Photopyroelectric Technique Research Articles

Photothermal properties of Fe3O4 nanoparticles coated with turmeric extract

In this study, we synthesized magnetite nanoparticles through a modified coprecipitation route and subsequently coated them directly with Curcuma longa extract. The resulting nanoparticles were then dispersed in distilled water to create a nanofluid. The particle size distribution ranged between 9 to 18 nm according to Transmission Electron Microscopy and Dynamic Light Scattering. The nanofluid’s thermal parameters were obtained by photothermal techniques, obtaining their thermal diffusivity, effusivity, conductivity, and heat capacity per unit volume. The Thermal Wave Resonator Cavity was employed to measure the thermal diffusivity, while the Inverse Photopyroelectric photothermal technique was used to determine the effusivity value. The obtained thermal parameters were close to the carrier liquid (distilled water), being a preliminary study that can be analyzed to improve the heat transfer application in other suspension fluids.

Photopyroelectric technique for the measurement of optical properties of pure liquids

Photopyroelectric technique, in the transmission configuration, was shown adequate for the measurement of the optical properties of pure liquids. The analytical scheme involves the scanning of the photopyroelectric signal as a function of the sample thickness. Optical absorption coefficients, at four wavelengths in the near infrared region (904 nm, 980 nm, 1310 nm, and 1550 nm), were measured for eight pure substances, distilled water and glycerol, among them. Strong optical absorption was obtained, particularly for pure liquids with a hydroxyl group in their molecular structure. In order to figure out about the influence of this chemical group on optical properties as function of the size of the molecule, optical absorption coefficient for a series of linear alcohols at 1550 nm was also measured.

Photopyroelectric technique to follow gelation and drying processes in alginate: a proof-of-concept

Photopyroelectric technique to follow gelation and drying processes in alginate: a proof-of-concept

Photopyroelectric spectroscopy and calorimetry

In this Tutorial, we present an overview of the development of the photopyroelectric (PPE) technique from its beginning in 1984 to the present day. The Tutorial is organized into five sections, which explore both theoretical and experimental aspects of PPE detection as well as some important spectroscopic and calorimetric applications. In the “Introduction” section, we present the fundamental basics of photothermal phenomena and the state-of-the-art of photopyroelectric technique. In the “Theoretical aspects” section, we describe some specific cases of experimental interest, with examples in both back and front detection configurations. Several mathematical expressions for the PPE signal in specific detection modes (combined back–front configurations and PPE–thermography methods) are also deduced. The “Instrumentation and experiment” section contains two subsections. The first describes several examples of setups used for both room temperature and temperature-controlled experiments. The second subsection is dedicated to the configuration of detection cells and to the various sensor/sample assemblies that are currently used in spectroscopic and calorimetric experiments for both liquid and solid samples. The “Applications” section is in fact a collection of experimental results dedicated to the thermal characterization of a wide range of solid and liquid samples. At the end of this section, we present some examples that have been selected to convey that the PPE technique is not only useful in the investigation of optical and thermal properties of a variety of condensed matter samples, but also to study physical and chemical processes such as molecular associations, food adulteration, or phase transitions. In “Concluding remarks,” we summarize the advantages of this technique in spectroscopic and calorimetric applications.

Study of the Thermal Properties and Lattice Disorder Effects in CdTe–Based Crystals: CdBeTe, CdMnTe, and CdZnTe

Mixed semiconductor ternary crystals were grown using the Bridgman–Stockbarger method. This is a high–temperature and high–pressure crystal growth method. Cd1–xBexTe crystals were grown in the range of composition 0 < x < 0.1, such as 0.00, 0.01, 0.03, 0.05, and 0.1. The main goal of this paper was to compare the thermal properties of CdBeTe with previously grown CdMnTe and CdZnTe–mixed ternary crystals. The photopyroelectric technique was applied to examine the thermal properties. The thermal diffusivity and effusivity values were obtained after testing all the samples, and the thermal conductivity was calculated then. As such, a complete thermal characterization of the crystals was carried out. For further characterization, the thermal conductivity versus composition was checked by applying the Sadao Adachi model. Thanks to that, we were able to determine the total thermal resistivity of the crystals and the additional resistivity which arises from the lattice disorder. As such, the disorder effects arising from substituting the native atom with a foreign one were characterized for all crystals. We were looking for the best substitution of the Cd atom in the CdTe matrix based on the compounds’ thermal properties. It turned out that Zn and Mn introduce a similar disorder, with Be being the highest one.

Analysis of various properties of l-alaninium p-toluenesulfonate single crystal for nonlinear optical applications

L-alaninium p-toluenesulfonate single crystal is a promising organic nonlinear optical material for second harmonic generation (SHG) and optical limiting applications. In this work, the slow evaporation solution growth technique was employed to grow a good quality single crystal at ambient conditions. The obtained crystal’s structure, unit cell dimensions and phase identification were done by Powder X-ray diffraction (PXRD) and found that it crystallizes in orthorhombic structure with space group P212121 and exhibits non-centrosymmetric nature. Its crystalline purity was characterized by High-Resolution X-ray diffraction (HRXRD) and found highly crystalline with minor grain boundaries. The Hirschfield surface analysis was carried out to identify major interactions. The photopyroelectric (PPE) technique was employed to determine the specific heat capacity (Cp) and thermal conductivity (k) of the grown sample. A low value of inhomogeneity in the birefringence of the titled crystal suggests its better optical quality. Photo-conductivity studies inferred that the titled compound features negative photoconductivity and the currents produced were in nanoscale. Further, the Piezoelectric coefficient (d33) was also measured. The mechanical strength was studied by giving shock waves to the crystals in terms of shock damage threshold (SDT) and by giving static indentations to the crystals in Vickers’s microhardness test. The third-order nonlinear optical properties were studied by Z-scan analysis.

Influence Of Co Doping On Structural And Band Gap Energy Properties Of ZnO Based Varistor Ceramic

Photopyroelectric (PPE) technique has been widely used in applied science and technology fields including the study of materials in thermal and optical properties. The sample, Zn1-xCox (x= 0.4, 0.8, 1.2, 1.6, 2.0 wt%) was prepared using solid state method sintered at 1200 ͦC to study the effect of concentration on the energy band gap (Eg). XRD, SEM with EDX analysis were used to characterise the materials' structure, morphology, and density. The PPE setup is used to determine band gap energy (Eg) values. The Eg shows the decreasing trend when the concentration of CoO increases

Optically induced effects on the nematic-smecticA and smecticA-smecticC phase transitions critical behaviour in photochromic liquid crystal mixtures with different nematic range

The effect of the UV light irradiation on the characteristics of the nematic-smectic-A and smecticA-smecticC phase transitions is investigated by the photopyroelectric calorimetric technique in mixtures of photochromic naphtopyran molecules with the 8¯S5 liquid crystal and the results are compared with those previously obtained in mixtures with the 8CB liquid crystal having a smaller nematic range. In 8¯S5, where the transition shows 3D-XY-like characteristics, the photoisomerization of the naphtopyran molecules to a more planar and elongated “open” form did not affect significantly the critical behaviour over the nematic-smecticA transition, while in 8CB it shifted it from a non universal to a the 3D-XY-like one. The results are discussed in terms of the effects caused by the naphtopyran molecules in their “open” form being able to be hosted in the smectic layers, while remaining confined between the planes when in their “closed” form. Similar arguments are used to also justify the dramatic increase of the transition temperature induced at the smecticA-smecticC phase transition by the UV irradiation of the 8¯S5 sample. Results obtained also in 8¯S5 -silica nanoparticles mixtures are also reported for comparison and discussed.

Thermal Diffusivity of Linear Alkanes and its Behaviour with the Size of the Chain: Study with a Photopyroelectric Technique

The knowledge of thermal properties, especially for substances in liquid phase, is very important since this state of matter is widely...

Thermal Diffusivity of Linear Alkanes and its Behaviour with the Size of the Chain: Study with a Photopyroelectric Technique

Thermal transport properties of substances are fundamental for science and engineering. Among these properties, thermal diffusivity characterizes the way materials transport heat under nonstationary conditions. The manner in which this thermal property behaves with the size or molecular configuration is very important to understand the mechanisms involved in heat transport. It is a complicated work to study variations on this thermal property taking these two variables (size and configuration) together. Linear alkanes have essentially the same spatial configuration, varying only the molecular size (the number of involved carbon atoms in the molecule), so they are ideal substances to study the behaviour of thermal properties with the molecular size alone. In this work photopyroelectric technique, taking the sample´s thickness as variable (the so-called TWRC method), is used for thermal diffusivity measurements of linear alkanes, from 1-heptane to 1-heptadecane. It is shown that this thermal property increases with the molecular size. This behaviour can be explained in a very simple way if it is considered that the increase in molecular size increases “routes” of heat transport.

Photopyroelectric Spectroscopy of Pure Fluids and Liquid Mixtures: Foundations and State-of-the-Art Applications

Since the mathematical foundations of photothermal effects in condensed phase materials were established in the middle 1970s, new photothermal methodologies have emerged based on the detection of heat generated from the absorption and non-radiative conversion of modulated radiation. Among them, photopyroelectric techniques have become very popular and widely used for a variety of studies ranging from calorimetry (photothermal calorimetry), phase transitions and the measurement of thermophysical (thermal diffusivity, effusivity and conductivity) and optical properties (photopyroelectric spectroscopy). More recently photopyroelectric detection has been used for the direct quantification of the optical absorption coefficient of condensed phase materials and has demonstrated its potential for quantitative analysis. In this work, a survey of various applications of photopyroelectric detection for the analysis of fluids and liquid mixtures is presented with special focus on theoretical and experimental progress in quantitative analytical measurements as new developments in this field.

Wheat germ, mamey seed, walnut, coconut, and linseed oil thermal characterization using photothermal techniques

The cosmetic industry has turned its attention to using vegetable products; the number of different vegetable oils used in the cosmetic industry has risen in the last years. In this work, the so-called photopyroelectric techniques are used for studying the thermal effusivity and diffusivity of wheat germ, mamey seed, walnut, coconut, and linseed oils. The thermal conductivity was calculated using a mathematical relationship and density was measured. Therefore, full thermal characterization is achieved. The obtained values for the studied oils are closed to other vegetable oils already reported. This similarity is partially a consequence of the similar chemical structure presented in this type of materials.

The high-energy milling process as a synergistic approach to minimize the thermal conductivity of PbTe nanostructures

The mechanochemical synthesis of PbTe nanostructures via the high-energy milling (HEM) process is proposed, as a synergistic approach, to minimize the thermal conductivity of this semiconductor material at room temperature. In this study, the effect of process control agent (PCA) addition on the microstructure and thermal properties of the as-milled PbTe nanostructures was also investigated. The synthesis design is based on a solid-state technique which allows enhancing the grain boundary scattering and consequently, decreases the thermal conductivity in the PbTe nanostructures. Moreover, the challenging part is the formation of coarse particles with embedded quantum dots and nanoparticles, which are expected to scatter long- and mid-wavelength phonons. In this sense, via the HEM-process, it is feasible to activate other phonon scattering modes by introducing rough-surfaced grains and nanoroughness to the particle surfaces. Overall, the thermal conductivity is decreased in the PbTe nanostructures by two means; namely, adding scattering processes and phonon group velocity, which were heightened due to the PCA added during milling. To elucidate the role of these components of the phonon thermal conductivity, atomic force microscopy and high-resolution transmission electron microscopy were used. On the other hand, photoacoustic (PA) and photopyroelectric (PP) techniques were applied to study the thermal properties of the PbTe nanostructures obtained by the HEM-process. The total thermal conductivity values of the PbTe nanostructures obtained by the PA and PP techniques were at least a half lower (1.06 W m−1 K−1) than that of bulk PbTe value counterpart (∼2.13 W m−1 K−1) and lower than those from PbTe nanomaterials (ranging from 1.5 to 2.2 W m−1 K−1) obtained via other means. The thermal conductivity values of the as-milled PbTe nanostructures were closely related to the carrier concentration experimental findings. We inferred that this strategy can be widely applicable to enhance existing thermoelectric compounds into their nanoforms by a scalable and a simple low-cost route.

Effect of the surface roughness on the measured thermal diffusivity of the ZnBeMnSe single-crystalline solids

In this work, the influence of the surface treatment of bulk samples of the single-crystals observed by means of the Atomic Force Microscopy on the measured thermal diffusivity of the material is presented and discussed. The mixed Zn1 − x − yBexMnySe crystals were grown from the melt by the modified high-pressure Bridgman method with different Be and Mn contents. The investigated specimens were first ground, then polished, chemically etched and finally annealed in zinc vapor. After each surface technological preparation the AFM images were taken and the thermal diffusivity of Zn1 − x − yBexMnySe compounds was determined by the photopyroelectric technique in the back configuration. The ground sample exhibited the highest roughness, whereas the annealed sample showed the lowest one. It has also been shown that the thermal diffusivity of the ground sample was significantly lower compared to the samples whose surface has been treated by other procedures. It was assumed that the measured thermal diffusivity had an effective value attained through the mediation of the thermal parameters of the bulk sample with those of the damaged surface layer. To analyze the results, a two-layer model proposed by J.J. Alvarado-Gil was employed. It turned out that the effective thermal diffusivity value depends much stronger on the conductivity of the system than on the diffusivity of the bulk.

Study of the electrocaloric effect in ferroelectric liquid crystals

ABSTRACTElectrocaloric effect (ECE) in two ferroelectric liquid crystalline (FLC) materials has been evaluated by mean of two indirect characterization methods: the photopyroelectric (PPE) technique and the polarization current reversal one. The obtained results show a good correspondence of the adiabatic temperature change associated with the ECE evaluated from both methods. This validates the possibility to use the PPE technique to investigate the ECE in FLCs. This study also demonstrates that FLCs can be used as electrocaloric material. More particularly, it shows that as for their solid homologous, liquid crystals displays more pronounced ECE in the vicinity of a first order transition than that measured near to second-order one.

Thermo-optical properties as complementary parameters for damage assessment of mineral oils aged under controlled conditions used in power transformers

Mineral oils are used in electric power transformers for their excellent dielectric properties. The continuous exposition to electrical discharges and thermal stresses may cause chemical adulteration in these substances which eventually could be cause of electrical catastrophic fails in the transformers. It is then important to evaluate periodically the quality of the oils to prevent major damages. The technique currently used for such purposes is gas chromatography, however its high inaccuracy iswell known. Chemical transformation of aged oils changes their thermal and optical properties and these could be used as alternative parameters for diagnostic purposes of electric power transformers. In this paper two configurations of photopyroelectric techniques were used for optical absorption coefficient (at 405 nm) and thermal diffusivity measurements of mineral oils aged up to 2300 h under controlled conditions. It was found that, at least up to this period of aging time, thermal diffusivity does not show significant differences, optical absorption coefficient at 405 nm, on the other hand, showed significant differences starting at 1000 h and then this optical parameter can potentially be used for diagnostic purposes.

Thermal Effusivity of Human Fluids

In the present study, the thermal effusivities of human fluids, such as human blood serum, urine, saliva and tears, were obtained by the photopyroelectric (PPE) technique in inverse configuration (IPPE). Human blood serum and urine were obtained from studies carried out in a government hospital for public servants in Mexico City, whereas saliva and tears were artificial. Making use of both, the amplitude and phase of the PPE signal, the thermal effusivities of each one of the mentioned human fluids were obtained. In order to obtain them, the experimental PPE data were normalized to the PPE signal with air as sample and the theoretical PPE equation was fitted to the normalized experimental data.

Thermal Characterization of a PPy/PLA Composite by Photoacoustic Calorimetry and Photopyroelectric Techniques

Recently, conductive polymers have attracted attention in the field of advanced materials. Conducting polymers include polypyrrole (PPy), which is a material with commercial applications due to its stability and electrical conductivity. As technology demands increasingly flexible devices, PPy was mixed with a biodegradable and flexible polymer, polylactic acid, in order to create a composite possessing of newer properties. As it is a new material, thermal properties of this composite such as thermal diffusivity, thermal effusivity, specific heat capacity, and thermal conductivity have been investigated through the application of photoacoustic calorimetry and photopyroelectric techniques.

Nonlinear optical single crystal of l-Cystine hydrochloride: Insights into the crystalline perfection, thermal, mechanical and optical properties for device fabrication

Now days, nonlinear optical materials are subjected to extensive research owing to their versatility towards various photonic applications. In the present article, twin free l-Cystine hydrochloride single crystals were grown using conventional slow evaporation solution technique. The powder X-ray diffraction pattern confirmed that the titled compound belongs to monoclinic crystal system having space group C2. Using FWHM of each diffracting peak, the strain present within the lattice was calculated. Through High Resolution XRD, the crystal quality was scrutinized and found that the grown single crystal is free from any type of defects and grain boundaries. For examination of optical homogeneity of the crystal, birefringence studies were conducted which revealed that there is only one fringe in the interferogram suggesting a good optical homogeneity. Further, various thermal transport parameters were calculated using Photopyroelectric technique. Apart from that, its mechanical strength was assessed at nanoscale through Nano indentation technique. Piezoelectric and ferroelectric studies were also carried out on the titled compound.

Photothermal Techniques for Thermal Characterization of Linear Alcohols

Photothermal techniques were used for the thermal characterization of linear alcohols. This was carried out by measuring the thermal diffusivity (by means of a photopyroelectric technique) and thermal effusivity (by means of a photoacoustic technique) of ten linear alcohols, from methanol to 1-decanol. The thermal conductivity and specific heat for these substances were obtained by means of their relations with the two previous thermal properties, by using the values reported for the densities of the alcohols. The values of thermal effusivity showed a decreasing behavior with the increase in length of the linear molecule, and the values of thermal diffusivity, on the other hand, showed a similar behavior but only up to 1-pentanol, from which these values began to increase; this latter behavior was also observed, although to a lesser extent, for thermal conductivities. This peculiar behavior for thermal diffusivity and thermal conductivities is attributed to the influence of the hydroxyl group, which is strong for low molecular weight alcohols, but it diminishes as the size of alcohol’s molecule increases.