Sub-micron Composition Research Articles

Assessment of submicron bone tissue composition in plastic-embedded samples using optical photothermal infrared (O-PTIR) spectral imaging and machine learning

Understanding the composition of bone tissue at the submicron level is crucial to elucidate factors contributing to bone disease and fragility. Here, we introduce a novel approach utilizing optical photothermal infrared (O-PTIR) spectroscopy and imaging coupled with machine learning analysis to assess bone tissue composition at 500 nm spatial resolution. This approach was used to evaluate thick bone samples embedded in typical poly(methyl methacrylate) (PMMA) blocks, eliminating the need for cumbersome thin sectioning. We demonstrate the utility of O-PTIR imaging to assess the distribution of bone tissue mineral and protein, as well as to explore the structure-composition relationship surrounding microporosity at a spatial resolution unattainable by conventional infrared imaging modalities. Using bone samples from wildtype (WT) mice and from a mouse model of osteogenesis imperfecta (OIM), we further showcase the application of O-PTIR spectroscopy to quantify mineral content, crystallinity, and carbonate content in spatially defined regions across the cortical bone. Notably, we show that machine learning analysis using support vector machine (SVM) was successful in identifying bone phenotypes (typical in WT, fragile in OIM) based on input of spectral data, with over 86% of samples correctly identified when using the collagen spectral range. Our findings highlight the potential of O-PTIR spectroscopy and imaging as valuable tools for exploring bone submicron composition.

Application of Optical Photothermal Infrared (O-PTIR) Spectroscopy for Assessment of Bone Composition at the Submicron Scale.

The molecular basis of bone structure and strength is mineralized collagen fibrils at the submicron scale (∼500 nm). Recent advances in optical photothermal infrared (O-PTIR) spectroscopy allow the investigation of bone composition with unprecedented submicron spatial resolution, which may provide new insights into factors contributing to underlying bone function. Here, we investigated (i) whether O-PTIR-derived spectral parameters correlated to standard attenuated total reflection (ATR) Fourier transform infrared spectroscopy spectral data and (ii) whether O-PTIR-derived spectral parameters, including heterogeneity of tissue, contribute to the prediction of proximal femoral bone stiffness. Analysis of serially demineralized bone powders showed a significant correlation (r = 0.96) between mineral content quantified using ATR and O-PTIR spectroscopy, indicating the validity of this technique in assessing bone mineralization. Using femoral neck sections, the principal component analysis showed that differences between O-PTIR and ATR spectra were primarily attributable to the phosphate ion (PO4) absorbance band, which was typically shifter toward higher wavenumbers in O-PTIR spectra. Additionally, significant correlations were found between hydrogen phosphate (HPO4) content (r = 0.75) and carbonate (CO3) content (r = 0.66) quantified using ATR and O-PTIR spectroscopy, strengthening the validity of this method to assess bone mineral composition. O-PTIR imaging of individual trabeculae at 500 nm pixel resolution illustrated differences in submicron composition in the femoral neck from bones with different stiffness. O-PTIR analysis showed a significant negative correlation (r = -0.71) between bone stiffness and mineral maturity, reflective of newly formed bone being an important contributor to bone function. Finally, partial least squares regression analysis showed that combining multiple O-PTIR parameters (HPO4 content and heterogeneity, collagen integrity, and CO3 content) could significantly predict proximal femoral stiffness (R2 = 0.74, error = 9.7%) more accurately than using ATR parameters. Additionally, we describe new findings in the effects of bone tissue orientation in the O-PTIR spectra. Overall, this study highlights a new application of O-PTIR spectroscopy that may provide new insights into molecular-level factors underlying bone mechanical competence.

Formation mechanisms of sub-micron pharmaceutical composite particles derived from far- and near-field Raman microscopy

Surface enhanced Raman spectroscopy (SERS) and confocal Raman microscopy are applied to investigate the structure and the molecular arrangement of sub-micron furosemide and polyvinylpyrrolidone (furosemide/PVP) particles produced by spray flash evaporation (SFE). Morphology, size and crystallinity of furosemide/PVP particles are analyzed by scanning electron microscopy (SEM) and X-ray powder diffraction (XRPD). Far-field Raman spectra and confocal far-field Raman maps of furosemide/PVP particles are interpreted based on the far-field Raman spectra of pure furosemide and PVP precursors. Confocal far-field Raman microscopy shows that furosemide/PVP particles feature an intermixture of furosemide and PVP molecules at the sub-micron scale. SERS and surface-enhanced confocal Raman microscopy (SECoRM) are performed on furosemide, PVP and furosemide/PVP composite particles sputtered with silver (40 nm). SERS and SECoRM maps reveal that furosemide/PVP particle surfaces mainly consist of PVP molecules. The combination of surface and bulk sensitive analyses reveal that furosemide/PVP sub-micron particles are formed by the agglomeration of primary furosemide nano-crystals embedded in a thin PVP matrix. Interestingly, both far-field Raman microscopy and SECoRM provide molecular information on a statistically-relevant amount of sub-micron particles in a single microscopic map; this combination is thus an effective and time-saving tool for investigating organic sub-micron composites.

Physical and chemical properties of atmospheric aerosols in Moscow and its suburb for climate assessments

The paper presents results of experimental study of the physicochemical properties of surface aerosols in the Moscow region in the summer of 2019. Microphysical parameters, mass concentration and elemental composition of submicron and micron aerosol particles are considered, and their morphological structure is described. The features of variability of aerosol characteristics under atypical weather conditions prevailing in June-July 2019 are shown. The spatial distribution of the elemental composition of aerosols is established, a significant degree of their enrichment with heavy metals and metalloids is revealed. Geochemical analysis of aerosols and soils in Moscow was performed, and the coefficients of local aerosol concentration were calculated. The obtained experimental data will be useful for the refinement and verification of climate models.

A Comprehensive Review on the Corrosion Pathways of Titanium Dental Implants and Their Biological Adverse Effects

The main aim of this work was to perform a comprehensive review of findings reported by previous studies on the corrosion of titanium dental implants and consequent clinical detrimental effects to the patients. Most studies were performed by in vitro electrochemical tests and complemented with microscopic techniques to evaluate the corrosion behavior of the protective passive oxide film layer, namely TiO2. Results revealed that bacterial accumulation, dietary, inflammation, infection, and therapeutic solutions decrease the pH of the oral environment leading to the corrosion of titanium. Some therapeutic products used as mouthwash negatively affect the corrosion behavior of the titanium oxide film and promote changes on the implant surface. In addition, toothpaste and bleaching agents, can amplify the chemical reactivity of titanium since fluor ions interacting with the titanium oxide film. Furthermore, the number of in vivo studies is limited although corrosion signs have been found in retrieved implants. Histological evaluation revealed titanium macro- and micro-scale particles on the peri-implant tissues. As a consequence, progressive damage of the dental implants and the evolution of inflammatory reactions depend on the size, chemical composition, and concentration of submicron- and nanoparticles in the surrounding tissues and internalized by the cells. In fact, the damage of the implant surfaces results in the loss of material that compromises the implant surfaces, implant-abutment connections, and the interaction with soft tissues. The corrosion can be an initial trigger point for the development of biological or mechanical failures in dental implants.

Enrichment of submicron sea-salt-containing particles in small cloud droplets based on single-particle mass spectrometry

Abstract. The effects of the chemical composition and size of sea-salt-containing particles on their cloud condensation nuclei (CCN) activity are incompletely understood. We used a ground-based counterflow virtual impactor (GCVI) coupled with a single-particle aerosol mass spectrometer (SPAMS) to characterize chemical composition of submicron (dry diameter of 0.2–1.0 µm) and supermicron (1.0–2.0 µm) sea-salt-containing cloud residues (dried cloud droplets) at Mount Nanling, southern China. Seven cut sizes (7.5–14 µm) of cloud droplets were set in the GCVI system. The highest number fraction of sea-salt-containing particles was observed at the cut size of 7.5 µm (26 %, by number), followed by 14 µm (17 %) and the other cut sizes (3 %–5 %). The submicron sea-salt-containing cloud residues contributed approximately 20 % (by number) at the cut size of 7.5 µm, which was significantly higher than the percentages at the cut sizes of 8–14 µm (below 2 %). This difference was likely involved in the change in the chemical composition. At the cut size of 7.5 µm, nitrate was internally mixed with over 90 % of the submicron sea-salt-containing cloud residues, which was higher than sulfate (20 %), ammonium (below 1 %), amines (6 %), hydrocarbon organic species (2 %), and organic acids (4 %). However, at the cut sizes of 8–14 µm, nitrate, sulfate, ammonium, amines, hydrocarbon organic species, and organic acids were internally mixed with > 90 %, > 80 %, 39 %–84 %, 71 %–86 %, 52 %–90 %, and 32 %–77 % of the submicron sea-salt-containing cloud residues. The proportion of sea-salt-containing particles in the supermicron cloud residues generally increased as a function of cut size, and their CCN activity was less influenced by chemical composition. This study provided a significant contribution towards a comprehensive understanding of sea-salt CCN activity.

Dielectric properties and surface potential decay characteristics of low density polyethylene/ZnO microvaristor composites

This paper focuses on the effects of submicron ZnO microvaristors on the microstructure and electrical properties of low density polyethylene (LDPE) based composites. The submicron ZnO microvaristors are obtained by ball milling method and are used as a filler of LDPE based composites. The submicron composites with the filler loading of 0, 10, 20, 30 and 40 wt% are prepared by melt-blending method. The morphology, crystallization behavior, dielectric properties and surface potential decay characteristics are characterized by scanning electron microscope, differential scanning calorimetry, dielectric spectrum and surface potential decay measurement, respectively. Experimental results show that the average speed of the surface potential decay characteristics of LDPE based composites increases distinctly with the increasing filler loading. The submicron ZnO microvaristors are in favorable to suppress the charge accumulation of LDPE based composites and can be used to regulate the charge distribution in electrical and electronic equipment.

Field investigations for evaluating green infrastructure effects on air quality in open-road conditions

Many people live, work and spend time during their commute in near-road environments (<50 m) where pollutant concentrations usually remain high. We investigated the influence of roadside green infrastructure (GI) on concentrations of particulate matter ≤10 μm (PM10), ≤2.5 μm (PM2.5), ≤1 μm (PM1), black carbon (BC) and particle number concentrations (PNC) under three GI configurations – (i) hedges only, (ii) trees only, and (iii) a mix of trees and hedges/shrubs – separately in close (<1 m) and away (>2 m) road conditions. These configurations gave us a total of six different real-world scenarios for evaluation. The changes in concentrations of PM10, PM2.5, PM1, BC and PNC at all six sites were estimated by comparing simultaneous measurements behind and in front of GI (or adjacent clear area). A portable battery-operated experimental set-up was designed for measuring the pollutant concentrations for 30 full days over a field campaign period of three months. On each day, around 10 h of continuous data were recorded simultaneously behind and in front of GI/adjacent clear area, capturing both morning and evening traffic peaks. Our objectives were to: (i) assess the effectiveness of different types of GI in reducing various pollutants; (ii) evaluate the impact of wind directions and density of vegetation on reducing different pollutant concentrations behind GI; (iii) investigate the changes in fractional composition of sub-micron (PM1), fine (PM2.5) and coarse (PM2.5-10) particles; and (iv) quantify the elemental composition of collected particles before and after the GI. In away-road conditions, all three configurations showed reductions behind the GI for all pollutants. The ‘hedges only’ configuration showed higher pollutant reductions than the other two configurations, with maximum reductions of up to 63% shown for BC. In close-road conditions, the results were mixed. The ‘trees only’ configuration reported increases in most of the pollutant concentrations, whereas the combination of trees and hedges resulted in reduced pollutant concentrations behind the GI. Among all pollutants, the highest relative changes in concentration were observed for BC (up to 63%) and lowest for PM2.5 (14%). Categorising the data based on wind directions showed the highest reduction during along-road wind conditions (i.e., parallel to the road). This was expected due to the sweeping of emissions by the wind and the wake of road vehicles whilst the barrier effect of GI enhanced this cleansing, limiting lateral diffusion of the pollutants. However, cross-road winds that took vehicular emissions to pass through the GI allowed us to assess their influence, showing up to 52, 15, 17, 31 and 30% reduction for BC, PM10, PM2.5, PM1 and PNC, respectively. The largest reductions were consistently noted for the mixed ‘trees and hedges’ configuration in close-road conditions and the ‘hedge only’ configuration in away-road conditions. The assessment of various fractions of PM showed that ‘hedges only’ and a combination of trees and hedges lowered fine particles behind GI. The SEM-EDS analysis indicated the dominance of natural particles (50%) and a reduction in vehicle-related particles (i.e., iron and its oxides, Ba, Cr, Mn) behind GI when compared with the in-front/adjacent clear area. The evidence contributed by this work enhances our understanding of air quality modifications under the influence of different GI configurations, for multiple pollutants. In turn, this will support the formulation of appropriate guidelines for GI design, to reduce the air pollution exposure of those living, working or travelling near busy roads.

Urban influence on the concentration and composition of submicron particulate matter in central Amazonia

Abstract. An understanding of how anthropogenic emissions affect the concentrations and composition of airborne particulate matter (PM) is fundamental to quantifying the influence of human activities on climate and air quality. The central Amazon Basin, especially around the city of Manaus, Brazil, has experienced rapid changes in the past decades due to ongoing urbanization. Herein, changes in the concentration and composition of submicron PM due to pollution downwind of the Manaus metropolitan region are reported as part of the GoAmazon2014/5 experiment. A high-resolution time-of-flight aerosol mass spectrometer (HR-ToF-AMS) and a suite of other gas- and particle-phase instruments were deployed at the “T3” research site, 70 km downwind of Manaus, during the wet season. At this site, organic components represented 79±7 % of the non-refractory PM1 mass concentration on average, which was in the same range as several upwind sites. However, the organic PM1 was considerably more oxidized at T3 compared to upwind measurements. Positive-matrix factorization (PMF) was applied to the time series of organic mass spectra collected at the T3 site, yielding three factors representing secondary processes (73±15 % of total organic mass concentration) and three factors representing primary anthropogenic emissions (27±15 %). Fuzzy c-means clustering (FCM) was applied to the afternoon time series of concentrations of NOy, ozone, total particle number, black carbon, and sulfate. Four clusters were identified and characterized by distinct air mass origins and particle compositions. Two clusters, Bkgd-1 and Bkgd-2, were associated with background conditions. Bkgd-1 appeared to represent near-field atmospheric PM production and oxidation of a day or less. Bkgd-2 appeared to represent material transported and oxidized for two or more days, often with out-of-basin contributions. Two other clusters, Pol-1 and Pol-2, represented the Manaus influence, one apparently associated with the northern region of Manaus and the other with the southern region of the city. A composite of the PMF and FCM analyses provided insights into the anthropogenic effects on PM concentration and composition. The increase in mass concentration of submicron PM ranged from 25 % to 200 % under polluted compared with background conditions, including contributions from both primary and secondary PM. Furthermore, a comparison of PMF factor loadings for different clusters suggested a shift in the pathways of PM production under polluted conditions. Nitrogen oxides may have played a critical role in these shifts. Increased concentrations of nitrogen oxides can shift pathways of PM production from HO2-dominant to NO-dominant as well as increase the concentrations of oxidants in the atmosphere. Consequently, the oxidation of biogenic and anthropogenic precursor gases as well as the oxidative processing of preexisting atmospheric PM can be accelerated. This combined set of results demonstrates the susceptibility of atmospheric chemistry, air quality, and associated climate forcing to anthropogenic perturbations over tropical forests.

One-step reduction synthesis of Ag/Ag3PO4/AgBr sub-micron composites for enhanced visible photocatalytic degradation of methyl orange

An efficient semiconductor composite, silver/silver orthophosphate/silver bromide, was successfully synthesized by a facile one-step reduction and ion exchange process. Its crystal structure, morphology, optical property, surface element composition were characterized by X-ray diffraction, scanning electron microscopy, ultraviolet-visible diffuse reflectance spectrometer and X-ray photoelectron spectrometer. The effects of composite proportion and synthesis duration on performances of as-prepared photocatalysts were investigated, and the results showed that Br/P molar ratio of 3 and the synthesis duration of 4 h were the optimum conditions. The radical scavenging experiments indicated that the hole and superoxide radical were the main active species in this reaction system. The Ag/Ag3PO4/AgBr-3 presented excellent stability and recyclability, maintaining 92% of degradation efficiency after 5 cycles. The good photocatalysis performance could be attributed to the formation of the heterojunction between Ag and Ag3PO4/AgBr.

Chemical composition of submicron and fine particulate matter collected in Krakow, Poland. Consequences for the APARIC project

Submicron particulate matter containing particles with an aerodynamic diameter ≤1 μm (PM1) are not monitored continuously by Environmental Protection Agencies around the World and are seldom studied. Numerous studies have indicated that people exposed to ultrafine (≤100 nm), submicron and fine particulate matter containing particles with an aerodynamic diameter ≤2.5 μm (PM2.5), can suffer from respiratory track diseases, cardiovascular, immunological or heart diseases and others. Inorganic pollutants containing redox active transition metals and small gaseous molecules, are involved in the generation of reactive oxygen and reactive nitrogen species. Inhalation of this kind of particles can affect immune-toxicity. Environmental pollution may aggravate the course of autoimmune diseases, in particular influence the mechanisms of the autoimmune system. Important factors that influence the toxicity of particulate matter, are particle size distribution, composition and concentration. This report deals with the composition of PM1 and PM2.5 fractions collected in Krakow, Poland. In spring 2015, the mean concentrations of PM1 and PM2.5 were 19 ± 14 and 27 ± 19 μg/m3, respectively. The PM2.5 fraction contained approximately 70 ± 17% of submicron particulate matter. In spring 2016, the mean concentrations of PM1 and PM2.5 were 12 ± 5 and 22 ± 12 μg/m3, respectively. The PM2.5 fraction contained approximately 60 ± 15% of submicron particulate matter. The concentrations of the elements Cl, K, Ca, Ti, Cr, Mn, Fe, Ni, Cu, Zn, Br, Rb, Sr and Pb in both fractions were determined by X-ray fluorescence spectrometry. Most of the analyzed metals had higher concentrations in the fine fraction than in the submicron one. Concentrations of V and As were below the detection limit in both fractions, whereas concentrations of Mn and Ca were below the detection limits in the PM1 fraction. The results are discussed in terms of the consequences they may have on the APARIC project presently underway in Krakow.

Heterogeneous catalytic activation of peroxymonosulfate for efficient degradation of organic pollutants by magnetic Cu0/Fe3O4 submicron composites

Magnetic Cu0/Fe3O4 submicron composites were prepared using a hydrothermal method and used as heterogeneous catalysts for the activation of peroxymonosulfate (PMS) and the degradation of organic pollutants. The as-prepared magnetic Cu0/Fe3O4 submicron composites were composed of Cu0 and Fe3O4 crystals and had an average size of approximately 220 nm. The Cu0/Fe3O4 composites could efficiently catalyze the activation of PMS to generate singlet oxygen, and thus induced the rapid degradation of rhodamine B, methylene blue, orange II, phenol and 4-chlorophenol. The use of 0.1 g/L of the Cu0/Fe3O4 composites induced the complete removal of rhodamine B (20 μmol/L) in 15 min, methylene blue (20 μmol/L) in 5 min, orange II (20 μmol/L) in 10 min, phenol (0.1 mmol/L) in 30 min and 4-chlorophenol (0.1 mmol/L) in 15 min with an initial pH value of 7.0 and a PMS concentration of 0.5 mmol/L. The total organic carbon (TOC) removal higher than 85% for all of these five pollutants was obtained in 30 min when the PMS concentration was 2.5 mmol/L. The rate of degradation was considerably higher than that obtained with Cu0 or Fe3O4 particles alone. The enhanced catalytic activity of the Cu0/Fe3O4 composites in the activation of PMS was attributed to the synergistic effect of the Cu0 and Fe3O4 crystals in the composites. Singlet oxygen was identified as the primary reactive oxygen species responsible for pollutant degradation by electron spin resonance and radical quenching experiments. A possible mechanism for the activation of PMS by Cu0/Fe3O4 composites is proposed as electron transfer from the organic pollutants to PMS induces the activation of PMS to generate 1O2, which induces the degradation of the organic pollutants. As a magnetic catalyst, the Cu0/Fe3O4 composites were easily recovered by magnetic separation, and exhibited excellent stability over five successive degradation cycles. The present study provides a facile and green heterogeneous catalysis method for the oxidative removal of organic pollutants.

Characterization of Al Matrix SiC Reinforced Sub-Micron Composites Produced by Mechanical Alloying

In this study, properties of the aluminum matrix silicon carbide reinforced sub-micron composite powders produced by mechanical alloying were investigated. High purity Al and SiC powders were used as initial powders. To investigate the effect of SiC quantity 5, 10, 15 and 20% weight ratio of SiC particles were added to the aluminum matrix. Milling operations were conducted at 250 rpm under high purity argon atmosphere for 120 h by planetary type ball mill. Milling balls and vial were made of tungsten carbide. The milling system stopped for by various time intervals and samples were taken from the powder mixture. After milling operations taken samples were analyzed by SEM, XRD and BET surface area and porosity measurement systems.

Amino-functionalized Fe3O4/SiO2 magnetic submicron composites and In3+ ion adsorption properties

Five kinds of amino-functionalized (polyaniline, poly(1,2-diaminobenzene), poly(1,3-diaminobenzene), poly(diphenylamine), and poly(o-toluidine)) Fe3O4/SiO2 submicron composites (SCs) were prepared. The SEM and TEM results showed that these SCs possessed a sphere-like core/shell structure with an average diameter of ~500 nm. The XRD results indicated good crystallinity of Fe3O4 core, the amorphous SiO2, and amino-functionalized shells. The XPS results confirmed that amino groups were plentiful rich outside the surface of these SCs which acted as the effective groups for adsorbing the metal ions. These SCs showed a good thermal stability at 20–250 °C. The high saturation magnetization of 60–70 emu/g is better than other similar reports. In3+ adsorption coefficients from aqueous solution by these SCs were higher than 106 mL/g, indicating the higher selectivity and affinity to In3+ compared with Cd2+ and Hg2+ ions. In addition, these SCs could be magnetically reclaimed within 30 s and regenerated with acid after adsorption. The adsorption capabilities only decreased by 6 % after five cycles. The present work indicates that the amino-functionalized Fe3O4/SiO2 SCs are promising for removal of In3+ ions in field application.

Influence of semiconductor/insulator/semiconductor structure on the photo-catalytic activity of Fe3O4/SiO2/polythiophene core/shell submicron composite

The Fe3O4/SiO2/polythiophene (FSP) submicron composite (SC) with a structure of semiconductor/insulator/semiconductor (SIS) was obtained. The characterization results showed that the FSP SC had a spherical core/shell shape with an average diameter of 506nm. The high saturated magnetization value (∼39emu/g) ensured the easy separation of FSP SC from aqueous solution. The photo-catalytic activity of the FSP SC was evaluated by the degradation of methyl orange (MO) under UV-irradiation in the presence of H2O2. Due to the SIS structure, the degradation rate constant by FSP SC (0.02177min−1) was 6.4, 1.6, and 2.5 times higher than that of Fe3O4/polythiophene (FP), polythiophene (P), and TiO2, respectively. The repetition results suggested the good photochemical stability of FSP SC. The mechanism was proposed by investigating the energy band variation of the SIS structure, the transfer of light generated carriers and the formation of effective hydroxyl radicals in the photo-catalysis progress.

Comparative evaluation of dental resin composites based on micron- and submicron-sized monomodal glass filler particles

ObjectivesA model resin composite containing a novel monomodal inorganic filler system based on submicron-sized Ba–Si–Al glass particles (NanoFine NF180; Schott) was formulated and compared with an experimental composite containing micron-sized particles (UltraFine UF1.0; Schott). MethodsThe filler particles were characterized using X-ray microanalysis and granulometry, while the composites were characterized in terms of filler–resin morphology, radiopacity, degree of CC conversion, hardness, flexural strength/modulus, work-of-fracture, surface roughness and gloss (before and after simulated toothbrushing abrasion), and bulk compressive creep. The composites were formulated from the same photoactivated dimethacrylate co-monomer, incorporating mass fractions of 75% micron- and 78% submicron-sized particles. Quantitative data were analyzed at a significance level of p<0.05. ResultsBoth filler systems exhibited a narrow grain size range (175±30 and 1000±200nm), with differences restricted to the size and specific area of the particles. The composites were similar in radiopacity, flexural strength, work-of-fracture, and creep. The submicron composite was harder but had lower flexural modulus and CC conversion. No significant differences in roughness were observed before brushing, although the submicron composite had higher gloss. Brushing increased roughness and decreased gloss on both materials, but the submicron composite retained higher gloss after brushing. SignificanceThe monomodal submicron glass filler system demonstrated potential for use in restorative dental composites, particularly due to improved esthetic properties.

Possibility of Implementation of the Complete Cycle of Synthesizing Bulk Polycrystalline Titanium Nitride with Submicron Composition by Plasmodynamic Methods

The possibility of direct plasmodynamic synthesis and production of ultradisperse titanium nitride as well of its application as a raw material for producing compact polycrystalline and nanostructured material by the spark plasma sintering method is demonstrated. Results of investigations of the grain sizes and phase composition of ultradispersed TiN and physicomechanical properties and composition of the compact material are presented.

Alumina reinforced eucryptite ceramics: Very low thermal expansion material with improved mechanical properties

Composite materials formed by a LAS matrix reinforced with second phases are promising materials in many applications where better mechanical properties than those corresponding to conventional low thermal expansion coefficient materials are required. In this study we will show the capability of the design of a LAS–alumina submicron composite. The main scope of this work is to test the sinterability of the composites and to design a composition for a very low thermal expansion submicron composite. For this purpose, Taimei alumina (TM-DAR) powders and an ad hoc synthesized β-eucryptite phase were used to fabricate the composite. XRD phase compositions and microstructures are discussed together with data from dilatometries in a wide temperature range. The results obtained show the possibility of designing a submicron composite with a very low thermal expansion coefficient and improved mechanical properties that can be used in oxidizing conditions.

Chemical composition of free tropospheric aerosol for PM1 and coarse mode at the high alpine site Jungfraujoch

Abstract. The chemical composition of submicron (fine mode) and supermicron (coarse mode) aerosol particles has been investigated at the Jungfraujoch high alpine research station (3580 m a.s.l., Switzerland) as part of the GAW aerosol monitoring program since 1999. A clear seasonality was observed for all major components throughout the period with low concentrations in winter (predominantly free tropospheric aerosol) and higher concentrations in summer (enhanced vertical transport of boundary layer pollutants). In addition, mass closure was attempted during intensive campaigns in March 2004, February–March 2005 and August 2005. Ionic, carbonaceous and non-refractory components of the aerosol were quantified as well as the PM1 and coarse mode total aerosol mass concentrations. A relatively low conversion factor of 1.8 for organic carbon (OC) to particulate organic matter (OM) was found in winter (February–March 2005). Organics, sulfate, ammonium, and nitrate were the major components of the fine aerosol fraction that were identified, while calcium and nitrate were the only two measured components contributing to the coarse mode. The aerosol mass concentrations for fine and coarse mode aerosol measured during the intensive campaigns were not typical of the long-term seasonality due largely to dynamical differences. Average fine and coarse mode concentrations during the intensive field campaigns were 1.7 μg m−3 and 2.4 μg m−3 in winter and 2.5 μg m−3 and 2.0 μg m−3 in summer, respectively. The mass balance of aerosols showed higher contributions of calcium and nitrate in the coarse mode during Saharan dust events (SDE) than without SDE.

Directed growth of single-crystal indium wires

Tailored electric fields were used to direct the dendritic growth of crystalline indium wires between lithographic electrodes immersed in solutions of indium acetate. Determination of the conditions that suppress sidebranching on these structures has enabled the fabrication of arbitrarily long needle-shaped wires with diameters as small as 370nm. Electron diffraction studies indicate that these wires are crystalline indium, that the unbranched wire segments are single-crystal domains, and that the predominant growth direction is near ⟨110⟩. This work constitutes a critical step towards the use of simply prepared aqueous mixtures as a convenient means of controlling the composition of submicron, crystalline wires.