Coarse Crystalline Research Articles

Influence of Additve on Over-Sulfur Phosphogypsum-Ground Granulate Blast-Furnace Slag Cement

The effect of sodium hydroxide (NaOH) and polycarboxylate superplasticizer amount on over-sulfur phosphogypsum–ground granulate blast-furnace slag cement was investigated. The mechanical performances and hydration mechanism of the cement with different proportions of NaOH and polycarboxylate superplasticizer (BASF) were analyzed based on setting time, the additive quantity of water, strength test, XRD and SEM analyses. The results showed that the polycarboxylate superplasticizer, can increase the densification and the strength of the cement ,to improve the performance of the cement anti-carbonation properties. NaOH as an alkali activator significantly reduces the cement setting time and improves the cement early strength. But the acceleration of hydration process produces coarse crystalline hydration products and the osteoporosis structure of hardened paste, which has a negative effect on long term strength.

Fragmentation of disordered titanium monoxide of stoichiometric composition TiO

Fragmentation was carried out for coarse crystalline disordered titanium monoxide of stoichiometric composition TiO containing up to 16 at.% of structural vacancies in each titanium and oxygen sublattices. According to X-ray diffraction analysis, the fragmentation attained the nanometric size of titanium monoxide particles. In spite of the small size of the nanoparticles (about 30 nm) and high degree of induced microstrains of the crystal lattice (~0.57%), their atomic structure retained the main features of the disordered cubic structure of coarse crystalline titanium monoxide with the space group Fm-3m.

The role of thermochemical sulfate reduction in the genesis of high-quality deep marine reservoirs within the central Tarim Basin, western China

Deeply buried Ordovician reservoirs within the central Tarim Basin, China, contain elevated concentrations of H2S. This study uses petrography, carbon and sulfur isotopes, and fluid inclusion microthermometry data to determine whether these elevated concentrations formed as a result of thermochemical sulfate reduction (TSR) and evaluates the influence of TSR on porosity. TSR-derived H2S is likely to have been incorporated into pyrite and minor sphalerite, as reflected by the similar δ34S values for H2S (15.0–23.4 ‰) and coarse crystalline pyrite (15–29.7 ‰). Sulfide precipitation caused an increase in acidity that allowed the dissolution of carbonates during TSR. The occurrence of dissolution during deep burial is indicated by: (1) the occurrence of dissolution pores within high-temperature (91.6–121 °C) burial calcite cement, (2) the coexistence of high-porosity sediments with elemental sulfur and pyrite in areas away from unconformities that would have undergone only limited interaction with meteoric water; (3) the presence of giant porous karst-filling calcites in association with coarse crystalline pyrite; and (4) a slightly negative shift in the δ13C values of some postbitumen calcite. Several factors probably limited the effect of TSR on the quality of reservoirs within the central Tarim Basin. The reactive SO4 −2 involved in the TSR process was supplied by deep hydrothermal waters that contained dissolved sulfate rather than by the dissolution of anhydrite, meaning that only a limited increase in TSR-generated porosity occurred, restricted to areas along faults. The heterogeneity of metal ion concentrations within the reservoirs also constrained TSR-related carbonate dissolution, as after ferric ions within the reservoirs were consumed during advanced diagenesis, TSR-derived CO2 accumulated within the reservoirs, causing a negative shift in present-day CO2 δ13C values.

Morphology and origin of dolomite in paleosols and lacustrine sequences. Examples from the Miocene of the Madrid Basin

The northern Madrid Basin contains paleosols and lacustrine sequences composed of ordered dolomite. Smectite-rich mudstones with analcime deposited in distal alluvial fans affected by pedogenic processes. Mudstones contain dolomite and silica laminae interpreted as mineralized root-mats. Dolostones with prismatic structure constitute Stage III dolocretes. Homogeneous lacustrine dolomudstones show some features indicative of subaerial exposure. Dolomite textures include: microcrystalline dolomite, coarse crystalline mosaics located in root cavities, dolomite dumbbells and dolomite spheroids replacing clays, dolomudstones or opal. Mol values of MgCO3 of dolomites vary between 47.67% and 53.34% mol. δ18O values range between −3.65 and −5.51‰ VPDB. δ13C values range between −7.19 and −8.38‰ VPDB.Dolomicrite formed in alkaline lakes by direct precipitation and replacement of clays in soils. The rhizosphere was favorable for dolomite mosaic and dumbbells formation. Spheroidal dolomite replaced clays and opal under early phreatic diagenesis. Trioctahedral smectites, silica and analcime indicate that these pedogenic and lacustrine environments were alkaline. Smectites and/or carboxyl groups acted as a catalyst favoring the incorporation of Mg into dolomite. In these non-saline settings the kinetic barriers for dolomite precipitation lowered by high pH and Mg enrichment. Ordered dolomite formation occurred under biogenic and abiogenic conditions, during sedimentation, pedogenesis and early diagenesis.

Dolomitization of Lower Cretaceous Peritidal Carbonates By Modified Seawater: Constraints From Clumped Isotopic Paleothermometry, Elemental Chemistry, and Strontium Isotopes

Abstract This study investigates one of the few examples of dolomitization of Lower Cretaceous shallow-water limestones from the southern Tethys carbonate platform from outcrops on the Haushi-Huqf High in central-east Oman. Mud-dominated peritidal carbonates rich in microbial mats are replaced by fine crystalline dolomite along at least 60 km in the lower 10 m of the Jurf Formation. Two, meter-thick beds in the overlying Qishn Formation are also dolomitized over lateral distances of one to two kilometers. The stratabound geometry and petrographic relations of the dolomite with all other diagenetic phases indicate that the dolomite precipitated early. The presence of only rare anhydrite relicts suggests that seawater was below gypsum saturation during most of the dolomitization, supporting the hypothesis that Cretaceous slightly evaporated water (δ18Ofluid values range from 2.8‰ to 3.5‰ SMOW) can affect pervasive dolomitization. Despite being composed of peritidal facies with features suggesting high salinity, most of the carbonate succession was not dolomitized, suggesting that the presence of microbial mats exerted a major control on the distribution of dolomite, and that salinity is only a minor control on dolomitization. Clumped-isotope results indicate that the early formed dolomite re-equilibrated with fluids at 44 ± 3°C in a shallow-burial setting. The elevated iron content (on average 6011 ppm) and 87Sr/86Sr (on average 0.70782) with respect to Cretaceous seawater suggests that the burial fluids interacted with Permian clay and feldspars of the Gharif Formation that underlies the Cretaceous carbonates. The vertical gradients of radiogenic Sr and the occurrence of small volumes of coarse crystalline dolomite in stylolites and fractures suggests that burial fluids were driven vertically and laterally by differential compaction, probably during maximum burial in the Late Cretaceous.

Synthesis and characterization of the Mars-relevant phosphate minerals Fe- and Mg-whitlockite and merrillite and a possible mechanism that maintains charge balance during whitlockite to merrillite transformation

Merrillite [Ca9NaMg(PO4)7] occurs as a dominant primary Ca-phosphate mineral in martian meteorites and therefore presumably also on Mars. The mineral is an important phase in exploring differences in geologic processes between Earth and Mars, and also has astrobiological implications due to its potential role as a significant source of the bio-essential nutrient phosphate. Merrillite does not occur terrestrially as a discrete mineral phase, making it difficult to obtain for Mars-relevant studies. It can, however, be synthesized from a similar terrestrial mineral, whitlockite (natural or synthetic), through dehydrogenation. Here we present methods for synthesizing relatively large quantities (0.5 g or greater per batch) of coarse crystalline (75 μm+) Mg-whitlockite, Fe-whitlockite, mixed Fe/Mg-whitlockites, and from these synthesized minerals produce Mg-merrillite, ferrous and ferric Fe-merrillite, and ferrous and ferric mixed Fe/Mg-merrillite. Chemistry and atomic structures of synthesized Fe- and mixed Fe/ Mg-whitlockite and ferrous and ferric Fe- and mixed Fe/Mg- merrillite resulting from single-crystal X-ray diffraction, infrared spectroscopy, and electron microprobe analyses are presented. We also present a mechanism for maintaining charge balance during the formation of merrillite from whitlockite. Our results shed light on these mineral structures for future martian studies, and provide methods for creating coarse crystalline merrillite for use in Mars-relevant thermodynamic, kinetic, soil/dust simulant, crystallographic, astrobiological, and other studies.

Origin and palaeo-environmental significance of the Berrazales carbonate spring deposit, North of Gran Canaria Island, Spain

The Berrazales carbonate spring deposit is a small outcrop constituted mainly by cascade-like geometries. Four main facies have been identified: fibrous dense macrocrystalline formed by rapid degassing under high-flow conditions; framestones of coated plant moulds formed in moderate energy flow favoured by the presence of biogenic support; micrite/microsparite are primary precipitates in which crystalline aggregates nucleated on organic filaments and/or EPS; banded micrite-coarse crystalline were the result of alternating physically, chemically and biologically induced precipitation in areas of varying flow-velocities. Most facies underwent different degrees of micritization processes. Micrite is distributed as thin lines penetrating the crystals, as irregular patches or as micrite layers. In the first case organic filaments penetrate crystals, suggesting that micritization is mainly biogenically driven. In the latter cases micritization is caused mostly by partial dissolution. Microbe participation in micrite formation increased micrite MgCO3 content in comparison with coarse crystalline facies.Isotopic analyses show positive δ13C values (+2.63 and +4.29‰ VPDB) and negative δ18O (−5.65 and −4.48‰ VPDB) values. Positive δ13C values clearly indicate “deep-sourced” fluids.The Berrazales spring deposit studied here very probably is a small part of a larger carbonate building that was largely eroded by fluvial incision. Calculations of spring water temperature give a range from 20°C to 35°C, characteristic of a cold to warm spring favouring precipitation of calcite and important biogenic activity (framestones). Although the study deposit has textural characteristics of tufas, proving that the CO2 sourced from deep fluids, it should be considered as thermogene travertine, being one more example of the difficulty of using those terms for ancient sedimentary deposits. Carbonate spring deposits, very rare in the Canary Islands, are good archives of recent volcanic activity, fluvial processes and vegetation regimes prevailing in the islands in recent times.

Analysis method for orange peel structure on aluminium–lithium alloy surface during stretch forming process

An innovative method of measuring the surface morphology and true train state synchronously was realised by the optical strain measuring instrument working together with the universal testing machine. The influences of stretching speed and stretching amount on the formation of an orange peel structure on 2060-T8 aluminium–lithium alloy surface were studied by this method, and the microstructure of the alloy was analysed by metallographic observation. Results showed that the formation of an orange peel structure was greatly influenced by the stretching rate, and the best stretching rate under experimental conditions was 0·05mm s−1, which delayed the occurrence of obvious orange peel structure until the true strain reaches 1·87%. Microstructure analysis showed that the grain grade of the alloy was 4·7, belonging to a coarse crystalline structure, and the gap between the sizes of the large and small grains was large, which explains the forming of an orange peel structure during stretching.

Studying the fine microstructure of the passive film on nanocrystalline 304 stainless steel by EIS, XPS, and AFM

The fine microstructure of the passive films on nanocrystalline (NC) and coarse crystalline (CC) 304 stainless steels (SSs) in 0.5 M H2SO4 were investigated by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The results indicate that the passive film on both CC and NC SSs exhibits a two-layer microstructure consisting of a compact inner layer and a porous outer layer. Some hydrated compounds (HC) were present in the porous outer layer of NC SS but not CC SS in 0.5 M H2SO4 solution. The pores in the outer layer of the NC SS were observed to be in the nanoscale by AFM. HC filling of the pores in the passive film on NC SS may occur due to capillary forces endowed by the nanosize pores. XPS analysis of the passive films on both CC and NC SSs, however, does not show such a composition difference which is attributed to dehydration occurring in the XPS vacuum chamber. Both the inner and outer layers of the NC SS were determined by EIS analysis to be more compact and protective than the corresponding films on CC SS as evidenced by the lower Q value, higher n, and much higher R value in the corresponding layer.

Noble gas concentrations in fluid inclusions as tracer for the origin of coarse-crystalline cryogenic cave carbonates

The chemically inert behaviour of noble gases, their well-known solubility in water and the long-term constancy of atmospheric noble gas mixing ratios make them a unique tool for paleoclimate studies of groundwater. This concept has recently been extended to fluid inclusions in speleothems. Here we use noble gas concentrations of fluid inclusions contained in calcite crystals to constrain the formation history of coarse crystalline cryogenic cave calcites from Heilenbecker Cave (Germany).Cryogenic cave carbonates form under conditions related to the freezing of cave pools and are a new archive for paleo-permafrost timing and extent. The cryogenic origin of these carbonates is typically deduced from their crystal habit and the carbon and oxygen isotope ratios, but this can be ambiguous in some cases. A geochemical method that provides clear-cut proof of the cryogenic origin of individual crystals has been lacking so far.We examined the formation process of cryogenic cave calcites using water and noble gases extracted from inclusions in these crystals. Based on their δ13C and δ18O values, these calcite crystals could have also formed as ‘normal’, i.e. non-cryogenic, speleothems. Noble gas concentrations derived from fluid inclusions in these cryogenic calcites, however, deviate significantly from commonly observed concentrations in atmospheric air, surface water, groundwater, and stalagmites. These concentrations cannot be explained simply by a solubility component nor by the addition of various amounts of excess-air to a solubility component. The data, however, are consistent with the scenario of a slowly freezing water body lacking exchange with the cave atmosphere. The gradual freezing process leads to a partitioning of the noble gases between ice and remaining water and thereby to a pronounced over-abundance of heavy noble gases in the liquid phase recorded in the fluid inclusions of the cryogenic calcite crystals.

Clumped isotope thermometry of cryogenic cave carbonates

Freezing of cave pool water that is increasingly oversaturated with dissolved carbonate leads to precipitation of a very specific type of speleothems known as cryogenic cave carbonates (CCC). At present, two different environments for their formation have been proposed, based on their characteristic carbon and oxygen isotope ratios. Rapidly freezing thin water films result in the fast precipitation of fine-grained carbonate powder (CCCfine). This leads to rapid physicochemical changes including CO2 degassing and CaCO3 precipitation, resulting in significantly 13C-enriched carbonates. Alternatively, slow carbonate precipitation in ice-covered cave pools results in coarse crystalline CCC (CCCcoarse) yielding strongly 18O-depleted carbonate. This is due to the formation of relatively 18O-enriched ice causing the gradual depletion of 18O in the water from which the CCC precipitates.Cryogenic carbonates from Central European caves were found to have been formed primarily during the last glacial period, specifically during times of permafrost thawing, based on the oxygen isotope ratios and U–Th dating. Information about the precise conditions of CCCcoarse formation, i.e. whether these crystals formed under equilibrium or disequilibrium conditions with the parent fluid, however, is lacking. An improved understanding of CCCcoarse formation will increase the predictive value of this paleo-permafrost archive.Here we apply clumped isotopes to investigate the formation conditions of cryogenic carbonates using well-studied CCCcoarse from five different cave systems in western Germany. Carbonate clumped isotope measurements yielded apparent temperatures between 3 and 18°C and thus exhibit clear evidence of isotopic disequilibrium. Although the very negative carbonate δ18O values can only be explained by gradual freezing of pool water accompanied by preferential incorporation of 18O into the ice, clumped isotope-derived temperatures significantly above expected freezing temperatures indicate incomplete isotopic equilibration during precipitation of CCC.

Permafrost occurrence during the Last Permafrost Maximum in the Western Carpathian Mountains of Slovakia as inferred from cryogenic cave carbonate

Coarse crystalline cryogenic cave carbonate (CCC) forms during the slow freezing of standing water pools and represents indirect proof of freezing temperature in the past. The dating by U‐series of CCC deposits from nine caves in the Western Carpathians Mountains of Slovakia suggests that freezing conditions, and possible permafrost conditions, occurred during the Last Permafrost Maximum (LPM, c. 20–18 ka BP). The CCC deposits occur in caves at elevations of between 800 and 1800 m a.s.l. They point to widespread alpine permafrost, the lower limit of discontinuous/sporadic permafrost being approximately 800 m a.s.l. The thickness of permafrost probably varied between 30 and 180 m. In the Vysoké Tatry Mountains at altitudes of ∼1800 m a.s.l., one occurrence of CCC suggests that subzero temperatures may have penetrated to a depth of over 285 m.

Alpine permafrost thawing during the Medieval Warm Period identified from cryogenic cave carbonates

Abstract. Coarse crystalline cryogenic cave carbonates (CCCcoarse) dated to the last glacial period are common in central European caves and provide convincing evidence of palaeo-permafrost during this time. Little is known, however, about the exact nature of the environment in which CCCcoarse formed as no modern analogue setting is known. Here, we report the first findings of sub-recent, albeit inactive, CCCcoarse from a cave of the Western Alps which is located in the present-day permafrost zone. The globular shape and the presence of ubiquitous euhedral crystal terminations are comparable to previously reported aggregates from the last glacial period and strongly suggest that these aggregates formed subaqueously in pools lacking agitation. Furthermore, stable isotope values of mm-sized spheroids point to calcite precipitation in a closed system with respect to CO2, strongly supporting the hypothesis of a cryogenic origin associated with the freezing of water ponds. U-series analyses revealed three clusters of late Holocene calcite precipitation intervals between 2129 and 751 a b2k. These ages correlate with known periods of elevated summer temperatures, suggesting that warming and thawing of the frozen catchment above the cave allowed water infiltration into the karst system. The growth of CCCcoarse resulted from the re-freezing of this water in the still cold karst cavities.

Dolomite textures in the Upper Cretaceous carbonate-hosted Pb–Zn deposits, Zakho, Northern Iraq

In the northeast of Zakho City, Northern Iraq, the host rocks of Pb–Zn deposits are composed predominantly of dolomites with subordinate dolomitic limestone intervals. This study is focused on the dolomites of the Bekhme Formation (Upper Campanian) carbonate-hosted Pb–Zn deposits. The amount of dolomites, however, increases toward the mineralized zone. Dolomites are dominated by replacement dolomite with minor dolomite cements. Petrography study allowed identification of six different dolomite textures. These are (1) fine crystalline, planar-s (subhedral) dolomite, RD1; (2) medium to coarse crystalline, planar-e (euhedral) to planar-s (subhedral) dolomites, RD2; (3) medium crystalline, planar-s (subhedral) to nonplanar-a (anhedral) dolomites, RD3; (4) coarse crystalline, planar-s (subhedral) to nonplanar-a (anhedral) dolomites, RD4; (5) planar (subhedral) void-filling dolomite cements, CD1; and (6) nonplanar (saddle) void-filling dolomite, CD2. The RD1, RD2, RD3, and RD4 dolomite textures are replacive in origin and are volumetrically the most important types, whereas CD1 and CD2 dolomites with sparry calcite are commonly cements that fill the open spaces. Although the dolomites of the Bekhme Formation are not macroscopically observed in the field, their different types are easily distinguished by petrographic examination and scanning electron microscopy. It was observed that the dolomites of the Bekhme Formation are formed in two different diagenetic stages: the early diagenetic from mixing zone fluids at the tidal–subtidal (reef) environments and the late diagenetic from basinal brines which partially mixed with hydrothermal fluids at the shallow-deep burial depths. The latter occurs often with sphalerite, galena, and pyrite within mineralized zone. These dolomite types are associated base-metal mineralization (Mississippi Valley type).

Pitting corrosion of 304ss nanocrystalline thin film

Pitting corrosion behavior of coarse crystalline (CC) 304ss and its nanocrystalline (NC) thin film have been investigated by electrochemical measurement and in situ AFM observation in 3.5% NaCl solution. Results show two effects of nanocrystallization on pitting corrosion behavior: (1) more frequent occurrence of metastable pits, but with lower probability of transition to stable pits, which is attributable to differences in morphologies of sulfur and manganese as well as outstanding repassivation ability of NC thin film; (2) nanocrystallization decreases stable pit generation rate and its propensity to form larger pit cavities, and modifies the morphology of stable pit cavity.

Types and Origin of Dolostones in Tarim Basin, Northwest China: Petrographic and Geochemical Evidence

Abstract:In the Tarim Basin of northwestern China hydrocarbon deposits have been discovered in parts of the thick strata of Cambrian dolostones. Based on petrographic study, six types of dolostone have been distinguished: Type‐1, pink mud‐bearing silty crystalline dolostone (PMSD); Type‐2, gypsum‐ and salt‐bearing fine crystalline dolostone (GSFD); Type‐3, fine crystalline dolostone with dolomite crystals with cloudy core and clear rim (CCFD); Type‐4, deep gray mud‐bearing silty crystalline dolostone (GMSD); Type‐5, euhedral coarse crystalline dolostone (ECD); and Type‐6, xenotopic coarse crystalline dolostone (XCD). Applying petrographic and geochemical methods, the genesis of the dolostones is studied in this paper. Normally, Type‐1 dolostone shows U‐ and Mo‐depleted characteristics, reflecting a more oxidized formation environment; High δ8O and the purple color are consistent with formation of Sabkha dolostones on a supratidal flat. Types 2, 3, 4 dolostones show strata formation, similar REE patterns and 87Sr/86Sr ratios with contemporaneous limestones, suggesting a penecontemporaneous origin from seawater. Types 5 and 6 dolostones commonly occur as interbedded rocks, indicating secondary genesis after diagenesis. Type‐6 dolostone has the highest order degree (OD) values (average 0.86), the lowest oxygen isotope values and positive Eu anomalies, which are consistent with previously reported hydrothermal dolostones. Differently, Type‐5 shows euhedral texture, higher δ18O value, similar REE characteristic and 87Sr/86Sr ratios in comparison with contemporaneous limestones, suggesting that this type might have been dolomitized by down‐transferring evaporated seawater during shallow burial stage. Dolostone fluid sources, formation environments and crystallizing dynamics are summarized and possible genetic models for the six types are proposed.

Origin of dolomite in the Late Jurassic platform carbonates, Bolkar Mountains, Central Taurides, Turkey: Petrographic and geochemical evidence

The Late Jurassic-early Senonian Cehennemdere Formation extending in an E-W direction in a wide area at the south of the Bolkar Mountains (Central Taurides, Turkey) is composed of platform carbonates. The formation was deposited in an environment that was being transformed from a shallow carbonate platform to an open shelf and a continental slope, and was buried until late Paleocene uplift. The formation, with a thickness of about 360m, was chiefly developed as textures consisting of mudstone and wackestone and has been commonly dolomitized. Based on petrographic and geochemical properties, four types of replacement dolomites and two types of dolomite cements were distinguished. Replacement dolomite (RD), which is cut by low-amplitude stylolites developed as (1) fine crystalline planar-s dolomite (RD1); (2) medium crystalline planar-s dolomite (RD2); (3) medium-coarse crystalline planar-e dolomite (RD3) and; (4) coarse crystalline planar-s (e) dolomite (RD4). Two types of dolomite cements (CD) observed in low abundance and overlie low-amplitude stylolites: (1) coarse crystalline dolomite cement (CD1) filling dissolution voids and fractures in RD1 dolomites, and; (2) rim dolomite cement (CD2) that commonly develops on the space-facing surfaces of RD4 dolomite. Replacement dolomites are non-stoichiometric (Ca54–59Mg41–46), have similar geochemical properties, and are generally dull red/non luminescent in appearance. Replacement dolomite is represented by δ18O values from −4.5 to −0.5‰ VPDB, δ13C values of −0.7 to 2.7‰ VPDB, and 87Sr/86Sr ratios ranging from 0.707178 to 0.707692. Petrographic and geochemical data indicate that replacement dolomite (particularly RD2, RD3, and RD4 dolomite) was formed at shallow-intermediate burial depths during the Late Jurassic-Early Cretaceous, from seawater and/or from slightly modified seawater. The replacement dolomite (RD) was then recrystallized at increased burial depths and temperatures. Dolomite cements are similar to replacement dolomites in that they are non-stoichiometric (Ca55Mg45) and have similar trace element compositions. CD1 dolomite, which cuts low-amplitude stylolites, was formed during intermediate to deep burial following stylolite development. CD2 dolomite was precipitated in intercrystal pores in association with RD4 dolomite. Remaining pore space was filled with bitumen.

The effect of lactose micro-spherical crystals prepared by conditioning with supercritical fluid on salbutamol sulphate inhalation performance

In this study, lactose crystalline powder was produced to improve its stability. The effect of micronised crystalline lactose on a dry powder inhalation formulation was investigated. Supercritical carbon dioxide (scCO2) modified with menthol was used for the conditioning of spray-dried amorphous lactose and salbutamol sulphate to generate micro-spherical crystalline powders. The optimum processing conditions, which include: menthol concentration, temperature and processing time, were determined by experimental design to produce crystalline and a desired particle size. The average particle size of spray-dried amorphous lactose decreased from 8.15±0.28μm to 7.60±0.10μm after conditioning with modified CO2 at 150bar and 50°C for a period of 5h. The SEM results shows that these particles kept their micro-spherical shape, however, the particle surface became rough due to crystallisation. This particle size reduction was most likely due to increasing surface roughness, which decreased agglomeration between particles. The blend of this fine powder and coarse crystalline lactose enhanced salbutamol sulphate inhalation performance. The emitted fine particle fraction of salbutamol sulphate was enhanced to 40±0.3% compare to the samples that contained only coarse lactose (38.2±0.6%) or conditioned lactose (24.6±0.4%).

Influence of grain size on the mechanism of fracture of the aluminum alloy V95

Mechanical behavior and mechanisms of fracture of the ultrafine-crystalline (UFC) and the coarse-crystalline (CC) aluminum alloy V95 (Al-6.0 Zn-2.3 Mg-2.0 Cu-0.4 Mn (wt %)) manufactured via using severe plastic deformation, namely, by dynamic equal-channel angular pressing (DCAP), have been studied. It has been demonstrated that the UFC material exhibits improved mechanical properties in comparison with the CC analog. A correlation analysis of fracture surfaces and the determination of the Hurst exponent have made it possible to perform a comparative estimation of the uniformity of the fracture structure and of the fractions of ductile and brittle fractures in the samples with the structure-scale characteristics different in value.

The Electrochemical Corrosion Behavior of Nanocrystalline 304 Stainless Steel Prepared by Magnetron Sputtering

The electrochemical corrosion behavior of magnetron sputtered nanocrystalline (NC) 304 stainless steel (ss) thin film as well as that of the conventional rolled coarse crystalline (CC) 304ss has been studied in 0.05 M H2SO4 + 0.2 M NaCl solution using electrochemical and imaging techniques. The experimental results indicate that the NC thin film exhibits superior corrosion resistance compared to CC 304ss. The semi-conductor properties of the passive films on both materials as predicted by the Mott-Schottky equation show that the donor and acceptor concentrations of the passive film on NC thin film are higher than that of CC 304ss, while diffusion coefficients of carriers are lower than for CC 304ss. The composition of the passive film on NC thin film measured by X-ray photoelectron spectroscopy (XPS) has a higher the ratio of Cr oxides to Fe oxides. In-situ AFM observation found that the growth rate of the passive film on NC thin film was significantly faster than that of CC 304ss. The higher content of Cr oxides and better passivation ability of the passive film enhance the corrosion resistance of the nanocrystalline specimen together.