Types Of Mineral Particles Research Articles

Effect of heat treatment on microcracking behaviors and Mode-I fracture characteristics of granite: An experimental and numerical investigation

Combining thermal stimulation and tensile fracture induced by cold water injection can synergistically enhance hydraulic fracturing, improving geothermal reservoir connectivity. To investigate the heat effect on the Mode-I fracture characteristics of granite, notched semi-circular bend (SCB) granite specimens were prepared and heat-treated at five temperatures ranging from 25 to 600 ℃. Mineralogical analysis and three-point bending tests were performed on the SCB specimens, and a grain-based model (GBM) incorporating four types of mineral particles was developed. The model was simulated for heat treatment and Mode-I loading and then validated against experimental results. The behavior and evolution of intra- and intergranular microcracks in the SCB specimens during heating, cooling, and mechanical loading were analyzed. Moreover, the fracture surface morphology and microcracking mechanisms observed in the SCB specimens at different heat-treatment temperatures were discussed. The results reveal a nonlinear trend in the Mode-I fracture toughness of the SCB specimens, initially increasing and then decreasing with heat-treatment temperature. The number of thermally induced cracks escalates with increasing heat-treatment temperature, predominantly as intergranular tensile cracks, followed by intragranular tensile cracks. Under Mode-I loading, the SCB specimens heat-treated below 450 ℃ predominantly exhibit intergranular cracks, while intragranular tensile cracks become more prevalent at 600 ℃. Thermally induced cracks can alter the propagation direction and path of mechanically induced cracks, causing macrocracks to deviate from the initial straight propagation path. Scanning electron microscope (SEM) analysis illustrates that at 300 ℃ and above, the fracture surface morphology becomes more fragmented and longer microcracks appear.

Adhesion and damage characteristics of wheel/rail using different mineral particles as adhesion enhancers

Mineral particles are used to improve adhesion between wheel and rail, but they might lead to severe damages of wheel and rail surfaces. To investigate the adhesion enhancement phenomena and damages of both wheel and rail induced by adhesion enhancers, the crushing strengths of four types of mineral particles (zinc oxide, sand, spinel and alumina) were firstly explored on a uniaxial compression tester. Then the adhesion, wear and damage of wheel/rail were studied on a twin-disc machine under the wet condition. The results show that the characteristic crushing strength was 24 MPa for zinc oxide, 40 MPa for sand, 51 MPa for spinel and 73 MPa for alumina, respectively. For particle with the lowest crushing strength (zinc oxide), the adhesion coefficient was the lowest (around 0.20). With the increase in the crushing strength to 40 MPa, the adhesion coefficient was improved to around 0.28. The particles with higher crushing strengths induced larger wheel/rail wear rates and severer rolling contact fatigue (RCF) damages on wheel and rail. The RCF cracks were large in lengths but small in angles, which finally developed into large pieces of material peeling off from the surface. Sand was the most suitable adhesion enhancer considering its good adhesion enhancement and the relatively mild damage on wheel/rail materials.

Attachment of APAM to mineral particles in seawater

Polymer injection is used in enhanced oil recovery (EOR) when an oil field ages and the pressure in the reservoir decreases, or for oil fields with heavy oil. By polymer injection, the viscosity of the water injected for pressure support is increased by mixing with a high concentration of a polymer solution. Polymers used in EOR operations are often high molecular weight polyacrylamides, including anionic polyacrylamide (APAM), which may subsequently enter the marine environment with produced water releases. Since seawater (SW) contains mineral particles (MPs) in low concentrations, and polymers like APAM are known to flocculate MPs, we investigated if APAM at different concentrations (0.5–10 mg/L) would attach and flocculate MPs, when these occurred in concentrations relevant for oceanic SW (1 mg/L). Two types of MPs, diatomaceous earth and kaolin, were exposed to fluorescence-tagged APAM (APAM-TAG). A low-energy carousel system with natural seawater (SW) was used for incubation of MPs and APAM-TAG at a temperature relevant for the Norwegian Continental Shelf (13 °C). Attachment to MPs and aggregates of these were analysed by fluorometry and fluorescence microscopy. Particle analyses showed that only minor fractions of the MPs aggregated. When samples were separated in steel filter with a mesh size of 20 μm, APAM-TAG was mainly measured in the flow-through fraction (<20 μm), and the results therefore showed that the polymer mainly remained in the water-phase, or was attached to small particles (<20 μm). For the small fraction of APAM attaching to aggregated MPs, attraction to kaolin was higher than to diatomaceous earth, and fluorescence microscopy analyses confirmed the presence of fluorescent particles at the higher APAM concentrations. MPs at concentrations relevant for oceanic SW are therefore not expected to significantly contribute to sedimentation of APAM dissolved in the water column.

Composite Bioceramics/Polymer Electrospun Scaffolds for Regenerative Medicine

The main goal of this study was to succeed in the relevant association of well-known osteoconductive biphasic calcium phosphate (BCP) made of Hydroxyapatite (20% HA) and β-Tricalcium Phosphate (80% β-TCP) crystallographic phases and resorbable poly (L-lactide-co-D,L-lactide)(PLDLLA) 3D matrices synthesized by electrospinning. Two types of mineral particles were obtained, BCP new hollow granules, and classical BCP particles. It appeared that hollow shells/PLDLLA composite 3D matrices allowed higher cell adhesion in vitro, thanks to internal concavities and are promising scaffolds in terms of cell carrying.

Community structure of bacteria on different types of mineral particles in a sandy soil

Various types of mineral particles in a soil probably provide different microenvironments for microorganisms. The purpose of this study is to investigate whether different types of mineral in a soil harbor different bacterial populations. DNA was extracted from five types (quartz, feldspar, pyroxene, magnetite, iron-coated reddish brown particles) of sand-size mineral particles separated from a sandy soil, and was amplified for partial 16 S rRNA gene by polymerase chain reaction (PCR). Twenty-nine to 69 amplicons per each type of mineral were cloned and sequenced, followed by phylogenetic affiliation of the sequences. As a result, some types of bacteria were detected on all of the types of mineral including the orders Rhizobiales, Bacillales, and Acidobacteriales. In the case of Acidobacteriales, higher percentages were found on magnetite and quartz. Some taxa were restricted to specific types of mineral; the class Actinobacteria was found on pyroxene but not on quartz, and rarely on magnetite and feldspar. Bacterial diversity at the order level estimated by Chao1 value was higher in feldspar and pyroxene than the other three types of mineral. The UniFrac Significance test indicated that the differences in bacterial communitiy structures among the particles were suggestive except that between feldspar and pyroxene. These results support the idea that different communities of bacteria were associated with each of the mineral types.

Studies of heterogeneous freezing by three different desert dust samples

Abstract. We present results of experiments at the aerosol interactions and dynamics in the atmosphere (AIDA) chamber facility looking at the freezing of water by three different types of mineral particles at temperatures between −12°C and −33°C. The three different dusts are Asia Dust-1 (AD1), Sahara Dust-2 (SD2) and Arizona test Dust (ATD). The dust samples used had particle concentrations of sizes that were log-normally distributed with mode diameters between 0.3 and 0.5 μm and standard deviations, σg, of 1.6–1.9. The results from the freezing experiments are consistent with the singular hypothesis of ice nucleation. The dusts showed different nucleation abilities, with ATD showing a rather sharp increase in ice-active surface site density at temperatures less than −24°C. AD1 was the next most efficient freezing nuclei and showed a more gradual increase in activity than the ATD sample. SD2 was the least active freezing nuclei. We used data taken with particle counting probes to derive the ice-active surface site density forming on the dust as a function of temperature for each of the three samples and polynomial curves are fitted to this data. The curve fits are then used independently within a bin microphysical model to simulate the ice formation rates from the experiments in order to test the validity of parameterising the data with smooth curves. Good agreement is found between the measurements and the model for AD1 and SD2; however, the curve for ATD does not yield results that agree well with the observations. The reason for this is that more experiments between −20 and −24°C are needed to quantify the rather sharp increase in ice-active surface site density on ATD in this temperature regime. The curves presented can be used as parameterisations in atmospheric cloud models where cooling rates of approximately 1°C min−1 or more are present to predict the concentration of ice crystals forming by the condensation-freezing mode of ice nucleation. Finally a polynomial is fitted to all three samples together in order to have a parameterisation describing the average ice-active surface site density vs. temperature for an equal mixture of the three dust samples.

Coal and coal ash characteristics to understand mineral transformations and slag formation

A knowledge of the composition and structure of minerals in coal is necessary in order to understand the mineral transformations and agglomerate or slag formation during combustion or gasification. Coal ash fusibility characteristics are difficult to determine precisely, partly because the ash contains many components with different chemical behaviours, and may vary from coal source to coal source. The first objective of this study was to determine if the most relevant characteristics of coal were representative of the typical coal from the South African Highveld region. Secondly, a detailed understanding of the coal and coal ash are needed in order to explain slag formation and mineral transformations. Based on standard coal properties, such as the ash content, volatile content, carbon content and maceral composition, it can be concluded that the coal sample used for this study was representative and comparable with the coal from the Highveld region. From the results obtained and the analysis done on the coal samples, it was observed that the mineral grains showed a wide range of types that ranged from pure coal to pure minerals. The types of mineral particles within the coal range from large irregular minerals to small irregular minerals on the edge of coal particles. Kaolinite and quartz can occur as fine inclusions in carbon rich particles or associated with mudstone, siltstone or sandstone, together with kaolinite infillings. The main minerals present in the coal feed are kaolinite, quartz, dolomite, calcite, muscovite, pyrite and microline. An abundance of calcium-rich particles, which are probably calcite and dolomite, were observed. These minerals are present throughout the coal structure and are not specific to one type of mineral grain or structure. An increase in Si and Al abundance in three different prepared coal fractions with increasing particle size distribution was observed the high density fractions are mainly situated in the coarser particles. After combustion or gasification, the major source of glass is derived from included minerals in carbon rich particles. It is clear that focus on the modification of the unclassified/amorphous phase, to increase viscosity (decrease slag formation or have a higher concentration of crystalline phases) at a certain temperature, or in general terms the ash fusion temperature of the coal, is important. Altering the ash chemistry involves the addition of a material to the coal to increase the viscosity.

An Update on the Detoxification Processes for Silica Particles and Asbestos Fibers: Successess and Limitations

Inhalation of asbestos fibers and crystalline silica produces a number of diseases including fibrosis and cancer. Investigations into the mechanisms involved in mineral particle-induced toxicity indicated the importance of their surfaces in the pathological consequences. Masking of the surface sites has therefore featured prominently in a number of detoxification processes that have been investigated. The majority of the detoxification processes were, however, conducted to elucidate the involvement of a particular surface site in the toxicity of a specific mineral. Others were investigated with the aim of large industrial applications to be applied during mining, handling, processing, transporting, and disposing of minerals. It can be concluded that, to date, there is no single detoxification process that could be applied universally to all different types of mineral particles. Those that have shown some success could not completely abolish all adverse effects. Further elucidation of mechanisms of particle-induced toxicity may open new possibilities for detoxification processes. The author thanks Professor J. C. A. Davies for his constructive comments and for proofreading the manuscript of this article.

Surface Assisted Nucleation and Growth of Polymer Latexes on Organically‐Modified Inorganic Particles

AbstractSummary: Polymer latex particles were synthesized in the presence of inorganic particles, which had been organically‐modified to promote favorable interactions with growing macromolecules. The organic modification was performed using three different routes: (1) surface covalent grafting of vinyl trialkoxysilanes, (2) surface adsorption of polyethylene glycol‐based macromonomers, and (3) bulk modification through ion exchange with cationic monomers or cationic initiators. Two types of mineral particles were studied: commercial and self‐prepared silica particles (with diameters from 80 nm to 1 µm), and commercial laponite clay particles with a cation exchange capacity of 0.75 meq · g−1. Emulsion polymerization was performed in the presence of styrene or butyl acrylate monomers. The morphologies of the nanocomposite particles were observed by (cryogenic) transmission electron microscopy and correlated to the organic modification procedure.

Identification of diesel exhaust particles at an Autobahn, urban and rural location using single-particle mass spectrometry

A single-particle mass spectrometer (LAMPAS-2) was operated at an Autobahn (high-speed highway with significant heavy-duty diesel traffic), an urban and a rural site in the vicinity of Aachen (Germany). The single-particle mass spectra could be classified into eight classes, representing different types of mineral particles, inorganic salt particles, and carbonaceous aerosol particles. At all three sites characteristic patterns of diesel exhaust particles with and without secondary compounds (ammonium sulfate/nitrate) were observed. The relative contribution of diesel soot to the number of 0.5 μm particles was 23% or 35% at the rural and the Autobahn site, respectively. The absolute number of diesel exhaust particles was three times larger at the Autobahn site. At the urban site the diesel exhaust particle contribution ranged from 10% to 35%, depending on the local operation of heavy-duty construction vehicles. Elemental carbon and carbonaceous particles made up the majority number of the 0.5 μm particles, and showed a decreasing percentage towards 2 μm particle size. As expected mineral-soil-derived particles showed the reverse size distribution. The data sets were also analyzed using a reference pattern obtained from exhaust particles of a light-duty diesel vehicle as a fingerprint. A similar trend of the contribution to the diesel-exhaust-like particle class was found, although the absolute numbers were somewhat different. On-line single-particle mass spectrometry proved to be a promising tool to identify individual particles if characteristic reference spectra were available.

Comparison of the Chemical Composition of Mineral Particles Collected in Dunhuang, China and those Collected in the Free Troposphere over Japan: Possible Chemical Modification during Long-Range Transport

The Asian continent is recognized as one of the most important sources of mineral (or soil) particles. These particles have a large potential to effect global changes through the biogeochemical cycle of particulates and through radiative balance (IPCC Third Assessment Report, 2001). Therefore, comparison of particle compositions near the source region and those after long-range transport is important in understanding the long-range particle transport phenomenon. Individual aerosolparticles were collected in Dunhuang (40°09′N; 94°41′E), China. Particles were collected at the campus of the Meteorological Bureau of Dunhuang City (17 August 2001) and near the Mogao Grots, located approximately 30 km from Dunhuang (18 August 2001, 18 October 2001 and 13 January 2002) using a two-stage low-volume impactor. The morphology of individual aerosol particles and their elemental compositions were examined via a scanning electron microscope (Hitachi, S-3000N) equipped with an energy dispersive X-ray (EDX) analyzer (Horiba, EMAX-500). The particles collected at these locations were comprised primarily of minerals, with the exception of sulphateparticles in the submicron range that were contained in thesample collected on 18 October 2001 (likely, ammonium sulphate). The most abundant elements were found to be Si and Al. Approximately 46–77% of the collected particles were Si-richparticles (composed primarily of quartz and aluminosilicate),and 13–41% of the collected particles were Ca-rich particles,such as calcite (CaCO3), dolomite (CaMg(CO3)2),and gypsum (CaSO4ċ2H2O). The fractions of Fe-rich, Mg-rich, Ti-rich, K-rich, and Cl-rich were 3–10, 0–7, 0–3, 0–1, and 0–1%, respectively. Similar types of mineral particles were found in the free troposphere over Japan(Trochkine et al., 2002). A number of differences were found to exist between the particles collected in China and thosecollected in Japan, and these differences can be explained bychemical modification of the particles during transport fromChina to Japan.

Mineral particles in bronchoalveolar lavage fluid (BALF): an attempt at designing a quantitative model.

The author examined by morphology, chemical composition, and crystalline structure, approximately 2 500 mineral particles from bronchoalveolar lavage fluids obtained from 25 residents of Rome. In addition, the author obtained the same structural data for approximately 3000 inhalable particles present in the atmosphere in Rome. The author constructed a model of the concentration and granulometry of the different types of mineral particles in bronchoalveolar lavage fluids, by estimating the clearance times of the different particle classes. The author based the model on the following: (a) data relative to the inhalable particulate to which involved subjects were exposed, (b) updated knowledge about the processes of deposition and retention of the mineral particulate in the human respiratory tract, and (c) the hypothesis that the mineral particle pattern in bronchoalveolar lavage fluid reflects the pattern of particulate in lung parenchyma. Finally, the author compared the model with the particulate pattern observed in the bronchoalveolar lavage fluid samples. Despite some drastic approximations, the model satisfactorily fits the data obtained from the experimental research on mineral particulate in bronchoalveolar lavage fluid.