Solid Solution Powders Research Articles

Preparation of CuCr1-xFexO2 Delafossite Solid Solution Powder Via a Self-Combustion Glycine Nitrate Process

Porous CuCr1-xFexO2 (x = 0 – 1) solid solution powders were successfully prepared by glycine nitrate process without post-annealing treatment or ambient control. The structure of the powders was confirmed by X-ray diffraction. The morphology of the powders was observed by scanning electron microscopy. The morphology varied from cotton candy-like to coral-like with increases in iron (x) content. The specific surface area of self-combusted CuCr1-xFexO2 (x = 0 – 1) powders varied from 25.723 m2/g to 4.94 m2/g with increases in iron (x) content, which is greater than the specific surface area of powders prepared by solid state reaction.

Effect of Y3+ substitution on structural and photoluminescence properties of solid solutions [(Lu1−xYx)1−z Cez]3Al5O12 phosphors

Cerium activated Lu3Al5O12 garnet, efficiently substituted by Y3+ doping, and has been developed for green-yellow emitting phosphors. The powder processing of [(Lu1−xYx)1−z Cez]3Al5O12 solid solution powder were achieved through synthesis via sol–gel method. The Y3+ cationic substitutions in the LuAG host matrix have been changed from 0.05 to 0.2 at%, and their effects on structural and luminescence properties were systematically investigated. The phase formation and characteristics of solid solution were studied by means of differential scanning calorimetry (DSC), X-ray diffraction technique (XRD), Fourier transforms infrared spectroscopy (FTIR) and photoluminescence spectroscopy (PL). The DSC result shows that the crystallization of the powder precursors started at 960 °C. X-ray diffraction analysis indicated that the single and pure cubic crystalline phase was formed and no secondary phases of the garnet structure are observed. The photoluminescence spectra of these solid solutions exhibit band edge emission at 500 nm in green-yellow region attributed to the interconfigurational 5d → 4f transitions of Ce3+ ions. Additionally, the evolution of crystallite size and photoluminescence spectra with the increasing of Y3+ content is studied and discussed.

Quenching Photoluminescence of Eu(III) by Cu(II) in ZnO:Eu3++Cu2+ Compounds by Solution Combustion Method

In this study Cu2++Eu3+ co-doped ZnO(ZnO/Cu2++Eu3+) solid solution powders were synthesized by solution combustion method using as oxidant agent zinc nitrate hexahydrate and as fuel urea; the Cu2+ concentrations were 0, 1, 2, 3, 10, and 20 %Wt; the Eu3+ ion concentration was fixed in 3%Wt. The samples after were annealed at 900°C by 20 h in air. The structural results showed the largely presence of a wurtzite solid solution of Cu2++Eu3+doped ZnO, at high Cu2+ doping CuO and Eu2CuO4 phases are also present. Morphological properties were analyzed using scanning electron microscopy (SEM) technique. However it is important to remark that the Cu2+ ions suppress the Eu3+ ion photoluminescence (PL) by means of an overlap mechanism between Cu2+ absorption band and Eu3+emission band (e.g. 5D0→7F2) of the Eu3+ emission spectra.

Synthesis of powders of solid solutions between barium, strontium, and lead titanates and zirconates

We have studied the crystallization conditions of single-phase nanopowders of solid solutions between mixed oxides based on titanium(IV), zirconium(IV), and divalent metals (barium, strontium, and lead). Our results demonstrate that hydrous ammonium-containing oxohydroxo precursors to titanium(IV) and zirconium(IV) have considerable potential for use in the synthesis of such materials.

Fabrication of a Ni/MgO Nanocomposite Catalyst by Exolution

Methane steam reforming reaction is the most important chemical process to produce hydrogen or synthesis gas. Hydrogen is heavily consumed for ammonia production, the cryogenics industry and methanol production. Recently, the hydrogen demand is expected to increase as fuel cells become more widely accepted and are used more in the near future. For effective production of hydrogen or synthesis gas, the role of the reforming catalyst becomes more significant. Especially, highly active and stable catalyst is necessary for an on-site reformer for fuel cell systems. In conventional technology, the methane steam reforming reaction is conducted on supported noble metals- (Pt, Pd, Rh, Ru, and Ir) or nickel-based catalysts at temperature up to 700~800°C and steam to methane rations between 2 and 4. However, these catalysts suffer from the deactivation by agglomeration and carbon deposition. Noble metal-based catalysts are less sensitive to carbon deposition than nickel-based catalyst. However, high cost and limited availability are major concern. In this study, nickel-based nanocomposite catalysts were fabricated by exolution process. The exsolution means the process to precipitate particles from solid solution by means of the heat treatment in a specially-controlled atmosphere. This process is distinguished from the infiltration in which particles are precipitated from solutions by evaporation. First, Mg1-xNixO solid solution powders were synthesized from aqueous magnesium and nickel nitrate solution by precipitation technique and then the powder was heat-treated in reducing atmosphere at 600 to 900°C. SEM and TEM images revealed that the nano-sized nickel particles were homogeneously dispersed in the Mg1-xNixO solid solution matrix and the size and morphology of nano nickel particles can be controlled by the heat-treatment condition. Catalytic activity for the methane steam reforming or methane particle oxidation reaction and durability of the Ni/Mg1-xNixO was investigated in terms of nickel contents and sizes. Figure 1

Mechanical alloying and thermal analysis of Ta–Ti alloys

Tantalum–titanium alloys have widespread potential in biomedical applications due to their superior biocompatibility, favorable mechanical properties, high corrosion resistance, and ability to exhibit shape memory behavior. However, this system is plagued by processing difficulties due to significant differences in melting temperatures, specific weights, and vapor pressures of Ta and Ti. In the present study, mechanical alloying (MA) using high‐energy ball milling of Ti–xTa (where x = 50, 60, 70, and 85 wt%) was investigated. The alloyed powders were characterized by X-ray diffraction, electron microscopy (SEM and TEM), and differential scanning calorimetry. It was established that α-Ti (hcp) gradually dissolves into α-Ta (bcc), with the alloyed particles becoming chemically homogeneous as a bcc structure. This structure corresponds to a meta-stable phase and should decompose to yield two solid solutions, Ti-rich hcp and Ta-rich bcc. To overcome this thermodynamic preference, MA-generated Ta–Ti bcc solid solution powders possess relatively high internal strain energy.

Preparation, Infrared Emissivity and Electromagnetic Property of Sn(1-x)Fe x O2 (x = 0, 0.03, 0.06, and 0.09) Solid Solution Powders by Coprecipitation Method

Sn(1-x)Fe x O2 (x = 0, 0.03, 0.06, 0.09) solid solution powders have been prepared by coprecipitation method using tin chloride (SnCl4 · 5H2O) as the starting material, ammonium hydroxide (NH3 · H2O) as the precipitator, and ferric nitrate (Fe(NO3)3 · 9H2O) as the doping source, respectively. The phase and microstructure of the prepared powders have been characterized by X-ray diffraction (XRD) and scanning electronic microscope (SEM), respectively. The electromagnetic property in the frequency range of 8.2–12.4 GHz and average infrared emissivity in the wavelength range of 8–14 μm of prepared powders have been determined. The electromagnetic properties ( $${\varepsilon^{\prime}, \varepsilon'', \mu^{\prime}}$$ , and $${\mu''}$$ ) of prepared powders increased with increasing Fe-doping content. The electromagnetic loss mechanism has been discussed. The average infrared emissivity has exhibited the opposite trend.

Fabrication of a Ni/MgO Nanocomposite Catalyst by Exolution

A Ni(NixMg1-x)O nanocomposite catalyst was fabricated by exsolution technique from a (NixMg1-x)O solid solution powder. On reduction, Ni2+ ion close to the surface exsolved as nano particles, which were homogeneously distributed in the matrix powder surface. TEM observation suggested that the exsolution occurred preferentially at the edge surface of the matrix powder. The methane partial oxidation and hydrogen selectivity over the nanocomposite catalysts were evaluated over the temperature range, 300 to 900ºC.

Characterization of Powders of Ceria-Zirconia Solid Solution Synthesized with Additives of Polymer-net Gel

Powders of ceria-zirconia solid solution were prepared by using different molar ratio of Ce(NO3)4·6H2O and Zr(NO3)4·5H2O as raw materials and appropriate additives of C3H5 NO, C7H10N2O2and(NH4)2S2O8as polymer-net gel. The influence of the polymer-net gel on the preparation process and the effect of Ce/Zr ratio on the properties of the powders of ceria-zirconia solid solution were investigated respectively. The results show that the additives of polymer are beneficial not only to the separation of the particulates of ceria-zirconia solid solution due to the formation of a three-dimensional network of the polymer- net gel, but also to the formation of nanoporous powders of ceria- zirconia solid solution due to the burn away of polymer during the subsequent calcinations. The powders of ceria- zirconia solid solution with particle size 10- 20 nm could be prepared when the mass ratio of C3H5 NO and C7H10N2O2 was 5: 1,the dissolvability of mixed solute was 0.04 mol/L and an appropriate heat treatment process was adopted. XRD analysis revealed that the ceria-zirconia solid solutions with molar ratio of Ce/Zr in a range of 3:7-5: 5 present tetragonal crystallographic structure, while those in a range of 6: 4-7: 3 present cubic structure respectively; their lattice constant decreased with the increasing Zr+content. N2 adsorption isotherm showed that the ceria- zirconia solid solution with Ce/Zr molar ratio of 6: 4 exhibited excellent features:specific surface area of 120 m2·g- 1; aperture of 8.12 nm; pore volume of 0.22 cm3/g. SEM images showed that the ceria-zirconia solid solution powders have an alveolate-like network structure.

Effects of Fe-dopings through solid solution and grain-boundary segregation on the electrical properties of CeO2-based solid electrolyte

The 1 and 10 mol% Gd-doped ceria (1- and 10-GDC) solid solution powders were synthesized by co-precipitation method, then which were doped with 0.5 mol% Fe by the means of solid solution (SS) and preferred grain-boundary segregation (GBS), named as GDC-0.5Fe (SS) and (GBS), respectively. All the synthesized powders only show the CeO2 solid solution phase with grain sizes of 15.8~16.8 nm. Then, the corresponding GDC ceramics before and after Fe-doping were sintered at 800 °C for 1 h. The sole ceria solid solution phase appears in all the sintered samples with grain sizes of 59.8~112 nm. The Fe doping through solid solution always leads to the decrement in the electrical conductivity of both 1- and 10-GDC samples, while that through controlled grain-boundary segregation results in the increment of 10-GDC sample. The ion transference numbers of 1- and 10-GDC-0.5Fe (GBS) samples are all above 0.95 in 300~650 °C.

Translucent zirconia polycrystals prepared from nanometric powders

The aim of the present study was investigation of synthesis and sinterability of nanometric zirconia solid solution powders containing 8mol% and 3mol% of Y2O3. The powders were prepared by the hydrothermal treatment of the co-precipitated gels, which resulted in very fine powders with particle sizes <10 nm. The main problem in application of such fine powders is their tendency to form hard agglomerates. To overcome this obstacle, the aqueous suspensions of the powders were subjected to the freeze drying. It resulted in the powders composed of very weak agglomerates which were broken under pressure as low as ~1MPa. The powder compacts were sintered in oxygen atmosphere to the state of closed porosity and then HIP-ed at 1300?C to fully dense ceramics. The spectrophotometric investigations in the wave length range of 190-1100 nm indicated higher translucency of the 8mol% Y2O3-ZrO2 than the 3mol% Y2O3-ZrO2 ceramics. Most probably it should be related to the birefringence phenomenon which occurs in the latter case due to the tetragonal symmetry of this material. In the polycrystal containing 8mol% of Y2O3 this phenomenon does not occur due to its cubic symmetry. The other two factors which lead to the decreased optical transparency of the material containing 3mol% Y2O3 are its smaller grain sizes and the presence of some amount of the monoclinic phase.

(hkl)-Specific defects of MgO–CoO alloy produced by pulsed laser ablation in water

MgO–CoO particles with (hkl)-specific paracrystalline defects by pulsed laser ablation of solid-solution powders in water.

Two‐Step Carbothermal Synthesis of AlN–SiC Solid Solution Powder Using Combustion Synthesized Precursor

In the present work, a two‐step carbothermal reduction method is employed to prepare the AlN–SiC solid solution (AlN–SiCss) powders by using a combustion synthesized precursor. The precursor is prepared by low‐temperature combustion synthesis (LCS) method using a mixed solution of aluminum nitrate, silicic acid, polyacrylamide, glucose, and urea. The synthesized LCS precursor exhibits a porous and foamy uniform mixture of Al2O3 + SiO2 + C consisting of flaky particles. The carbothermal reduction in the LCS precursor is carried out in two steps. First, the precursors are calcined at 1600°C in argon for 3 h. Subsequently, the precursors are further calcined at 1600°C–1900°C in nitrogen for 3 h. The results indicate that the precursor calcined at and above 1850°C in nitrogen for 3 h yields the single‐phase AlN–SiCss powders. The synthesized AlN–SiCss powder exhibits near‐spherical particles with diameter of 200–500 nm. The experimental and thermodynamical results reveal that the formation of AlN–SiCss occurs via the diffusion of AlN into SiC by virtue of formation of a highly defective β′ intermediate during the second step reaction.

The Molten Salt Synthesis of (Y1−xEux)4Al2O9 Solid Solution Powders and Their PL Properties

(Y1−xEux)4Al2O9 solid solution powders can be easily prepared by a simple and convenient method, which effectively combined a molten salt process with a chemical co‐precipitation technique. All the samples were characterized by XRD, SEM, and photoluminescence (PL) spectra techniques. The results show that the incorporation of NaCl salt can greatly promote the formation and crystallization of (Y1−xEux)4Al2O9 crystallites, and lower their synthesizing temperature, and that their particle size and morphology strongly rely on x value, which finally dominates their PL properties. The prominent emission intensity of 5D0→7F2 transition rather than 5D0→7F1 indicates doped Eu3+ cations occupy Y3+ position in monoclinic Y4Al2O9, which is sensitive to Eu3+ local environment, and at x = 0.10, there exist a maximum PL intensity due to the concentration quenching effect.

Fabrication of NbC Reinforced Low Carbon Steel by Immersing Nb(C)–Fe Powders in Steel Melt

The preparation of in situ NbC particles reinforced steel by adding prefabricated blocks comprising Nb(C) solid solution and Fe powders into a low carbon steel melt was studied. Experimental results demonstrate that nano-sized NbC particles can be distributed uniformly in the steel matrix. Furthermore, the as-casted microstructure is refined, and the strength, ductility, and wear resistance of the steel improved notably. The proposed approaches can be practically applied to produce cast steel with significant enhancement in mechanical properties and lower cost in fabrication.

Determination of the equilibrium miscibility gap in the Pd–Rh alloy system using metal nanopowders obtained by decomposition of coordination compounds

The Pd–Rh phase diagram has been reinvestigated in the subsolidus region using X-ray diffraction, scanning and transmission electron microscopy. The true equilibrium at the miscibility boundary was achieved with the two-way approach. Nanosized powders of metastable solid solutions and two-phase palladium–rhodium mixtures were used to shorten the time required to equilibrate the system. The initial samples were prepared by decomposition of coordination compounds [Pd(NH3)2Cl2], [Rh(NH3)5Cl]Cl2, [Pd(NH3)4]3[Rh(NO2)6]2 and [Pd(NH3)4][Rh(NH3)(NO2)5].The obtained phase diagram exhibits miscibility gap wider than generally accepted with the critical point of solubility at 58at.% Rh and 820°C.

Solid Solution Cermet: (Ti,Nb)(CN)–Ni Cermet

Solid solution powders without W, (Ti,Nb)(CN) powders with a B1 structure (NaCl like), were synthesized by high energy milling and carbothermal reduction in nitrogen. The range of molar ratios of Ti/Nb for forming complete (Ti,Nb)(CN) phase was broader than that of Ti/W for the (Ti,W)(CN) phase because carbide or carbonitride of Nb had a B1 crystal structure identical to Ti(CN) while WC had a hexagonal crystal structure. The results revealed that the hardness of (Ti,Nb)(CN)-Ni cermets was higher than that of (Ti,W)(CN)-Ni cermets. The lower density of the (Ti,Nb)(CN) powder contributed to the higher hardness compared to (Ti,W)(CN) because the volumetric ratio of (Ti,Nb)(CN) in the (Ti,Nb)(CN)-Ni cermets was higher than that of (Ti,Nb)(CN) in the (Ti,W)(CN)-Ni cermets at the same weight ratio of Ni. Additionally, it was assumed that intrinsic the properties of (Ti,Nb)(CN) could also be the cause for the high hardness of the (Ti,Nb)(CN)-Ni cermets.

Microfabrication of high aspect ratio BST pillar arrays by epoxy gel casting from aqueous suspensions with added water soluble epoxy resin

The present paper reports on the successful fabrication of micro-sized pillar arrays of Ba0.6Sr0.4TiO3 (BST) electroceramics via cost effective epoxy gel casting (EGC) consolidation method based on the in situ polymerization of aqueous suspensions with added water soluble epoxy resin. The synthesized BST solid solution powder was fine milled and surface protected against hydrolysis to avoid its degradation in the aqueous environment. The micro patterning process was divided in the following steps: (i) production of high quality SU-8 master moulds by photolithography and of the respective negative replicas in PDMS (soft mould); (ii) casting of stable high solid loading BST suspensions in the soft moulds with added setting agents followed by de-moulding, drying and sintering. Patterned array of hexagonal shaped pillars with 320μm of height and side length ∼40μm were obtained with smooth side wall features along height. Various structural, mechanical and electrical properties of BST material after sintering were also measured to demonstrate the feasibility of the proposed aqueous processing route.

Preparation and electromagnetic property of Al-doped SnO2 powders by coprecipitation method in the GHz range

Al-doped SnO2 powders have been prepared by coprecipitation method at 550 °C, using tin chloride (SnCl4·5H2O) as the raw material, ammonium hydroxide (NH3·H2O) as the precipitator, and aluminum nitrate (Al(NO3)3·9H2O) as the doping source, respectively. The microstructure of the prepared powders has been characterized by X-ray diffraction and scanning electron microscope, respectively. Results show that the prepared powders were Sn(1−x)AlxO2 (x = 0, 0.03, 0.06, and 0.09) solid solution powders and the lattice constant decreased with increasing Al doping content. The electromagnetic property in the frequency range of 8.2–12.4 GHz of prepared powders has been determined. The real part (e′) and imaginary part (e″) of permittivity of prepared powders increased with increasing Al doping content. There was little change of real part (μ′) and imaginary part (μ″) of permeability of prepared powders. The electromagnetic loss mechanism has been discussed.

Ferromagnetic properties of Cu- and Fe-codoped nanocrystalline CdO powders: Annealing in hydrogen promote long-range ferromagnetic order

A mixture of cadmium acetate dihydrate, bis(acetylacetonato)copper, and tris(acetylacetonato)iron complexes is thermally co-decomposition to synthesizes Cu and Fe-codoped CdO (CdO:Cu:Fe) powders. The aim of this study is to examine the effect Fe doping on the appearance and development of room temperature ferromagnetism (RT-FM) in the presence of Cu ions as catalyst. X-ray diffraction (XRD) and X-ray fluorescence (XRF) measurements were carried out to study powders purity and crystalline structure. The XRD results show that Cu and Fe ions are incorporated in the ZnO crystal lattice by occupying Zn sites thereby forming ZnO:Cu:Fe solid solution (SS), whereas XRF confirms the purity of the obtained SS. The magnetic properties of the as-prepared and H-annealed (CdO:Cu:Fe–H) SS powders was investigated as a function of %Fe doping level. It was observed that the magnetic behaviour of pure as-synthesised CdO is mainly diamagnetic with slight FM phase. However, its behaviour with Cu and Fe codoping transforms to the mostly paramagnetic overlapped with small FM behaviour. More importantly, it was found that that annealing under H2 atmosphere induces the reduction of CdO to form pure Cd metal, resulting in total transformation to FM behaviour with strength increases consistently with doping. Furthermore, with hydrogenation a tremendous enhancement of FM parameters takes place so that the Ms increases by about 1230% reaching a very high value of 1.43emu/g for 1.8%Fe doping level of CdO.