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Literatura académica sobre el tema "Zirconi"

Autor: Grafiati

Publicado: 14 de marzo de 2023

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Artículos de revistas sobre el tema "Zirconi"

Karlina, Elin, Nina Djustiana, I. Made Joni, Renny Febrida, Camellia Panatarani y Akhyar Dyni Zakyah. "Analisis Mikrostruktur Partikel Zirkoniakalsia-silika (ZrO 2 -CaO-SiO ) Dari Pasir Zirkon Alam Indonesia Menggunakan Metode Spray Pyrolysis". Jurnal Material Kedokteran Gigi 6, n.º 1 (1 de marzo de 2017): 23. http://dx.doi.org/10.32793/jmkg.v6i1.261.

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Indonesian Natural Sand, Zircon, is an Indonesia’s natural resource that contains zirconia, silica, titania and alumina. In Dentistry, zirconia as one of the content in natural zircon sand, have the potential to be the material for filler composites. The purpose of this research was to analyze the Zirconia-Calcium-Silicate Particle (ZrO2CaO-SiO2) synthesized from Indonesia natural sand, zircon, in microstructural way. Methods: By synthesizing ZirconiaCalcium-Silicate particle (ZrO2-CaO-SiO2) from Indonesia natural zircon sand, using spray pyrolysis method. A precursor solution that is used consists of zirconil nitrate (Zr (NO3) 2), sodium silicate (Na2SiO3), and calcium hydroxide (Ca (OH) 2). Variations in the temperature of the reactor that are used were 4000C, 4500C, and 5000C with a feed rate of 6 L / min and a piezoelectric frequency of 1.7 MHz. Result showed that the better content in zirconia-calcium-silicate is the one that was synthesized at a temperature of 4500C, based on the results of EDS, SEM and XRD. The composition that is obtained in the zirconia-calcium-silicate particle has a ratio of 1: 14: 4 with the size of 500-1000nm, and has a tetragonal crystal zirconium silicate structure and dicalcium monoclinic silicate. From this research it can be concluded that the result that was synthesized at a temperature of 4500C is adequate to use as a filler based on the characterization result of SEM and XRD.

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Li, Bing Qiang, Yao Shu, Wen Bin Dai y Jing Kun Yu. "Effect of Zirconia, Zirconite and Zircon Mullite Additives on the Properties of Alumina Castable". Applied Mechanics and Materials 151 (enero de 2012): 346–49. http://dx.doi.org/10.4028/www.scientific.net/amm.151.346.

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The effect of the zirconia, zirconite, and zircon mullite additives on the properties of alumina-spinel castable has been investigated in present work. Results showed that the density of castables calcined at 110oC with the addition of zirconia and zirconite was higher than that of zircon mullite. With the increasing amount of additives, the densities of castables added with zirconia and zirconite were increased and that added with zircon mullite had not obviously difference. The apparent porosities of castables heated at 1600oC for 1h were about twice of those calcined at 110oC. The bulk densities of castables heated at 1600oC were lower than those calcined at 110oC. All the samples were expanded and the increasing amount of additives led to higher expansion rate. Though the densities of castables heated at 1600oC were lower than those calcined at 110oC, the cold crushing strength were much higher. When the amount of zirconia was less than 4maa%, the addition of zirconia was beneficial to improve the bending strength, and the addition of 4mass% zirconia led to the 18.2% improvemnt at the strength.

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Meor Sulaiman, Meor Yusoff, Khaironie Mohamed Takip y Ahmad Khairulikram Zahari. "In Situ XRD Study of Zirconia Phase Transformation Produced from Chemical and Mineral Processes". Materials Science Forum 840 (enero de 2016): 375–80. http://dx.doi.org/10.4028/www.scientific.net/msf.840.375.

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The high temperature phase transition of zirconia produced from commercial zirconyl chloride chemical was compared with that produced from a Malaysian zircon mineral. Zirconyl chloride was produced from zircon by using the hydrothermal fusion method. Initial XRD diffractogram of these samples at room temperature show that they are of amorphous structure. High temperature XRD studies was then performed on these samples; heated up to 1500°C. The XRD diffractograms shows that the crystalline structure of tetragonal zirconia was first observed and the monoclinic zirconia becomes more visible at higher heating temperature.

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Subuki, Istikamah. "Influence on Ratio of NaOH/ZrSiO4 in Alkali Fusion for Amang Zircon Sand". ASM Science Journal 17 (25 de noviembre de 2022): 1–10. http://dx.doi.org/10.32802/asmscj.2022.1093.

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Amang Zircon Sand from Amang Onn Sdn. Bhd. mineral company has a high composition of zirconium at 61.63 wt% and low silicon composition at 4.90 wt%. The high composition of zirconium in Amang zircon sand indicates the possibility to synthesise it into a zirconia. Zirconium was synthesised using alkali fusion method with different ratio of NaOH/ZrSiO4 to determine the optimum ratio based on the zirconium yield. Alkali fusion method is coupled with thermal treatment as it will produce a higher yield of zirconium with lower impurities. Then it will be leached with deionised water and hydrochloric acid (HCl). The synthesised zirconium was characterised through X-Ray fluorescence (XRF) spectroscopy, X-Ray diffraction (XRD) and particle size distribution (PSD) analysis. The XRF analysis after the fusion and thermal treatment shows a high composition of zirconium as well as great reduction of silicon. 1.2NaOH/ZrSiO4 is determined to be the optimum ratio as it has the lowest silicon impurity of 2.11 wt% and high yield of zirconium at 71.40 wt%. The low impurities will reduce the chance of cracking and maximising the efficiency of zirconia. It is supported by XRD patterns that are dominated by high zirconium peaks. The zirconium oxychloride obtained after acid leaching has a high zirconium composition. This shows that it is possible to use Amang zircon sand as a precursor to synthesis a zirconia using alkali fusion method with sodium hydroxide.

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Djustiana, Nina, Renny Febrida, Camellia Panatarani, Yuliafanny Imarundha, Elin Karlina y I. Made Joni. "Microstructure Analysis of Zirconia-Alumina-Silica Particles Made from Indonesia Natural Sand Synthesized Using Spray Pyrolysis Method". Key Engineering Materials 720 (noviembre de 2016): 285–89. http://dx.doi.org/10.4028/www.scientific.net/kem.720.285.

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Zircon sand is one of Indonesian natural resource that is potential to be used as composite filler. Natural zircon sand can be found in several places in Indonesia, i.e. Riau Islands, Bangka-Belitung, and the Borneo. Zircon sand contains zirconia compound; while ZrO2 is the oxide crystal of zirconia compound. The mechanical and esthetical supremacy of zirconia is the reason why the usage of zirconia as nanocomposite filler mixed with alumina and silica increases. Spray pyrolysis method was used to synthesized natural zircon sand of Indonesia with temperature variety of 400°C, 500°C and 600°C. Spray pyrolysis decomposed zircon sand into powder in nano-sized. Microstructure analysis conducted were SEM, EDS, and XRD. SEM analysis showed that the morphology of particle was spherical, uniform, and regular with size of 100-500nm. EDS and XRD showed best results at the temperature of 400°C. Analysis result of EDS indicated that the largest atomic percentage was owned by sodium with ratio of Zr:Al:Si of 1:2:54 at temperature of 400°C. The XRD pattern of 400°C revealed that the crystal structure of zirconium silicate (ZrSiO4) was tetragonal, the structure of quartz (SiO2) was trigonal, and the structure of corundum aluminum oxide (Al2O3) was rhombohedral. Synthesis of zirconia-alumina-silica particles from natural zircon sand of Indonesia could be used as composite filler based on the characterization results.

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Ngọc. "NGHIÊN CỨU BIẾN TÍNH BỀ MẶT HẠT NANO ZIRCONI OXIT BẰNG POLYDIMETYL SILOXAN". Journal of Military Science and Technology, n.º 72 (12 de abril de 2021): 66–72. http://dx.doi.org/10.54939/1859-1043.j.mst.72.2021.66-72.

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Nano zirconi oxit (ZrO2) được sử dụng rộng rãi trong nhiều ngành công nghiệp để cải thiện tính chất cơ lý cũng như khả năng chịu nhiệt của vật liệu nền. Tuy nhiên, các hạt nano ZrO2 thường có xu hướng kết tụ với nhau nên dẫn đến hiệu quả sử dụng nano ZrO2 không được như mong muốn. Bài báo này trình bày kết quả nghiên biến tính nano ZrO2 bằng polydimetyl siloxan (PDMS). Nghiên cứu đã đưa ra được các điều kiện phản ứng tối ưu là tỷ lệ về khối lượng giữa bột nano ZrO2/PDMS: 1/0,5 và nhiệt độ phản ứng là 200 oC. Các kết quả phân tích phổ hồng ngoại FT-IR, phân tích phổ tán xạ năng lượng tia X, phân tích cấu trúc hình thái TEM đã chỉ ra các hạt nano ZrO2 sau quá trình biến tính bề mặt đã ghép được các nhóm siloxan lên trên bề mặt. Hạt nano ZrO2 biến tính có khả năng phân tán tốt hơn trong dung môi xylen so với hạt nano ZrO2 chưa biến tính. Do đó, các hạt hạt nano ZrO2 biến tính có thể sử dụng tốt trong công nghiệp chế tạo sơn và keo dán.

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Stankovic, Jovan, Slobodan Milonjic y Slavica Zec. "The influence of chemical and thermal treatment on the point of zero charge of hydrous zirconium oxide". Journal of the Serbian Chemical Society 78, n.º 7 (2013): 987–95. http://dx.doi.org/10.2298/jsc121010149s.

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Two zirconia samples were prepared by precipitation from aqueous zirconium oxychloride and zirconil sulphate solutions with potassium hydroxide. The prepared zirconia samples were amorphous. The pHpzc values of zirconia samples, determined from NaCl and NaNO3 solutions, were 6.6 ? 0.1 and 6.9 ? 0.1, respectively. After prolonged hydration of zirconia in doubly distilled water, pHpzc decreased to 4.7 ? 0.3. Crystallization into tetragonal (metastable) + monoclinic zirconia appeared at 691 K. Above 873 K, tetragonal metastable phase changes to monoclinic one. It was shown that crystallite sizes of zirconia treated at 673 - 1273 K increased from 9.5 nm to 40.5 nm, respectively. The increase in temperature from 385 K to 1070 K increased the pHpzc of zirconia samples from 6.6 to 9.0, respectively.

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Valéro, Rémi, Bernard Durand, Jean-Louis Guth y Thierry Chopin. "Influence des ions fluorure et de la silice amorphe sur la solubilité des gels de zircone et caractérisation des fluoro-complexes de zirconium en milieu moyennement acide". Canadian Journal of Chemistry 77, n.º 12 (5 de diciembre de 1999): 2099–104. http://dx.doi.org/10.1139/v99-204.

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The solubility of zirconia gels versus pH is studied in order to state first the influence of F- ions alone, then the influence of the simultaneous presence of F- and amorphous silica. Two concentrations of F- ions are chosen, 0.094 and 0.314 mol L-1, corresponding to initial molar ratios F/Zr = 0.6 and 2.0. Metal fluorocomplexes formed at pH 0.5 and 2.5 are characterized by 19F NMR. The influence of F- on the solubility of zircon is also studied. It is shown that the formation of silicon complexes rich in fluorine shifts the equilibriums between the zirconium fluorocomplexes toward the complexes poor in fluorine and that, in the presence of F-, the crystallization of zircon by hydrothermal synthesis can be forecasted, for pH values in the range 0-10.Key words: zirconia gels, silica, zircon, fluoride ions, solubility, 19F NMR.

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Lin, Cui Hua, Xiong Fei Zhang, Yang Hou, Ya Li Wang y Gui Wang. "Synthesis of Calcium Oxide Stabilized Cubic Zirconia Powders by Electrochemical Method". Advanced Materials Research 233-235 (mayo de 2011): 2403–8. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.2403.

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Calcium oxide stabilized cubic zirconia powders were synthesized with electrochemical method using analytical reagent zirconium oxychloride and calcium oxide as the raw materials. From XRD analysis, zirconia powders doped calcium oxide are mainly being as cubic phase under the temperature lower than 1100°C. While the zirconia powders which did not doped calcium oxide were transformed from cubic phase to monoclinic phase when the powders were sintered at 750°C. The calcium oxide used as dopant in zirconia has two advantages, the first is that it can stabilize the cubic zircnnia, the second is that it can restrain the zirconia powders’ growing up.

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Damonte, Laura C., Patricia C. Rivas, Alberto F. Pasquevich, Fernanda Andreola, Federica Bondioli, Anna M. Ferrari, Laura Tositti y Giorgia Cinelli. "Structural Characterization of Natural and Processed Zircons with X-Rays and Nuclear Techniques". Advances in Condensed Matter Physics 2017 (2017): 1–9. http://dx.doi.org/10.1155/2017/9707604.

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In ceramic industry, zircon sand is widely used in different applications because zirconia plays a role as common opacifying constituent. In particular, it is used as a basic component of glazes applied to ceramic tiles and sanitary ware as well as an opacifier in unglazed bulk porcelain stoneware. Natural zircon sands are the major source of zirconium minerals for industrial applications. In this paper, long, medium, and short range studies were conducted on zirconium minerals originated from Australia, South Africa, and United States of America using conventional and less conventional techniques (i.e., X-Ray Diffraction (XRD), Positron Annihilation Lifetime Spectroscopy (PALS), and Perturbed Angular Correlations (PAC)) in order to reveal the type and the extension of the regions that constitute the metamict state of zircon sands and the modifications therein produced as a consequence of the industrial milling process and the thermal treatment in the production line. Additionally, HPGe gamma-ray spectroscopy confirms the occurrence of significant levels of natural radioactivity responsible for metamictization in the investigated zircon samples. Results from XRD, PALS, and PAC analysis confirm that the metamict state of zircon is a dispersion of submicron disordered domains in a crystalline matrix of zircon.

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Más fuentes

Tesis sobre el tema "Zirconi"

LIBERATO. "Stratigraphic, sedimentological and provenance study on the Permian-Triassic sequences of southern Gondwana: comparison between Victoria Land (Antarctica) and Tasmania and paleoenvironmental implications". Doctoral thesis, Università di Siena, 2020. http://hdl.handle.net/11365/1118448.

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La tesi di dottorato è stata svolta seguendo un approccio multidisciplinare che ha riguardato lo studio stratigrafico-sedimentologico, petrografico e geochimico di depositi fluviali Permo-Triassici affioranti in Terra Vittoria meridionale e settentrionale. Con lo scopo di ottenere e comprendere le varie peculiarità di ogni singola unità deposizionale (Permo-Triassica, affiorante ad Allan Hills, Terra Vittoria meridionale), è stato eseguito uno studio di dettaglio multidisciplinare con diverse tecniche e metodologie analitiche. I risultati prodotti sono stati utilizzati per comparare aree limitrofe come il Morris Basin (zona transizionale tra la TVm e TVs), in modo da poter ricostruire l’evoluzione geologico-stratigrafica. I dati sono presentati nella Tesi nell’ordine seguente: 1) comprensione e ricostruzione geologico-stratigrafica dell’area di interesse ad Allan Hills (Terra Vittoria meridionale, TVm, Antartide) 2) analisi sedimentologica (analisi di facies) 3) analisi composizionale delle arenarie di Allan Hills (TVm) e Morris Basin (TVm-TVs, analisi modale con metodo Gazzi-Dickinson) 4) studio dei minerali pesanti presenti in sezione sottile (Allan Hills e Morris Basin, conteggio per clasti) 5) analisi composizionale dei granati e delle muscoviti detritici di Allan Hills (TVm) 6) geocronologia degli zirconi detritici di Allan Hills (TVm) Nella prima parte del dottorato è stato fondamentale reinterpretare ed elaborare circa 800 metri di colonne stratigrafiche ottenute nella fase di campagna dai ricercatori in Antartide, per comprendere i rapporti stratigrafici e la geologia dell’area (punto 1). La sezione geologica del settore nord-est di Allan Hills mostra un andamento degli strati debolmente inclinati verso N-NE (monoclinale) di una decina di gradi. La successione Permo-Triassica affiora in relativa continuità fatta eccezione per aree con diffuse coperture detritiche-nivali e dicchi Giurassici. Il punto 2 è stato acquisito con uno studio ad alta risoluzione (scala decimetrica) eseguendo un’analisi di facies, al fine di ricostruire i paleoambienti della successione di Allan Hills. Seguendo lo schema classificativo ed interpretativo di Miall (2014), più di una decina di litofacies e associazioni di facies sono state interpretate. Il risultato più rilevante sembrerebbe evidenziare fasi trasgressive nel Permiano medio-superiore e nel Triassico medio-superiore, come probabile risposta a cambiamenti morfo-strutturali bacinali dovuti a fattori tettonici e a possibili cambiamenti climatici (come evidenziato nella Formazione Feather Conglomerate). In seguito, a scala microscopica sono state caratterizzate in modo quantitativo le arenarie (punti 3 e 4), al fine di poter individuare differenti petrofacies suddivise per unità formazionali. Differenze rilevanti sono state riscontrate tra le arenarie Permiane e quelle Triassiche; in primis una maggiore maturità composizionale dovuta ad un maggiore trasporto (più cicli di sedimentazione) e ad un clima umido con un weathering index intenso al passaggio PTT (Permian-Triassic Transition). Allo stesso modo, lo studio composizionale del granato e della muscovite (punto 5) sembra evidenziare un maggiore grado metamorfico di provenienza, nel Permiano medio-superiore (Formazione della Weller Coal Measures) e Triassico medio-superiore (Formazione della Lashly), rispetto al Triassico inferiore (Feather Conglomerate). In quest’ultima infatti, le muscoviti sono meno ricche in fengite ed i granati diminuiscono drasticamente (nessun dato composizionale). Questo fenomeno indica probabilmente un repentino cambiamento climatico a favore dell’alterazione. Questo approccio è stato di aiuto nel definire ulteriormente le differenze tra le unità Permiane e Triassiche e le loro provenienze. Con lo stesso scopo, sono state effettuate le datazioni su zirconi detritici di Allan Hills (TVm, punto 6). Tre aspetti fondamentali ne risultano: - nei sedimenti Permiani lo spettro di età è più ampio e si hanno buone percentuali in tutti i range, variabili dal Devoniano all’Archeano. Picchi di età “greenvilliana” sono da evidenziare mentre non sono presenti zirconi Permo-Triassici. - Gli zirconi detritici del Triassico inferiore hanno origine principalmente dall’Orogene di Ross, mostrando forse un unroofing regionale. Con un picco minore, ma pur sempre evidente, ci sono età “greenvilliane”. - Nel Triassico medio-superiore si registra l’attività vulcanica Permo-Triassica del margine meridionale del Gondwana. Sembra evidente come il bacino della Terra Vittoria meridionale fosse, durante il Permiano, morfologicamente separato dal bacino contiguo nelle Central Transantarctic Mountains (CTM). Un processo di cattura fluviale, probabilmente da porsi alla transizione tra il Permiano superiore ed il Triassico inferiore, potrebbe spiegare sia lo spettro composizionale che di età degli zirconi. Una volta ottenuto un quadro completo di ogni singola unità stratigrafica, è stata effettuata una prima comparazione litologico-petrografica con una parte significativa di campioni arenacei sparsi per la Terra Vittoria (Morris Basin e Terra Vittoria settentrionale). Con la missione in Tasmania (febbraio 2019), è stato possibile confrontare in modo preliminare le arenarie delle successioni Tasmane coeve a quelle antartiche. Granulometricamente più fini di quelle del Victoria Group, mostrano rapporti sabbia/fango in alcuni casi confrontabili (dal Triassico inferiore al superiore). Il PTT sembra collocarsi tra superfici di discordanza semplice meno erosivi a sud rispetto al settore nord-nord-est del bacino Tasmano. Questo potrebbe essere attribuito ad una estrema variabilità degli ambienti sedimentari paleozoici e dei processi deposizionali e tettonici. Si rinvengono spessori ingenti di livelli di siltiti argillose rossastre (paleosuoli) con spessori molto variabili. Al contrario, dai dati di questo studio, il PTT ad Allan Hills potrebbe connotarsi per avere caratteri transizionali o di paraconcordanza. Il confronto geologico tra macroregioni diverse e distanti, Terra Vittoria settentrionale e meridionale (TVs TVm), è stato anche rafforzato grazie allo studio analitico di tesi e articoli prodotti negli anni precedenti da altri studiosi. I risultati più importanti provengono dall’analisi di facies e dalle composizioni mineralogiche: - Tutte le petrofacies del Morris Basin sono correlabili con quelle di Allan Hills (TVm) - Una parte dei depositi del Permiano nel bacino della TVs sembra contenere più litici plutonici e metamorfici (circa 5%) rispetto a successioni analoghe ad Allan Hills ed in Terra Vittoria meridionale in generale. - La litostratigrafia di Thern Promontory (TVs) sembra affine, in termini di facies e petrofacies, ad una fase post-glaciale Permiana, come evidenziano alcuni dati in TVm, anche se con spessori notevolmente ridotti. - Le arenarie di Stewart Heights (TVs) e di Pudding Butte (Morris Basin) hanno caratteri sedimentologici e petrologici comparabili con quelle del Triassico inferiore ad Allan Hills (TVm). - Nella Section peak Fm. (simil-Lashly Fm) sono composizionalmente litareniti e litareniti feldspatiche come quelle della SVL. - I bacini della TVs e TVm, in un periodo compreso tra il Triassico medio-Giurassico inferiore, registrano la comparsa di litici vulcanici lavici (Formazioni di Section Peak e Lashly). - Anche per i granati e le miche detritiche triassiche le composizioni sono correlabili tra la TVs e TVm. In conclusione, il presente studio pone nuovi vincoli petro-stratigrafici e paleogeografici in Terra Vittoria meridionale e settentrionale, in quello che era il paleomargine meridionale del Gondwana. In particolare, lo studio sedimentologico e di provenienza dei sopracitati depositi ha consentito di produrre ed apportare una grande mole di nuovi dati, la cui elaborazione consente di evidenziare una storia geologica evolutiva ben più articolata e complessa di quella conosciuta.

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PASTORE, GUIDO. "Sand provenance and dispersal in the Sahara and Kalahari deserts: fluvial aeolian interactions and climatic implications". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2023. https://hdl.handle.net/10281/404096.

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Questa tesi presenta lo studio della composizione delle sabbie dei più grandi deserti africani e dei fiumi limitrofi al fine di illustrare gli effetti dell'interazione tra processi fluviali ed eolici sul trasporto di sedimenti in ambiente arido. Le sabbie del Sahara, del Kalahari e dello Zambesi sono state analizzate mediante petrografia, mineralogia della frazione pesante e geocronologia U-Pb di zirconi detritici. Per il caso di studio dello Zambesi sono stati analizzati anche la geochimica elementare, gli isotopi del Nd e i minerali delle argille. I campi di dune del Sahara sono, con poche eccezioni, composti da pura sabbia quarzosa con suite di minerali pesanti molto impoverite, dominate da minerali ultrastabili. La composizione varia solamente lungo la Valle del Nilo, in prossimità della catena dell'Anti-Atlante e alla provincia vulcanica libica. La sabbia delle dune del Kalahari è costituita principalmente da quarzo associato a minerali pesanti ultrastabili. La composizione varia solo ai margini occidentali e orientali del deserto, riflettendo in parte l’apporto fluviale di primo ciclo dai basamenti cristallini nella Namibia centrale, nello Zimbabwe occidentale e nelle dune vicino alle cascate Vittoria dove i sedimenti sono erosi dalle lave del Karoo. La morfologia segmentata del fiume Zambesi si riflette nella sua mineralogia e geochimica. La sabbia quarzosa erosa dalle dune del deserto del Kalahari viene progressivamente arricchita in frammenti litici basaltici e clinopirosseno. Successivamente nuovo apporto di sedimenti avviene a valle del lago Kariba, documentando una graduale diminuzione del quarzo e dei minerali ultrastabili. La composizione diventa quarzo-feldspatica nel tratto finale. L'abbondanza di feldspato nella sabbia del basso Zambesi non ha equivalenti tra i grandi fiumi sulla Terra e supera di gran lunga quella nei sedimenti del delta e della piattaforma, rivelando che il segnale di provenienza dell’alto Zambezi ha cessato di essere propagato a valle dopo la chiusura delle grandi dighe. La smectite, dominante nei fanghi generati dai basalti del Karoo o nel clima equatoriale delle pianure mozambicane, prevale su illite e kaolinite. La geochimica indica: l'aggiunta di quarzo per riciclo; l'erosione dei basalti del Karoo; l’erosione dei basamenti precambriani. Lo studio di Sahara e Kalahari consente di mettere a confronto deserti dominati dai processi eolici e deserti caratterizzati da una consistente interazione fluvio-eolica. Nel Sahara, la maggior parte della sabbia sembra essere riciclata da arenarie quarzose e il principale meccanismo erosivo e di trasporto è il vento. Nel Kalahari, i sedimenti sono trasportati dai fiumi che, erodendo gli orogeni ai fianchi del deserto, accumulano e omogeneizzano il detrito al centro del bacino grazie all’azione eolica. Lo studio permette di riconsiderare criticamente diversi dogmi della sedimentologia, come il presunto aumento della “maturità” mineralogica durante il trasporto fluviale: i sedimenti dell’alto Zambezi, erosi dalle dune del Kalahari e ricchi di quarzo, vengono progressivamente diluiti da sedimenti lito-feldspatici lungo il corso del fiume. Gli indici geochimici e la composizione dei fanghi sembrano indicare maggiore alterazione chimica nell'arido bacino dell’alto Zambesi rispetto al più umido Zambesi centrale e inferiore, testimoniando che il segnale di “paleo-alterazione del Kalahari” registrato nei sedimenti delle dune viene trasportato a valle fino alla foce.
This thesis presents a study of the composition of sand from desert dunes and adjacent rivers across the African continent to illustrate the effects of the interplay between fluvial and aeolian processes on sediment transport in desertic environments. The Sahara, Kalahari and Zambezi samples were analyzed by bulk-petrography, heavy-mineral, and detrital-zircon U–Pb geochronology. For the Zambezi case study, elemental geochemistry, Nd isotopes and clay minerals were also analyzed. Saharan dune fields are generally composed of pure quartzose sand with very poor heavy-mineral suites dominated by ultrastable minerals. Relatively varied compositions characterize sand along the Nile Valley, the southern front of the Anti-Atlas belt and near a basaltic field in Libya. Kalahari dune sand mostly consists of monocrystalline quartz associated with durable heavy. Composition varies only at the western and eastern edges of the desert, reflecting partly first-cycle fluvial supply eroded from crystalline basements of Cambrian to Archean age in central Namibia and western Zimbabwe. Basaltic detritus from Jurassic Karoo lavas is dominant in dunes near Victoria Falls. The segmented morphology of Zambezi River is reflected by its mineralogy and geochemistry. Pure quartzose sand recycled from Kalahari Desert dunes in the uppermost tract is next progressively enriched in basaltic rock fragments and clinopyroxene. Sediment load is renewed ﬁrst downstream of Lake Kariba, documenting a stepwise decrease in quartz and durable heavy minerals. Composition becomes quartzo-feldspathic in the lower tract. Feldspar abundance in Lower Zambezi sand has no equivalent among big rivers on Earth and far exceeds that in sediments of the northern delta, shelf, and slope, revealing that provenance signals from the upper reaches have ceased to be transmitted across the routing system after closure of the big dams. Irumide ages predominate over Pan-African, Eburnean, and Neoarchean ages. Smectite, dominant in mud generated from Karoo basalts or in the equatorial climate of the Mozambican lowlands, prevails over illite and kaolinite. Elemental geochemistry reflects quartz addition by recycling, supply from Karoo basalts, and first-cycle provenance from Precambrian basements. Sahara and Kalahari case studies allow to study in situ sand generation by wind erosion versus external fluvial supply in arid environment. In the Sahara, most sand appears to be recycled from rocks with high sand-generation potential, and the main transport mechanism is the wind saltation and dune movement. In Kalahari, sediments are fed by rivers by first cycle erosion of exposed orogens at the flanks of the desert and therein homogenised. The contrasting effect of strong recycling by wind and fresh supply from rivers are the key factor for most deserts studied in literature and their identification in terms of mineralogy and provenance is proved to be precious for present and past climatic debate. In addition, evaluating the results from the Kalahari and Zambezi studies allows to critically reconsider several dogmas, such as the supposed increase of mineralogical “maturity” during long-distance ﬂuvial transport. This is strongly affected by provenance factors: quartz-rich recycled Kalahari dune sand is progressively diluted along the Zambezi River by sediment supplied by different crustal domains. Inheritance of the “Kalahari paleo-weathering signal” by Zambezi River is highlighted also by geochemical indexes and mud composition which appear to be oddly more affected by weathering in the arid Uppermost Zambezi catchment than in the wetter Middle and Lower Zambezi.

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Carbonneau, Xavier. "Etude des propriétés thermomécaniques de mullite zircone et de zircon". Lyon, INSA, 1997. http://theses.insa-lyon.fr/publication/1997ISAL0105/these.pdf.

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Cette étude porte sur la caractérisation du comportement mécanique de mullite zircone et de zircon entre 1000 et l 300°C. Une caractérisation microstructurale fine des différentes nuances est tout d'abord réalisée, avec notamment de nombreuses observations en microscopie transmission. Ceci a pour but de mieux connaître la localisation et la composition de la phase vitreuse. La propagation des fissures à haute température est ensuite étudiée grâce à des essais de double torsion. La guérison des fissures observée au cours de ces essais est plus particulièrement étudiée dans le cas du zircon. Des mesures de spectrométrie mécanique ont aussi été réalisées pour mettre en évidence des mécanismes liés à la présence de phase vitreuse. Enfin une étude du comportement en fluage a été réalisée par des essais de flexion. Ces résultats sont complétées par une série d'essais sur des éprouvettes préalablement indentées ce qui permet de mieux comprendre le comportement à la rupture, et a montré l'existence d'un seuil dans le mode de propagation des fissures. Ces résultats ont pu être rapprochés de ceux obtenus en double torsion
The high temperature mechanical properties of mullite zirconia obtained by reaction sintering, and zircon have been studied. Numerous transmission electron microscopy observations have been conducted to obtain an accurate microstructural characterization, and a better knowledge of the glassy phase composition and localization. Crack propagation is then measured at high temperature using the double torsion technique. Crack healing observed during these tests is especially studied in the case of zircon. Internal friction measurements have also been conducted to try to characterize the glassy phase. In addition, the creep behavior has been studied using bending tests. These results are completed with others obtained on previously indented specimens to better understand the fracture behavior. A threshold has been observed in the crack propagation in zircon. These results are close to those obtained with the double torsion technique

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Carbonneau, Xavier Fantozzi Gilbert. "Etude des propriétés thermomécaniques de mullite zircone et de zircon". Villeurbanne : Doc'INSA, 1998. http://docinsa.insa-lyon.fr/these/pont.php?id=carbonneau.

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Lê, Đưc Huy Daniel Philippe Laffez Patrick. "Contribution à l'étude structurale et vibrationnelle des couches minces de zircone ZrO2 déposées sur alliage Zy-4". [S.l.] : [s.n.], 2004. http://cyberdoc.univ-lemans.fr/theses/2004/2004LEMA1021.pdf.

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Reproduction de : Thèse de doctorat : Sciences des matériaux : Le Mans : 2004. Reproduction de : Thèse de doctorat : Sciences des matériaux : Ecole Normale Supérieure de Hanoï : 2004.
Thèse soutenue en co-tutelle. Titre provenant de l'écran-titre. Bibliogr. en fin de chapitres.

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Minnaar, Ettiénne Gerald. "Microstructural and analytical characterization of plasma dissociated zircon". Thesis, Nelson Mandela Metropolitan University, 2012. http://hdl.handle.net/10948/d1015972.

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This dissertation focuses on the microstructural and analytical characterization of plasma dissociated zircon (PDZ) which was produced by the South African Nuclear Energy Corporation (NECSA). The techniques used in the analysis of the material include scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy and wavelength dispersive X-ray spectrometry (EDS and WDS), infrared spectroscopy, Raman spectroscopy and X-ray diffraction (XRD). The differences in morphology of the zirconia (ZrO2) crystals observed in the PDZ are related to the thermal history of the material. Large zirconia crystals grow in a spherulitic manner and have the monoclinic crystal structure. Some smaller crystals formed via a rapid cooling process appear to retain the tetragonal or cubic crystal structures rather than relaxing to the monoclinic structure, and this may be because such nanocrystals are stabilised by small surface area or constraints from surrounding materials. Impurity distribution analysis of the PDZ showed that majority of the impurities present in zircon segregates to the silica phase during the dissociation process. The infrared and Raman spectroscopy analysis of the PDZ material indicated that the zirconia is present in the monoclinic and tetragonal polymorphs. X-ray diffraction revealed the presence of monoclinic, tetragonal and cubic zirconia phases. Rietveld refinement of the XRD patterns revealed zirconia to be predominantly found in the monoclinic polymorph followed by the tetragonal and cubic polymorphs. A Fourier transform infrared (FTIR) spectrometer equipped with an attenuated total reflectance (ATR) cell proved to be a viable method for determining the percentage dissociated zircon in PDZ.

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Vickerfält, Amanda. "Investigation of the possibility for using ZrO2 and ZrSiO4 for Zr additions to liquid ferrosilicon". Thesis, KTH, Materialvetenskap, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-214009.

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Ferrosilicon containing 50-75% Si and 1.0-5.0% Zr is used as inoculant in the cast iron industry. Zr can be added to liquid ferrosilicon by use of Zr metal or zirconium ferroalloy (FeSiZr). Then the recovery of Zr, i.e. the fraction of Zr transferred from the additive to the ferrosilicon, as well as the hit rate on specification is high. The aim of this study was to investigate the recovery of Zr from zircon sand, ZrSiO4, and zirconia, ZrO2, in comparison to zirconium ferroalloy when added to liquid ferrosilicon with 75% Si at 1600⁰C. Also the refining effect of the different additives on Al was investigated. The experiments were carried out by stirring samples of controlled amounts of ferrosilicon and Zr additive in a graphite crucible at 1600⁰C and under inert Ar atmosphere for certain amounts of time. The reaction between ferrosilicon and Zr additive was stopped by rapid cooling of the samples. ICP-OES provided the concentration of Zr and Al and LECO O/N the concentration of O. SEM-ESD was used to examine the microstructures of ferrosilicon and Zr additive after experiments. It was found that ZrO2 was reduced by Si at the particle surface to yield dissolved Zr and ZrSiO4. The ZrSiO4 additive decomposed via two simultaneous reactions, one yielding ZrO2, Si and O2 and the other Zr, Si and O2. The recovery of Zr from ZrO2 and ZrSiO4 was significantly lower than from FeSiZr. Of ZrO2 and ZrSiO4, ZrO2 yielded the highest Zr recovery; the difference was much bigger than predicted by thermodynamics. It was discussed if that could be due to a higher reaction rate of the ZrO2, caused by the smaller size (APS 1 µm compared to d50 91 µm) and larger surface area of this addition. It was also found that utilization of density differences to separate the ferrosilicon and Zr additive did not work for zirconia under the same conditions as it worked for zircon sand, although zirconia has a higher density than zircon sand. The reason was the smaller particle size of the ZrO2 powder. No refining of Al was observed.

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Manhique, A. J. (Arao Joao). "Optimisation of alkali-fusion process for zircon sands: A kinetic study of the process". Diss., University of Pretoria, 2003. http://hdl.handle.net/2263/27817.

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Giry, Jean-Paul. "Etude du frittage-réaction alumine-zircon préparation et propriétés des céramiques zircone-mullite /". Grenoble 2 : ANRT, 1987. http://catalogue.bnf.fr/ark:/12148/cb37605469n.

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Khazeni, Nasser. "Synthesis And Characterization Of Zirconium Tungstate-zirconia Core-shell Composite Particles". Master's thesis, METU, 2013. http://etd.lib.metu.edu.tr/upload/12615316/index.pdf.

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Thermal mismatch between different components of a system could cause of problems like residual stress induced cracking, thermal fatigue or even optical misalignment in certain high technology applications. Use of materials with customized thermal expansion coefficient is a counter-measure to resolve such problems. Zirconium tungstate (ZrW2O8) with negative thermal expansion coefficient is capable of being used in synthesis of composites with tailored coefficient of thermal expansion (CTE). In this work, the sol-gel method which had been already set up in our group was characterized and the sources of the factors imposing impurities in the product were distinguished in all the steps of precursor preparation and heat treatment. In the second part of study, zirconium tungstate particles synthesized by the sol-gel method were utilized as core in synthesis of ZrW2O8&ndash
ZrO2 core&ndash
shell composite particles. Shell layer was composed of ZrO2 nanocrystallites and precipitated from an aqueous solution by urea hydrolysis. Volume of the shell was effectively controlled by concentration of the initial zirconium ion in the solutions. The rate of precipitation was a function of the ratio of initial urea concentration to zirconium ion. It is hypothesized that isolation of the ZrW2O8 within a layer of ZrO2, will be a key element in solving problems associated with reactivity of ZrW2O8 towards other components in sintering of ceramic&ndash
ceramic composites with tuned or zero thermal expansion coefficient.

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Más fuentes

Libros sobre el tema "Zirconi"

Arnold, Bożena. Zircon, Zirconium, Zirconia - Similar Names, Different Materials. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6.

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M, Ondik Helen, McMurdie Howard F. 1905-, American Ceramic Society y Phase Equilibria Diagrams Data Center (U.S.), eds. Phase diagrams for zirconium and zirconia systems. Westerville, Ohio: American Ceramic Society, 1998.

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Volʹfson, F. I. (Fedor Iosifovich), ed. Metall zlatot︠s︡vetnogo kamni︠a︡. Moskva: "Nauka", 1989.

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Dijk, Gilles van. Zircon and olivine: Characteristics, types, and uses. Hauppauge, N.Y: Nova Science Publishers, 2011.

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R, Stevens. Zirconia and zirconia ceramics. 2^a ed. Manchester, U.K: Magnesium Elektron Ltd, 1986.

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Zirconia. New York, NY: Fence Books, 2001.

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Minnis, Chelsey. Zirconia. New York, NY: Fence Books, 2001.

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E, Fletcher Andrew y Mitchell Market Records, eds. Zirconia. 3^a ed. Oxford, UK: Elsevier Advanced Technology, 1993.

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M, Hanchar John, Hoskin Paul W. O y Mineralogical Society of America, eds. Zircon. Washington, DC: Mineralogical Society of America, 2003.

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M, Hanchar John, Hoskin Paul W. O y Mineralogical Society of America, eds. Zircon. Washington, D.C: Mineralogical Society of America, 2003.

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Capítulos de libros sobre el tema "Zirconi"

Arnold, Bożena. "Zirconium: A Hardly Known Metal". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 21–27. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_6.

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Arnold, Bożena. "The Constant Confusion: An Introduction". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 1–3. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_1.

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Arnold, Bożena. "The Crystal World of Zirconium Oxide". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 53–57. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_13.

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Arnold, Bożena. "Zirconium Oxide and the Lambda Sensor". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 85–88. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_19.

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Arnold, Bożena. "Zirconium Oxide in Technology". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 75–82. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_17.

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Arnold, Bożena. "Zirconium Materials and Their Application". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 33–37. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_8.

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Arnold, Bożena. "Natural Zirconium Oxide". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 45–46. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_11.

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Arnold, Bożena. "Zircon: A Genuine Gemstone". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 9–11. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_3.

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Arnold, Bożena. "Zircon Sand: An Important Raw Material". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 17–20. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_5.

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Arnold, Bożena. "Zirconium Oxide in Dentistry". En Zircon, Zirconium, Zirconia - Similar Names, Different Materials, 89–93. Berlin, Heidelberg: Springer Berlin Heidelberg, 2022. http://dx.doi.org/10.1007/978-3-662-64269-6_20.

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Actas de conferencias sobre el tema "Zirconi"

Suzuki, M., S. Sodeoka y T. Inoue. "Study on Zircon-Based Ceramic Coating for High Temperature Oxidation Resistant Application". En ITSC2001, editado por Christopher C. Berndt, Khiam A. Khor y Erich F. Lugscheider. ASM International, 2001. http://dx.doi.org/10.31399/asm.cp.itsc2001p0049.

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Abstract Zircon is widely used as a refractory material, because of its excellent mechanical and chemical properties. Several studies on plasma sprayed zircon were reported since 70's, and it is known that zircon dissociate into silica and zirconia during the plasma spray process. Authors have been studied on plasma sprayed zircon for a protective coating application, and successfully obtained very dense coating with excellent adhesive strength by optimizing the spray parameter. However, it was also revealed that the coating had poor stability above 1500K. In this study, the effects of two different oxides additive (yttria and ceria) on the structure and stability of the plasma sprayed zircon coating above 1500K are evaluated. The addition of these oxides enhanced the amount of residual zirconia and decreased zircon after the heat treatments. Addition of yttria resulted in the coating composed of cubic zirconia and zircon, while monoclinic zirconia was formed by ceria addition.

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Suzuki, M., S. Sodeoka y T. Inoue. "Zircon-Based Ceramics Composite Coating for Environmental Barrier Coating". En ITSC2007, editado por B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima y G. Montavon. ASM International, 2007. http://dx.doi.org/10.31399/asm.cp.itsc2007p0523.

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Abstract Studies on plasma spraying of zircon (ZrSiO4) have been carried out by the authors as one of the candidates for an environmental barrier coating (EBC) application, and had reported that substrate temperature is one of the most important factors to obtain crack-free and highly-adhesive coating. In this study, several amount of yttria were added to zircon powder, and the effect of the yttria addition on the structure and properties of the coatings were evaluated in order to improve the stability of the zircon coating structure at elevated temperature. The coatings obtained were composed of yttria stabilized zirconia (YSZ), glassy silica, while the one prepared from monolithic zircon powder composed of the metastable high temperature tetragonal phase of zirconia and glassy silica. After the heat treatment over 1473K, silica and zirconia formed zircon in all the coatings. However, the coatings with the higher amount of yttria had less amount of zircon formed. This resulted in the less open porosity of the coating at elevated temperature. These yttria added coatings also showed good adhesion even after the heat treatment, while monolithic zircon coating had pealed off.

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Li, Y. y K. A. Khor. "Plasma Spray Dissociation of ZrSiO4 As the Basis of Forming ZrO2-Mullite Composites From a ZrSiO4 + AI2O3 Mixture". En ITSC2001, editado por Christopher C. Berndt, Khiam A. Khor y Erich F. Lugscheider. ASM International, 2001. http://dx.doi.org/10.31399/asm.cp.itsc2001p0237.

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Abstract Zirconia is effective in improving the fracture toughness to a number of ceramics when introduced as a reinforcement either in the form of particulate, dispersed phase, or whiskers because of its unique tetragonal-monoclinic (t → m) transformation. In this paper, the authors attempt to prepare ZrO2 reinforced Mullite by plasma spraying mixtures of zircon and alumina. Pre-mixed powders of zircon (ZrSiO4) and alumina are injected into a dc plasma jet. The plasma sprayed particles are collected in distilled water and analyzed. The dissociation of zircon in thermal plasma is a well-established fact. The present investigation aims to utilize the plasma dissociation of zircon to produced ZrO2-toughened mullite from a zircon + alumina mixture. The results indicate that the plasma sprayed powders consist of zirconia, amorphous SiO2, zircon, and alumina. It was found that ball milling and plasma spraying could yield fine grained, even amorphous and chemically homogeneous, composite powders. Recrystallization of amorphous phases and formation of mullite occurred at about 1000 °C in plasma sprayed powders. This value is more than 500 °C lower than the formation of mullite in as-milled powders. Uniform coatings with good structural integrity were obtained by plasma spraying. The relative quantity of mullite in coatings after heat treatment is about 4 times as much as that obtained in the spheroidized powders. Preheat treatment of the spheroidized powder promoted dissociation of zircon. Zirconia remained as tetragonal under 1000 °C in the sprayed coatings.

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Khor, K. A. y Y. Li. "Novel ZrO2-Mullite Composites Produced by Plasma Spraying". En ITSC 1998, editado por Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p1233.

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Abstract Zirconia can induce enhanced fracture toughness to a number of ceramics when introduced as a reinforcement either in the form of particulates, dispersed phase or whiskers because of its unique tetragonal-monoclinic transformation. This paper presents the preparation of ZrO2 reinforced mullite by plasma spraying a mixture of zircon and alumina. The dissociation of zircon into zirconia and silica in a plasma flame is well-known. Pre-mixed powders of zircon and alumina are injected into a dc plasma jet. The plasma sprayed particles are collected in distilled water and analyzed. The results indicate that the plasma sprayed powders consist of zirconia, zircon and alumina. It was found that fine, mostly amorphous and chemically homogeneous composite powders can be obtained by ball milling and plasma spraying. Recrystallization of amorphous phases and formation of mullite occurred at about 1000 °C in plasma sprayed powders. This value is more than 500 °C lower than the formation of mullite in as-milled powders. Uniform coatings with good structural integrity were obtained by plasma spraying. The amount of amorphous phases was much higher in plasma sprayed coatings than in spheroidized powders, and the relative quantity of mullite in coatings after heat treatment is about 4 times as much as that obtained in the spheroidized powders.

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Toplan, N., F. Ustel, H. O. Toplan y G. Erdogan. "Mullite-Zircon Thermal Barrier Coating Production by Plasma Spraying Process". En ITSC2008, editado por B. R. Marple, M. M. Hyland, Y. C. Lau, C. J. Li, R. S. Lima y G. Montavon. Verlag für Schweißen und verwandte Verfahren DVS-Verlag GmbH, 2008. http://dx.doi.org/10.31399/asm.cp.itsc2008p1001.

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Abstract Zircon (ZrSiO4) is a technologically important oxide ceramic material known for its high refractoriness and chemical stability. It shows excellent thermal shock resistance as a result of its very low thermal expansion coefficient and a low heat conductivity coefficient. Plasma spraying is a convenient method to produce large area coatings with high growth rates, necessary for many applications. ZrSiO4 is among the least expensive spraying materials for refractory applications. In this study, a single-step process was used to prepare mullite/zirconia ceramic composites by plasma spraying zircon/alumina mixtures. Mixtures of ZrSiO4 and Al2O3 powders with Al2O3 to SiO2 molar ratios of 3:2 were milled for 2 h in a zirconia medium using a ball mill. The as–milled powders were dried in the furnace and sintered at 1300 and 1350 °C for 2h then crushed to a size less than 100 μm. The powders were sprayed by an atmospheric plasma spray gun (Metco 3MB) using C/C+SiC ceramic matrix composite substrates. Scanning electron microscopy (SEM) was used to analyze the microstructures of the powders and plasma coatings. The phase composition analysis of the powder showed the presence of alumina and zircon. After plasma coating, alumina, zircon, and zirconia phases were determined.

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Tompkins, Hannah, Mauricio Ibanez-Mejia, Francois L. H. Tissot, Yanling Wang y Dustin Trail. "EXPERIMENTAL CONSTRAINTS ON ZIRCONIUM STABLE ISOTOPE FRACTIONATION DURING MAGMATIC ZIRCON CRYSTALLIZATION". En GSA Connects 2021 in Portland, Oregon. Geological Society of America, 2021. http://dx.doi.org/10.1130/abs/2021am-368502.

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Suzuki, M., S. Sodeoka, T. Inoue, K. Shimosaka y S. Oki. "Structure and Properties of Plasma-Sprayed Zircon Coating". En ITSC 2000, editado por Christopher C. Berndt. ASM International, 2000. http://dx.doi.org/10.31399/asm.cp.itsc2000p0333.

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Abstract Effects of spray parameters, such as spray distance, SD, and substrate temperature, Ts, and post heat treatment on the structure and properties of plasma-sprayed zircon coatings were investigated. Zircon was totally decomposed by plasma spray; the coatings were composed of tetragonal zirconia (t-ZrO2) and amorphous silica (a-SiO2), because of the rapid cooling of molten particle right after the impingement to the substrate. Porosity of the as-sprayed coatings was highly affected by both of substrate temperature and spray distance. In all range of the spray distance which had been tried in this study, higher substrate temperature resulted in lower porosity of the coatings; the coating with porosity of 2% was obtained at Ts = 1573K with SD = 95mm. Porosity also decreased with decrease of spray distance. By the heat treatment at 1473K, t-ZrO2 transformed to monoclinic zirconia (m-ZrO2) and a-SiO2 crystallized to cristobalite, respectively. Cracks in the coating disappeared, and open porosity decreased. This can be attributed to sintering of SiO2 and phase transformation of ZrO2. After the heat treatment at 1673K, the coating was composed of ZrSiO4 with dispersed fine m-ZrO2 particle. Open porosity of all the coatings increased up to 10% at this temperature. This is because of volume shrinkage during the formation of zircon.

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Lwin, Maung Tin Moe, Yusoff Mohd Amin, Hasan Abu Kassim, Burhanuddin Kamaluddin, A. K. Yahya y Shah Alam. "Modeling of Zircon (ZrSiO[sub 4]) and Zirconia (ZrO[sub 2]) using ADF-GUI Software". En PROGRESS OF PHYSICS RESEARCH IN MALAYSIA: PERFIK2009. AIP, 2010. http://dx.doi.org/10.1063/1.3469653.

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Sun, Guocheng, Shi Lin, Xu Wang y Liutao Chen. "Study of Pre-Oxidization Law and Fretting Wear Resistance of CZ2 Alloy Cladding". En 2022 29th International Conference on Nuclear Engineering. American Society of Mechanical Engineers, 2022. http://dx.doi.org/10.1115/icone29-93804.

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Abstract In the core of pressurized water nuclear reactor, coolant flow-induced vibration of Grid to rod fretting (GTRF) is the dominant factor leading to fuel rod damage. pre-oxidization treatment of zirconium cladding forming a ceramic layer on its surface is the main way to reduce the GTRF wear. In this paper, the growth law of CZ2 alloy cladding pre-oxidization zirconia ceramic layer formed in air was studied. The micro-hardness and elastic modulus of CZ2 alloy cladding and zirconia ceramic layer were measured by in-situ nano-mechanical testing system., while the morphology of these pre-oxidization zirconia ceramic layer were observed by scanning electron microscope. The fretting wear properties of the pre-oxidization zirconia ceramic layer were studied by high temperature and high pressure fretting wear tests. The results show that the pre-oxidization zirconia ceramic layer growth law of CZ2 alloy cladding at 560°C and 600°C is consistent, and the pre-oxidization zirconia ceramic layer are compact and crack-free. The pre-oxidization zirconia ceramic layer can improve the fretting wear resistance of CZ2 alloy cladding at high temperature and high pressure, and the maximum wear depth were reduced by 80%.

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Alexander, Ellen W., Casey A. Yamamoto-Hillman, Matthew Wielicki y Mark Harrison. "UNDERSTANDING OXYGEN ISOTOPES OF ZIRCON INCLUSIONS: A CASE STUDY OF QUARTZ INCLUSIONS IN TIBETAN GRANITOID ZIRCONS". En GSA Annual Meeting in Phoenix, Arizona, USA - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019am-339224.

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Informes sobre el tema "Zirconi"

Traczinski, Adriana, Felipe Carvalho de Macêdo, Ivete Aparecida de Mattias Sartori y José Mauro Granjeiro. Advantages and limitations related to the rehabilitation of edentulous jaw with implant supported prostheses made of monolithic zirconia: systematic review. INPLASY - International Platform of Registered Systematic Review and Meta-analysis Protocols, enero de 2022. http://dx.doi.org/10.37766/inplasy2022.1.0111.

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Review question / Objective: P: edentulous maxillary arch; I: Full arch rehabilitation with monolithic zirconia or veneered prosthesis retained by implants; C: none; O: Biomechanical complications (framework fracture, chipping, complications, advantages, limitations); S: RCT, nor randomized clinical trials. Condition being studied: Biomechanical complications resulting from the oral rehabilitation of edentulous maxillary arch through the use of implant-supported full arc prostheses made of monolithic zirconia. Eligibility criteria: Total edentulous maxillary arch patients; rehabilitated with implants; monolithic zirconia prostheses with full contour or vestibular face with application of feldspathic ceramics or full veneered or with segmented zirconia crowns; the condition of the opposing arch must be described; the number of maxillary implants that support the prosthesis must be a minimum of 4 implants.

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Jansen, H. J. F. Theoretical studies of zirconia and defects in zirconia. Final report. Office of Scientific and Technical Information (OSTI), noviembre de 1995. http://dx.doi.org/10.2172/132732.

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Nicholson, L. N. y J. T. Dillon. Procedures for picking zircons. Alaska Division of Geological & Geophysical Surveys, 1986. http://dx.doi.org/10.14509/1183.

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Raman, S. V., R. Bopp, T. A. Batcheller y Q. Yan. Zirconia solubility in boroaluminosilicate glass. Office of Scientific and Technical Information (OSTI), diciembre de 1995. http://dx.doi.org/10.2172/188530.

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van Breemen, O. y R. R. Parrish. Zircons record ancient geological processes. Natural Resources Canada/CMSS/Information Management, 1986. http://dx.doi.org/10.4095/210544.

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Fallas, K. M. y W. Matthews. Age dating of a bentonite in the Duo Lake Formation, western Mackenzie Mountains, Northwest Territories. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/328830.

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In the Misty Creek Embayment of the western Mackenzie Mountains, Duo Lake Formation locally includes minor volcanic deposits associated with Marmot Formation volcanism. A bentonite layer from an outcrop of graptolitic shale found in NTS map area 106-B, in the upper part of the Duo Lake Formation, was sampled for U-Pb zircon dating. Analytical results yielded a dominant population of grains with a concordia age of 439.8 ± 3.0 Ma, interpreted as the age of deposition. Minor inherited zircon populations yielded ages ranging from approximately 1200 to 2850 Ma. Observed graptolites from the same outcrop likely range from Middle Ordovician to Early Silurian and are compatible with the interpreted U-Pb age of the bentonite. Previously known Middle and Late Ordovician volcanic activity in the Misty Creek Embayment is here expanded to include Early Silurian activity, and serves as a proxy for the timing of active extensional tectonism in the basin.

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Shetty, D. Alumina reinforced tetragonal zirconia (TZP) composites. Office of Scientific and Technical Information (OSTI), enero de 1990. http://dx.doi.org/10.2172/6903642.

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Kellett, D. A. y A. Zagorevski. Overlap assemblages: Laberge Group of the Whitehorse Trough, northern Canadian Cordillera. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/326064.

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The Laberge Group was deposited during the Early to Middle Jurassic in a marginal marine environment, in the northern Canadian Cordillera. It occurs as a narrow, elongated siliciclastic unit along more than 600 km of strike length, overlapping the Intermontane terranes of southern Yukon and northwestern British Columbia. The Laberge Group was deposited on the Late Triassic Stuhini and Lewes River groups, a volcano-plutonic complex of the Stikine terrane (Stikinia), and, locally, the Kutcho Arc. It is overlain by Middle Jurassic to Cretaceous clastic units. The variations in clast composition and detrital zircon populations among these units indicate major changes in depositional environment, basin extent, and sources during the latest Triassic to Middle Jurassic. Detrital zircon populations are dominated by near contemporary Stuhini-Lewes River arc grains, consistent with dissection of an active arc. Detrital rutile and muscovite data show rapid cooling and exhumation of metamorphic rocks during the Early Jurassic. Thermochronological data indicate that basin thermal evolution was domainal, with at least five regional temperature-time histories.

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Chui, Chi On. Zirconia-germanium interface photoemission spectroscopy using synchrotron radiation. Office of Scientific and Technical Information (OSTI), abril de 2005. http://dx.doi.org/10.2172/839877.

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Worrell, W. L. Zirconia-based electrodes for solid oxide fuel cells. Office of Scientific and Technical Information (OSTI), diciembre de 1989. http://dx.doi.org/10.2172/7022625.

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