Infrared Reflectance Spectroscopy Research Articles

Non-destructive characterization of silicon nanowires and nanowire coatings using mid-infrared spectroscopy

Silicon nanowires (SiNWs) have attracted much attention owing to their potential applications in electronics and photonics, while remaining as a cost-effective material platform. Key material properties in engineering SiNWs for different applications include their length, density, and presence of oxides or other chemicals on the surface. However, monitoring these properties is challenging, as scanning electron microscopy and atomic force microscopy (AFM), which directly image the wires, require destructive cleaving of the sample. This paper uses polarized, variable-angle Fourier Transform IR reflectance spectroscopy as a nondestructive technique to characterize the areal density and length of metal-assisted chemically etched SiNW arrays. In addition to the ability to characterize “as-etched” wires, we show that IR spectroscopy can also measure few-nanometer thick layers of aluminum oxide (AlOx) grown radially around the length of the SiNWs utilizing atomic layer deposition. Despite sample inhomogeneities, an effective medium theory (EMT) model can determine the length and density of the NWs for a range of lengths between 3 and 14 μm. The EMT can also reproduce the experimentally measured vibrational bands for coated NWs, demonstrating that IR spectroscopy can also evaluate the presence of molecular contaminants on the wires.

Identification of rare earth elements in synthetic and natural monazite and xenotime by visible-to-shortwave infrared reflectance spectroscopy

To support the role of proximal and remote sensing in geological rare earth element (REE) resource exploration, we studied the reflectance spectroscopy of synthetic single- and mixed-REE phosphate phases. Synthesis yielded monazite for the elements La to Gd, and xenotime for Dy to Lu and Y. Visible-to-shortwave infrared (350–2500 nm) reflectance spectra of synthetic single-REE monazites and xenotimes can be used to identify the ions responsible for the absorption features in natural monazites and xenotimes. Nd3+, Pr3+ and Sm3+ produce the main absorption features in monazites. In natural xenotime, Dy3+, Er3+, Ho3+ and Tb3+ ions cause the prevalent absorptions. The majority of the REE-related absorption features are due to photons exciting electrons within the 4f subshell of the trivalent lanthanide ions to elevated energy levels resulting from spin-orbit coupling. There are small (< 20 nm) shifts in the wavelengths of these absorptions depending on the nature of the ligands. The energy levels are further split by crystal field effects, manifested in the reflectance spectra as closely spaced (∼ 5–20 nm) multiplets within the larger absorption features. Superimposed on the electronic absorptions are vibrational absorptions in the H2O molecule or within [OH]−, [CO3]2− and [PO4]3− functional groups, but so far only the carbonate-related spectral features seem usable as a diagnostic tool in REE-bearing minerals. Altogether, our study creates a strengthened knowledge base for detection of REE using reflectance spectroscopy and provides a starting point for the identification of REE and their host minerals in mineral resources by means of hyperspectral methods.

Analysis of four heavy metal concentrations in sediments from the Jiaozhou Bay, China by visible and near infrared spectroscopy (225–975 nm)

As an important component ofbiogeochemical cyclein coastal ecosystems, sediments are the sink of heavy metals. Therefore, distribution and dynamics of heavy metals in sediments could assess ecological quality and predict ecological risks. In the new era, rapid and green technology are highly needed, especially that could determine multi-parameters simultaneously. Here, we explored a new method to rapidly determine concentrations of heavy metals in sediments by visible and near infrared reflectance spectroscopy (VIRS).We sampled sediments in the Jiaozhou Bay, China, collected their reflectance spectra, and measured concentrations of four heavy metals (As, Cr, Cu, and Zn). Heavy metal models were established and evaluated using substances highly correlated with heavy metals. This study provides an effective reference for rapid analysis of As, Cr, Cu, and Zn simultaneously in sediments, at least in the Jiaozhou Bay, and for ecological environment protection and resource development of the Jiaozhou Bay.

MnO2 enhanced low temperature HCHO sensing performance of SnO2

The exploration of gas sensing materials holds significant importance for practical applications. This work introduces a novel SnO2/MnO2 nanocomposite designed to achieve formaldehyde monitoring at ppb level with a relative low temperature. The as prepared sensor demonstrates a response of 8.1–50 ppb formaldehyde at 100 °C. These remarkable formaldehyde sensing capabilities were explained by the heterojunction structure of the composite, and the low-temperature catalytic properties of MnO2. Moreover, in-situ infrared reflectance spectroscopy was employed to investigate the underlying mechanism by monitoring the evolution of reaction intermediates, and the result suggested that the addition of MnO2 can reduce the ineffective occupation of active sites and promote the generation of intermediate intermediates.

Synthesis and Exploration of Barium Stannate-Zirconate BaSn1-xZrxO3 (0 ≤ X ≤ 1) Solid Solutions as Photocatalysts.

Employing ionic liquid-assisted microwave synthesis and moderate heat treatment allows for the preparation of otherwise difficult-to-obtain perovskite-type BaSn1-xZrxO3 solid solutions (0 ≤ x ≤ 1). The impact of substituting Sn for the crystal structure, crystallinity, morphology, and photocatalytic performance was investigated. The obtained materials are characterized by X-ray diffraction, scanning electron microscopy, Brunauer-Emmett-Teller (BET) surface area analysis, X-ray photoelectron spectroscopy, UV-Vis diffuse reflectance spectroscopy, photoluminescence spectroscopy, and Raman and IR spectroscopy. SEM images show that the morphology of the samples varies from rods for x = 0, 0.2 to spherical for x = 0.5, 0.8, 1. Upon Zr for Sn substitution, the band gap changes from 3.1 to 5.0 eV as the valence and conduction bands move to lower and higher energies. The photocatalytic activities of the BaSn1-xZrxO3 samples in the hydroxylation of terephthalic acid (TA) follow the order BaSn0.5Zr0.5O3> BaSn0.8Zr0.2O3> BaSnO3> BaSn0.2Zr0.8O3> BaZrO3. The superior photocatalytic activity of BaSn0.5Zr0.5O3 can be attributed to the synergistically favorable combination of a suitable band structure, band gap size, and increased surface area-to-volume ratio, resulting in a diminished crystalline particle size unattainable from samples prepared via traditional synthetic routes or without ionic liquid.

UV photo-degradation of the secondary lichen substance parietin: A multi-spectroscopic analysis in astrobiology perspective

The cortical anthraquinone yellow-orange pigment parietin is a secondary lichen substance providing UV-shielding properties that is produced by several lichen species. In our work, the secondary metabolite has been extracted from air-dried thalli of Xanthoria parietina. The aims of this study were to characterize parietin absorbance through UV–VIS spectrophotometry and with IR spectroscopy and to evaluate its photodegradability under UV radiation through in situ reflectance IR spectroscopy to understand to what extent the substance may have a photoprotective role. This allows us to relate parietin photo-degradability to the lichen UV tolerance in its natural terrestrial habitat and in extreme environments relevant for astrobiology such as Mars. Extracted crystals were UV irradiated for 5.59 h under N2 flux. After the UV irradiation, we assessed relevant degradations in the 1614, 1227, 1202, 1160 and 755 cm−1 bands. However, in light of Xanthoria parietina survivability in extreme conditions such as space- and Mars-simulated ones, we highlight parietin UV photo-resistance and its relevance for astrobiology as photo-protective substance and possible bio-hint.

The dependence of electrical conductivity of MgxZn1–xO ceramics on phase composition

The structural and electrical characteristics of (Mg,Zn)O ceramics produced using the solid state reaction at 1100 °C for 3 hours were studied applying X-ray diffraction and IR reflection spectroscopy as well as means of direct current measurements versus MgO content in initial charge (varied from 0 to 100 mol.%). It has been shown that electrical conductivity extracted from the IR reflection spectra corresponds to that of hexagonal phase in a solid solution, while plasmon in cubic phase was not observed. The electron concentration in the hexagonal grains of solid solution prepared with MgO content below 30 mol. % in the charge was found to be close to that of ZnO grains. It shows the tendency to decrease with further growth of the MgO content, which was explained by extraction of zinc interstitials, responsible for ZnO conductivity, from ZnO under formation of the MgZnO cubic phase. The direct current measurements have shown the lower conductivity as compared to the value estimated from IR reflection spectra. This fact along with the superlinearity of current-voltage characteristics has been explained by the presence of intergranular barriers, which does not allow obtaining information on the concentration of free electrons in the grain by this method. The possible nature of intergranular barriers as well as the role of grain boundaries in the DC conductivity of samples has been discussed.

Geographic origin classification and simultaneous determination of methylxanthines in vietnamese tea using chemometrics based on the near infrared reflectance spectroscopy

This paper reported the results of classification of geographic origin and simultaneous analysis of three methylxanthines (caffeine, theobromine, theophylline) in Vietnamese tea samples by the infrared reflectance spectrophotometry coupled with chemometrics. The spectral range was 10,000-4,000cm-1 and each spectrum was measured at 2 cm-1 intervals. For the purpose of geographic origin classification, this study used FT-NIR spectroscopy combined with Partial Least Squares Discriminant Analysis (PLS-DA), and Principal Component Analysis-Discriminant Analysis (PCA-DA). The ability to determine the origin of tea samples in the prediction set of PLS-DA model is 100%. Using the same IR spectral database combined with the partial least squares (PLS), three methylxanthines in tea samples are also quickly quantified. The PLS model based on the spectra of 24 tea samples in which the contents of 3 analytes were determined by high performance liquid chromatography- HPLC) were applied for simultaneous determination of caffeine, theobromine and theophylline in samples. The determination of methylxanthines in 7 tea samples in test set gave the good accuracy of the PLS model. The correlation coefficients (R2) in the prediction set were of 0.9582, 0.8894 and 0.9303 for theobromine, theophylline, and caffeine, respectively. This work demonstrated that infrared reflectance spectrophotometry combined with chemometrics could be applied to rapidly classify the geographic origin and simultaneous determination of main contents in green tea.

Gemological and Spectral Characteristics of Gem-Quality Blue Gahnite from Nigeria

Gem-quality blue octahedral crystalline gahnite was produced in Nigeria. This paper investigated gemological and spectroscopic characteristics by basic gemological experiments, electron probes, infrared reflectance spectroscopy, laser Raman spectroscopy, photoluminescence spectroscopy, and ultraviolet-visible spectroscopy. The results show that the refractive index (RI) of Nigerian gahnite is 1.792∼1.794, and the specific gravity is 4.45∼4.66, with no fluorescence. The main chemical composition is ZnAl2O4, accounting for 93.57%, and the rest is mainly FeAl2O4, which also contains Na, Mg, Co, Mn, Cr, Cu, Si, K, and Ca elements. The infrared spectra showed midinfrared absorption bands near 510 cm−1, 559 cm−1, and 664 cm−1 in the fingerprint region, corresponding to the Zn-O stretching vibration, bending vibration, and Al-O bending vibration, respectively. The Raman spectra showed three of the five Raman active modes of the spinel group, with characteristic Raman absorption peaks located at 418 cm−1, 508 cm−1, and 660 cm−1, corresponding to Eg, T2g(2), and T2g(3) modes, respectively, and the comparison revealed a higher degree of Zn and Al ordering in this paper for gahnite. The photoluminescence spectra show the common Cr3+-activated fluorescence splitting peaks of natural spinel, of which the 686 nm (R-line) fluorescence peak is obvious and sharp. The UV-vis absorption spectra located at 444 nm and 489 nm are the most obvious, which are caused by the d-d electron leap of TFe2+ (5E ⟶ 5T2), and the blue-gray tones of the samples are mainly caused by the spin-forbidden electronic transitions in TFe2+ and MFe2+ ↔ MFe3+; the weak absorption peak at 609 nm was determined to be associated with Co2+ by derivative spectra.

Detection of counterfeiting rice bran using near-infrared reflectance spectroscopy (NIRS)

This study aims to compare rice bran quality from different origins and to differentiate rice bran from rice husk based on the spectrum produced by Near Infrared Reflectance Spectroscopy (NIRS) technology. The rice bran used in this study comes from mills and poultry shops in West Java and Sumatra. This study used husks as an adulteration mixing material in rice bran with mixing levels of 25% rice bran: 75% husk, 50% rice bran: 50% husk, and 75% rice bran: 25% husk. Proximate compositions (water content, ash content, ether extract (EE), crude protein (CP), and crude fiber (CF)) were observed. NIRS spectra were collected using the Buchi NIRCal 5.2 application. The results showed an interaction between provider and origin on rice bran EE, CP, and CF contents. Rice bran provided by the miller had better quality with higher CP (17.3% vs. 12.2%) and lower CF (12.0% vs. 16.6%) content in the West Java origin case and higher EE (16.5% vs. 11.1%) in West Sumatera case. The broad spectra distribution showed the variety of the rice bran quality from the poultry shop. The artificial adulteration spectra confirm the impure rice bran quality from the poultry shop.

Assessment of Beeswax Adulteration by Paraffin and Stearic Acid Using ATR-IR Spectroscopy and Multivariate Statistics-An Analytical Method to Detect Fraud.

A spectroscopic investigation of beeswax adulteration by paraffin and/or stearic acid was undertaken via Attenuated Total Reflectance Infra-Red spectroscopy (ATR-IR) combined with multivariate statistical analyses. Principal Component Analysis (PCA) was successfully applied for the first time as an exploratory tool for the differentiation among pure beeswax and adulterated beeswax by paraffin and stearic acid with detection limits (LOD) of ~5% and 1%, respectively. Partial Least Square (PLS) modelling was used to build chemometric models based on beeswax/paraffin and beeswax/stearic acid calibration mixtures and subsequently used to predict concentrations of paraffin and stearic acid on a set of unknown test samples. PLS predictions demonstrated that beeswax adulteration by paraffin is much more prominent (74%) than the one by stearic acid (26%) and that commercial beeswax products (candles, pearls, blocks, etc.) are more prone to adulteration (27%) than honeycomb-type samples (12.5%).

Modified electronic structure and enhanced hydroxyl adsorption make quaternary Pt-based nanosheets efficient anode electrocatalysts for formic acid-/alcohol-air fuel cells

Surface/interface engineering of a multimetallic nanostructure with diverse electrocatalytic properties for direct liquid fuel cells is desirable yet challenging. Herein, using visible light, a class of quaternary PtAgBiTe ultrathin nanosheets is fabricated and used as high-performance anode electrocatalysts for formic acid-/alcohol-air fuel cells. The modified electronic structure of Pt, enhanced hydroxyl adsorption, and abundant exterior defects afford Pt1Ag0.1Bi0.16Te0.29/C high intrinsic anodic electrocatalytic activity to boost the power densities of direct formic acid-/methanol-/ethanol-/ethylene glycol-/glycerol-air fuel cells, and the corresponding peak power density of Pt1Ag0.1Bi0.16Te0.29/C is respectively 129.7, 142.3, 105.4, 124.3, and 128.0 mW cm−2, considerably outperforming Pt/C. Operando in situ Fourier transform infrared reflection spectroscopy reveals that formic acid oxidation on Pt1Ag0.1Bi0.16Te0.29/C occurs via a CO-free direct pathway. Density functional theory calculations show that the presence of Ag, Bi, and Te in Pt1Ag0.1Bi0.16Te0.29 suppresses CO* formation while optimizing dehydrogenation steps and synergistic effect and modified Pt effectively enhance H2O dissociation to improve electrocatalytic performance. This synthesis strategy can be extended to 43 other types of ultrathin multimetallic nanosheets (from ternary to octonary nanosheets), and efficiently capture precious metals (i.e., Pd, Pt, Rh, Ru, Au, and Ag) from different water sources.

Temperature dependence of the anisotropy of the infrared dielectric properties and phonon-plasmon coupling in n-doped 4H-SiC

Polarized infrared reflectivity spectroscopy is used to measure the temperature dependence of the anisotropy of the infrared dielectric properties and the coupling between phonon and plasmon modes in n-doped 4H-SiC. The advantage of polarized infrared spectroscopy over the commonly used Raman spectroscopy is that it enables dielectric, plasmonic, and transport properties to be probed along and perpendicular to the c-axis, which is impossible with Raman spectroscopy due to its selection rules. In addition, the infrared spectrum, comparatively rare for Raman spectroscopy, can be described at high temperatures with simple classical theory, providing more precise information on the properties of the material being measured. Analysis of the s- and p-polarized infrared reflectivity spectra of an n-doped 4H-SiC substrate shows that the strength and damping of the oscillators, the response of the bound electrons to an infrared excitation, the effective ion mass, and the transverse frequency and anharmonicity of the phonons of n-doped 4H-SiC are temperature-sensitive and strongly anisotropic. It also shows that the plasmonic properties of n-doped 4H-SiC, namely the relaxation time and the collective oscillation frequency of free electrons, are also highly anisotropic and, due to the long relaxation time of free electrons in the direction parallel to the c-axis, only the axial longitudinal phonon-plasmon modes split into low-frequency and high-frequency modes at temperatures above 700 K.

Infrared Spectroscopy Study of Edge Water Penetration at Hydrophilic Bonding Interface

Hydrophilic wafer bonding is a process used to bond two wafers without adding material between the two surfaces. Water has a definite impact both during the bonding (bonding wave propagation, adhesion) (1) and after annealing (mechanical strength of the bonding interface, adherence) (2) during such a process. To have a better understanding of mechanisms ruling direct hydrophilic wafer bonding, it is thus important to quantify the amount of water present at the bonding interface.It is known that water is able to penetrate at the bonding interface at room temperature and 40% relative humidity. This has been demonstrated by analyzing defects with scanning acoustic microscopy (SAM) and from X-Ray Reflectivity (XRR) measurements (3,4). Kinetics observed by Tedjini et al. were consistent with a Lucas-Washburn flow through a one nm gap driven by the capillary forces of the hydrophilic surfaces.Nevertheless, no investigation of this phenomenon was performed using Fourier Transform Infra-Red Multiple Internal Reflection (FTIR-MIR) spectroscopy (5). Infrared spectroscopy of silanols, hydrogen bonded water and free water is well documented (6–8) and provides knowledge about water content and organization at the bonding interface. Here FTIR-MIR spectroscopy yields a direct measurement of the relative amount of water and its structure at the interface.More precisely this study will enable us to compare Si-Si, Si-SiO2 and SiO2-SiO2 water penetration kinetics at a fixed distance from the edge of the bonded substrates. A schematic view of the FTIR-MIR setup is shown in Figure 1 to explain the measurement principle.We report the study of water kinetics penetration at bonding interface by FTIR-MIR characterization. A Gaussian decomposition of the OH stretching absorption band signal allows identifying the contributions of silanols, surface bonded water and free liquid water as shown on Figure 2. The integral of each Gaussian peak is otherwise proportional to the relative amount of water. Surface preparation will be discussed and results compared to other characterizations techniques.REFERENCES Larrey V, Mauguen G, Fournel F, Radisson D, Rieutord F, Morales C, et al. Adhesion Energy and Bonding Wave Velocity Measurements. ECS Transactions. 23 sept 2016;75(9):145-52.Fournel F, Tedjini M, Larrey V, Rieutord F, Morales C, Bridoux C, et al. Impact of Water Edge Absorption on Silicon Oxide Direct Bonding Energy. ECS Transactions. 23 sept 2016;75(9):129-34.Tedjini M, Fournel F, Moriceau H, Larrey V, Landru D, Kononchuk O, et al. Interface water diffusion in silicon direct bonding. Appl Phys Lett. 12 sept 2016;109(11):111603.Rieutord F, Tardif S, Landru D, Kononchuk O, Larrey V, Moriceau H, et al. Edge Water Penetration in Direct Bonding Interface. ECS Trans. 24 août 2016;75(9):163-7.Rochat N, Olivier M, Chabli A, Conne F, Lefeuvre G, Boll-Burdet C. Multiple internal reflection infrared spectroscopy using two-prism coupling geometry: A convenient way for quantitative study of organic contamination on silicon wafers. Appl Phys Lett. 2 oct 2000;77(14):2249-51.Baum M, Rébiscoul D, Juranyi F, Rieutord F. Structural and Dynamical Properties of Water Confined in Highly Ordered Mesoporous Silica in the Presence of Electrolytes. J Phys Chem C. 30 août 2018;122(34):19857-68.Caër SL, Pin S, Esnouf S, Raffy Q, Ph. Renault J, Brubach JB, et al. A trapped water network in nanoporous material: the role of interfaces. Physical Chemistry Chemical Physics. 2011;13(39):17658-66.Davis KM, Tomozawa M. An infrared spectroscopic study of water-related species in silica glasses. Journal of Non-Crystalline Solids. 2 juin 1996;201(3):177-98. Figure 1

Alfalfa (Medicago sativa L.) quality is improved from tractor traffic implemented during harvest

Studies documenting the consequences of harvest traffic in alfalfa production have addressed soil and plant growth parameters. One response was larger leaf/stem ratios in plants that were trafficked, which suggests higher quality. To fully understand how harvest traffic affects alfalfa quality a need for further analysis is warranted. Our objectives were to quantify differences in plant quality between trafficked and non-trafficked plants through 4 years of alfalfa production and to determine when these differences occur. The experimental units were furrow-irrigated raised beds with four harvests per year in Youngston clay loam soil in Fruita, Colorado. A John Deere 2280 swather and a John Deere 2955 tractor, driven over the alfalfa 7 days after swathing, were used to create four traffic treatments; plants that were never trafficked, plants trafficked only by the swather, plants trafficked only by the tractor, and plants trafficked by both the swather and the tractor. Quality was determined by measuring relative feed value, acid detergent fiber, neutral detergent fiber, and crude protein using near infrared reflectance spectroscopy. Alfalfa trafficked by the tractor had increased quality throughout the 4 years of production.

Rice bean-adzuki bean multitrait near infrared reflectance spectroscopy prediction model: a rapid mining tool for trait-specific germplasm.

In the present era of climate change, underutilized crops such as rice beans and adzuki beans are gaining prominence to ensure food security due to their inherent potential to withstand extreme conditions and high nutritional value. These legumes are bestowed with higher nutritional attributes such as protein, fiber, vitamins, and minerals than other major legumes of the Vigna family. With the typical nutrient evaluation methods being expensive and time-consuming, non-invasive techniques such as near infrared reflectance spectroscopy (NIRS) combined with chemometrics have emerged as a better alternative. The present study aims to develop a combined NIRS prediction model for rice bean and adzuki bean flour samples to estimate total starch, protein, fat, sugars, phytate, dietary fiber, anthocyanin, minerals, and RGB value. We chose 20 morphometrically diverse accessions in each crop, of which fifteen were selected as the training set and five for validation of the NIRS prediction model. Each trait required a unique combination of derivatives, gaps, smoothening, and scatter correction techniques. The best-fit models were selected based on high RSQ and RPD values. High RSQ values of >0.9 were achieved for most of the studied parameters, indicating high-accuracy models except for minerals, fat, and phenol, which obtained RSQ <0.6 for the validation set. The generated models would facilitate the rapid nutritional exploitation of underutilized pulses such as adzuki and rice beans, showcasing their considerable potential to be functional foods for health promotion.

Towards controlling the morphology of cobalt loaded nanocomposites in polyol process with polyethylene glycol

The polyol process is one of the simple, efficient and productive methods for the synthesis of metal loaded polymer composites. Functional properties of metal-polymer nanocomposites are determined by chemical composition, size and morphology of their particles. Finding effective ways to control the nanoparticle's properties during the polyol process is a crucial task. The effect of molar ratio Mn+/OHPEG on the formation of cobalt loaded metal-polymer nanocomposites during a one-pot two-component polyol process by polyethylene glycol with Mr = 4000 g·mol–1 (PEG) was studied. The PEG-based polyol process and the formation of cobalt nanophase were studied at molar ratios νCo2+/νOH(PEG) = 1:1, 1:10, 1:100 and 1:500 using UV-Vis, diffuse reflectance IR and ATR FT-IR spectroscopy, nanoparticle tracking analysis (NTA), dynamic light scattering (DLS). It was found that PEG can act as a reducing agent and stabilizing matrix for the cobalt nanophase at a ratio higher than Mn+/OHPEG= 1:10. The composition and morphology of Co/PEG nanocomposites were determined by XRD and TEM methods. Two types of spheroid particles with average diameters of 88±55 nm / 8±4 nm and 12±3 nm / 3±1 nm, respectively, represent Co/PEG nanocomposites 1:500 and 1:100. Scaly structures with a diameter of 15±5 nm are formed at a molar ratio of νCo2+/νOH(PEG) = 1:10. An increase in the Co2+ content in the PEG-based polyol process leads to the immobilized cobalt nanophase Co3O4 (1:500), Co0/CoO (1:100), CoO (1:10) in PEG. Co/PEG nanocomposites are hemocompatible. The HC50value depends on the composition and morphology of the nanoparticles.

Infrared spectroscopy as a tool for hydrothermal alteration mineral analysis to support geothermal reservoir characterization at The Geysers, California, USA

Infrared reflectance spectroscopy (IRS), an analytical method for characterizing geologic materials, is becoming more commonly applied to geothermal energy applications. However, few case studies are available in the literature and are restricted to relatively few volcanic/geologic environments. We present an interpretation of reservoir mineralogy using IRS on drill cuttings from an active magmatic-heat-sourced geothermal system hosted in metamorphic rocks known as “The Geysers”, located in northern California and operated by Calpine Corp. Wavelength ranges investigated include the Short Wave Infrared (SWIR; 1000–2500 nm) and the Long Wave Infrared (LWIR; 2.5–20 μm). We apply this technique to a 2848 m-deep geothermal production well in the northwest Geysers, inferred to overlie a Holocene intrusion and zone of partial melt as indicated by geophysics. We utilized this non-destructive technique to analyze every drill-cuttings sample (3000+ measurements collected at ∼3.3 m intervals). We identify a zonation in mineralogy that changes from illite + chlorite ± kaolinite ± smectite ± calcite at shallow depths (0–1000 m), to illite + chlorite ± calcite at intermediate depths (1000–2200 m), to actinolite + biotite + chlorite ± tourmaline at greatest depths (2200–2848 m). We find the change at 2200 m is proximal to the inferred transition from the “normal” temperature reservoir (∼240 °C vapor-dominated convective zone) to the high temperature reservoir (up to 400 °C, conduction-dominated). We identify a possible association between 1900 nm H2O absorptions and current steam entry locations. The results of the SWIR and LWIR analysis are consistent with some caveats with newly collected bulk rock X-Ray Diffraction (XRD) data, and support and compliment previous work at the Geysers utilizing XRD and petrographic analysis.

Magnetic and intrinsic dielectric properties of multiferroic GdFe1-xNixO3 (0.0 ≤ x ≤ 0.2) perovskites

Rare-earth transition-metal oxides with a perovskite crystal structure are at the forefront of the quest for new multifunctional materials, focusing on rare-earth orthoferrites ReFeO3. GdFeO3 is a multiferroic material that exhibits antiferromagnetic behavior, weak ferromagnetism, and ferroelectricity. The multiferroism of GdFeO3 can be tailored by substituting Fe with Ni. Recently, it was reported that the polycrystalline GdFe1-xNixO3 (x = 0, 0.1, 0.2) samples are materials with high dielectric constant at radio frequencies and room temperature, showing an increase in dielectric constant by introducing Ni3+ ions at Fe sites and reaching values in the order of ε'∼103 to 104, enabling their application as capacitors and miniaturized microwave resonators. In this paper, we examined the impact of Ni-substitution on the magnetic and intrinsic dielectric properties of GdFeO3 perovskite by analyzing the active-polar phonons through infrared reflectance spectroscopy and showed that its high dielectric constant has an extrinsic origin.

Crystal structure, chemical bonding and infrared reflectivity of microwave dielectric SrIn2O4 ceramics

In this work, the orthorhombic structured SrIn2O4 ceramics with a space group Pnam were synthesized by a solid-state reaction method. A high relative density (96.5%) coupled with excellent microwave dielectric properties (εr ~ 12.3, Q × f = 96,900 GHz, τf ~ -61.6 ppm/°C) were obtained as sintered 1300 °C for 4 h. The bond valence analysis demonstrates that the large sized cation Sr2+ exhibits a compressed state, while the In3+ exhibits a weaken rattling effect. The P-V-L chemical bond theory analysis indicates that the In-O bonds play a key role in affecting the dielectric loss. The thermally conductivity activation energy Edc (0.94 eV) of SrIn2O4 was obtained by the dielectric spectroscopy, indicating that the Edc was contributed to the double ionized oxygen vacancies. Furthermore, the intrinsic dielectric properties (εr ~ 11.2, Q × f = 148,900 GHz) of SrIn2O4 were obtained by infrared reflectivity spectroscopy.