Characterization Techniques in Nanotechnology …
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difference between the sample and reference material, then the sample does not
undergo any chemical or physical change. On the other hand, if any reaction (physical
or chemical change) takes place, temperature difference will occur between sample
and reference material. Some changes involved absorption of heat by the sample,
and are referred to as endothermic. Examples of endothermic changes are phase
changes including melting (fusion), vaporization, sublimation, and some transitions
between two different crystal structures for a material. Chemical reactions such
as dehydration, decomposition, oxidation–reduction, and solid–state reactions can
also result in endothermic changes. Other changes result in heat that is released by
the sample and are termed exothermic. Examples of exothermic changes are phase
changes including freezing (crystallization) and some transitions between different
crystal structures. Chemical reactions such as decomposition, oxidation–reduction,
and chemisorption can also result in exothermic changes.
Typical examples of TGA/DTA curves are presented in Fig. 35. According to
Fig. 35a, b for rice husk and sugarcane bagasse (Dele-afolabi et al. 2018a, b), TGA
curves indicate that the decomposition of both rice husk and sugarcane bagasse is
gradual below 200 °C, and becomes rapid within the ranges of 316–345 °C and 300–
324 °C, respectively. DTA curves indicate exothermic peaks at 61 and 345 °C for rice
husk and 66 and 324 °C for sugarcane bagasse at higher heat flow. For two rice husks,
one obtained by combustion in a slanted moving grate reactor (RHA-MG), one in a
fluidized bed reactor (RHA-FB), and gradual weight loss is observed according to the
TGA curves (Fernandes et al. 2017). DTA for RHA-FB shows an exothermic peak
before 200 °C and endothermic peak near 800 °C. For the RHA-MG, the endothermic
reaction due to decomposition occurs before 800 °C.
3.3.4 Differential Scanning Calorimetry
Differential scanning calorimetry (DSC) measures the temperatures and heat flows
involving transitions in materials due to time and temperature change in a controlled
atmosphere. The analysis offers quantitative and qualitative information about physical and chemical changes that involve endothermic or exothermic processes, or
changes in heat capacity. DSC measures glass transitions, melting and boiling points,
crystallization time and temperature, percent crystallinity heats of fusion and reactions, specific heat capacity, oxidative/thermal stability, rate and degree of cure,
reaction kinetics, and purity. Samples to be tested usually within a weight range
of 3–5 mg can be in the bulk solid, powder (pressed), and liquid forms. Figure 36
presents the DSC scans for carbon nanotubes-reinforced Sn-5Sb composite leadfree solder showing a slight reduction in melting temperature of composite solders
compared to the unreinforced solder system (Fernandes et al. 2017).
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difference between the sample and reference material, then the sample does not
undergo any chemical or physical change. On the other hand, if any reaction (physical
or chemical change) takes place, temperature difference will occur between sample
and reference material. Some changes involved absorption of heat by the sample,
and are referred to as endothermic. Examples of endothermic changes are phase
changes including melting (fusion), vaporization, sublimation, and some transitions
between two different crystal structures for a material. Chemical reactions such
as dehydration, decomposition, oxidation–reduction, and solid–state reactions can
also result in endothermic changes. Other changes result in heat that is released by
the sample and are termed exothermic. Examples of exothermic changes are phase
changes including freezing (crystallization) and some transitions between different
crystal structures. Chemical reactions such as decomposition, oxidation–reduction,
and chemisorption can also result in exothermic changes.
Typical examples of TGA/DTA curves are presented in Fig. 35. According to
Fig. 35a, b for rice husk and sugarcane bagasse (Dele-afolabi et al. 2018a, b), TGA
curves indicate that the decomposition of both rice husk and sugarcane bagasse is
gradual below 200 °C, and becomes rapid within the ranges of 316–345 °C and 300–
324 °C, respectively. DTA curves indicate exothermic peaks at 61 and 345 °C for rice
husk and 66 and 324 °C for sugarcane bagasse at higher heat flow. For two rice husks,
one obtained by combustion in a slanted moving grate reactor (RHA-MG), one in a
fluidized bed reactor (RHA-FB), and gradual weight loss is observed according to the
TGA curves (Fernandes et al. 2017). DTA for RHA-FB shows an exothermic peak
before 200 °C and endothermic peak near 800 °C. For the RHA-MG, the endothermic
reaction due to decomposition occurs before 800 °C.
3.3.4 Differential Scanning Calorimetry
Differential scanning calorimetry (DSC) measures the temperatures and heat flows
involving transitions in materials due to time and temperature change in a controlled
atmosphere. The analysis offers quantitative and qualitative information about physical and chemical changes that involve endothermic or exothermic processes, or
changes in heat capacity. DSC measures glass transitions, melting and boiling points,
crystallization time and temperature, percent crystallinity heats of fusion and reactions, specific heat capacity, oxidative/thermal stability, rate and degree of cure,
reaction kinetics, and purity. Samples to be tested usually within a weight range
of 3–5 mg can be in the bulk solid, powder (pressed), and liquid forms. Figure 36
presents the DSC scans for carbon nanotubes-reinforced Sn-5Sb composite leadfree solder showing a slight reduction in melting temperature of composite solders
compared to the unreinforced solder system (Fernandes et al. 2017).