Open Photoacoustic Cell Research Articles

Open photoacoustic cell for concentration measurements in rapidly flowing gas

High temporal resolution concentration measurements in rapid gas flows pose a serious challenge for most analytical instruments. The interaction of such flows with solid surfaces can generate excessive aero-acoustic noise making the application of the photoacoustic detection method seemingly impossible. Yet, the fully open photoacoustic cell (OC) has proven to be operable even when the measured gas flows through it at a velocity of several m/s. The OC is a slightly modified version of a previously introduced OC based on the excitation of a combined acoustic mode of a cylindrical resonator. The noise characteristics and analytical performance of the OC are tested in an anechoic room and under field conditions. Here we present the first successful application of a sampling-free OC for water vapor flux measurements.

Fractional dual-phase-lag heat conduction with periodic heating and photo-thermal response

We apply an extension of dual-phase-lag in thermal systems to predict the photoacoustic signal for transmission configuration and characteristics of the open photoacoustic cell technique. For this, we consider a particular case from Jeffrey?s equation as an extension of the generalized Cattaneo equations. In this context, we obtain the temperature distribution under the effects of fractional differential operators, allowing the calculation of the Photoacoustic signal for the transmission set-up. The results show a rich class of behaviors related to the anomalous diffusion connected to these fractional operators.

Use neural network in photoacoustic measurement of thermoelastic properties of aluminum foil

The objective of this paper is to present methodology of the precise and reliable determination of thermal diffusivity and linear coefficient of thermal expansion of the photoacoustic signal recorded (obtained) using open photoacoustic cell where thickness of the sample served as a control parameter. The methodology was based on the application of neural networks that were trained on numerical experiments and optimized by adding Gaussian noise to the training base that corresponded in percentage to maximum measurement uncertainty. By comparing the predictions of the neural network with theoretical fitting curve for experimental results for the aluminum sample that was 197 μm thick, it was shown that the proposed methodology achieves high precision in the determination of thermoelastic and geometrical properties of the sample.

Enhancement of the thermoelastic component of the photoacoustic signal of silicon membranes coated with a thin TiO2 film

The reduction of the photogenerated charge carriers' influence in periodically illuminated thin silicon membranes is investigated by using the experimental setup of an open photoacoustic cell in the standard range of modulation frequencies from 20 Hz to 20 kHz. It is confirmed that the deposition of a 200 nm thin film of titanium dioxide on the 30- and 50 μm silicon membrane leads to a large increase of the thermoelastic component of the photoacoustic signal, which restores the flexibility lost to the membrane under the influence of photogenerated carriers. The effect of the thermoelastic component enhancement is analyzed by observing the displacement of the tested samples along the heat propagation axis, depending on the carrier density and temperature differences on the illuminated and unilluminated sides, for different membrane thicknesses and a constant film thickness. It is found that the effect of enhancement of several orders of magnitude is more visible in thinner membranes due to higher ratios between the film and membrane thicknesses.

Numerical comparative study on the performance of open photoacoustic cells

An open photoacoustic cell has the merit of not having to frequently disassemble and reassemble to fill up with the gas, compared to the closed counterpart, whereas it has the demerit of causing acoustic radiation losses through the openings. In this paper, we have performed numerical simulations on three different types of open photoacoustic cells, H-type and T-type resonant cells and Helmholtz cell, made by attaching a couple of pipe-shaped extensions to both openings with the intent to lessen the acoustic losses and simultaneously understand the geometrical effect of the opening extensions on their performance. For the numerical study, the perturbed forms of the continuity equation, Navier-Stokes equation, energy equation, and equation of state are solved for the quality factor, acoustic pressure and resonance frequency to evaluate the performance. To predict the acoustic losses through the openings, the computational domain for the measurement of acoustic pressure is extended out of the cells. Results show that the geometrical effect of the opening extensions on the performance varies greatly with the type of open cell. In particular, the H-type open cell is the most desirable choice among the three types because of its high acoustic pressure response and enhanced quality factor. We believe that the results of this study would help us select the right type of open cell required for various practical applications.

Experimental photoacoustic observation of the photogenerated excess carrier influence on the thermoelastic response of n-type silicon

Based on the experimental and theoretical signals of an open photoacoustic cell operating with modulation frequencies from 20 Hz to 20 kHz, a significant contribution of photogenerated excess carriers on the thermal and thermoelastic responses of an n-type silicon plate is observed for the very first time. This is achieved by comparing the measured amplitude and phase of the photoacoustic signal with their corresponding theoretical thermoelastic counterparts, for high enough modulation frequencies mainly. It is shown that the amplitude of the thermoelastic component of plasma-thin samples varies about two orders of magnitude with respect to the corresponding one of plasma-thick samples. Furthermore, we find a maximal temperature difference ΔT = − 35 nK between the illuminated and non-illuminated sample surfaces, which shows that thin silicon plates with excess carriers could be used as heat sinks.

Thermal and Elastic Characterization of Nanostructured Fe2O3 Polymorphs and TiO2-Coated Fe2O3 Using Open Photoacoustic Cell

Thermal and Elastic Characterization of Nanostructured Fe2O3 Polymorphs and TiO2-Coated Fe2O3 Using Open Photoacoustic Cell

The application of artificial neural networks in solid-state photoacoustics for the recognition of microphone response effects in the frequency domain

An analysis of the application of neural networks as a reliable, precise, and fast tool in open-cell photoacoustics setups for the recognition of microphone effects in the frequency domain from 10 Hz to 100 × 104 Hz is presented. The network is trained to achieve simultaneous recognition of microphone characteristics, which are the most important parameters leading to the distortion of photoacoustic signals in both amplitude and phase. The training is carried out using a theoretically obtained database of amplitudes and phases as the input and five microphone characteristics as the output, based on transmission measurements obtained using an open photoacoustic cell setup. The results show that the network can precisely and reliably interpolate the output to recognize microphone characteristics including electronic effects in the low and acoustic effects in the high frequency domain. The simulations reveal that the network is not capable of interpolating an input including modulation frequencies. Consequently, in real applications, the network training must be adapted to the experimental frequencies, or vice versa. The total number of frequencies used in the experiment must also be in accordance with the total number of frequencies used in the network training.

Photoacoustic signal with two heating sources: theoretical predictions and experimental results for the open photoacoustic cell technique

A theoretical model for the photoacoustic signal with an analytical solution for the open photoacoustic cell technique is performed. The thermal diffusion (TD) and thermoelastic bending (TE) contributions from the sample and window of the open-cell are considered in the model. The analytical solution was submitted to simulations varying the thermal diffusivity, optical absorption coefficient, thickness and the amplitudes of the TD and TE contributions. The proposed theoretical model was applied to experimental data from different glasses, and quantitative analysis was achieved by calibrating the PA signal based on the TD and TE in an aluminum foil. The results demonstrate the reliability of the analytical solution for determining the thermal diffusivity of the samples.

Theoretical predictions for photoacoustic signal: Fractionary thermal diffusion with modulated light absorption source

We develop a theoretical framework, in the context of the anomalous thermal diffusion, for the photoacoustic signal. We obtain analytical predictions for the open photoacoustic cell technique by considering the thermal diffusion and thermoelastic bending effects. In these contexts, we consider different conditions for the thermal diffusivity, coefficient of optical absorption, the sample thickness and the amplitudes of thermal diffusion and thermoelastic bending contributions. Furthermore, opaque samples are also simulated as a special case of the optically transparent samples.

Experimental investigation on thermal properties of Ag nanowire nanofluids at low concentrations

New nanofluids containing Ag nanowires with different concentrations were prepared by chemical reduction method. The metallic nanowires were monodispersed and soluble in distilled water. Thermal properties of nanofluids containing Ag nanowires were obtained using photothermal techniques. The thermal-wave resonator cavity (TWRC) technique was used to obtain the samples’ thermal diffusivity. Open Photoacoustic Cell (OPC) technique was used to obtain the thermal effusivity of Ag nanowires. The thermal diffusivity and effusivity were obtained by fitting the theoretical expressions for each configuration as a function of the sample thickness and frequency to the experimental data. The thermal properties of the nanofluids seems to be strongly dependent of Ag nanowire concentration. It was observed an increase of thermal parameters when concentration of nanowires increased. Thermal conductivity behavior of the nanofluids is explained. UV–vis spectroscopy, Scanning Electron Microscopy (SEM), Energy-dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) techniques were used to characterize the nanofluids.

Characterization of Heat Diffusion Properties of Rubberized Two-Layer Systems Using Open Photoacoustic Cell Spectroscopy.

We applied the open photoacoustic cell method operating at high frequency as an efficient and highly precise tool for the measurement of thermal properties of rubberized two-layer systems. The heat-coupling between the two layers is treated using the analogy between thermal and electrical resistances widely used in heat transfer problems. The thermal resistance between the two layers is considered effective and the problem is decoupled for each layer. Measurements are performed in two-layer samples of aluminum foil coated with layers of rubberized paint with different thicknesses. Thermal diffusivity and thermal conductivity are determined for the paint. The results are retrieved from the thermal resistance model assuming the effective thermal diffusivity of the composite material.

Thermal properties of centrifuged oils measured by alternative photothermal techniques

In this work, thermal characterization of centrifuged aromatic citrus oils was studied using thermal lens (TL) and open photoacoustic cell (OPC). The thermal diffusivity (D) was obtained by TL, fitting the critical time parameter of the experimental curves to the theoretical values. An experimental arrangement of non-matched mode lasers with a probe and an excitation lasers was used. On the other hand, the thermal effusivity (e) of the samples was obtained by using OPC. The thermal conductivity (k) was calculated from the relationship between D and e. The thermal parameters obtained were compared with theoretical values ​​in the literature. UV–vis spectroscopy, Attenuated Total Reflectance-Fourier Transform Infrared spectroscopy (ATR-FTIR) and 1H Nuclear Magnetic Resonance (NMR) were used to determine the absorption coefficients and chemical structure of the citrus oils. The importance of this research work was the determination of the thermal parameters of essential oils as an alternative technique for quality control application.

Application of photoacoustic spectroscopy to characterize thermal diffusivity and porosity of caprocks

Photoacoustic spectrometry (PAS) was used to determine thermal diffusivity and porosity of three sealing caprocks originating from oil and gas fields in Brazil. In the petroleum industry developments in the low permeability rocks characterization are a key issue for safe exploitation. Also to assess the potential for using depleted reservoirs as a geologic repository for radioactive waste disposal or CO2 sequestration involves the knowledge of thermal properties parameters in caprocks. The experimental PAS technique using the open photoacoustic cell (OPC) method was employed to determine the porosity through correlation based on the thermal diffusivity values for consolidated and unconsolidated caprocks using small amounts of rocks and a few adjustments of empirical equations. The values obtained for thermal diffusivity were between 0.01667 (±0.0013) and 0.09298±(0.00018) cm2/s while the porosity ranged from 1.42% to 9%. It was observed that thermal diffusivity declines as the apparent porosity of the samples decreases. The variations in thermal diffusivity between the analyzed gas and oil fields were supported by field emission scanning electron microscopy and X-ray diffraction analyses, while porosity values were in a good agreement from those measured using the combination of nitrogen gas adsorption and mercury intrusion capillary pressure techniques. The use of PAS data on determining thermal diffusivity and subsequently low-porosity of porous media, such as caprocks, has not, to the best of our knowledge, been previously reported in the literature.

Thermal study of calcium silicate material synthesized with solid wastes

This work focuses on the thermal characterization of a calcium silicate-based material synthesized with different solid wastes (chamotte and marble) for use as thermal insulation material. Thermal and structural changes occurring during heating were accompanied by differential thermal analysis, thermogravimetric analysis, dilatometric analysis, open photoacoustic cell technique, X-ray diffraction (XRD), and scanning electron microscopy. An endothermic event at 823.2 °C was interpreted as decomposition of carbonates. An exothermic event around 900 °C is associated with the crystallization of calcium silicate phases mainly wollastonite. The themophysical properties of the calcium silicate-based material (thermal diffusivity, thermal conductivity, specific thermal capacity, and thermal effusivity) are influenced by the synthesis temperature. The thermal analysis results agree well with the XRD. The calcium silicate pieces presented low thermal conductivity values (0.227−0.376 W m−1 K−1). These results suggest that the calcium silicate-based materials produced essentially with chamotte and marble wastes has high potential to be used as thermal insulation construction material.

Open photo-acoustic cell configuration for measuring the thermal diffusivity of n-type silicon and silver/n-type silicon

An open photo-acoustic cell was used to measure the thermal diffusivity (TD) of silicon by photo-acoustic technique. The samples were heated for a period 3 h to perform sample annealing at 960, 1050, 1200 and 1300 °C in air. The TD of Si coated-silver (Ag/n-Si) was measured by fitting experimental data for the equation thermally thick in (RG) theory. For uncoated silver n-Si (single layer) samples, the TD can be obtained by fitting experimental data and by finding the intersection of the thermal thin and thermal thick (critical frequency fc). It was found that when the annealing temperature was increased, the TD of the (n-type Si) samples was also increased. However, at a temperature of 1050 °C, the TD value of the Ag/n-Si samples was found to be 2.93 cm2 s−1. Beyond this point TD showed a degrading behavior due to a complete silver melting on silicon surface.

Ultrasensitive photoacoustic sensor based on quantum cascade laser spectroscopy

The paper focuses on development of ultra-sonic detection system based on laser photoacoustic spectroscopic technique and processing of signal for detection of very low quantity chemicals, explosive materials, and mixtures of these hazardous molecules. The detection system has been developed for the first time with specially designed one side open photo-acoustic cell having high quality factor. Explosive and Hazardous materials like RDX, DNT, PETN, Gun Powder, TATP (Tri acetone tri-peroxide) and their simulants like Acetone were detected in 7 to 9μm wavelength band. Lock in amplifier electronic instrument was used for the detection of hazardous chemicals and mixture of explosives in very low quantity. Detection limit of the photoacoustic ultrasonic sensor was also carried out of powder, liquid and adsorbed on surfaces.

Thermal characterization of a liquid resin for 3D printing using photothermal techniques

Thermal properties of a liquid resin were studied by thermal lens spectrometry (TLS) and open photoacoustic cell (OPC), respectively. In the case of the TLS technique, the two mismatched mode experimental configuration was used with a He–Ne laser, as a probe beam and an Argon laser was used as the excitation source. The characteristic time constant of the transient thermal lens was obtained by fitting the theoretical expression to the experimental data in order to obtain the thermal diffusivity (α) of the resin. On the other hand, the sample thermal effusivity (e) was obtained by using the OPC technique. In this technique, an Argon laser was used as the excitation source and was operated at 514 nm with an output power of 30 mW. From the obtained thermal diffusivity (α) and thermal effusivity (e) values, the thermal conductivity (k) and specific heat capacity per unit volume (ρc) of resin were calculated through the relationships k = e(α)1/2 and ρc = e/(α)1/2. The obtained thermal parameters were compared with the thermal parameters of the literature. To our knowledge, the thermal characterization of resin has not been reported until now. The present study has applications in laser stereo-lithography to manufacture 3D printing pieces.

Closed/Open-Cell Photoacoustic Imaging for Spectroscopic Measurements

Photoacoustic imaging using a closed photoacoustic cell and an open photoacoustic cell with gas- microphone detection scheme was described. R/G/B LED light sources were used for the closed photoacoustic (PA) cell configuration. The colored specimen enclosed in a PA cell was imaged with R/G/B color light sources, and an image restored from the inverted PA images was compared with the original image. For open cell configuration, an open PA cell using a spheroidal acoustic resonator was applied to measure the amount of large-sized colored specimens. A calibration curve for a food red dye was obtained that apparently showed the ability of the present scheme to measure as a spectroscopic measurement tool.

Thermal Diffusivity Measurement for p-Si and Ag/p-Si by Photoacoustic Technique

Thermal diffusivity (TD) of p-Si and Ag/p-Si samples were measured by photoacoustic technique using open photoacoustic cell (OPC). The samples were annealed by heating them at 960, 1050, 1200, and 1300 °C for 3 h in air. The thermal diffusivity of Ag-coated samples was obtained by fitting the photoacoustic experimental data to the thermally thick equation for Rosencwaig and Gersho (RG) theory. For the single layer samples, the thermal diffusivity can be obtained by fitting as well as by obtaining the critical frequency f c . In this study, the thermal diffusivity of the p-Si samples increased with increasing the annealing temperature. The thermal diffusivity of the Ag/p-Si samples, after reaching the maximum value of about 2.73 cm2/s at a temperature of 1200 °C, decreased due to the silver complete melt in the surface of the silicon.