Synthesis of Amorphous Zirconium Dioxide from Zirconyl Nitrate in Presence of Oxalic Acid

The article presents the results of studies on preparation of amorphous zirconium dioxide from zirconium nitrate by its hydrolysis in the presence of oxalic acid. It is determined that the balance of reagents taken for synthesis (1 ml 0,025 M ZrO(NO3)2 is 1.35 ml 4 M HOOC-COOH), and the optimum temperature of the received gel drying, which is 230 ̊С, is established, too. Morphology of the obtained ZrO2 samples was explored. It has been found that the calcining temperature is independent of the size and shape forming irregular agglomerates, consisting of smaller spherical particles, whose diameter varies between 50 and 300 nm. The X-ray analysis of the sample is represented, which showed a low degree of crystallinity of the substance. IR spectroscopy data showed the presence of zirconium dioxide-characteristic peaks on the IR spectrum. The same spectrum reflects the presence of a large amount of sorbed water in the obtained sample, as well as peaks characteristic of the gas adsorbed by the sample from the environment.

Refitting of Zirconia Toughening into Open-Cellular Alumina Foams by Infiltration with Zirconyl Nitrate

The present work describes the combination of the well-established dispersion infiltration of the hollow struts in reticulated porous ceramics (RPCs) and the salt solution infiltration of the remaining strut porosity. This approach is applied on alumina foams, which are loaded subsequently with a dispersion of sub-micrometer alumina particles and a ZrO(NO3)2 solution. The zirconyl nitrate is converted into a ZrO2 transformation toughening phase during the final sintering step. As a consequence of the complex microstructure evolution during the consecutive infiltration cycles, the reinforcement phase concentrates selectively at the weak spots of RPC structures—namely, the hollow strut cavities and longitudinal cracks along the struts. As a consequence, a severe improvement of the compressive strength is observed: The average compressive strength, normalized to a porosity of 91.6 vol.%, is 1.47 MPa for the Al2O3/ZrO2 infiltrated foams, which is an improvement by 40% with respect to alumina-only loaded foams (1.05 MPa) or by 206% compared to uninfiltrated alumina RPCs (0.48 MPa). The compressive strength results are correlated to infiltration parameters and the properties of the infiltration fluids, for example the rheological behavior and the size of the Zr solute species in the respective ZrO(NO3)2 solution.

Production of zirconia-based ceramic fibers using viscose material

The paper focuses on the technology of producing ZrO2-Y2O3 ceramic fibers by impregnating twisted viscose yarns with zirconyl nitrate solutions with the addition of yttrium nitrate and subsequent heat treatment. We determined the effect of the impregnating solution concentration on the strength characteristics of the obtained ceramic fibers. As a result, we proposed a method for determining the tensile strength of discrete ceramic fibers

An Analysis of the Effect of the Zirconium Precursor of MOF-808 on Its Thermal, Structural, and Surface Properties

<p>Due to their thermal and chemical stability zirconium based Metal-Organic Frameworks (Zr-MOFs) have been extensively studied in the literature. However, many details of the influence of preparation conditions are still unclear. Most papers tend to use one type of metallic precursors for synthesizing Zr-MOFs such as MOF-808. Therefore, as far as we know, a systematic analysis of the effect of the zirconium precursor on the properties of MOF-808 has not been conducted. In this work, three different metallic precursors were employed; namely, zirconium chloride, zirconyl chloride, and zirconyl nitrate for synthesizing MOF-808 keeping all other synthesis conditions constant. The results of the study indicated the following: (i) the nature of the zirconium precursor impacts the crystalline and porous structure of MOF-808. Particularly, the presence of structural water in the precursors causes a detriment in these properties which was reflected in an increase of the relative percentage of amorphicity of the materials as well as on the formation of disorganized mesopores. (ii) In contrast to (i), the surface properties of the materials and their thermal stability under an air atmosphere were not altered by the use of the different precursors. All materials exhibited a surface populated by free and uncoordinated carboxylates as well as inorganic zirconium structures corresponding to uncoordinated oxo-clusters. The ensemble of these findings contributess to a better understanding of the features that make MOFs interesting for diverse applications. Particularly, works on defect engineering may be benefited from the insight on surface chemistry provided in this contribution.</p>

An Analysis of the Effect of the Zirconium Precursor of MOF-808 on Its Thermal, Structural, and Surface Properties

<p>Due to their thermal and chemical stability zirconium based Metal-Organic Frameworks (Zr-MOFs) have been extensively studied in the literature. However, many details of the influence of preparation conditions are still unclear. Most papers tend to use one type of metallic precursors for synthesizing Zr-MOFs such as MOF-808. Therefore, as far as we know, a systematic analysis of the effect of the zirconium precursor on the properties of MOF-808 has not been conducted. In this work, three different metallic precursors were employed; namely, zirconium chloride, zirconyl chloride, and zirconyl nitrate for synthesizing MOF-808 keeping all other synthesis conditions constant. The results of the study indicated the following: (i) the nature of the zirconium precursor impacts the crystalline and porous structure of MOF-808. Particularly, the presence of structural water in the precursors causes a detriment in these properties which was reflected in an increase of the relative percentage of amorphicity of the materials as well as on the formation of disorganized mesopores. (ii) In contrast to (i), the surface properties of the materials and their thermal stability under an air atmosphere were not altered by the use of the different precursors. All materials exhibited a surface populated by free and uncoordinated carboxylates as well as inorganic zirconium structures corresponding to uncoordinated oxo-clusters. The ensemble of these findings contributess to a better understanding of the features that make MOFs interesting for diverse applications. Particularly, works on defect engineering may be benefited from the insight on surface chemistry provided in this contribution.</p>

An Analysis of the Effect of the Zirconium Precursor of MOF-808 on Its Thermal, Structural, and Surface Properties

<p>Due to their thermal and chemical stability zirconium based Metal-Organic Frameworks (Zr-MOFs) have been extensively studied in the literature. However, many details of the influence of preparation conditions are still unclear. Most papers tend to use one type of metallic precursors for synthesizing Zr-MOFs such as MOF-808. Therefore, as far as we know, a systematic analysis of the effect of the zirconium precursor on the properties of MOF-808 has not been conducted. In this work, three different metallic precursors were employed; namely, zirconium chloride, zirconyl chloride, and zirconyl nitrate for synthesizing MOF-808 keeping all other synthesis conditions constant. The results of the study indicated the following: (i) the nature of the zirconium precursor impacts the crystalline and porous structure of MOF-808. Particularly, the presence of structural water in the precursors causes a detriment in these properties which was reflected in an increase of the relative percentage of amorphicity of the materials as well as on the formation of disorganized mesopores. (ii) In contrast to (i), the surface properties of the materials and their thermal stability under an air atmosphere were not altered by the use of the different precursors. All materials exhibited a surface populated by free and uncoordinated carboxylates as well as inorganic zirconium structures corresponding to uncoordinated oxo-clusters. The ensemble of these findings contributess to a better understanding of the features that make MOFs interesting for diverse applications. Particularly, works on defect engineering may be benefited from the insight on surface chemistry provided in this contribution.</p>

Preparation and Characterization of Pb(Zr,Ti)O3 Obtained by the Pechini Method

The aim of this work was to synthesize lead zirconate titanate, Pb(Zr0.52Ti0.48)O3 (PZT) via Pechini method, to characterize the polymeric precursor through differential thermal analysis and thermogravimetric analysis, as well as to characterize the PZT powder through x-ray diffraction and scanning electron microscopy with energy-dispersive spectroscopy. In this work, the metallic precursors used during the PZT synthesis were titanium IV isopropoxide, zirconyl nitrate and lead nitrate; citric acid and ethylene glycol were used as chelating and polymerizing agents, respectively. The polymeric precursor was calcined at 800°C for two hours in a muffle oven. The main results showed that the polymeric precursor undergoes decomposition at approximately 316°C and PZT is crystallized around 722°C. It was confirmed that the PZT powder has chemical composition in the morphotropic phase boundary and its morphology consists of agglomerates of particles. Finally, it was proved that the PZT powder is crystalline, with the predominance of the tetragonal phase.