Synthesis of metastable tetragonal (t′) zirconia-calcia solid solution by pyrolysis of organic precursors and coprecipitation route

1996 ◽  
Vol 11 (6) ◽  
pp. 1410-1420 ◽  
Author(s):  
Masatomo Yashima ◽  
Masato Kakihana ◽  
Koutaroh Ishii ◽  
Yasuro Ikuma ◽  
Masahiro Yoshimura
Keyword(s):  
Solid Solution ◽  
Aqueous Solution ◽  
Axial Ratio ◽  
Chemical Processes ◽  
The Other ◽  
Ca Ions ◽  
Scattering Study ◽  
Citrate Gel Process ◽  
Organic Precursors ◽  
Coprecipitation Route

Three kinds of chemical processes, citrate gel process, acetate gel process, and coprecipitation route, have been applied to the synthesis of homogeneous metastable tetragonal (t′) and cubic solid solutions of ZrO2−X mol% CaO (X = 4–20). From a Raman scattering study, the citrate gel process based on the gelation of the aqueous solution of citric acid containing Zr and Ca ions was found to produce compositionally homogeneous samples in comparison with the other two methods. The axial ratio c/a decreases with increasing concentration of CaO and becomes unity around 8–10 mol% CaO composition.

scholarly journals Removal of Chromium from Aqueous Solution Using Modified Pomegranate Peel:Mechanistic and Thermodynamic Studies

2009 ◽  
Vol 6 (s1) ◽  
pp. S153-S158 ◽  
Author(s):  
Tariq S. Najim ◽  
Suhad A. Yassin
Keyword(s):  
Activation Energy ◽  
Solid Solution ◽  
Aqueous Solution ◽  
Adsorption Process ◽  
Batch Process ◽  
The Other ◽  
Water Molecules ◽  
Pomegranate Peel ◽  
Solution Interface ◽  
Adsorbent Surface

Modified pomegranate peel (MPGP) and formaldehyde modified pomegranate peel (FMPGP) were prepared and used as adsorbent for removal of Cr(VI) ions from aqueous solution using batch process. The temperature variation study of adsorption on both adsorbents revealed that the adsorption process is endothermic, from the positive values of ∆H˚. These values lie in the range of physisorption. The negative values of ∆G˚ show the adsorption is favorable and spontaneous. On the other hand, these negative values increases with increase in temperature on both adsorbents, which indicate that the adsorption is preferable at higher temperatures. ∆S˚ values showed that the process is accompanied by increase in disorder and randomness at the solid solution interface due to the reorientation of water molecules and Cr(VI) ions around the adsorbent surface. The endothermic nature of the adsorption was also confirmed from the positive values of activation energy, Ea, the low values of Ea confirm the physisorption mechanism of adsorption. The sticking probability, S*, of Cr(VI) ion on surface of both adsorbents showed that the adsorption is preferable due to low values of S*(0< S*< 1 ), but S*values are lower for FMPGP indicating that the adsorption on FMPGP is more preferable .

scholarly journals Structural and Raman Vibrational Studies ofCeO2-Bi2O3Oxide System

2009 ◽  
Vol 2009 ◽  
pp. 1-4 ◽  
Author(s):  
L. Bourja ◽  
B. Bakiz ◽  
A. Benlhachemi ◽  
M. Ezahri ◽  
J. C. Valmalette ◽  
...  
Keyword(s):  
Solid Solution ◽  
Raman Spectroscopy ◽  
Phase Changes ◽  
Phase System ◽  
X Ray Diffraction ◽  
X Ray ◽  
Vibrational Studies ◽  
Coprecipitation Route

A series of ceramics samples belonging to theCeO2-Bi2O3phase system have been prepared via a coprecipitation route. The crystallized phases were obtained by heating the solid precursors at600∘Cfor 6 hours, then quenching the samples. X-ray diffraction analyses show that forx<0.20a solid solutionCe1−xBixO2−x/2with fluorine structure is formed. For x ranging between 0.25 and 0.7, a tetragonalβ′phase coexisting with the FCC solid solution is observed. For x ranging between 0.8 and 0.9, a new tetragonalβphase appears. Theβ′phase is postulated to be a superstructure of theβphase. Finally, close tox=1, the classical monoclinicα Bi2O3structure is observed. Raman spectroscopy confirms the existence of the phase changes as x varies between 0 and 1.

A new three-dimensional anionic cadmium(II) dicyanamide network

2014 ◽  
Vol 70 (11) ◽  
pp. 1054-1056 ◽  
Author(s):  
Qiang Li ◽  
Hui-Ting Wang
Keyword(s):  
Crystal Structure ◽  
Aqueous Solution ◽  
Unit Cell Volume ◽  
Three Dimensional ◽  
Building Blocks ◽  
The Other ◽  
Dimensional Structure ◽  
Cadmium Nitrate ◽  
Nitrate Tetrahydrate ◽  
Anionic Framework

A new cadmium dicyanamide complex, poly[tetramethylphosphonium [μ-chlorido-di-μ-dicyanamido-κ4N1:N5-cadmium(II)]], [(CH3)4P][Cd(NCNCN)2Cl], was synthesized by the reaction of tetramethylphosphonium chloride, cadmium nitrate tetrahydrate and sodium dicyanamide in aqueous solution. In the crystal structure, each CdIIatom is octahedrally coordinated by four terminal N atoms from four anionic dicyanamide (dca) ligands and by two chloride ligands. The dicyanamide ligands play two different roles in the building up of the structure; one role results in the formation of [Cd(dca)Cl]2building blocks, while the other links the building blocks into a three-dimensional structure. The anionic framework exhibits a solvent-accessible void of 673.8 Å3, amounting to 47.44% of the total unit-cell volume. The cavities in the network are occupied by pairs of tetramethylphosphonium cations.

Protein cluster formation in aqueous solution in the presence of multivalent metal ions – a light scattering study

Soft Matter ◽  
2014 ◽  
Vol 10 (6) ◽  
pp. 894-902 ◽  
Author(s):  
Daniel Soraruf ◽  
Felix Roosen-Runge ◽  
Marco Grimaldo ◽  
Fabio Zanini ◽  
Ralf Schweins ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Light Scattering ◽  
Metal Ions ◽  
Cluster Formation ◽  
Protein Cluster ◽  
Scattering Study ◽  
Multivalent Metal

A BGK MODEL FOR CHEMICAL PROCESSES: THE REACTION-DIFFUSION APPROXIMATION

1994 ◽  
Vol 04 (01) ◽  
pp. 35-47 ◽  
Author(s):  
RENATO SPIGLER ◽  
DAMIÁN H. ZANETTE
Keyword(s):  
Kinetic Model ◽  
Diffusion Approximation ◽  
Reaction Diffusion ◽  
Chemical Processes ◽  
Reaction Diffusion Equations ◽  
The Other ◽  
Diffusion Equations ◽  
Bgk Model ◽  
Chemical Substances ◽  
Chemical Effects

A BGK-type kinetic model is derived for describing the interaction of chemical substances. The ensuing equation is then solved asymptotically on certain space-time scales on which an appreciable interplay between kinetic and chemical effects, or the prevailing of one on the other, can be observed. The description of the interaction at the macroscopic level consists of a hierarchy of reaction-diffusion equations satisfied by the densities. Comparison is made with similar results previously obtained from certain phenomenological models, and illustrative examples are given.

Synthesis of ZrO2 Nanotubes by Anodization of Zr Foil

2015 ◽  
Vol 799-800 ◽  
pp. 125-129
Author(s):  
Mary Donnabelle L. Balela ◽  
April Alexa S. Lagarde ◽  
Stephen Jann A. Tamayo ◽  
Nikko S. Villareal ◽  
Ann Marielle Parreno
Keyword(s):  
Aqueous Solution ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Surface Preparation ◽  
The Other ◽  
Preparation Methods ◽  
X Ray ◽  
Anodization Time ◽  
Other Hand ◽  
Scanning Electron

Zirconia (ZrO2) nanotubes were synthesized by anodization of zirconium (Zr) foil in NH4Fand (NH4)2SO4 aqueous solution. Different surface preparation methods (electropolishing and etching) were applied on the Zr foil prior to anodizaton. In addition, the anodization time and NH4F concentration were varied. The structure and morphologies of the nanotubes and their crystallinity were confirmed using scanning electron microscope and x-ray diffractometer, respectively. ZrO2 nanotubes with large diameters and thick walls were formed at lower NH4F concentration and longer anodization time. On the other hand, smaller nanotubes with thinner walls were produced when the NH4F concentration was increased. The synthesized nanotubes were predominantly tetragonal ZrO2 with small amounts of monoclinic ZrO2.

Microstructure and Hydrogen Permeability of Duplex Phase M-ZrNi (M=V, Nb, Ta) Alloys

2006 ◽  
Vol 980 ◽  
Author(s):  
Kazuhiro Ishikawa ◽  
Naoshi Kasagami ◽  
Tomoyuki Takano ◽  
Kiyoshi Aoki
Keyword(s):  
Crystal Structure ◽  
Solid Solution ◽  
High Performance ◽  
Gas Flow ◽  
Hydrogen Permeation ◽  
Hydrogen Permeability ◽  
The Other ◽  
Cast State ◽  
X Ray ◽  
Scanning Electron

AbstractIn order to develop non-Pd based high performance hydrogen permeation alloys, microstructure, crystal structure and hydrogen permeability of duplex phase M-ZrNi (M=V and Ta) alloys were investigated using a scanning electron microscope, an X-ray diffractometer and a gas flow meter. These results were compared with those of Nb-ZrNi ones which have been previously published. The hydrogen permeation was impossible in the V-ZrNi alloys, because they were brittle in the as-cast state. On the other hand, duplex phase alloys consisting of the bcc-(Ta, Zr) solid solution and the orthorhombic ZrNi (Cmcm) intermetallic compound were formed and hydrogen permeable in the Ta-ZrNi system. The Ta40Zr30Ni30 alloy shows the highest value of hydrogen permeability of 4.1×10-8 [molH2m-1s-1Pa-0.5] at 673 K, which is three times higher than that of pure Pd.

Anisotropic Microstructure and Hydrogen Permeability of Nb-Ti-Ni Duplex Phase Alloy Prepared by Hot Forging-Rolling Technique

2006 ◽  
Vol 980 ◽  
Author(s):  
Sho Tokui ◽  
Kazuhiro Ishikawa ◽  
Kiyoshi Aoki
Keyword(s):  
Solid Solution ◽  
Hydrogen Embrittlement ◽  
Hydrogen Permeability ◽  
Rolling Direction ◽  
Hot Forging ◽  
The Other ◽  
Rolling Reduction ◽  
Eutectic Microstructure ◽  
Ni Alloys ◽  
Other Hand

AbstractIt has been demonstrated that the as-cast Nb40Ti30Ni30 duplex phase alloy, which consists of the primary (Nb, Ti) solid solution and the fine lamellar type eutectic {TiNi+(Nb, Ti)} phase, shows higher hydrogen permeability ¶ than that of pure Pd without the hydrogen embrittlement at 673K. In this alloy, the eutectic phase contributes to the suppression of the hydrogen embrittlement, while the primary one does mainly to the hydrogen permeation. It is important to note that even if the eutectic microstructure disappears and is replaced by the small spherical (Nb, Ti) phase embedded in the TiNi matrix by rolling and subsequent annealing, its high hydrogen permeability and large resistance to the hydrogen embrittlement are sustained. Furthermore, the present authors have observed that the primary (Nb, Ti) phase is largely elongated along the rolling direction. Consequently, it is expected that rolled and annealed Nb-Ti-Ni alloys show the large anisotropy of the microstructure and the hydrogen permeability. In the present work, the microstructure and hydrogen permeability ¶nof the Nb40Ti30Ni30 alloy after rolling and annealing treatments are examined in order to develop highly hydrogen permeable alloys utilizing the anisotropic microstructure.The primary (Nb, Ti) phase and the very fine eutectic {TiNi+(Nb, Ti)} phase are observed in the as-cast Nb40Ti30Ni30 alloy by scanning electron microscopy (SEM). The X-ray diffractometry (XRD) indicates that this alloy consists of the B2-TiNi intermetallic compounds and the bcc- (Nb, Ti) solid solution. The primary (Nb, Ti) phase is largely elongated along the rolling direction by forging and subsequent rolling at 1173 K. On the other hand, the eutectic microstructure becomes unclear with increasing the rolling reduction. The composite alloys in which the (Nb, Ti) phase is elongated along to the rolling direction are obtained by 69 % rolling reduction. ¶n of this sample is four times higher than that of as-cast one. On the other hand, ¶ for the sample vertical to the rolling direction is reduced to about one third of that of as-cast one. Thus, the hydrogen permeability of the Nb40Ti30Ni30 alloy varies about ten times or more depending on the direction of the primary¡]Nb, Ti¡^ phase. We conclude that it is possible to produce highly hydrogen permeable Nb-Ti-Ni alloys using the anisotropy of the microstructure prepared by hot forging and rolling.

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