Optical Diffraction Method Research Articles

Investigating the Role of Microclimate and Microorganisms in the Deterioration of Stone Heritage: The Case of Rupestrian Church from Jac, Romania

Natural stone can undergo disaggregation from various causes, including physical actions such as freeze–thaw cycles, temperature and humidity variations, chemical actions such as the solubilization of minerals by organic and inorganic acids, as well as biological actions due to the colonization of organisms that can produce biocorrosion and biomineralization. This research investigates the impact of microclimatic conditions and microbial activity on the physical and chemical integrity of stone heritage, particularly the biodeterioration caused by fungi in the case of a Romanian rock church. Various analytical techniques were employed, including macroscopic and optical microscopy, Raman spectroscopy, X-ray diffraction, and culture-based identification methods, to characterize the mineral composition and microbial contamination of the rock samples. The analyses revealed that the sandstone consists primarily of quartz (over 90%), muscovite (5–10%), and feldspars. The identified fungi included Cladosporium herbarium, Aspergillus niger, and Mortierella hyalina. The SEM images showed fungal hyphae and spores within the kaolinite–illite matrix, indicating significant microbial colonization and its role in rock deterioration. Additionally, microclimatic data collected over a 12-week period highlighted the substantial fluctuations in temperature and relative humidity within the church, which contribute to the physical and chemical weathering of the stone. This study also noted high levels of particulate matter (PM2.5 and PM10) and volatile organic compounds, which can exacerbate microbial growth and stone decay. The comprehensive analysis underscores the need for targeted preservation strategies that consider both microclimatic factors and microbial colonization to effectively conserve stone heritage sites, ensuring their longevity and structural integrity.

Mineralogical Studies of the Tanjung Iron Mine in the Bone, South Sulawesi: Implication for AMD Generation

The iron ore of abandoned iron mine at the Tanjung Arae in Bone Regency has been investigated with the aim to analyze mineralogical characteristics and its potential for generating acid mine drainage (AMD). Mineralogical properties of the iron ore were analyzed using optical microscopy and X-ray diffraction (XRD) methods. Results of analysis reveal that the samples are dominated by iron oxide minerals such as magnetite, hematite and goethite. Other minerals are also present such as quartz, birnessite, pyrite and chalcopyrite. Mostly pyrite [FeS2] and chalcopyrite [CuFeS2] have been undergoing alteration which are characterized by weathering rims of those crystals and transformed into goethite and hematite. It is shown that the existence of pyrite [FeS2] and chalcopyrite [CuFeS2] may have significant roles in triggering the generation of AMD.

Thermal stability of microstructure and corresponding hardness variations in two high-carbon nanostructured bainitic steels

The autotempering phenomenon and carbon partitioning from bainitic subunits during the bainite transformation suggest that the tempering behavior of the nanostructured bainite may be different compared to that of martensite. This article aims to investigate the thermal stability of the microstructure in two low alloy nanostructured bainitic steels containing 0.89 wt% carbon content. Nanostructured bainite was obtained after austempering at 250 °C for optimum heat treatment time. Nanostructured bainitic steels were tempered at the temperature range of 300–700 °C for 30 min. Additionally, the effect of prolonged austempering beyond the optimum heat treatment condition at austempering temperature was studied. Microstructural characteristics were evaluated using optical and field emission gun scanning electron microscopes and X-ray diffraction methods. Hardness variations during tempering of nanostructured bainite compared with that of martensite microstructure obtained in the same primary steels after austenitizing and quenching. Results indicated that microstructural characteristics of nanostructure bainite didn’t change significantly at heat treatment times longer than that needed for bainite transformation completion at isothermal bainite heat treatment temperature. Moreover, results approved the higher tempering resistance of nanostructured bainite compared to that of martensite in the same steel. It has been shown that tempering the nanostructured bainite up to 400 °C didn’t change the microstructure and hardness, while the changes were pronounced at higher tempering temperatures. It has been suggested that cementite precipitation was more significant when a higher number of dislocations were present in nanostructured bainite before starting the tempering process.

Influence of Texture Effects on the Laser-Irradiated Tool Performance

Introduction. Laser surface treatment of mechanical engineering products makes it possible to increase their durability. However, the laser hardening process is not good at the consistency of results, since choosing the irradiation modes and schemes of specific products, texture effects in the zones of laser exposure are not taken into account. This leads to premature wearing and even destructing the working surfaces of irradiated products. Therefore, the work objective is to study the mechanism of influence of the structure of the laser-hardened layer on the operational properties of the tool.Materials and Methods. The materials for this study were tool steels: R6M5 and R18 (according to the EN 10027 standard tool steels: 1.3355, 1.3343). Pulsed laser irradiation was carried out at the technological device Kvant-16 with a radiation power density of 70–250 MW/m2. Scanning probe and optical microscopy, X-ray diffraction and durometric methods for analyzing the steels structure were used. The values of steel strength in bending and impact strength were determined before and after laser treatment.Results. It has been experimentally proven that it is necessary to strengthen the sections of the products working surfaces that are subject to maximum wear and are under the action of compressive stresses during operation. It is shown that textural effects in the laser treatment zones lead to a decrease in the friction coefficients and contribute to an increase in the wear and adhesion resistance of the steels surface layers.Discussion and Conclusion. The results of the research carried out make it possible to rationally select the surface laser processing modes and schemes of products for various functional purposes and ensure their operability with a guarantee. The possibilities increasing the structural strength and properties of the tool due to laser alloying the surface layers of powder-coated steels and stabilizing tempering after laser irradiation are determined.

Study of the Sensitivity Limit of Detection of α-Particles by Polymer Film Detectors LR-115 Type 2 Using X-ray Diffraction and UV-Vis Spectroscopic Methods.

This work is devoted to the applicability assessment of optical spectroscopy and X-ray diffraction methods to establish the lower detection limit for the density of latent tracks from α-particles in polymer nuclear-track detectors, in the case of simulation of the formation of radon decay daughter products using Am-241 sources. During the studies, the detection limit for the density of latent tracks-traces of the interaction of α-particles with the molecular structure of film detectors-was established using optical UV spectroscopy (104 track/cm2) and X-ray diffraction (104 track/cm2). At the same time, analysis of the connection between structural and optical changes in polymer films indicates that a growth in the density of latent tracks above 106-107 results into the formation of an anisotropic change in the electron density associated with distortions in the molecular structure of the polymer. An analysis of the parameters of diffraction reflections (the position and width of the diffraction maximum) showed that in the range of latent track densities of 104-108 track/cm2, the main changes in these values are associated with deformation distortions and stresses caused by ionization processes during the interaction of incident particles with the molecular structure of the polymer. The increase in optical density, in turn, is caused by the accumulation of structurally changed regions (latent tracks) in the polymer as the irradiation density increases. A general analysis of the obtained data showed good agreement between the optical and structural characteristics of the films depending on the irradiation density.

A study on microstructure development and mechanical properties of pure copper subjected to severe plastic deformation by the ECAP-Conform process

Commercially pure copper rod was successfully subjected to severe plastic deformation by applying the continuous equal channel angular pressing (ECAP-Conform) method at room temperature. Microstructural characterizations of copper rod samples at various stages of plastic deformation were carried out by optical microscopy and electron backscatter diffraction methods. X-ray diffractometry and Kernal average misorientation were used for dislocation density estimations. Microstructural evaluations revealed grain size change of 30 μm for the initial annealed copper rod to less than 5 μm and even 100 nm for severely deformed samples. Mechanical behaviors of samples after different deformation stages were characterized using tensile and hardness tests. The ultimate tensile strength of the severely deformed copper rod was increased threefold by ECAP-Conform while elongation halved in comparison to the initial annealed copper. Low-temperature annealing of severely plastic deformed samples led to bi-modal grain size distribution and lowering of strength accompanied by the increase of elongation. Tensile properties of severely deformed and then annealed copper samples showed around a 40% increase in both ultimate tensile strength and elongation in comparison to the initial annealed copper rod.

Mineralogical Properties of the Copper Slags from the SarCheshmeh Smelter Plant, Iran, in View of Value Recovery

Annually, hundreds of thousands of tons of slags are involved in the reverberator and flash smelting as well as converting operations of Cu-Fe sulfide concentrates to produce matte in the Sar Cheshmeh copper smelter plant, Iran, disposed in the landfill and cooled in air. Due to their relatively high average copper content (about 1.5 wt%), a mineral processing plant based on the flotation process has recently been established to produce thousands of tons of Cu-sulfide concentrate after slag crushing and fine grinding operation. In order to make the flotation process more efficient, more knowledge is required on the form and origin of the copper losses in the slag. To achieve this, mineralogical studies of the slags using optical microscopy, X-ray diffraction (XRD), and scanning electron microscopy (SEM) methods have been carried out. Mineralogical analyses showed the main part of copper losses into the semi- to fully-crystallized magnetite-rich reverberator and flash slags characterized by crystal–glass matrix ratio ≤ 1 is moderate to coarse particles of Cu-Fe sulfides, i.e., chalcopyrite (CuFeS2) and bornite (Cu5FeS4), that are mainly chemically entrapped. In contrast, the mechanically entrapped fine- to coarse-grain (from 20 up to 200 µm) spherical-shaped of high-grade matte particles with chalcocite (Cu2S) composition containing droplets or veinlets of metallic copper (Cu0) are the dominant forms of copper losses into the converter slags characterized by crystal–glass matrix ratio > 1. From the value recovery point of view, our result show that the fully crystallized slags containing moderate- to coarse-grain copper-bearing particles will result in efficient recovery of a significant amount of entrained copper due to better milling response compared to semi-crystallized ones due to locking the fine- to moderate-grain copper particles in the silicate glassy matrix. Laboratory-scale grinding experiments showed that normal (≤74 μm) to fine (≤44 μm) grinding of high- Cu grade slags lead to a significant increase in the liberation degree of copper particles. in contrast, the increase in fine particle fractions (<37 μm) due to re-grinding or ultra-fine grinding of the originally low-Cu grade slags does not lead to the liberation of copper particles, but it will reduce the efficiency of the flotation process. This study suggests that the highest rate of copper recovery of the slag by the flotation process will be obtained at particle size 80% passing 44 µm which has also reached the optimal liberation degree of copper-bearing particles.

Application of UV-Vis Optical Spectroscopy and X-ray Diffraction Methods to Describe the Effect of Alpha-Emitting Radionuclides (Radon) When They Are Detected by Solid-State Film Detectors.

This work aims to evaluate the application of optical and X-ray spectroscopy methods to determine the effect of alpha-emitting radionuclides on the properties of solid-state nuclear track detectors (SSNTD) based on nitrocellulose during their detection. The proposed estimation methods are alternative methods to standard technologies, making it possible to determine the concentration of radon and its decay products without the chemical etching of film detectors and subsequent direct counting of the formed latent tracks from interacting particles. During the research, it was found that the use of optical spectroscopy and X-ray diffraction methods makes it possible to qualitatively determine the irradiation effect on changes in the properties of film detectors when α-particles with different energies pass through them. At the same time, a comparison of the data of optical spectroscopy, X-ray diffraction and the visualization of latent tracks after chemical etching made it possible to establish that a part of the registered α-particles in living quarters has an energy of less than 2.5 MeV, which is not enough to pass through the polymer film of the detector, as a result of which well-like tracks are formed. An increase in the intensity of the interference bands in the region above 700 nm and a decrease in the intensity of diffraction reflection characterized the changes in optical transmission. The penetration of the α-particles through the detecting film decreases the film’s transmission capacity, forming an anisotropic change in diffraction reflections associated with a change in the film’s structure and defective fractions distorting the molecular structure.

Broadband acoustic resonance dissolution spectroscopy of natural edible salts: Visualization and interpretation for descriptive and diagnostic analysis

Broadband acoustic resonance dissolution spectroscopy (BARDS) has been recently introduced as a low-cost method for the analysis of powdered materials. In this study, ten Iranian natural table salts, each separated into five particle size fractions, were analyzed with BARDS. The compositions and crystalline structure of samples were investigated with inductively coupled plasma optical emission spectroscopy, flame photometry, and X-ray diffraction methods. Moreover, different linear and nonlinear dimensionality reduction methods were used to visualize the ten salt types. The analyses revealed the presence of halite, sylvite, and anhydrite in the rock salts, and halite, bischofite, and periclase in the sea salts. Subjecting bubble volume spectra to nonlinear dimensionality reduction using the t-distributed stochastic neighbor embedding algorithm, the salts were clearly distinguished in a two-dimensional space with the distances and positions relative to their composition, crystalline structure, and particle morphology. The results of this study provide a roadmap toward unraveling the underlying mechanisms behind the BARDS spectra for further applications in characterizing natural edible salts.

Toward Improved Charge Separation through Conformational Control in Copper Coordination Complexes.

The continued development of solar energy as a renewable resource necessitates new approaches to sustaining photodriven charge separation (CS). We present a bioinspired approach in which photoinduced conformational rearrangements at a ligand are translated into changes in coordination geometry and environment about a bound metal ion. Taking advantage of the differential coordination properties of CuI and CuII, these dynamics aim to facilitate intramolecular electron transfer (ET) from CuI to the ligand to create a CS state. The synthesis and photophysical characterization of CuCl(dpaaR) (dpaa = dipicolylaminoacetophenone, with R = H and OMe) are presented. These ligands incorporate a fluorophore that gives rise to a twisted intramolecular charge transfer (TICT) excited state. Excited-state ligand twisting provides a tetragonal coordination geometry capable of capturing CuII when an internal ortho-OMe binding site is present. NMR, IR, electron paramagnetic resonance (EPR), and optical spectroscopies, X-ray diffraction, and electrochemical methods establish the ground-state properties of these CuI and CuII complexes. The photophysical dynamics of the CuI complexes are explored by time-resolved photoluminescence and optical transient absorption spectroscopies. Relative to control complexes lacking a TICT-active ligand, the lifetimes of CS states are enhanced ∼1000-fold. Further, the presence of the ortho-OMe substituent greatly enhances the lifetime of the TICT* state and biases the coordination environment toward CuII. The presence of CuI decreases photoinduced degradation from 14 to <2% but does not result in significant quenching via ET. Factors affecting CS in these systems are discussed, laying the groundwork for our strategy toward solar energy conversion.

Green Synthesis of Nanoparticles Selenium

The reaction of sodium selenite source with various extracted orange covers in an acidic suspension during ambient circumstances has been devised as a simple sol gel technique to generate selenium nanoparticles. The selenium nanoparticles were stabilized with polyvinyl alcohol. A high-speed centrifuge can be used to isolate the nanoparticles from their sol, and a sonicator can be used to redisperse them in an aqueous media. The produced selenium nanoparticles were characterized using UV-visible optical absorption spectroscopy and X-ray diffraction methods.

Microstructural Characterization of Additively Manufactured Metal Components Using Linear and Nonlinear Ultrasonic Techniques.

Metal additive manufacturing (AM) is an innovative manufacturing technology that uses a high-power laser for the layer-by-layer production of metal components. Despite many achievements in the field of AM, few studies have focused on the nondestructive characterization of microstructures, such as grain size and porosity. In this study, various microstructures of additively manufactured metal components were characterized non-destructively using linear/nonlinear ultrasonic techniques. The contributions of this study are as follows: (1) presenting correlation analyses of various microstructures (grain size and texture, lack of fusion, and porosity) and ultrasonic properties (ultrasonic velocity, attenuation, and nonlinearity parameters), (2) development of nondestructive microstructural characterization techniques for additively manufactured components; and (3) exploring the potential for the online monitoring of AM processes owing to the nondestructive nature of the proposed technique. The performance of the proposed technique was validated using additively manufactured samples under varying laser beam speed conditions. The characteristics of the target microstructures characterized using the proposed technique were consistent with the results obtained using destructive optical microscopy and electron back-scattered diffraction methods.

Noncontact evaluation of the conductivity of CuPc thin films by near-field microwave microprobe method

AbstractThe conductivity of copper II phthalocyanine (CuPc) thin films with different crystal structures andmorphologies was evaluated by using a near-field microwave microprobe (NFMM) technique in thefrequency range of 4-4.5 GHz. CuPc thin films annealed at 200 °C and 350 °C showed the a- and yS-phasecrystal structures, respectively. Crystal phase structure and morphology of CuPc thin films werecharacterized by optical absorption spectra measurement, X-ray diffraction, and scanning electronmicroscopy methods. Conductivity measurements of CuPc thin films were done in the temperatures rangeof25-160 °C.

Application of the optical spectroscopy and X-ray diffraction methods for determining the effect of irradiation of the LR-115 type 2 track detector

The aim of this work is to evaluate the application of optical spectroscopy and X-ray diffraction methods as alternative methods for determining the dose dependence of the irradiation of solid-state nuclear track detectors (SSNTD) based on polymer films of nitrocellulose when irradiated with He particles. The choice of this type of film detectors as an object of research was due to its wide application for the detection of ionizing radiation during radionuclide decay. According to the data obtained, using optical analysis methods, it was found that an increase in exposure time leads to an increase in the transmission value and a shift in the fundamental absorption edge, which indicates the occurrence of changes in optical density in the material during accumulation of defects arising from the formation of latent tracks. The obtained data of structural changes using X-ray diffraction, showed that at small periods of exposure to ionizing radiation, the change of structural parameters is more severe than the change of optical characteristics. This is due to the fact that in the case of formation of single isolated tracks, the change in electron density along the trajectory of the ions is isolated and has a local character, while the change in structural characteristics, including the deformation is more pronounced. Such difference is also related to different mechanisms of energy losses of incident particles contributing to the change of structural and optical properties. Changing of optical properties is connected with electron losses of incident particles because the electron density changes as a result of particle passing along its trajectory, and this effect in case of single tracks is isolated and has a local character in a very small region. At the same time, the change of structural characteristics, in particular, deformations and displacements occur as a result of both elastic and non-elastic interactions of interacting particles with materials.

Recommendation for lateritic Ni-ore processing: garnierite mineralogical and geochemical approach

The objective of this study is to analyze the mineralogy and geochemistry of garnierite and its implication for Ni laterite processing. Mineralogical analysis using optical microscopic and X-ray diffraction (XRD) methods were performed, whereas chemical composition was obtained by X-ray fluorescence (XRF) method. Genetically, Ni in laterite ore is associated with SiO2 and MgO and is not accompanied by the elements of Co, Fe, Cr, Al, Mn, and Ca. In this study, Ni-laterite ore has Ni content of 2.1%, SiO2 25.42%, S/M ratio 3.7, and Fe/Ni ratio 15.5, meaning that it is more suitable to be processed by pyrometallurgical route. However, there are some characters that still have to go through treatment, namely reducing of Fe from 32.63% to 20%, increasing MgO, and reducing SiO2 by blending. Result of mineralogical analysis shows that the dominant mineral is quartz (44.8%) and talc (38.85%) with small amount of lizardite (16.35%). The high content of quartz and talc and the low in lizardite of the Ni-laterite ore in the study area indicated that it is recommended for pyrometallurgical processing which is also in accordance with its geochemical characteristics.

Ardennite-bearing mineral association related to sulfide-free ores with chalcophile metals at Nežilovo, Pelagonian Massif, North Macedonia

Abstract. Among numerous minerals determined at Nežilovo, Pelagonian Massif, North Macedonia, ardennite-(As) has been discovered in two different associations and studied by means of optical microscopy, electron microprobe analysis (EMPA), and single-crystal and powder X-ray diffraction methods. The refractive indices of ardennite-(As) from Nežilovo are α=1.537(2), β=1.579(1) and γ=1.741(1), where γ corresponds to the c direction. The optical axial angle is 2Vx=49(1)∘. EMPA of the investigated samples yields the following empirical formulae: [Mn3.272+Ca0.73]Σ4.00[Al4.18Mg1.24Fe0.29Mn0.193+Zn0.10]Σ6.00(Si4.73Al0.27)Σ5.00(As0.96Si0.03V0.01)Σ1.00O22 [OH5.36(H2O)0.64]Σ6.00 for ardennite-(As) and (K0.95Na0.04Ba0.02)Σ1.01(Al1.44Fe0.303+Mg0.20Mn0.03Ti0.02 Zn0.01)Σ2.00(Si3.21Al0.79O10) (OH1.97O0.03)Σ2.00 for the associated red mica. The unit cell parameters of ardennite-(As) determined by X-ray powder diffraction are a=8.757(2) Å, b=5.836(2) Å, c=18.578(2) Å and V=941.97 Å3. The unit cell parameters of ardennite-(As) were also determined by single-crystal X-ray diffraction and are a=8.760(1) Å, b=5.838(1) Å, c=18.582(2) Å and V=950.30 Å3. Regularities of isomorphism in ardennite-related minerals are discussed. The presence of ardennite-(As) in association with 2M1 and 3T phengite polytypes provides evidence for three separate stages of formation. Conditions at which ardennite-(As) crystallized have been estimated based on compositional features of associated micas.

DETERMINATION OF PIROCARBON MATRIX CHARACTERISTICS IN CARBON/CARBON COMPOSITES

One of the methods of carbon/carbon composites (C/C composites) production is the deposition of a pyrocarbon (pyC) matrix in a porous preform. The investigation of the pyC matrix characteristics is based on the optical anisotropy with determination of the extinction angle Ae and X-ray diffraction determination of the interplanar spacing d002, crystallite size in the direction of stacking of graphite layers Lc and average size of graphite planes parallel layer in crystallites La. In this study, three previously produced by the thermal gradient method with different parameters specimens of C/C composites were investigated by optical microscopy and X-ray diffraction methods. The studied specimens have a different type of a texture and different structural characteristics of the pyC matrix. Extinction angle Ae for specimen 1, specimen 2 and 3 was 5°, 19° and 41°, respectively. The range of the extinction angle for the pyC matrix is wider than that presented in literature. And according to the classification of pyC the matrix of specimen 1, specimen 2 and 3 is dark laminar pyC, rough laminar pyC and highly textured pyC. For specimen 2 the largest d002 equal to 0.3476 nm was observed. The lowest degree of three-dimensional ordering relative other specimens was for the specimen 2 with rough laminar pyC matrix. The highest degree of three-dimensional ordering was for the specimen 3 with highly textured pyC matrix. However, there is no direct relationship between the textural and structural characteristics of the pyC matrix. Therefore, the study of the pyC matrix should be based on optical and X-ray diffraction methods.

Influence of Crystallographic Texture on the Corrosion Product Morphology and Corrosion Rate of AZ31 Plate in Simulated Body Fluid

This paper investigates the effect of crystallographic texture on the corrosion product morphology and corrosion behavior of AZ31 magnesium alloy after immersion in simulated body fluid for 3 days. The microstructure and macrotexture analyses are performed through optical microscopy and x-ray diffraction methods, respectively. The polarization test evaluated the corrosion, and the FESEM electron microscope equipped with EDS was used to investigate the morphology of the corrosion products. According to the results, the morphology of calcium phosphate deposit as a corrosion product at the surface with basal texture was a porous cauliflower shape. In contrast, the calcium phosphate deposit at the surface of the nonbasal texture was uniform and nanoworm-like. The corrosion rate at the basal texture surface was higher than the nonbasal one, which is attributed to the difference in the morphology of calcium phosphate film.

Oscillations of tunneling magnetoresistance on bias voltage in magnetic tunnel junctions with periodic grating barrier

A spintronic theory is developed to describe the effect of bias voltages on the magnetic tunnel junctions (MTJs) with a single-crystal barrier. The theory is founded on a conventional optical diffraction method and has already explained the barrier thickness effect, the temperature effect, and the half-metallic electrode effect in the MTJs with a periodic grating barrier. We find that the tunneling magnetoresistance (TMR) will oscillate with the bias voltage. This theoretical result can interpret the bias dependence observed in experiments. The range of bias voltage where the oscillations arise can be regulated by the barrier thickness and the spin polarization of the electrodes. In particular, it demonstrates that the bias voltage smaller than 100mV can hardly change the properties of TMR oscillations on the barrier thickness, which is in agreement with the experiments. Finally, a practical method is proposed to enhance and optimize the output voltage.

Comparison of Bubble Size Distributions Inferred from Acoustic, Optical Visualisation, and Laser Diffraction

Bubble measurement has been widely discussed in the literature and comparison studies have been widely performed to validate the results obtained for various forms of bubble size inferences. This paper explores three methods used to obtain a bubble size distribution—optical detection, laser diffraction and acoustic inferences—for a bubble cloud. Each of these methods has advantages and disadvantages due to their intrinsic inference methodology or design flaws due to lack of specificity in measurement. It is clearly demonstrated that seeing bubbles and hearing them are substantially and quantitatively different. The main hypothesis being tested is that for a bubble cloud, acoustic methods are able to detect smaller bubbles compared to the other techniques, as acoustic measurements depend on an intrinsic bubble property, whereas photonics and optical methods are unable to “see” a smaller bubble that is behind a larger bubble. Acoustic methods provide a real-time size distribution for a bubble cloud, whereas for other techniques, appropriate adjustments or compromises must be made in order to arrive at robust data. Acoustic bubble spectrometry consistently records smaller bubbles that were not detected by the other techniques. The difference is largest for acoustic methods and optical methods, with size differences ranging from 5–79% in average bubble size. Differences in size between laser diffraction and optical methods ranged from 5–68%. The differences between laser diffraction and acoustic methods are less, and range between 0% (i.e., in agreement) up to 49%. There is a wider difference observed between the optical method, laser diffraction and acoustic methods whilst good agreement between laser diffraction and acoustic methods. The significant disagreement between laser diffraction and acoustic method (35% and 49%) demonstrates the hypothesis, as there is a higher proportion of smaller bubbles in these measurements (i.e., the smaller bubbles ‘hide’ during measurement via laser diffraction). This study, which shows that acoustic bubble spectrometry is able to detect smaller bubbles than laser diffraction and optical techniques. This is supported by heat and mass transfer studies that show enhanced performance due to increased interfacial area of microbubbles, compared to fine bubbles.