Preparation of Stabilized Zirconia Using A Mixture of Rare Earth Oxides as Dopant

1994 ◽  
Vol 346 ◽  
Author(s):  
Adelina P. Santos ◽  
Rosana Z. D. Fernandes
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Phase Diagrams ◽  
Chemical Properties ◽  
Dopant Distribution ◽  
Stabilized Zirconia ◽  
Stabilization Process ◽  
Physical Chemical ◽  
Natural Mixture ◽  
Cubic Structure

ABSTRACTThe present work deals with the effect of the rare earth nature and the content of the oxide dopants on the stabilization process of zirconia based ceramics. There are two main interests in our work. The first is to verify the possibility of stabilizing a cubic structure of zirconia using a natural mixture of rare earth elements as dopant, and second, to study and to characterize its basic physical-chemical properties such as phase diagrams, zirconia stabilization models and dopant distribution.

scholarly journals Pengaruh Berbagai Parameter Ekstraksi dalam Pemisahan Unsur Tanah Jarang dengan Metode Emulsion Liquid Membrane (ELM)

2021 ◽  
Vol 17 (1) ◽  
pp. 1
Author(s):  
Handias Meilinda ◽  
Novi Noviyanti ◽  
Anni Anggraeni ◽  
Diana Hendrati ◽  
Husein H Bahti
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Liquid Membrane ◽  
Chemical Properties ◽  
Membrane Phase ◽  
Emulsion Liquid Membrane ◽  
Phase Concentration ◽  
Stirring Time ◽  
Feed Phase ◽  
Physical And Chemical

<p>Unsur Tanah Jarang (UTJ) adalah 15 elemen kelompok lantanida, ditambah skandium dan itrium yang termasuk kelompok aktinida. UTJ memiliki banyak manfaat di berbagai bidang. Sifat fisik dan kimia yang mirip antar UTJ membuatnya sulit dipisahkan sehingga pemisahan UTJ menarik dipelajari dengan berbagai macam metode, salah satunya adalah dengan menggunakan <em>Emulsion Liquid Membrane </em>(ELM). ELM merupakan metode pemisahan yang dikembangkan dari ekstraksi pelarut terdiri dari tiga fase, yaitu fase eksternal (fase umpan) yang berisi UTJ yang akan dipisahkan, fase internal (fase pengupasan), dan fase membran. Fase membran berisi surfaktan sebagai penstabil dan ligan yang akan membentuk kompleks dengan UTJ pada antarmuka fase umpan dan membawanya berdifusi ke dalam fase pengupasan. ELM merupakan metode efektif untuk pemisahan karena tahap ekstraksi dan pengupasan (<em>stripping</em>) terjadi secara bersamaan dalam satu tahap dan fase membrannya dapat digunakan kembali. Pemisahan UTJ menggunakan metode ELM dengan berbagai ligan, seperti D2EHPA, Cyanex 572, P204, dan (RO)2P(O)OPh-COOH dipengaruhi oleh berbagai parameter, seperti konsentrasi ligan, pH fase umpan, waktu pengadukan ekstraksi, kecepatan pengadukan ekstraksi, rasio fase umpan, konsentrasi fase pengupasan, konsentrasi surfaktan, dan konsentrasi fase umpan. Parameter tersebut diseleksi untuk mendapatkan kondisi optimum sehingga meningkatkan efisiensi ekstraksi dan pengupasan yang berbeda.</p><p><strong>Effect of Various Parameters in Separation of Rare Earth Elements using the Emulsion Liquid Membrane (ELM) Method. </strong>Rare Earth Elements (REEs) are 15 elements of the lanthanide group, plus scandium and yttrium, which belong to the actinide group. REEs have many benefits in various fields. Similar physical and chemical properties between REEs make it difficult to separate, thus REEs separation is interesting to study by various methods, one of which is by using an emulsion liquid membrane (ELM). ELM is a method developed from solvent extraction consisting of three phases: the external phase (feed phase) which contains REEs to be collected, the internal phase (stripping phase), and the membrane phase. The membrane phase contains surfactants as stabilizers and ligands which will form complexes with REEs in the feed phase and are designed to diffuse into the stripping phase. ELM is an effective method to involve because extraction and stripping occur together in one glass and the membrane phase can be reused. Separation of REEs using the ELM method with various ligands, such as D2EHPA, Cyanex 572, P204, and (RO)2P(O)OPh-COOH influenced by various parameters, such as ligand concentration, feed phase pH, extraction stirring time, extraction stirring speed, feed phase ratio, stripping phase concentration, surfactant concentration, and feed phase concentration. These parameters are selected to obtain optimum conditions thereby increasing the efficiency of different extraction and stripping.</p><p> </p>

Using Electron Energy-Loss Spectroscopy (EELS) To Study Rare Earth Elements In Natural Crystals

2000 ◽  
Vol 6 (S2) ◽  
pp. 206-207
Author(s):  
Huifang Xu
Keyword(s):  
Rare Earth ◽  
Energy Loss ◽  
Rare Earth Elements ◽  
Electron Energy ◽  
Energy Resolution ◽  
Electron Energy Loss Spectroscopy ◽  
Relative Concentration ◽  
Chemical Properties ◽  
Similar Chemical ◽  
Electron Energy Loss

Because of similar chemical properties of the rare earth elements (Ree), whole series of the Ree may occur in natural Ree-bearing crystals. Relative concentration of the Ree may vary as the crystallization environments change. Electron energy-dispersive spectroscopy (EDS) associated with TEM is unable to resolve Ree and other coexistence elements, such as Ba nd Ti, because of peak overlap and energy resolution (∼ 150 eV) of EDS. Figure A indicate multiple peaks from Ce only. The Cu peaks are from Cu grid holding the specimen. Electron energy-loss spectroscopy (EELS) with energy resolution of < 1 eV is able to resolve all Ree in natural Ree-bearing crystals.Natural carbonate crystals from a Ree ore deposit were investigated by using EELS associated with field emission-gun (FEG) TEM. The crystals are in a chemical series of BaCO3 - Ree(CO3)F [1]. In Figure B, EEL spectra A and B are from Ce-rich and La-rich bastnaesite (Ree(CO3)F), respectively; spectrum D is from cordylite (BaCO3 (Ree(CO3)F); spectrum E is from huanghoite (BaCO3 Ree(CO3)F), spectrum F is from BaCO3; spectrum C is from an unknown Ree-rich phase.

Oxygen diffusion in ceria doped with rare-earth elements

2017 ◽  
Vol 19 (21) ◽  
pp. 13723-13730 ◽  
Author(s):  
Johan O. Nilsson ◽  
Mikael Leetmaa ◽  
Olga Yu. Vekilova ◽  
Sergei I. Simak ◽  
Natalia V. Skorodumova
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Oxygen Diffusion ◽  
Dopant Distribution ◽  
Ion Diffusion

We examine the effects of the dopant type and the dopant distribution on the ion diffusion in ceria doped with rare-earth elements (Pr, Nd, Pm, Sm, Eu, and Gd).

scholarly journals Ecotoxicity Responses of the Macrophyte Algae Nitellopsis obtusa and Freshwater Crustacean Thamnocephalus platyurus to 12 Rare Earth Elements

2020 ◽  
Vol 12 (17) ◽  
pp. 7130
Author(s):  
Levonas Manusadžianas ◽  
Rimantas Vitkus ◽  
Brigita Gylytė ◽  
Reda Cimmperman ◽  
Mindaugas Džiugelis ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Chemical Properties ◽  
Nitellopsis Obtusa ◽  
Ionic Radii ◽  
Eu Directive ◽  
Thamnocephalus Platyurus ◽  
Median Lethal Concentrations ◽  
Freshwater Crustacean ◽  
Ree Group

Due to unique chemical properties, rare earth elements (REEs) are increasingly used in versatile technological applications. They are considered emerging environmental contaminants, since they become mobile instead of being bound in rocks. At present, the information on REE effects to aquatic biota is scarce and contradictory. This study aims to explore the ecotoxicity of 11 lanthanides (La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Er, and Lu) and yttrium (Y) to charophyte algae Nitellopsis obtusa and microcrustaceans Thamnocephalus platyurus. Median lethal concentrations (LC50) were assessed in characean cells at 8, 12, 16, 20, and 24 days of exposure, and 24-h LC50s were determined in shrimps. According to the EU−Directive 93/67/EEC hazard classification scheme and 24-day LC50 values generated for N. obtusa, REE effects were assigned from “harmful” to “very toxic” (Gd), while 24-h LC50s for T. platyurus were classified as “harmful” or “toxic” (based on nominal concentrations) and as “toxic” or “very toxic” (based on REE free ion concentrations calculated with CHEAQS Next software). The data obtained for algae showed correlations with the REE atomic numbers (r = −0.68, p < 0.05) and ionic radii (r = 0.65, p < 0.05) at the most extended 24-day exposure only. The analysis of the trends of concentration−response (c–r) curves obtained at increasing exposure durations (8–24 days), alongside the 24-day LC50s ranging within almost two orders of magnitude, allowed a more-toxic heavy REE group to be distinguished, and somewhat different modes REE actions to be envisioned for N. obtusa.

scholarly journals Garnets from Val d’Ala Rodingites, Piedmont, Italy: An Investigation of Their Gemological, Spectroscopic and Crystal Chemical Properties

Minerals ◽  
2019 ◽  
Vol 9 (12) ◽  
pp. 728 ◽  
Author(s):  
Valeria Diella ◽  
Rosangela Bocchio ◽  
Nicoletta Marinoni ◽  
Franca Caucia ◽  
Maria Iole Spalla ◽  
...  
Keyword(s):  
Rare Earth ◽  
Rare Earth Elements ◽  
Inductively Coupled Plasma ◽  
Chemical Properties ◽  
Western Alps ◽  
Drift Spectroscopy ◽  
X Ray ◽  
Heavy Rare Earth Elements ◽  
Diffuse Reflectance Infrared

In Val d’Ala (Piedmont, Western Alps, Italy), the more interesting rocks for the mineralogical research are represented by rodingites (rich in mineralized veins and fractures) associated with serpentinites in the eclogitized oceanic crust of Piemonte Zone, south of Gran Paradiso Massif. Among the vein-filling minerals, garnets are the most appreciated as mineral specimens and, in less degree despite their vivid and rich colors, for their potential as gem-quality materials. This study provides a complete gemological characterization of five faceted samples and offers new information by means of Synchrotron X-ray computed micro-tomography imaging gem features. Electron-probe microanalysis (EMPA) and laser ablation–inductively coupled plasma–mass spectrometry (LA–ICP–MS) established that the chemical composition of garnets from different localities, resulted both close to pure andradite, enriched in light rare earth elements (LREE) with a positive Eu anomaly, and grossular-andradite solid solution (grandite), enriched in heavy rare earth elements (HREE). X-ray powder diffraction analyses indicate the possible coexistence of almost pure grossular and andradite. A spectroscopic approach, commonly used with gem-like material, by Raman and diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, completes the characterization of the samples. The new data on the textural and geochemical features of the grandite and andradite garnets suggest local growth processes under various chemical and oxidation conditions of metasomatic and metamorphic fluids interacting with the host-rocks. Garnets represent long-lasting mineral records of the complex geological history of the Val d’Ala rodingitic dikes during their oceanic- and subduction-related metamorphic evolution.

Sign in / Sign up

Export Citation Format

Share Document