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indicative of a transition between thermal regimes. For larger modulations frequencies, the signal-to-noise ratio becomes too small (especially for CDHA\_D sample) to obtain reliable data. The previous results must be corroborated by other photothermal techniques, such as IR

CDHA\_A 5.75 30.29 1.90 CDHA\_B 7.78 16.53 1.02 CDHA\_C 6.75 21.93 2.42 CDHA\_D 6.49 23.73 2.58

1/2 vs. f∙S plot of (a) CDHA\_A, (b) CDHA\_B, (c) CDHA\_C, and (d) CDHA\_D. The red line shows the best fit.

1/2) <sup>f</sup><sup>c</sup> ( <sup>10</sup><sup>3</sup> Hz) <sup>α</sup><sup>s</sup> ( <sup>10</sup><sup>7</sup> <sup>m</sup><sup>2</sup>

∙s 1 )

The sol–gel synthesis of calcium-deficient hydroxyapatite was successfully achieved, for four different drip rates during synthesis procedures, describing the distinctive features of the pH evolution, for each case. For the samples synthesized at drip rate values of 5, 8, 10, and

photothermal radiometry or lock-in thermography [25, 26].

7. Conclusions

Figure 11. f

92 Powder Technology

Sample Slope (mV∙s

Table 6. Thermal diffusivity of the samples.

José Bruno Rojas Trigos<sup>1</sup> \*, Yolanda Jiménez-Flores<sup>1</sup> , Víctor Suárez<sup>2</sup> , Moseratt Suárez-Quezada<sup>1</sup> and Uriel Nogal<sup>3</sup>

\*Address all correspondence to: jrojast@ipn.mx

1 Instituto Politécnico Nacional, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Unidad Legaria, Ciudad de México, Mexico

2 Cátedras CONACYT, Departamento de Química, ECOCATAL, Universidad Autónoma Metropolitana-Iztapalapa, Ciudad de México, Mexico

3 Cátedras CONACYT, Instituto Politécnico Nacional, Centro de Investigación en Ciencia Aplicada y Tecnología Avanzada, Ciudad de México, Mexico
