Peak Intensity Ratio Research Articles

Quantitative 1-D LIBS measurements of fuel concentration in natural gas jets at high ambient pressure

Fuel concentration information is critical to the development of high-efficiency combustion system of direct-injection natural gas engines. In this study, a one-dimensional (1-D) measurement approach based on laser induced breakdown spectroscopy (LIBS) is developed to quantitatively measure 1-D fuel concentration distributions in gas jets at high ambient pressures. Except for the spectral dimension, another dimension of the intensified charge coupled device (ICCD) is employed for the spatial resolution of measurements. The effects of laser energy and ambient pressure on plasma dynamics are investigated to explore the feasibility of 1-D LIBS in concentration measurements at high ambient pressure. Since the peak intensity ratio (PIR) of H656/N746 shows significant spatial variations in the plasma volume, a 1-D calibration strategy is developed by establishing respective calibration curves at different spatial positions to quantify the fuel concentration distributions. The measurement uncertainties are evaluated, including both the systematic and random errors. The temporal variations of the 1-D fuel concentration distributions in methane jets are presented, and the shot-to-shot fluctuations are analyzed in detail. The results show that the coefficient of variation of equivalence ratio is lowest at the end of injection (EOI), suggesting that ignition at the EOI could enable a relatively stable flame kernel formation. Along the radial direction of the jet, a high ignitable mixture percentage appears at approximately 3.0 mm from the jet axis at the EOI, suggesting an optimal ignition position. The results reveal that the 1-D LIBS could be a powerful tool for calibration of numerical models and optimal designs of combustion engines taking advantage of high-pressure gas jets.

Structure and properties of graphene oxide during the synthesis process at fixed temperatures

Graphene oxide (GO) is the most versatile derivative of graphene; however, the choice of oxidation temperature in the synthesis of GO varies from person to person. In this article, various spectroscopy techniques have been used to characterize carbon and oxygen structure of GO synthesized at fixed oxidation temperatures. Our results show that GO synthesized at a relatively low temperature possesses a decreased D-to-G peak intensity ratio (ID:IG) and obvious single-crystal lattice with a six-fold pattern. As the oxidation temperature increase, a polycrystalline ring structure forms, accompanied by an increasing ID:IG, which indicates that the disorder of the basal plane of GO increases with increasing temperature. Notably, the layer spacing of GO decreases with an increase in temperature, which does not show the expected proportional relationship to the degree of oxidation. Furthermore, chemical composition analysis shows that moderate temperatures contribute to the formation of C–O–C and ≥CO bonds, while the contents of C–OH and sp2 domains decreases, and the content of COOH does not change with temperature. Interestingly, GO is successfully synthesized at 75 °C, indicating that Mn2O7 is not the only oxidant playing a dominant role in the oxidation stage of GO. This work can provide in-depth insight into the viable selection of the oxidation temperature of GO for industrial applications.

Raman spectroscopy provides insight into carbonate rock fabric based on calcite and dolomite crystal orientation.

Carbonate rocks record the oldest forms of life on Earth, and their geologic reconstruction requires multiple methods to determine physical and chemical processes before conclusions of ancient biosignatures are made. Since crystal orientation within rock fabric may be used to infer geologic settings, we present here a complementary Raman method to study the orientation of calcite (CaCO3) and dolomite [CaMg (CO3)2] minerals. The relative peak intensity ratio of the carbonate lattice Eg modes T and L reveals the crystallographic orientation of calcite and dolomite with respect to the incident light polarization. Our results for calcite show that when the incident laser light propagates down the crystallographic a/b axis: (1) the L mode is always greater in intensity than the T mode (I T < I L), and (2) the spectra are most intense at 45° and least intense at 90° polarization angles measured from around the c axis. Our results for dolomite show that (1) I T > I L when the incident light propagation is down the crystallographic c axis and (2) I T < I L when the incident light propagation is down the crystallographic a/b axis. This study reveals mineral orientation variation related to deposition and paragenesis within limestone and dolostone samples. The method presented yields information related to growth and deformation during diagenetic and metamorphic alteration and may be used in research seeking to identify the fabric parameters of any calcite or dolomite containing rock. The compositional and structural data obtained from Raman mapping is useful in structural geology, materials science, and biosignature research.

Analysis of single‐cell microbial mass spectra profiles from single‐particle aerosol mass spectrometry

Single-particle aerosol mass spectrometry is a practical method for studying microbial aerosols. However, the related mass spectra characteristics of single-cell microorganisms have not yet been studied systematically; hence, further investigations are necessary. Different microbial cells were grown and directly aerosolized in the laboratory. These aerosols were then drawn into a single-particle mass spectrometer platform, and single-cell mass spectra profiles were obtained in real-time. The biological characteristics, ion variation trends, and microbial types were analyzed with either laser pulse energy or laser fluence. The single-particle mass spectra contained prominent peaks that could be attributed to the presence of biological matter, such as organic phosphate and nitrogen, amino acids, and spore-associated calcium complexes. Limited types of average mass spectrum patterns were present, and a significant correlation was found between the ion intensity trend (presence and absence of peaks) and laser ionization energy (expressed by the total positive ion intensity). Although a single spectral data point does not contain all peaks of the average spectrum, it covers most of the characteristics peaks and could be identified using a machine learning algorithm. After the analysis of single-particle mass spectra, we found that using multi-group features (e.g., peak intensity ratio of m/z +47 and +41, peak intensity ratio of 59 N(CH3 )3 + and 74 N(CH3 )4 + , and 12 peak variables) led to an identification accuracy of approximately 92.4% with the random forest algorithm. The results indicate that single-cell mass spectra profiles can be used to distinguish microbial aerosols and further illustrate their origin in a laboratory setting.

Carbonate and cation substitutions in hydroxylapatite in breast cancer micro-calcifications

Abstract Calcification within breast cancer is a diagnostically significant radiological feature that generally consists of hydroxylapatite. Samples from 30 cases of breast carcinoma with calcification were investigated using optical microscopy, energy-dispersive X-ray analysis, transmission-electron microscopy, Fourier-transform infrared spectroscopy, Raman spectroscopy, synchrotron radiation X-ray diffraction and X-ray fluorescence. Under optical microscopy, the calcifications were found to consist of either irregular aggregates with widths &gt; 200 μm or spherical aggregates similar to psammoma bodies with an average diameter of 30 μm. Transmission-electron microscopy showed that short columnar or dumbbell-shaped crystals with widths of 10–15 nm and lengths of 20–50 nm were the most common morphology; spherical aggregates (~1 μm in diameter) with amorphous coatings of fibrous nanocrystals were also observed. Results indicated that hydroxylapatite was the dominant mineral phase in the calcifications, and both CO32– and cation substitutions (Na, Mg, Zn, Fe, Sr, Cu and Mn) were present in the hydroxylapatite structure. Fourier-transform infrared spectra show peaks at 872 and 880 cm–1 indicating that CO32– substituted both the OH– (A type) and PO43– (B type) sites of hydroxylapatite, making it an A and B mixed type. The ratio of B- to A-type substitution was estimated in the range of 1.1–18.7 from the ratio of peak intensities (I872/I880), accompanied with CO32– contents from 1.1% to 14.5%. Trace arsenic, detected in situ by synchrotron radiation X-ray fluorescence was found to be distributed uniformly in the calcifications in the form of AsO43– substituting for PO43–. It is therefore proposed that identifying these trace elements in breast cancer calcifications may be promising for future clinical diagnostics.

Early evaluation of treatment response to transarterial chemoembolization in patients with advanced hepatocellular carcinoma: The role of dynamic three-dimensional contrast-enhanced ultrasound.

Dynamic three-dimensional contrast-enhanced ultrasound (3D-CEUS) with quantitative analysis is available in recent years. It can reduce the quantitative sampling error caused by the inconsistency of different sections in order to evaluate local treatment response of hepatocellular carcinoma (HCC) accurately. To investigate the value of dynamic 3D-CEUS in evaluating the early response to transarterial chemoembolization (TACE) treatment in patients with advanced HCC lesions. In this prospective study, both two-dimensional (2D) CEUS and dynamic 3D-CEUS were performed on 40 HCC patients who scheduled for TACE at baseline (T0) and 1-3 days (T1) after treatment. Tumor microvascular perfusion changes were assessed by CEUS time-intensity curve (TIC) and quantitative parameters. According to contrast-enhanced computed tomography (CT) and magnetic resonance (MR) imaging 1 month after treatment results, patients were divided into responders and non-responders groups. The changes of perfusion parameters of both 2D-CEUS and 3D-CEUS were compared between responders and non-responders groups before and after TACE treatment. Before and after TACE treatment, no significant difference in maximum diameter of HCC lesions between the two groups could be found. There were more significant differences and ratios of perfusion parameters in 3D-CEUS quantitative analysis than in 2D-CEUS. The mutual significant differences and ratios of 2D-CEUS and 3D-CEUS included peak intensity (PI) difference, PI ratio, ratio of area under the curve (A), ratio of area under the wash-out part (AWO) and slope (S) difference. The former 4 corresponding parameters were better on 3D-CEUS than on 2D-CEUS. Dynamic 3D-CEUS can be used as a potential imaging method to evaluate early treatment response to TACE in advanced HCC patients.

Ratiometric Electrochemical Detection of MicroRNA Based on Construction of A Hierarchical C@SnS2 Nanoflower Sensing Interface

Abstract Building a precise, sensitive, and selective sensing platform is highly significant for microRNA (miRNA) detection. Herein, an innovative ratiometric electrochemical biosensor sensitized with carbon nanoparticles-functionalized SnS2 nanoflowers (C@SnS2 NFs) and enzyme-assisted target recycling was explored for analysis of miRNA-21. In this strategy, the application of hierarchical C@SnS2 NFs structure as electrode material not only enhanced the surface loading capability for subsequent reactions but also improved the interfacial electron transfer. After introducing enzyme-assisted target recycling, single-target miRNA-21 could initiate the cleavage of multiple capture DNA strands by duplex-specific nuclease (DSN), leading to numerous rest single-strand DNAs on the electrode. Two probes, methylene blue-labeled probe 1 (probe 1-MB) and ferrocene-labeled probe 2 (probe 2-Fc), could selectively and competitively hybridize with the capture DNA and the rest single-strand DNA, depending on the completeness of DNA hybridization. By measuring the peak current intensity ratio of Fc and MB, miRNA-21 was quantified in a wide concentration range from 1 fmol/L to 10 pmol/L, with a detection limit of 300 amol/L. Moreover, this sensing system showed good analytical performance in the presence of interfering sequences and complex matrices, illuminating excellent selectivity and practical application potential of the hierarchical C@SnS2 NF sensing interface.

Enantioselective recognition of amino acid based on electrochemical deposition and X-ray diffraction technology

Addition of D-Asp in the electrochemical deposition process of Bismuth film resulted the generation of a new diffraction peak in X-ray diffraction (XRD) spectrum. This phenomenon was not observed in the situation of L-Asp. The new diffraction peak might suggest D-Asp could result in the generation of a specific Bismuth structure. Enantioselective recognition of D- and L-Asp can be realized based on this new XRD peak. The limit of detection was determined to be 3.5 × 10−8 and 1.7 × 10−8 mol L−1 for D- and L-Asp, respectively. The XRD spectra of electrodeposited Copper films fabricated in the presence of D- or L-Asp showed different lattice plane diffraction peak intensity ratios. The reason was believed to be chirality induced different binding capabilities of Asp enantiomers that influenced Copper film growth. Therefore, the combination of electrochemical deposition using Copper as metal source and XRD technology can be used to achieve enantioselective recognition of Asp. The limit of detection for D- and L-Asp were determined to be 1.5 × 10−10 and 1.2 × 10−11 mol L−1, respectively.

Spin-Orbit Coupling Effects in Au 4f Core-Level Electronic Structures in Supported Low-Dimensional Gold Nanoparticles.

Despite their many advantages, issues remain unresolved over the variability in catalytic activities in supported gold nanoparticle (AuNP)-based catalysts, which requires precise characterization to unravel the presence of any fine features. Herein, upon analyzing the Au 4f core-level spin-orbit components in many as-synthesized AuNP-based catalysts, we observed that like deviations in the Au 4f7/2 binding energy positions, both the Au 4f7/2-to-Au 4f5/2 peak intensity and linewidth ratios varied largely from the standard statistical bulk reference values. These deviations were observed in all the as-synthesized supported AuNPs irrespective of different synthesis conditions, variations in size, shape or morphology of the gold nanoparticles, and different support materials. On the other hand, the spin-orbit-splitting values remained almost unchanged and did not show any appreciable deviations from the atomic or bulk standard gold values. These deviations could originate due to alterations in the electronic band structures in the supported AuNPs and might be present in other NP-based catalyst systems as well, which could be the subject of future research interest.

Oxidation degree or sheet size: What really matters for the photothermal effect and ecotoxicity of graphene oxide?

A set of thirteen GO samples obtained following different methodologies and described by eight structural parameters – hydrodynamic diameter (658 nm–142 nm), size polydispersity index, optical absorption coefficient, lambda maximum, D/G peak intensity ratio, crystallite size, distance between defects, and pH – was submitted to NIR 808 nm irradiation (experiment 1) and fish embryo toxicity (FET) test performed with zebrafish embryos (experiment 2). Principal component analysis (PCA) applied to the obtained data shows that the optical absorption coefficient and lambda maximum, which are strongly dependent on the GO oxidation degree and presence of carboxylic acid groups, are the most relevant features for the photothermal effect. Conversely, size is the predominant parameter for the ecotoxicity. Only samples exhibiting the smallest sheet size (below 200 nm) do not interfere either on the hatching time or the rate of alive hatched individuals. GO samples composed of larger sheets, regardless their oxidation and carboxylation degrees, impart negative effects to the embryo’s development stages, including hatching delay, death of embryos and abnormalities on hatched individuals. It is therefore concluded that the photothermal effect is more dependent on the oxidation degree, whereas ecotoxicity is more dependent on the size of GO sheets.

Variations of Peak He/H Ratios in Solar Energetic (E &gt; 4 MeV) Particle Events and Comparisons with Solar Wind He/H Ratios

Abstract We determine solar energetic particle (SEP) event He/H peak intensity ratios A He observed in the four energy channels of the SOHO EPHIN detector covering 4–53 MeV nuc−1. Those SEP A He values range over two orders of magnitude for 43 large western hemisphere SEP events through the period 1997–2017. A He of each SEP event are compared with average solar wind (SW) A He values measured for 8 hr after the SEP event onsets with the solar wind experiment Faraday Cup instrument on Wind. A He in the 4–8 and 8–21 MeV nuc−1 range are significantly correlated with SW A He (CC = 0.45 and 0.41), but less so in the 21–41 and 41–53 MeV nuc−1 range, where uncertainties of the A He values are higher. Median SEP A He values decline slightly with increasing energy and are ≤0.5 their associated SW values. Both median SEP and SW A He decline by a factor of ∼2 from the 27 events of cycle 23 to the 16 of cycle 24. Those results suggest a connection between the SW and the seed population of SEP events. An unexpected result is that SEP A He increases with event peak intensities in our 43 events as He peak intensities increase faster than those of H in larger events.

Development, characterization and comparison of spark plasma-sintered Gr–Cu and Gr–Al composites reinforced with SiC and ZrB2 particles for thermal management

Graphite–copper (Gr–Cu) and graphite–aluminum (Gr–Al) composites are potential candidates for enhanced thermal management for different engineering applications. However, their applications are limited by inadequate thermal conductivity, high coefficient of thermal expansion (CTE) and low microhardness. In this study, SiC and ZrB2 were incorporated into Gr–Cu and Gr–Al powders, and then sintered in a spark plasma sintering (SPS) system to produce Gr–Cu + 8wt%SiC, Gr–Cu + 4wt%SiC + 4wt%ZrB2, Gr–Al + 8wt%SiC and Gr–Al + 4wt%SiC + 4wt%ZrB2 composites. After sintering, the physical, morphological, thermal, electrical and mechanical properties of the composites were evaluated. Results indicated 8.5% increase in relative density for reinforced Gr–Cu composites over the unreinforced Gr–Cu. The porosity of the reinforced Gr–Cu composites is 40.5% lower than that of the unreinforced and ~ 8% for reinforced Gr–Al. For all the sintered samples, Gr–Cu + 4wt%SiC + 4wt%ZrB2 sample has the highest hardness value of 44.5 HV0.1, highest peak intensity ratio of 80.19% and minimum CTE of 2.02 × 10–5/K. The huge increase in the microhardness and peak intensity ratio of Gr–Cu + 4wt%SiC + 4wt%ZrB2 is partially attributed to the formation of hard ZrC phase and three-bond system in ZrB2. This composite is recommended for thermal management of heat sinks and heat spreaders in electronics and pistons in automobiles.

Boron Isotope Tag-Assisted Ultrahigh-Performance Liquid Chromatography Coupled with High-Resolution Mass Spectrometry for Discovery and Annotation of cis-Diol-Containing Metabolites.

cis-Diol-containing metabolites are widely distributed in living organisms, and they participate in the regulation of various important biological activities. The profiling of cis-diol-containing metabolites could help us in fully understanding their functions. In this work, based on the characteristic isotope pattern of boron, we employed a boronic acid reagent as the isotope tag to establish a sensitive and selective liquid chromatography-high-resolution mass spectrometry method for the screening and annotation of cis-diol-containing metabolites in biological samples. Boronic acid reagent 2-methyl-4-phenylaminomethylphenylboronic acid was used to label the cis-diol-containing metabolites in biological samples to improve the selectivity and MS sensitivity of cis-diol-containing metabolites. Based on the characteristic 0.996 Da mass difference of precursor ions and the peak intensity ratio of 1:4 originating from 10B and 11B natural isotopes, the potential cis-diol-containing metabolites were rapidly screened from biological samples. Potential cis-diol-containing metabolites were annotated by database searching and analysis of fragmentation patterns obtained by multistage MS (MSn) via collision-induced dissociation. Importantly, the cis-diol position could be readily resolved by the MS3 spectrum. With this method, a total of 45 cis-diol-containing metabolites were discovered in rice, including monoglycerides, polyhydroxy fatty acids, fatty alcohols, and so forth. Furthermore, the established method showed superiority in avoiding false-positive results in profiling cis-diol-containing metabolites.

Breath-by-breath measurement of intraoperative propofol by unidirectional anisole-assisted photoionization ion mobility spectrometry via real-time correction of humidity

Humidity as a major issue affects the quantitative performance of ion mobility spectrometry (IMS) in field applications. According to the kinetic equations of ion-molecular reaction, the intensity ratio of the product ion peak (PIP) over the reactant ion peak (RIP) is proposed as a quantitative factor to correct real-time humidity variation. By coupling this method with a unidirectional anisole-assisted photoionization IMS, direct breath-by-breath measurement of intraoperative propofol was achieved for the first time, which provided more clinical information for studying the anesthetics pharmacokinetics. Although the signal intensities of the RIP and the propofol PIP both declined along with the increase of humidity, the intensity ratio of Propofol/(RIP + Propofol) kept almost constant in a wide relative humidity range of 0%–98%, enabling direct quantitation of exhaled propofol with varying humidity. Furthermore, interfering ion peaks resulted from the high concentration humidity and anesthetics in single exhalation were eliminated during the balanced anesthesia as the exhaled sample was diluted by the unidirectional gas flow scheme. As a demonstration, breath-by-breath variation profiles of propofol were obtained via monitoring end-tidal propofol concentration of intraoperative anesthetized patients (n = 7). The analyses were quantitative, corrected for humidity in real-time, without measuring the humidity content of each breath sample during operation, which show potential for the quantitative analysis of other high humidity samples.

Carbon Monoxide Oxidation over Gold Nanoparticles Deposited onto Alumina Film Grown on Mo(110) Substrate: An Effect of Charge Tunneling through the Oxide Film.

Formation of gold nanosized particles supported by aluminum oxide film grown on Mo(110) substrate and oxidation of carbon monoxide molecules on their surface have been in-situ studied in ultra-high vacuum by means of Auger electron spectroscopy (AES), reflection-absorption infrared spectroscopy (RAIRS), low energy electron diffraction (LEED), atomic force microscopy (AFM), temperature-programmed desorption (TPD), and work function measurements. The main focus was to follow how the thickness of the alumina film influences the efficiency of CO oxidation in an attempt to find out evidence of the possible effect of electron tunneling between the metal substrate and the Au particle through the oxide interlayer. Providing the largest degree of surface identity of the studied metal/oxide system at different thicknesses of the alumina film (two, four, six, and eight monolayers), it was found that the CO oxidation efficiency, defined as CO2 to CO TPD peaks intensity ratio, exponentially decays with the oxide film thickness growth. Taking into account the known fact that the CO oxidation efficiency depends on the amount of excess charge acquired by Au particle, the latter suggests that electron tunneling adds efficiency to the oxidation process, although not significantly.

Contrast-Enhanced Ultrasound in the Differential Diagnosis of Primary Thyroid Lymphoma and Nodular Hashimoto's Thyroiditis in a Background of Heterogeneous Parenchyma.

ObjectiveTo investigate the diagnostic performance of contrast-enhanced ultrasound (CEUS) in the differentiation of primary thyroid lymphoma (PTL) and nodular Hashimoto’s thyroiditis (NHT) in patients with background of heterogeneous diffuse Hashimoto’s thyroiditis (HT).MethodsSixty HT patients with 64 thyroid nodules (31 PTL and 33 NHT) who had undergone CEUS examination were included in this study. With histopathological results as the reference, we evaluated the imaging features of each nodule on both conventional ultrasonography (US) and CEUS. Quantitative CEUS parameters including peak intensity (PI), time to peak (TTP), and area under the time–intensity curve (AUC) were gathered in the nodule and background parenchyma. The ratio indexes of theses parameters were calculated by the ratio of the lesion and the corresponding thyroid parenchyma. Logistic regression and receiver operating characteristic (ROC) curves analyses of valuable US indicators were further preformed to evaluate the diagnostic capability of CEUS in discrimination of PTL and NHT.ResultsAmong all the observed US imaging features and CEUS parameters, 10 indicators showed significant differences between PTL and NHT (all P < 0.05). All the significant indicators were ranked according to the odds ratios (ORs). Eight of them were CEUS associated including imaging features of enhancement pattern, degree, homogeneity, and quantification parameters of PI, AUC, ratios of PI, AUC, and TTP, while indicators on conventional US, including vascularity and size ranked the last two with ORs less than 3. The five single CEUS parameters showed good diagnostic performance in diagnosis of PTL with areas under ROC curves of 0.72–0.83 and accuracies of 70.3–75.0%. The combination of CEUS imaging features and the ratios of PI, AUC, and TTP demonstrated excellent diagnostic efficiency and achieved area under ROC curve of 0.92, which was significantly higher than any of the five single parameters (all P < 0.05), with a sensitivity of 83.9%, specificity of 87.9%, and accuracy of 85.9%.ConclusionsCEUS is an efficient diagnostic tool in the differential diagnosis of PTL and NHT for patients with diffuse HT. Conjoint analysis of CEUS imaging features and quantification parameters could improve the diagnostic values.

Facile Synthesis of a Color-Tunable Microcrystal Phosphor for Anti-Counterfeit Applications.

Developing luminescent materials with tunable emission colors provides exciting opportunities for application in the display, anti-counterfeiting, and optical sensors. Here, we report a convenient, versatile approach to synthesize color-tunable, up/down-conversion luminescence in an inorganic host material. The emission color can be tuned by varying the excitation wavelength, allowing dynamic color tuning in the visible spectrum. We demonstrate that an unprecedented luminescence tunability from these phosphors can be achieved by tailoring the intensity ratio of different emission peaks. These findings provide valuable insights into controlling multiple emission color processes while offering the possibility for dynamic anti-counterfeiting and visual sensing of ultraviolet light in the range from 250 to 320 nm. These results open the opportunity for developing next-generation stimuli-responsive luminescent materials and smart devices.

Revealing the evolving mixture of molecular aggregates during organic film formation using simulations of in situ absorbance.

In this work, we introduce a method for modeling the evolving absorbance spectrum of an organic molecule, pseudoisocyanine (PIC), measured during the process of molecular aggregation. Despite being historically considered a J-aggregate, we find that the absorbance spectrum of PIC cannot be adequately modeled using solely J-aggregates either during molecular aggregation or in the final dry film. The collection of absorbance spectra during solution-casting is particularly difficult since a distribution of aggregates with various sizes and structures can coexist. Here, spectra measured during film formation are fit to a weighted sum of simulated spectra of two aggregate species, revealing the combinations of Coulombic coupling values, Huang-Rhys parameters, and aggregate sizes that provide good fits to measured spectra. The peak intensity ratios and relative peak positions are highly sensitive to the aggregate structure, and fitting only these features enables the rapid comparison of aggregate combinations. We find that the spectra of PIC aggregates cannot be modeled using the Huang-Rhys factor of the PIC monomer, as is typically assumed, leading us to consider models that utilize independent Huang-Rhys factors for each aggregate species. This method of fitting only the key spectral features allows an experimental spectrum to be modeled within 1 h-2 h when using a single Huang-Rhys factor, making the simulation of a series of in situ measurements during aggregation computationally feasible.

Effects of the degree of oxidation of pitch fibers on their stabilization and carbonization behaviors

The stabilization of isotropic pitch (IP)-derived pitch fibers (PFs) and mesophase pitch (MP)-derived PFsin air was performed at different heating rates and with different final stabilization temperatures. The stabilized fibers (SFs) and carbon fibers (CFs) were characterized by elemental analysis, FT-IR, TG-MS and SEM to investigate the influence of the degree of oxidation of the SFs on the microstructures and mechanical properties of the CFs. Results showed that a slow heating rate during stabilization was beneficial to the oxidative cross-linking of PFs, and the corresponding CFs had a higher carbonization yield and tensile strength at the lower heating rate. When both IPF and MPF were stabilized at 270 oC, the two resulting CFs all reached their optimal performance. In addition, the FTIR peak intensity ratio of the C=O band at about 1700 cm–1 to the C=C band at 1600 cm–1 of the SFs had a good relationship to the carbonization yield and tensile strength of the CFs, and thiscan beusedto optimize the degree of oxidation of the SFs. Moreover, insufficiently stabilized fibers released a great deal of H2 and CH4, causing some porosity in the resulting CFs with a low tensile strength, especially forthe insufficiently stabilized IPCF. While over-stabilized fibers released a large amount of CO and CO2, causing cracked textures in the corresponding CFs, especially inthe over-stabilizedMPCF. Therefore, this research into the stabilization and carbonization behaviors of pitch fibers has great significance for improving the mechanical properties of pitch-based CFs.

Morphology evolution and quantitative analysis of β-MoO3 and α-MoO3

AbstractThe morphology evolution from monoclinic molybdenum trioxide (β-MoO3) to orthorhombic molybdenum trioxide (α-MoO3) and quantitative analyses of their mixtures were examined. It was found that the morphology (from spherical to elliptical shape) and color (from green to white) displayed obvious changes when β-MoO3converted to α-MoO3in ambient air at 773 K. The transformation from β-MoO3to α-MoO3resulted from a change of the internal crystalline structure. The mass percent of β-MoO3in MoO3mixtures showed an excellent linear relationship with the relative intensity ratio of the strongest peaks in X-ray diffraction patterns. This approach provides a simple and time-saving method to evaluate the amount of β-MoO3, which is a promising material in catalyst and electrochemical applications, in such mixtures. This finding may provide guidance for the analysis of catalytic performance of MoO3mixtures. In addition, it was found that β-MoO3can be easily decomposed into suboxides such as MoO2and Mo4O11in pure argon gas atmosphere. The possible decomposition mechanism of β-MoO3is discussed.