Scale Morphology Research Articles

The effects of Ca2+ and Mg2+ ion concentrations in brine on scaling formation and morphology on metal surfaces

The effects of Ca2+ and Mg2+ ion concentrations in brine on scaling formation and morphology on metal surfaces

Structure and protective properties of Si-Ti-epoxy organic–inorganic hybrid film

Sol–gel method was used to prepare a Si-Ti-epoxy organic–inorganic hybrid composite sol, which was cured on the carbon steel surface at room temperature to obtain a transparent film. Based on the scanning electron microscopic image, the microscopic morphology of the film is flat, smooth, and dense. The atomic force microscopic image shows a nanometer scale morphology, and the structure of the Si-Ti-epoxy hybrid film is more uniform and denser than that of the Si-epoxy hybrid film. The film/carbon steel attenuated total reflection infrared spectrum presents a Si-O-Fe absorption peak at 831 cm−1, which indicates the chemical bonding of the organic–inorganic hybrid film and the carbon steel substrate. The contact angle of the film is greater than 90°, indicating hydrophobicity. The dense nanostructure of the film and the chemical combination with the metal substrate confer the film with excellent electrochemical protection performance. The low-frequency impedance modulus (|Z|0.01Hz =1010Ω∙cm2) of the Si-Ti-epoxy hybrid film (15–20μm) is an order of magnitude higher than the double-thick epoxy film (30–35μm). The corrosion current density (10−11A/cm2) obtained by the polarization curve is two orders of magnitude lower than the double-thick epoxy film.

Morphological evolution of silica scales in the freshwater genus Synura (Stramenopiles).

A high degree of morphological variability is expressed between the ornately sculptured siliceous scales formed by species in the chrysophycean genus, Synura. In this study, we aimed to uncover the general principles and trends underlying the evolution of scale morphology in this genus. We assessed the relationships among thirty extant Synura species using a robust molecular analysis that included six genes, coupled with morphological characterization of the species-specific scales. The analysis was further enriched with addition of morphological information from fossil specimens and by including the unique modern species, Synura punctulosa. We inferred the phylogenetic position of the morphologically unique S.punctulosa, to be an ancient Synura lineage related to S.splendida in the section Curtispinae. Some morphological traits, including development of a keel or a labyrinth ribbing pattern on the scale, appeared once in evolution, whereas other structures, such as a hexagonal meshwork pattern, originated independently several times over geologic time. We further uncovered numerous construction principles governing scale morphology and evolution, as follows: (i) scale roundness and pore diameter decreased during evolution; (ii) elongated scales became strengthened by a higher number of struts or ribs; (iii) as a consequence of scale biogenesis, scales with spines possessed smaller basal holes than scales with a keel and; and (iv) the keel area was proportional to scale area, indicating its potential value in strengthening the scale against breakage.

The effect of fluid flow on CO2 corrosion of high-strength API carbon steels

This paper presents and discusses the outcomes of a recent study on the corrosion resistance of API carbon steels (T95 and Q125). The scope includes experimental investigation as well as theoretical modeling. To predict CO2 corrosion under dynamic conditions, an existing model is improved and validated using experimental measurements.Corrosion tests were conducted under static and dynamic conditions. API casings were cut and machined to prepare test specimens used for measuring Average Corrosion Rate (ACR) and Load-Carrying Capacity (LCC). The dynamic test condition was simulated using the flow between two concentric cylinders (Couette type flow). The test solution (2% wt. NaCl) was saturated with a gas mixture containing 50% CO2 and 50% methane. Tests were carried out at 41.37 MPa with varying temperature and the speed of the inner cylinder, and subsequently, changing the wall shear stress (τw). The ACR was determined by applying the Weight Loss (WL) method. A digital microscope was utilized to inspect the morphology of the corrosion scale (product). The change in LCC of the specimens was compared with the theoretically predicted change in LCC to identify the presence of localized corrosion and/or intergranular attack. In addition to LCC, the ultimate tensile strength (UTS) of corroded specimens is determined and compared with that of uncorroded specimens.Results show that the CO2 corrosion of API steels is sensitive to the fluid velocity regardless of temperature. The corrosion of Q125 is more affected by fluid flow than that of T95. Below critical shear stress, CO2 corrosion was strongly affected by fluid flow. Under a static condition, Q125 demonstrated higher corrosion resistance than T95 but under a dynamic condition, T95 exhibited higher corrosion than Q125. At high temperature (71 °C), the occurrence of localized corrosion was observed. Corrosion model predictions show reasonable agreement with measurements.

Centrohelid Heliozoans (Centroplasthelida Febvre-Chevalier et Febvre 1984) from Vietnam

The morphology of the inorganic scales of ten species of centrohelid heliozoans collected from various types of aquatic habitats in Vietnam has been examined. All the species identified are new to Vietnam. The spine scales of Acanthocystis turfacea are distinguished by the characteristic conically pointed tips of furcae and longer furcae relative to the shaft length in long spine scales. Morphologically, the plate scales of Pterocystis tropica examined correspond to those of the subspecies P. tropica paucistriata; the spine scales, to those of the subspecies P. tropica tropica. The examined plate scales of Raineriophrys erinaceoides undulata lack radial slits, unlike those indicated in the original description of this subspecies. Two new species of centrohelid heliozoans are described. Pterocystis vietnamica sp. n. is characterized by leaf-shaped spine scales with transverse slits on the lateral wings and a large, spherical, subapical protrusion. Pseudoraphidocystis dentata sp. n. has marginal teeth at the edges of funnel-shaped spine scales.

Effect of Simulated Annealing Conditions on Scale Formation and Neutral Electrolytic Pickling

Scale formation of AISI 304 stainless steel during annealing at temperatures between 1100 and 1200 °C under a water vapor‐containing atmosphere is studied. Characterization of the oxide scale is performed with field‐emission scanning electron microscopy–energy dispersive spectroscopy (FESEM–EDS) and glow discharge optical emission spectroscopy (GDOES) and removal of oxide scale is done via neutral electrolyte pickling. The pickling conditions are kept constant and the effect of the annealing conditions and scale properties on the pickling result are examined. The effectiveness of pickling is evaluated using analysis FESEM images taken on polished sections of pickled surfaces. Research shows that the thickness, morphology, and composition of the oxide scale are dependent on annealing temperature and time. The thicknesses of the scale formed under the established conditions vary from 0.2 to over 30 μm, and morphologies between the chromium rich oxide layer and layered scale structure formed by breakaway oxidation. The pickling response of oxide scales remains good at all annealing temperatures with the shortest exposure time.

Effects of Process-Induced Supersaturation on the Oxidationbehavior of Alloy718 Fabricated By Additive Manufacturing Technologies

Alloy718 is widely used in gas turbines and related aerospace applications due to its excellent mechanical properties and structural stability at elevated temperatures. Alloy718 is a precipitation-strengthened superalloy which is generally manufactured through casting, forging, and heat treatment. Over the past decade a variety of additive manufacturing (AM) technologies involving laser and electron beam have become increasingly attractive fabrication methods due to their several advantages over conventional manufacturing methods, such as a large degree of design flexibility, and reductions in the lead time and investment cost. However, the selective laser melting process (rapid heating and cooling) will make matrix gets supersaturated in alloying elements, in particular Nb, Ti and Al, which have significant effects on the formation of the strengthening phases in austenite matrix, e.g., γ′′ (Ni3Nb,), γ′ (Ni3Al,Ti) phases.Up to now, the specific influences of supersaturation on the oxidation behavior of the scales in a Cr-forming Ni-based alloy have not been dealt with in depth.In this study, the oxidation behavior of Alloy718 specimens produced by selective laser melting (SLM) and electron beam melting (EBM) process were comparatively examined. A slower cooling rate and a preheating process in the EBM process contribute relatively lower degree of saturation in \U0001d6fe matrix. On the other hand, the high thermal gradient and rapid solidification rate in SLM process lead to supersaturation in \U0001d6fe matrix. All alloys were studied in two versions to compare the order of supersaturation: “As-received” and heat treated (HT). The heat treatment procedure was carried out at 980 °C for 1 h/air cooling to room temperature and a two-step aging treatment consisting of 718 °C for 8 h/furnace cooling to 621 °C and holding at 621 °C for 10 h before AC to room temperature. The oxidation kinetics as well as the surface morphology of the oxide scales were characterized by means of weight gain measurements, scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS), electron probe microanalysis (EPMA), X-ray diffraction (XRD) and transmission electron microscope (TEM) analysis techniques.The experimental results indicated that the oxidation performance of as-received SLM samples were better than those of as-received EBM samples due to the formation of thinner Cr2O3 scale without spallation. In addition, the morphology of their chromia scale was different. Coarse and columnar chromia grains developed on SLM samples, whereas the chromia scale of EBM samples consisted of extremely fine grains. After heat treatment process, the oxidation kinetics of heat-treated samples were increased compare to as-received samples. Moreover, the fine-grained chromia scale which is similar to that formed on EBM samples was formed on heat-treated SLM samples. The mentioned results indicate that the degree of supersaturation in the matrix did affect the morphology of chromia scale resulting in the oxidation kinetics.

Investigation of graphite/CNTs on the equiatomic AlCoNi alloy: Hardness and surface morphology of the oxide scale

Equiatomic AlCoNi alloys with 0.1 wt% of carbon addition in different forms such as graphite and carbon nanotubes were fabricated by powder metallurgy. The effect of carbon addition on the microstructure and oxide scale formation was investigated as a function of carbon type. Evidence showed that both carbon forms addition reduced the porosity of the sintered AlCoNi alloy. A mixture of Al and Ni-Co oxide scale was formed in all samples after a heat treatment at 1000 °C for 2 h in air. After subsequent oxidation at 900 °C for 100 h, graphite induced the Ni-Co oxide growth; meanwhile, carbon nanotubes favored the Al oxide growth. The dispersion of carbon nanotubes produced the lowest growth rate of the oxide scale.

Assignment of Gilthead Seabream Sparus aurata to Its Origin through Scale Shape and Microchemistry Composition: Management Implications for Aquaculture Escapees

This study tests the suitability of the gilthead seabream scales as a proxy for origin selection in wild and anthropogenically pressured environments. Scale morphology and microchemistry were used to discriminate the habitat selection of two wild, farmed and wild farm-associated populations where landmark and outline-based scale morphometrics, trace-element chemistry and scale microstructure characteristics were analysed. The morphometric techniques successfully differentiated between the farmed and wild origin scale phenotypes. Reduced discrimination sensitivity between the wild and wild farm-associated origin was, however, reported. The discrimination based on microchemistry (B, Ba, Mn, K, Sr and Zn) classified the scales with high accuracy according to their origin (wild vs. farmed vs. wild farm-associated) and sampling locations, thus proving itself as a powerful tool in provenance study of gilthead seabream. Disparity in scale microstructure characteristics accounted for radii, circuli and inter-circulus spacing, hence unveiling the differences in growth and environmental conditions between the wild and farmed fish. In brief, scale shape was found to be a potent exploration tool for farmed fish identification, whereas scale microchemistry yielded a good resolution in identifying gilthead seabream membership among different habitats. Considering the importance of this species in aquaculture and fisheries throughout the Mediterranean, more research is needed to assess the usefulness of scales as nonlethal biogeochemical tags.

Systematics and distribution of spruce species in the North-West of Russia

Norway spruce (Picea abies) and Siberian spruce (P. obovata) are among the most important forest-forming coniferous species in the boreal part of Eurasia. Despite numerous publications on the taxonomy of Norway spruce and closely related taxa (P. obovata Ledeb. and P. fennica (Regel) Kom.), the problem of their identification, as well as clarification of their taxonomic status, has not been solved so far. Species delimitation is particularly challenging when P. abies, P. obovata and P. fennica occur in sympatry. Our study aims to assess taxonomic value of proposed earlier and search for stable diagnostic characters of cones and their scales to distinguish Picea abies and its sympatric in the North-West of Russia P. fennica and P. obovata. In addition, we analyzed and updated information on geographical distribution and phytocenotic characteristics of the above-mentioned species in the North-West of the European part of Russia. We examined herbarium specimens and cones sampled from 88 trees from 22 Picea stands located throughout the study region. Each tree was represented on average by 5 cones, in total 415 cones were analyzed. Morphometric analyses included 16 morphological characters of cones and their scales selected based on our own observations and published data. Multivariate comparison had shown a large overlap between P. obovata and P. fennica, while individuals of P. abies formed a separate and less overlapping cluster. Among the six qualitative (discrete) characters, shape of seed scale and shape of its upper margin have non-overlapping frequency distributions and can separate P. abies and P. obovata. Several new diagnostic characters are proposed: morphology and size of bract scales and ratio of the size of seed scales and bract scales. Phytocenotic analysis showed that different spruce taxa occupy specific habitats, which in their turn connected with the latitudinal gradient: in normally drained habitats, Picea obovata is found mainly in poor shrubby-green-mossy forests, which are typical of the northern and middle parts of the Northern taiga; Picea abies – in richer green-mossy habitats (Vaccinioso-hylocomiosum, Oxalidoso-hylocomiosum, Hylocomiosum), which begin to occur already from the middle part of the Northern taiga. Picea fennica occupies both habitats.

Modifying\xa0the thickness, pore size, and composition of diatom frustule in Craspedostauros sp. with Al3+ ions

Diatoms are unicellular photosynthetic algae that produce a silica exoskeleton (frustule) which exposes a highly ordered nano to micro scale morphology. In recent years there has been a growing interest in modifying diatom frustules for technological applications. This is achieved by adding non-essential metals to the growth medium of diatoms which in turn modifies morphology, composition, and resulting properties of the frustule. Here, we investigate the frustule formation in diatom Craspedostauros sp., including changes to overall morphology, silica thickness, and composition, in the presence of Al3+ ions at different concentrations. Our results show that in the presence of Al3+ the total silica uptake from the growth medium increases, although a decrease in the growth rate is observed. This leads to a higher inorganic content per diatom resulting in a decreased pore diameter and a thicker frustule as evidenced by electron microscopy. Furthermore, 27Al solid-state NMR, FIB-SEM, and EDS results confirm that Al3+ becomes incorporated into the frustule during the silicification process, thus, improving hydrolysis resistance. This approach may be extended to a broad range of elements and diatom species towards the scalable production of silica materials with tunable hierarchical morphology and chemical composition.

Differences in otolith shape and fluctuating-asymmetry between reared and wild gilthead seabream (Sparus aurata Linnaeus, 1758).

Otolith structure is a useful tool in discrimination among fish populations as it is a permanent record of the influence of endogenous and exogenous factors. In the present study we examined otolith morphology and fluctuating asymmetry (FA) for differences between wild-caught (by bottom trawl) and reared specimens of Gilthead seabream (Sparus aurata). Based on the frequency of regenerated scales (degree of scale regeneration, SRD) on each specimen, a threshold of 30% SRD was used to assign wild-caught fish individuals as wild (≤30% SRD, LR group) or as possible aquaculture escapees (>30% SRD, HR group). Based on the analysis of elliptic Fourier descriptors, significant differences were found in otolith shape between reared (Rr) and the wild-caught groups (LR, HR). Reared fish had otoliths with significantly larger perimeter (OP ) than wild-caught fish. Furthermore, FA was significantly higher in the Rr than the LR group for OP and all except one shape descriptors (harmonics 2-7). The HR group exhibited intermediate levels of FA between the low and high FA levels observed in the LR and Rr groups. Results are discussed in terms of the value of combining otolith and scale morphology for the identification of escapees in wild Gilthead seabream stocks.

Exploring the mechanisms of exciton diffusion improvement in ternary polymer solar cells: From ultrafast to ultraslow temporal scale

Long-range exciton diffusion on picosecond time scale, which serves to efficient charge separation at the donor/acceptor (D/A) interfaces, has been regarded as a key step for the working mechanisms of organic photovoltaics. Rationally understanding and manipulating this vital process over a wide temporal scale remains some challenges, especially in ternary organic solar cells (OSCs). Herein, we reveal how exciton migration behaviors are reasonably improved and maintained relying on the simultaneously enhanced efficiency and thermal stability in the PM6:IT4F:PC71BM and PM6:BTP-4Cl:PC71BM ternary devices. Two separate factors can be responsible for these benefits: (1) the coexistence of dual Förster-type energy transfer (FRET) can contribute to the directed exciton diffusion and rapidly quench the highly excited states to stabilize the “energy donors”. (2) The more favorable multi-length scale morphologies optimized by the addition of guest PC71BM yield the plentiful interfacial region to shorten the real distance of diffusion process and boost the stability of microstructure. In particular, the diffusion lengths > 10 nm of IT4F singlet excitons induced by dual FRET effects were obtained by employing the exciton-exciton annihilation strategy. These experimental results open a novel horizon for further strengthening efficiency and stability of ternary OSCs from the perspective of improving exciton diffusion.

High temperature molten salt corrosion investigations on P22/P91 power plant dissimilar welds

This article investigates the hot corrosion behavior of P22/P91 dissimilar welds used in power plant applications. The hot corrosion behavior of P22/P91 dissimilar welds was observed under the exposure of molten salts Na2SO4 + 60% V2O5 (SM1) and Na2SO4 + 50% NaCl (SM2) at the temperature of 650°C and 750°C. The welds were fabricated by shielded metal arc welding (SMAW) process using the laboratory developed electrode. This study is an attempt to develop welding electrodes which provide better mechanical and hot corrosion properties as compared to the commercially available electrodes for joining P22/P91 alloys. Thermogravimetric analysis was used to study the oxidation kinetics. XRD, SEM/EDS characterization has been performed to analyze the oxide scale morphology. Results obtained indicate that the welds exposed to SM2 gain more weight as compared to that of SM1. A significant gain in weight was observed with an increase in the exposure temperature. Dissimilar welds fabricated using laboratory-made electrodes (CM1, CM2) show enhanced corrosion resistance in all the exposed environments.

Microanalysis of scale morphology in killifish, Aphaniops hormuzensis inhabiting ecologically diverse environments (Cyprinodontiformes; Aphaniidae)

Ecologically, Aphaniops hormuzensis populations occupying diverse environments in southern Iran and showed substantial morphological variation across its range. In this study, three different habitats were chosen and identified as group A (sulfur rich spring), group B (salty River), and group C (urban canal), and scale microstructures and scale shape was inspected among three groups. The SEM imaging indicated that lepidonts were more developed on the scale of larger (group C, SL > 30 mm) than younger fish (group A, SL < 30 mm). We tentatively concluded that lepidonts are formed during scale development so that in the earlier stages of fish development, scales probably do not have lepidont. Also, the size and shape of lepidonts vary between the populations, and their shape and orientation within a given species affected by the fish size rather than the local ecological conditions of habitats. The number of radii was relatively higher in group C (12.58 ± 0.66 in males and 13.00 ± 1.89 in females). Similar to what is mentioned before in the case of lepidont, the inter-population variation in the number of radii seems to be influenced by fish size. Group A (SL < 30 mm) had a relatively large focus diameter (0.14 ± 0.02 in males and 0.36 ± 0.44 in females). It is assumed that the focus size is large at the earlier stage of fish development, but later during the fish growth, and by increasing the scale size, the focus diameter is reduced. In conclusion and agreement with previous studies, scale surface morphology and microstructure could be employed to discriminate certain populations, while scale size and J-indices could not help in distinguishing the populations. It is also proposed that the characteristics of scale morphology in the population-level are influenced by the combination of genetic, and environmental factors, as well as fish development.

Nondestructive thickness measurement of silica scale using cathodoluminescence.

The knowledge of the composition, morphology, and thickness of surface protective scales, such as SiO2 and Al2O3, is important to control the performance of heat-resistant alloys operated at high temperatures above 1000°C. Cathodoluminescence (CL) analysis is one of the most promising methods to acquire such information nondestructively. Unlike Al2O3 scale, the use of the brightness of CL image to determine SiO2 scale thickness is difficult because the brightness and color of its acquired CL image depend not only on the thickness of the scale but also on its oxygen potential and impurity concentration. In this study, we investigated the CL spectra of SiO2 scales formed on Fe-20%Si alloy, Si, and MoSi2 to present a method for measuring the thickness of SiO2 scale on silica-forming materials from their CL spectra. A linear calibration curve was obtained from the intensity of the CL peak at 445nm which originated from the intrinsic defects in SiO2 and the thickness of the SiO2 scale for each heat-treatment temperature (1000°C, 1200°C, 1300°C, and 1400°C). Data in this study can be adequately employed to derive CL calibration curves at different temperatures because the CL intensity and heat-treatment temperature were fitted according to Arrhenius relationship at different SiO2 scale thickness, regardless of the type of base materials. These results indicated that the thickness of the SiO2 scale formed on silica-forming alloys can be determined by acquiring their CL spectra. Therefore, CL analysis has the potential to be employed as a novel analytical method to control the performance of silica-forming alloys.

Effect of oxide scale structure on shot-blasting of hot-rolled strip steel

Background The effect of oxide scale composition of hot-rolled strip (Q235) on shot blasting is studied in this article. The properties of the oxide scale on the strip surface change during storage. The shot blasting is an important on-line acid-less descaling technology. The effect of shot blasting is affected by many factors, among which the composition of oxide scale may play an important role. However, there are few studies on the relationship between the oxide layer content and the descaling effect. Methods The morphologies of oxide scales at different storage times are observed by scanning electron microscopy (SEM), and the compositions are analyzed by X-ray diffraction. These strips are then shot blasted and descaled with different amounts of abrasive, and the descaling effects are compared by SEM. Results The results show that the eutectoid structure Fe3O4/Fe in the oxide scale will gradually transform into Fe3O4. In the case of short storage time, the content of the eutectoid structure is high, and it is difficult to remove the oxide scale. While the strip with a long storage time has no eutectoid structure Fe3O4/Fe and FeO, it is easy to remove the oxide scale during the shot blasting process. The composition of the oxide scale has a significant effect on the effect of shot blasting, and it provides significant guidance to the optimization of the descaling process parameters.

The effect of manganese and silicon additions on the corrosion resistance of a polycrystalline nickel-based superalloy

The service lives of nickel superalloys are often limited by environmental degradation. The present study compares oxidation, sulfidation and hot corrosion at 750 °C of three variants of a polycrystalline superalloy: a baseline alloy, a variant containing 1 wt% Mn and one containing 0.5 wt% Si. Mn reduced the oxidation rate without changing the scale morphology. The MnCr2O4 scale formed proved more protective against sulfidation and hot corrosion, but internal sulfides extended the damage depth. Si modified the oxide morphology to a continuous Cr2O3-Al2O3 dual layer. This provided improved protection, reducing the sulfidation depth by 2/3 and the hot corrosion depth by ½.

Morphology of oxide scales formed on chromium-silicon alloys at high temperatures

Oxide scales formed on chromium-silicon model alloys at 1200 °C in synthetic air were characterized using electron microscopy and diffraction methods. Additions of Si to chromium led to SiO2 growth underneath the chromia scale. The chromia scale was mostly fine-grained, but also contained numerous abnormally large single crystals growing out of the scale surface. Evaluation of mass transport rates shows that growth of the large grains can be supported by gas phase transport of CrO3, but not by lattice diffusion.

Role of Alloyed Niobium on the Isothermal Oxidation of Fe-40Ni-24Cr Alloy

Fe-40Ni-24Cr alloy is the heat-resistant alloy usually use at high temperature service. The alloying elements normally added to the alloy to enhance the resistance to severe oxidation during service. The Fe-40Ni-24Cr alloy was experienced a high temperature oxidation at 700 °C for 500 h exposure time in laboratory air. The discontinuous isothermal oxidation test was carried out at different time intervals to record the weight change of the oxidized alloy throughout the experiment. The oxidized Fe-40Ni-24Cr alloy was characterized in terms of oxidation kinetics, phase analysis by using x-ray diffraction (XRD) technique and oxide surface morphology determination by using scanning electron microscope (SEM) equipped with energy dispersive x-ray (EDX) spectrometer. The oxidation kinetics of oxidized Fe-40Ni-24Cr alloy was exhibited a weight gain trend. The calculation of oxidation rate law was proved that this oxidized Fe-40Ni-24Cr alloy was obeyed parabolic rate law indicating the growth of oxide scales was followed a diffusion-controlled mechanism. The phase analysis of the oxidized Fe-40Ni-24Cr alloy recorded the formation of several oxide phases consists of Cr-rich, Fe-rich, Ti-rich, Nb-rich and spinel oxides structure. These oxides were served as a protective barrier between base metal and environment. The surface morphology of oxide scale after different exposure displayed a continuous oxide layer formed on the alloy surface with evidence of overgrown Nb-rich oxide particle at discrete area on the alloy surface starting from 150 h exposure time.