reflection spectroscopy, TG analysis, N2 physisorption. The relation between synthesis procedure and precursor properties was established.

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Zhou, Min, Cheng Zhang, Wen Bo Bu, Lei Wang et Qiang Li. « YAG:Ce³⁺ Nanopowders : Synthesis, Characteristics and Luminescent Properties ». Key Engineering Materials 368-372 (février 2008) : 429–31. http://dx.doi.org/10.4028/www.scientific.net/kem.368-372.429.

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By means of co-precipitation, pure YAG phase was synthesized from the reaction of aluminum yttrium and cerium nitrates with ammonia as precipitator. In order to obtain the special coating oxide precursor, the metal ions solution and ammonia were respectively added with fixed ratio by two peristaltic pumps to maintain an expired pH value and reaction rate. The as-received precursor was annealed at 700°C and 900°C respectively. The structure, phase evolution and morphology of the as-prepared YAG nanopowders were tested by XRD, BET and SEM. At lower temperature (900°C), coating oxide precursor was directly transformed to nanopowders of pure YAG phase. The high salt solution concentration was critical for the control of chemical homogeneity within the precursors. The YAG nanopowders were less-aggregated and better-dispersed. The luminescent properties were examined and discussed.

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Harruna, Issifu I., Kofi B. Bota et Sherita D. McLamore. « Precursor polymers : 1. Synthesis and characterization of processable precursors to aramids ». Polymer 34, n^o 15 (janvier 1993) : 3328–31. http://dx.doi.org/10.1016/0032-3861(93)90413-5.

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PENG, CHAO, DESEN ZHAO, GANG HE, MINGZHONG HE, JIANHE HONG, HAIFENG LI et YANSHENG GONG. « CONVENIENT PREPARATION OF Pb(ZrxTi1-x)O3 THIN FILMS BY A COMBINATORIAL SYNTHESIS PROCESS ». Functional Materials Letters 04, n^o 03 (septembre 2011) : 231–35. http://dx.doi.org/10.1142/s1793604711002068.

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In order to carry out a convenient preparation of Pb ( Zr x Ti 1-x) O 3 thin films by combinatorial chemical solution deposition process, two kinds of Pb ( Zr x Ti 1-x) O 3 precursor solutions ( PbTiO3 precursor solution and PbZrO3 precursor solution) were prepared by a simple process. There is no distillation and no inert gas shielding in the process, and the precursors are more stable than the conventional precursor solution. A series of Pb ( Zr x Ti 1-x) O 3 samples (x = 0.1–0.9, in step of 0.1 amount change) were prepared using the two precursor solutions. The process was fast and saved time. There were strong exothermic reactions for the samples with the Zr content x in a short range from x = 0.23 to 0.27 at 161–200°C. The Pb ( Zr x Ti 1-x) O 3 thin films showed perovskite structure with strong (111)-preferred orientation. The structure and ferroelectric property of the PZT thin films are comparable with those of the PZT fabricated by conventional process.

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Cai, Rong, Zhao Kun Ma, Hai Peng Qiu, Shan Hua Liu, Wei Jie Xie et Ming Wei Chen. « Synthesis of the ZrB₂-SiC Ceramic from Polymeric Precursor Pyrolysis ». Solid State Phenomena 281 (août 2018) : 382–88. http://dx.doi.org/10.4028/www.scientific.net/ssp.281.382.

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A ZrB2-SiC multiphase ceramic was fabricated with a precursor pyrolysis method by using zirconium boride organic precursor and polycarbosilane. In order to study the pyrolysis process of complex phase ceramics, the pyrolysis process of the two precursors was studied respectively at the beginning. The precursor and the mixture with different weight ratios both pyrolyzed at 800°C. ~1500°C. under argon atmosphere. The specimens were characterized by thermo-gravimetric analysis, infra-red, X-ray diffraction. It was found that the pyrolysis products of PCS remained amorphous below 1000°C. and converted into crystallization with temperature increasing. ZrO2as the intermediate pyrolysis product of ZrB2precursor initiate convert to t-ZrO2from m-ZrO2at 1200°C.. Finally, all kinds of ZrB2-SiC multiphase ceramic are successful obtained via pyrolysis of precursor after 1500°C. And the 40wt%ZrB2precursor initial carbothermal reduction temperature below the ZrB2precursor reactive temperature and the crystal degree of SiC is higher than pyrolysis product of PCS.

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Bansal, M. K., et R. M. Mason. « Evidence for rapid metabolic turnover of hyaluronate synthetase in Swarm rat chondrosarcoma chondrocytes ». Biochemical Journal 236, n^o 2 (1 juin 1986) : 515–19. http://dx.doi.org/10.1042/bj2360515.

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Synthesis of [3H]hyaluronate from [6-3H]glucosamine was investigated in cultures of Swarm rat chondrosarcoma chondrocytes treated with various concentrations (0.1 microM-0.1 mM) of cycloheximide for various times. Concentrations greater than 1 microM inhibited protein synthesis by greater than 90%. Hyaluronate synthesis was decreased, with a t1/2 for 50% inhibition of 80-120 min, depending on the concentration of cycloheximide present. Similar experiments using [1-3H]glucose as a precursor label gave similar results. Experiments using [6-3H]glucosamine as a precursor label and 0.18 mM-puromycin to inhibit protein synthesis inhibited hyaluronate synthesis (t1/2 = 82 min) with similar kinetics to cycloheximide-induced inhibition. Cultures incubated with 3.6 microM-cycloheximide for up to 9 h and supplemented with p-nitrophenyl beta-D-xyloside during the last 75 min of treatment showed increased synthesis of [3H,35S]chondroitin sulphate, demonstrating that UDP-hexose precursors for glycosaminoglycan synthesis are not rapidly depleted on blockage of protein synthesis. Rapid metabolic turnover of hyaluronate synthetase is the most likely cause for decreased hyaluronate synthesis in chondrocytes in which protein synthesis is inhibited.

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Krayer, Michael, Thiagarajan Balasubramanian, Christian Ruzié, Marcin Ptaszek, David L. Cramer, Masahiko Taniguchi et Jonathan S. Lindsey. « Refined syntheses of hydrodipyrrin precursors to chlorin and bacteriochlorin building blocks ». Journal of Porphyrins and Phthalocyanines 13, n^o 10 (octobre 2009) : 1098–110. http://dx.doi.org/10.1142/s1088424609001406.

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Bromo-substituted hydrodipyrrins are valuable precursors to synthetic bromo-chlorins and bromo-bacteriochlorins, which in turn are versatile substrates for derivatization in pursuit of diverse molecular designs. 8-bromo-2,3-dihydro-1-(1,1-dimethoxymethyl)-3,3-dimethyldipyrrin (1) is a crucial precursor in the rational synthesis of the bacteriochlorin building block 3,13-dibromo-8,8,18,18-tetramethylbacteriochlorin ( H2BC-Br3Br13) . 8-bromo-2,3,4,5-tetrahydro-1,3,3-trimethyldipyrrin (2) is a crucial precursor in the rational synthesis of the analogous 3,13-disubstituted chlorin building block (e.g. H2C-Br3M10Br13 ). The routes to 1 and 2 share a common precursor, namely 4-bromo-2-(2-nitroethyl)-1-N-tosylpyrrole (6-Ts), which is derived from pyrrole-2-carboxaldehyde. The prior seven-step synthesis of 1 from pyrrole-2-carboxaldehyde has limited access to H2BC-Br3Br13 given the large excesses of materials, extensive reliance on column chromatography, and low overall yield (1.4%). Refined procedures for synthesis of the common precursor 6-Ts as well as 1 and 2 afford the advantages of (1) diminished consumption of solvents and reagents, (2) limited or no use of chlorinated solvents, (3) limited or no chromatography, and (4) improved yields of most steps. Streamlined procedures enable the final two or three transformations to be performed without purification of intermediates. The new procedures facilitate the expedient preparation of 1 and 2 at the multigram scale.

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Antunes, Isabel, Miguel F. Baptista, Andrei V. Kovalevsky, Aleksey A. Yaremchenko et Jorge R. Frade. « Thermodynamic Guidelines for the Mechanosynthesis or Solid-State Synthesis of MnFe2O4 at Relatively Low Temperatures ». Materials 17, n^o 2 (7 janvier 2024) : 299. http://dx.doi.org/10.3390/ma17020299.

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Herein, thermodynamic assessment is proposed to screen suitable precursors for the solid-state synthesis of manganese ferrite, by mechanosynthesis at room temperature or by subsequent calcination at relatively low temperatures, and the main findings are validated by experimental results for the representative precursor mixtures MnO + FeO3, MnO2 + Fe2O3, and MnO2 +2FeCO3. Thermodynamic guidelines are provided for the synthesis of manganese ferrite from (i) oxide and/or metallic precursors; (ii) carbonate + carbonate or carbonate + oxide powder mixtures; (iii) other precursors. It is also shown that synthesis from metallic precursors (Mn + 2Fe) requires a controlled oxygen supply in limited redox conditions, which is hardly achieved by reducing gases H2/H2O or CO/CO2. Oxide mixtures with an overall oxygen balance, such as MnO + Fe2O3, act as self-redox buffers and offer prospects for mechanosynthesis for a sufficient time (>9 h) at room temperature. On the contrary, the fully oxidised oxide mixture MnO2 + Fe2O3 requires partial reduction, which prevents synthesis at room temperature and requires subsequent calcination at temperatures above 1100 °C in air or in nominally inert atmospheres above 750 °C. Oxide + carbonate mixtures, such as MnO2 +2FeCO3, also yield suitable oxygen balance by the decomposition of the carbonate precursor and offer prospects for mechanosynthesis at room temperature, and residual fractions of reactants could be converted by firing at relatively low temperatures (≥650 °C).

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Zhuang, Weiwei, Fengyang Zhang, Jer Shen Maa et Sheng Teng Hsu. « PGO spin-coating precursor synthesis ». Integrated Ferroelectrics 36, n^o 1-4 (janvier 2001) : 235–43. http://dx.doi.org/10.1080/10584580108015545.

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Devadas, Malini, et Ian Morgan. « Light controls scleral precursor synthesis ». NeuroReport 7, n^o 12 (août 1996) : 2010–12. http://dx.doi.org/10.1097/00001756-199608120-00031.

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Xu, Yebin, Xiao Yuan, Guohua Huang et Hua Long. « Polymeric precursor synthesis of Ba2Ti9O20 ». Materials Chemistry and Physics 90, n^o 2-3 (avril 2005) : 333–38. http://dx.doi.org/10.1016/j.matchemphys.2004.10.022.

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Rao, Lin, Edward G. Gillan et Richard B. Kaner. « Rapid synthesis of transition-metal borides by solid-state metathesis ». Journal of Materials Research 10, n^o 2 (février 1995) : 353–61. http://dx.doi.org/10.1557/jmr.1995.0353.

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A rapid self-sustaining solid-state precursor route to transition-metal borides, boride solid solutions, and boride composites has been developed. Solid-state metathesis (SSM) reactions between transition-metal chlorides and magnesium boride (MgB2) produce crystalline borides and magnesium chloride. Boride solid solutions are formed using mixed chloride precursors. By using a third precursor, such as NaN3, boride-nitride composites are synthesized. The reaction products are characterized by powder x-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, and inductively coupled plasma atomic absorption spectroscopy. These boride reactions become self-propagating when the adiabatic temperature is greater than the melting point of the by-product salt, MgCl2 (mp 987 K).

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Liu, J., R. Czerw et D. L. Carroll. « Large-scale synthesis of highly aligned nitrogen doped carbon nanotubes by injection chemical vapor deposition methods ». Journal of Materials Research 20, n^o 2 (février 2005) : 538–43. http://dx.doi.org/10.1557/jmr.2005.0069.

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In this study, we compare the effects of pyridine (C5H5N) and pyrimidine (C4H4N2) precursors, using ferrocene as a metal source, in the production of nitrogen containing multiwalled carbon nanotubes. Using standard chemical vapor deposition techniques, highly aligned mats of carbon-nitrogen carbon nanotube were synthesized. The maximum nitrogen concentration in these materials is between 1% and 2% when pyridine is used as the precursor and can be increased to 3.2% when pyrimidine is used as the precursor. However, the electronic structure of both materials, as determined using scanning tunneling spectroscopy, suggests that the nitrogen is incorporated into the nanotube lattice in the same way for both precursors.

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Bolden, Nydeia W., Vijaya K. Rangari, Shaik Jeelani, Seyhan Boyoglu et Shree R. Singh. « Synthesis and Evaluation of Magnetic Nanoparticles for Biomedical Applications ». Journal of Nanoparticles 2013 (15 janvier 2013) : 1–9. http://dx.doi.org/10.1155/2013/370812.

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In this study, iron oxide (IO) nanoparticles from various precursors have been synthesized using sonochemical method and characterized for their structural variability and toxicity. The iron oxide (IO) precursor solutions were prepared from iron acetate (IA), iron pentacarbonyl (IP), decalin, PEG (poly(ethylene glycol)), EG (ethylene glycol), PVA (poly(vinyl alcohol)), β-cyclodextrin (CD), and distilled water. These precursor solutions were irradiated with high power ultrasound for 3 hours and heat treated as needed. These as-prepared iron oxide nanoparticles were characterized using X-ray diffraction (XRD), Mössbauer spectroscopy, transmission electron microscopy (TEM), and magnetization measurements. XRD results show that all the particles are highly crystalline in nature and the particles sizes measured from TEM are approximately 5–20 nm. The maximum magnetization was observed for IO-IP at approximately 60.17 emu/g and the minimum was approximately 30.56 emu/g for IO-IA. These results confirm that the particles are superparamagnetic (SPM) in nature. Mössbauer spectroscopy verified the magnetic nanoparticles are purely Fe3O4 and particles sizes varied by the nature of the precursor and coatings.

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Chan, Yee Seng, Hironobu Hayashi, Naoki Aratani et Hiroko Yamada. « Polyazaacenes Generation By Using Precursor Methods ». ECS Meeting Abstracts MA2022-01, n^o 10 (7 juillet 2022) : 794. http://dx.doi.org/10.1149/ma2022-0110794mtgabs.

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Azaacenes are the analogue of acenes, comprising nitrogen atoms in the carbon-based molecular skeleton, have been gaining attention because of their potential application in organic electronics and material science. However, it is normally difficult to synthesize such large aromatic molecules because of the poor solubility and low stability. On the other hand, we have developed precursor methods to overcome these problems. Briefly, bicyclo[2.2.2]octadiene(BCOD)-fused acenes can be converted its corresponding acenes by thermally induced retro-Diels–Alder reaction, while α-diketone-type precursors can be converted simply by photoirradiation.[1] Significantly, these precursor molecules are often more soluble and stable than its converted forms. More crucially, their corresponding acenes can be prepared quantitatively in solutions or in films, if the precursors are sufficiently pure. So far, by using the precursor methods, we have successfully synthesized polyacenes under anaerobic conditions either at ultrahigh vacuum conditions or at the interior of single crystals to avoid undesirable oxidation of the resulting polyacenes.[2–4] Here we report a series of tetraazapolyacene precursors synthesis. Briefly, the BCOD moieties were introduced in the tetraazaacenes as the thermally removable leaving group. The possibility of conversion of the precursors into its corresponding tetraazaacenes was examined by thermogravimetric analysis respectively. In addition, α-diketone-type precursor of tetraazaheptacene was also synthesized. Furthermore, we also report the one-pot synthesis of macrocyclic azacyclacene precursor by reacting bis-α-diketo-tetrahydro-diethanopentacene with benzene-1,2,4,5-tetraamine tetrahydrochloride. Here, the targeted compound was clearly confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The obtaining precursor compounds will be subjected to transformation to investigate its optical and physical properties. References H. Yamada, D. Kuzuhara, M. Suzuki, H. Hayashi, N. Aratani, Bull. Chem. Soc. Jpn. 2020, 93, 1234–1267. J. I. Urgel, S. Mishra, H. Hayashi, J. Wilhelm, C. A. Pignedoli, M. D. Giovannantonio, R. Widmer, M. Yamashita, N. Hieda, P. Ruffieux, H. Yamada, F. Roman, Nat. Commun. 2019, 10, 861. H. Hayashi, N. Hieda, M. Yamauchi, Y. S. Chan, N. Aratani, S. Masuo, H. Yamada, Chem. Eur. J. 2020, 26, 15079–15083. K. Eimre, J. I. Urgel, H. Hayashi, M. D. Giovannantonio, P. Ruffieux, S. Sato, S. Otomo, Y. S. Chan, N. Aratani, D. Passerone, O. Gröning, H. Yamada, R. Fasel, C. A. Pignedoli, Nat. Commun. in press.

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Chen, Hong Yu, et Ru Yang. « Co-Precipitation Synthesis and Supercritical Ethanol Drying of Yttrium Aluminum Garnet (YAG) Powders ». Advanced Materials Research 11-12 (février 2006) : 11–14. http://dx.doi.org/10.4028/www.scientific.net/amr.11-12.11.

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YAG precursors were co–precipitated from a mixed solution of aluminum and yttrium nitrates using urea as precipitant. After being washed by ethanol several times, the gel–like precursor was dispersed in absolute ethanol to form suspended liquid. The mixture was placed into a high–pressure autoclave, which followed by heating ethanol to supercritical state (Tc > 243°C and Pc > 6.3Mpa). The precursor dried via supercritical ethanol fluid technique was sintered at different temperature according to requirement. The phase transformation, composition and micro–structural features of the products were characterized by XRD, TG/DSC, BET and TEM techniques. It was found that after supercritical ethanol fluid drying the precursor was well dispersed, uniform and caused better sinterability of the resultant YAG powder. XRD results indicated that the precursor was partial crystalline and the pure phase YAG can be obtained at 1200°C calcinated for 2h. TG/DSC revealed the formation process of YAG phase. The averaged size of YAG nanocrystalline powder was 30–40nm and well dispersed according to TEM.

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