Nanocrystalline <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">LiFePO</mml:mi><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:math>LiFePO4 was obtained by heating amorphous nanosized <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">LiFePO</mml:mi><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:mo>.</mml:mo></mml:math>LiFePO4. The amorphous material was obtained by lithiation of <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">FePO</mml:mi><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:math>FePO4 synthesized by spontaneous precipitation from equimolar aqueous solutions of <mml:math display="inline"><mml:mi mathvariant="normal">Fe</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mo>NH</mml:mo><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo stretchy="false">)</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mo>SO</mml:mo><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo stretchy="false">)</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>⋅</mml:mo><mml:mn>6</mml:mn><mml:msub><mml:mo>H</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>O</mml:mo></mml:math>Fe(NH4)2(SO4)2⋅6H2O and <mml:math display="inline"><mml:msub><mml:mo>NH</mml:mo><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo>H</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo>PO</mml:mo><mml:mrow><mml:mn>4</mml:mn><mml:mo>,</mml:mo></mml:mrow></mml:msub></mml:math>NH4H2PO4, using hydrogen peroxide as the oxidizing agent. The materials were characterized by chemical analysis, thermogravimetric and differential thermal analysis, X-ray powder diffraction, and scanning electron microscopy. The Brunauer- Emmett-Teller method was used to evaluate the specific surface area. Nanocrystalline <mml:math display="inline"><mml:msub><mml:mi mathvariant="normal">LiFePO</mml:mi><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub></mml:math>LiFePO4 showed very good electrochemical performance delivering about the full theoretical capacity <mml:math display="inline"><mml:mo stretchy="false">(</mml:mo><mml:mn>170</mml:mn><mml:mo> </mml:mo><mml:msup><mml:mi mathvariant="normal">Ah kg</mml:mi><mml:mrow><mml:mo>−</mml:mo><mml:mn>1</mml:mn></mml:mrow></mml:msup><mml:mo stretchy="false">)</mml:mo></mml:math>(170 Ah kg−1) when cycled at the C/10 rate. A capacity fade of about 0.25% per cycle affected the material upon cycling. © 2002 The Electrochemical Society. All rights reserved.

Amorphous iron(III) phosphate was synthesized by spontaneous precipitation from equimolar aqueous solutions of <mml:math display="inline"><mml:mi mathvariant="normal">Fe</mml:mi><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mo>NH</mml:mo><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo stretchy="false">)</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo stretchy="false">(</mml:mo><mml:msub><mml:mo>SO</mml:mo><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo stretchy="false">)</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>⋅</mml:mo><mml:mn>6</mml:mn><mml:msub><mml:mo>H</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:mo>O</mml:mo></mml:math>Fe(NH4)2(SO4)2⋅6H2O and <mml:math display="inline"><mml:msub><mml:mo>NH</mml:mo><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo>H</mml:mo><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub><mml:msub><mml:mo>PO</mml:mo><mml:mrow><mml:mn>4</mml:mn></mml:mrow></mml:msub><mml:mo>,</mml:mo></mml:math>NH4H2PO4, using hydrogen peroxide as the oxidizing agent. The material was characterized by chemical analysis, thermogravimetrical analysis, differential thermoanalysis, X-ray powder diffraction, and scanning electron microscopy. The material was tested as a cathode in nonaqueous lithium cells. Galvanostatic intermittent titration technique was used to follow the lithium intercalation process. The effect of firing on the specific capacity was also tested. The material fired at 400°C showed the best electrochemical performance, delivering about 0.108 Ah g⁻¹ when cycled at C/10 rate. The capacity fade upon cycling was found as low as 0.075% per cycle. © 2002 The Electrochemical Society. All rights reserved.

Titanium biomaterials’ response has been recognized to be affected by particles size, crystal structure, and surface properties. Chemical and structural properties of these nanoparticle materials are important, but their size is the key aspect. The aim of this study is the synthesis of TiO₂ nanoparticles by the sol-gel method, which is an ideal technique to prepare nanomaterials at low temperature. The heat treatment can affect the structure of the final product and consequently its biological properties. For this reason, the chemical structure of the TiO₂ nanoparticles synthesized was investigated after each heat treatment, in order to evaluate the presence of different phases formed among the nanoparticles. FTIR spectroscopy and XRD have been used to evaluate the different structures. The results of these analyses suggest that an increase of the calcination temperature induces the formation of mixed-crystalline-phases with different content of anatase and rutile phases. The results obtained by SEM measurements suggest that an increase in the particles size accompanied by a noticeable aggregation of TiO₂ nanoparticles is due to high temperatures achieved during the thermal treatments and confirmed the presence of different content of the two crystalline phases of titanium dioxide.