Cauliflower Structure Research Articles

Depositional environments, hematite–chamosite differentiation and origins of Middle Ordovician iron ooids in the Upper Yangtze region, South China

ABSTRACTMiddle Ordovician iron ooids in the Upper Yangtze region of South China are composed mainly of hematite and/or chamosite, found in mixed siliciclastic and carbonate successions, with hematitic ooids occurring in the west, and predominantly chamositic ooids in the east of the study area. In the three iron ooid‐bearing Middle–Upper Ordovician successions, 19 microfacies are recognized and grouped into eight facies associations, representing a shallow‐water mosaic comprising restricted and semi‐restricted lagoons, and open marine subtidal deposits interfingering with tidal flat and shoal facies. Hematitic ooids with well‐sorted and well‐rounded quartz grains formed in the transgressive shoal setting when the depositional environments changed from restricted lagoon to bioclast–quartz shoal and open marine subtidal. Episodic stasis and erosional intervals during transgression controlled the formation of hematite‐rich and mixed hematite–chamosite laminae within the cortices of hematitic ooids. In contrast, chamositic ooids formed in a semi‐restricted lagoonal environment, under long‐term transgressive condensation. Alternating episodes of relatively oxic conditions with thriving organisms and eutrophication‐driven anoxia resulted in the alternation of porous and dense laminae consisting mainly of chamosite in chamositic ooids. The stromatolite‐like cauliflower structures associated with chamositic ooids suggest microbial activity that promoted iron concentration, similar to the origin of approximately coeval iron‐rich oncoids in South China. Various iron ooid types demonstrate that these coated grains could form in a range of depositional setting and palaeooceanographic conditions on a generally shallow‐marine platform during the Ordovician.

Fabrication and characterization of Ni-TiO2 and Ni-V2O5 single-layer and double-layer coatings with the approach of improving the wear and corrosion properties

The main purpose of this study is to investigate the metallurgical behavior of Ni-TiO2 and Ni-V2O5 single-layer coatings and compare them with Ni-TiO2/Ni-V2O5 and Ni-V2O5/Ni-TiO2 double-layer coatings. The general attitude is the optimal choice of coatings in terms of wear and corrosion properties. The dimensions of TiO2 and V2O5 ceramic powders were 20 nm and 500 nm, respectively, and their morphology was also different. The presence of the submicron V2O5 particles was more than the TiO2 nanoparticles in the nickel matrix deposit. Also, with double layering the coatings (Ni-TiO2/Ni-V2O5 and Ni-V2O5/Ni-TiO2), the presence of ceramic particles in the upper layer had increased compared to the same single-layer coatings. Therefore, the increase in the hardness of the deposits was directly related to the percentage of ceramic powders in the coating. The surface morphology of the Ni-TiO2 layers was formed as a cauliflower shape while the Ni-V2O5 deposits had a smooth morphology. Increasing participation of TiO2 particles in the Ni-TiO2 layer had made the morphology rougher. Also, by applying the Ni-TiO2 layer under the Ni-V2O5 deposit, the surface morphology of the Ni-V2O5 layer became smooth, which can be due to the increase in the V2O5 content in this layer. The lowest amount of fluctuation appeared in the roughness profiles related to the Ni-V2O5 layers, and the large fluctuation range in the Ni-TiO2 layers was due to the smooth and cauliflower structure, respectively. The crystallite size in double-layer coatings was smaller than the single-layer coatings due to the higher nucleation and growth rate of nickel deposition in the nickel matrix upper layers. According to the presented results, the Ni-V2O5 and Ni-V2O5/Ni-TiO2 coatings were the most wear resistant coatings. Also, the Ni-V2O5/Ni-TiO2 and Ni-TiO2/Ni-V2O5 double-layer coatings were suitable candidates for corrosion resistance and to consider both properties, Ni-V2O5/Ni-TiO2 was very suitable. Hardness, surface morphology, roughness, preferred planar texture, and ceramics powder participation were important parameters in determining the wear and corrosion properties of coatings. Also, it seems that the effect of the double layering of nickel matrix deposits on the metallurgical properties was greater than the dimensions of the ceramic particles participating in the coating.

Toxicity reduction of ZnO cauliflower-like structure through trivalent neodymium ion substitution and investigation via computer vision and AI image analysis

The synthesis of ZnO and ZNDO NPs was carried out via simple chemical precipitation. The synthesized ZnO and ZNDO NPs exhibit hexagonal wurtzite structures from the XRD patterns. In the FESEM analysis, the ZnO and ZNDO NPs formed spherical (stone-like) and nano (cauliflower) structures. The chemical composition was identified by EDX analysis. The PL spectrum identified the surface defects, such as zinc and oxygen vacancies. The ZnO and ZNDO acquire radical rummaging and antioxidant behaviors as estimated by DPPH free radicals, H2O2 radicals, decreasing in power, and hydroxyl scavenging techniques. Our observations imply that ZnO and ZNDO were excellent platforms to scavenge the ROS, and there was a impressive prospective for the chemically created ZnO and ZNDO NPs as a source of antioxidants. From the hemolytic studies, Nd3+ ion ZnO NPs changed the material matrix to slow down the release of Zn2+ ion in the ZNDO NPs. It was indicated that the Nd3+ ion decreases the cytotoxicity of ZNDO compared to the ZnO NPs. Cytotoxicity analyses were carried out for ZnO and ZNDO NPs using health fibroblast (L929) cells; ZNDO NPs exhibit minimum toxicity compared to the ZnO NPs. Furthermore, the pixel perspective of the NPs through computer vision tools gave us the image-based surface morphology that correlates to the relevant toxicology studies. The customized pipeline of AI and computer vision curated algorithms such as autoencoder based data augmentation for sample size enhancement, roughness-induced porosity estimation, roughness metrics Ra and Rq, Edge density estimation using Sobel gradients were put forward to investigate the component's non-toxic behavior from a pixel perspective.

Examining the microstructure, morphological features, and wetting characteristics of Ti/TiN/TiAlN thin films produced through RF/DC magnetron co-sputtering

This study reports synthesizing and characterizing Ti/TiN/TiAlN thin films deposited on 316 L stainless steel and silicon wafer substrates using the reactive RF/DC magnetron sputtering technique. The films' microstructure, morphology, thickness, roughness, and wettability were investigated experimentally and theoretically using density functional theory (DFT) calculations with the CASTEP program. X-ray diffraction analysis confirmed the formation of the fcc-TiAlN phase for coatings deposited at a DC power of 100 W, while increasing DC power to 150 W resulted in the appearance of a second phase, w-AlN. Field emission scanning electron microscopy images showed the formation of nanostructured coatings with a grain size range of 70–100 nm. The morphology of coatings was altered from a pyramid-like structure to a cauliflower structure by increasing the nitrogen amount in the N2/(Ar+N2) flow ratio. An increase in aluminum amount by increasing the DC power to 150 W enhanced the deposition rate and thickness of the coatings. The coatings deposited at a high N2/(Ar+N2) flow ratio exhibited minor surface roughness attributed to the compact structure. The contact angles obtained from the fabricated Ti/TiN/TiAlN coatings ranged from 86.2° to 114.2°, demonstrating values higher than the contact angle of uncoated 316 L stainless steel, which measured at 82°. Theoretical analysis using DFT calculations with CASTEP provided a fundamental understanding of the thin films' electronic structure and properties, consistent with the experimental results. This study highlights the importance of combining practical and theoretical analyses for a comprehensive understanding of material properties and the design of materials for various applications.

Probing photothermal superhydrophobic behaviors of graphene&SiO2 hybrid coating for anti-freeze application

An active @ passive anti-icing surface coating was successfully prepared using graphene&SiO2 hybrid structure toward photothermal superhydrophobic performance. The coating consists of polydimethylsiloxane (PDMS) with E51 epoxy resin linked to fumed silica (nano-SiO2) to provide a multistage rough structure and graphene as the primary photothermal nanoparticle for various surface anti-freeze application. The surface morphology of this photothermal superhydrophobic coating is validated to be as a uniformly rough cauliflower structure with a large number of “air valley”. More importantly, the addition of 0.2 g graphene could exhibit the best photothermal effect (2 sun (≈ 200 mW/cm2), stable average temperature of 49.56 °C) along with superhydrophobic effect (162.2°), excellent chemical stability properties. In order to improve the organic-inorganic interfacial bonding and the mechanical durability of photothermal superhydrophobic coatings, using micro-arc oxidation technology to establish the microporous structure on the surface of substrate for exerting interlocking effect, after pushing and pulling under applied load of 300 g for 200 cm, the outstanding wear resistance of the composite coating was verified. Thanks to the interlocking effect, the excellent superhydrophobic properties provided by the construction of the typical Cassie-Baxter model of the surface and the use of multiple layers of graphene increasing the probability of π-π* electron leap, the multi-stage photothermal superhydrophobic composite coating is able to show a long-lasting anti-icing and de-icing effect.

The WC and CrC Coatings Deposited from Carbonyls Using PE CVD Method-Structure and Properties.

This article presents a comparative study of WC and CrC coatings deposited by the plasma-enhanced chemical vapor method using the hexacarbonyls of W and Cr as precursors. The measured thicknesses of the WC and CrC coatings are equal to ca. 1.5 µm. The WC coating consists of microcolumns with a conical end, with gaps between the microcolumns up to approximately 100 nm, and their structure is formed by nanoparticles in the shape of globules with a diameter of up to 10 nm. In the case of the CrC coating, a cauliflower structure with gaps ranging from 20 to 100 nm was achieved. The diameter of cauliflower grains is from 50 nm to 300 nm. The C content in the WC and CrC coating is 66.5 at.% and 75.5 at.%. The W content is 1.4 at.% and the Cr content in the CrC coating is 1.2 at.%. The hardness and Young's modulus of the WC coating are equal to 9.2 ± 1.2 GPa 440.2 ± 14.2 GPa, respectively. The coefficients of friction and wear volume of the WC coating are equal to 0.7 and -1.6 × 106/+3.3 × 106 µm3, respectively. The hardness and Young's modulus of the CrC coating are 7.5 ± 1.2 GPa and 280 ± 18.5 GPa, respectively. The coefficients of friction and wear volume of the CrC coating are 0.72 and -18.84 × 106/+0.35 × 106 µm3, respectively.

Fabrication of osteogenesis induced WE43 Mg-Hydroxyapatite composites with low biodegradability and increased biocompatibility for orthopedic implant applications

Good biocompatibility, low biodegradation rate and excellent mechanical properties are essential for desirable performance of metallic biomaterials during osseointegration process. In the present study, bioabsorbable WE43 Mg alloy was used for fabrication of bio-composites with addition of nanosized hydroxyapatite (HA) particles by means of multi pass friction stir processing (FSP) for orthopedic implant applications. Microstructure, in vitro biodegradation and biocompatibility, wettability, and microhardness of resultant bio-composites were characterized. Results showed that applying severe plastic deformation through FSP caused significant grain refinement of Mg matrix and homogenous dispersion of fragmented secondary phase particles. Moreover, applying higher number of FSP passes increased uniformity of distribution of HA nanoparticles throughout Mg matrix. Compared to coarse grain samples, grain refined samples showed lower Mg2+ concentration and H2 evolution in simulated body fluid (SBF). Moreover, addition of HA into Mg matrix, reduced Mg2+ release and H2 evolution. The bio-composites illustrated uniformly and flatly corroded surface compared to samples without HA nanoparticles. During immersion of the bio-composites in SBF solution, a cauliflower structure of Ca–P compounds deposited on the surface of bio-composites which confirmed acceptable biomineralization. Contact angle measurement demonstrated that wettability of fabricated bio-composites increased by increasing number of FSP passes. Mouse osteoblast MC3T3 cell culture indicated that the fabricated bio-composites with uniform distribution of HA nanoparticles showed excellent in vitro biocompatibility, cell viability, and cell proliferation. Eventually, it was found that applying further FSP and presence of HA nanoparticles resulted in increased microhardness which is an indication of higher load-bearing capability of the fabricated bone implants.

Efficient preparation of multifunctional superhydrophobic surfaces on Zr-based bulk metallic glass by electrochemical machining

It is well known that metallic glasses (MGs) are ideal superhydrophobic substrate materials. However, the preparation methods and application fields of superhydrophobic MGs are presently limited. For the first time, the superhydrophobic layers on both the cathode and anode surfaces of Zr-based bulk metallic glasses (BMGs) were efficiently fabricated through combining the electrochemical etching with electrochemical deposition. The superhydrophobic Cu/Cu2O coating with cauliflower structure on the cathode surface shows excellent photocatalytic and antibacterial performance. In the meantime, the corrosion inhibition rate of the superhydrophobic anode surface reached ∼99.62% and the surface shows good long-term corrosion resistance. This study provides a new horizon for designing superhydrophobic surface on MGs showing mutifunctional performance.

A novel preparation and characterization of electroless NiP/MWCNT composite coated UHMWPE fabric in terms of wettability, electrical conductivity, thermal stability and breaking load resistance

Poor wettability results in fragile bonding between the ultra-high molecular weight polyethylene (UHMWPE) fabric and matrix of the composites. To overcome this issue, the present study proposes a novel approach for the deposition of electroless nickel-phosphorus (NiP) and nickel-phosphorus/multi walled carbon nanotube (NiP/MWCNT) coating on the surface of UHMWPE. The influence of coatings on the morphology, phase structure, crystal size, functional groups, surface roughness, wettability, water absorption property, electrical conductivity, thermal stability, peeling load and breaking load of UHMWPE fabric are detailed. After MWCNT was reinforced, the cauliflower structure reported for NiP coated UHMWPE (NiP-UHMWPE) was altered for NiP/MWCNT-coated UHMWPE (NiP/MWCNT-UHMWPE). The crystal size of NiP has slightly increased to 1.307 nm for NiP/MWCNT-UHMWPE from 1.22 nm of NiP-UHMWP. The contact angle of NiP-UHMWPE (84.36°) was relatively lower than the NiP/MWCNT-UHMWPE (92.46°) and UHMWPE (102°), due to the formation of more nickel globules in the surface of NiP-UHMWPE. Though the wettability was high for the NiP and NiP/MWCNT coating, the water absorption percentage has not increased for NiP-UHMWPE and NiP/MWCNT-UHMWPE. The electrical conductivity was improved for NiP/MWCNT-UHMWPE after the reinforcement of MWCNT. The breaking load of the NiP and NiP/MWCNT coated UHMWPE fabric improved by 6.24% and 12.11% respectively. The more detailed study in terms of functional group, crystal structure, compounds, electrical conductivity, thermal stability, peeling load, and tensile failure analysis of coated UHMWPE fabric are reported in this article.

Nickel-Cadmium-Sulfide Anchored on rGO Nanocomposite for Removal of Textile Industry Dyes

The design and development of a novel route for the preparation of efficient photocatalysts for the treatment of polluted water is an essential need. Due to rapid expansion of pharmaceutical and textile industries, the discharge of drugs and sewage contaminants leads to water contamination. To address these issues, hydrothermally synthesized Ni–Cd–S/rGO nanocomposite with a cauliflower structure was developed. The prepared nanocomposite was studied using advanced characterization techniques to confirm crystal structure, surface morphology, optical studies and material composition in detail. Further, the photodegradation process of textile-based Methylene Blue (MB) and Methyl Orange (MO) dyes using Ni–Cd–S/rGO nanocomposite with desired time interval under natural sunlight was also investigated. The maximum photocatalytic performance of > 90% was achieved for the photocatalyst. The photodegradation rate can be maintained after 5 recycling tests in the presence of MB and MO dyes. The remarkable degradation efficiency, high rate constant and reusability of the Ni–Cd–S/rGO nanocomposite make it an excellent choice for textile effluent treatment.

Hydrothermal preparation of lightweight calcium silicate powder from alumina-leaching residue of low-calcium sintering red mud

In order to realize the complete and high-value utilization of red mud, a hydrothermal process was proposed to prepare the lightweight calcium silicate powder from a sodium calcium silicate residue after alumina extraction. The synthesized products were characterized by XRD, XRF, SEM, EDS, and PSD, and the corresponding transition mechanism and physical properties were also studied. The main silicon- and aluminum-bearing phases in the clinker after the low-calcium sintering are Na2CaSiO4 and NaAlO2, and the former silicate keeps stable during the alumina leaching process under atmospheric pressure. In the hydrothermal process, Na2CaSiO4 in the alumina-leaching residue is converted into NaOH and Ca5Si6O16(OH)2·4H2O in the alkali solution, and the residual alumina is converted into Ca3Al2SiO8·4H2O which promotes the generation of Ca5Si6O16(OH)2·4H2O. Increasing the reaction temperature, duration and liquid-solid ratio of the hydrothermal process can facilitate the alkali removal efficiency in calcium silicate powder and decrease its bulk density, while the excessive hydrothermal temperature and duration reduce the alkali removal efficiency. The Na2O residue and bulk density of the calcium silicate powder are 0.42% and 0.30 g·cm−3 obtained at the optimal hydrothermal conditions. The flaky particles of Ca5Si6O16(OH)2·4H2O are aggregated into a porous cauliflower structure, which improves the absorption and insulation properties of calcium silicate powder.

The effect of pulse current density on the microstructure, magnetic, mechanical, and corrosion properties of high-entropy alloy coating Fe–Co–Ni–Mo–W, achieved through electro co-deposition

This paper describes the preparation of novel FeCoNiMoW high-entropy alloy coatings using the pulse current electrodeposition method and the effect of pulse current densities of 2, 6, and 10 A/dm2 on the coatings' characteristics. XRD, TEM, EDS, and FESEM were used to perform phase, elemental, and morphological evaluations, respectively. The coatings’ microhardness, magnetic, wear, and corrosion properties were also investigated. The results confirmed the formation of FeCoNiMoW alloy coatings with high entropy. When the current density increased, the morphology changed from a dome to a cauliflower structure. The coexistence of amorphous and nanocrystalline phases was demonstrated by XRD and TEM. Small coercivity (11 Oe-18 Oe) was achieved due to the unique microstructure. The lowest coercivity (11Oe), highest hardness (682 HV), highest wear resistance (COF= 0.5), and highest corrosion resistance (icorr = 3.2 μm/cm2) were obtained at a current density of 6 A/cm2.

Projevy interakcí vulkanické aktivity Velkého Roudného s vodním prostředím

Velký Roudný scoria cone represents the most prominent volcanic edifice of the Plio-Pleistocene Bruntál Volcanic Field (according to Cajz et al. 2012). Various types of volcaniclastic deposits and volcanic features were interpreted in various ways in the past. However, several features remained overlooked, and the investigated ones required critical revision. Velký Roudný is an asymmetric horseshoe-shaped cone, with a crater open towards the southeast (Fig. 1a). The lava flows emitted from this cone flew southwards and also to the east/ southeast, where the lava filled a paleo-canyon of the Moravice River. In the paleo-canyon, the lava (up to 60 m thick) buried earlier fluvial sediments (Horský et al. 1972; Fig. 2). The best exposure of the lava flow is accessible in the active Bílčice quarry. The two levels of columnar jointing separated by a platy- to blocky-jointed domain represent the upper and lower colonnade of a single lava flow (Fig. 3a, b). The columnar jointing domains are interrupted by subvertically platy-jointed, piston-like features filled with breccia (Fig. 3c, d). These monomictic breccias are dominated by basaltic clasts with signs of abrupt quenching, like cauliflower structures (Fig. 3e, f ). The shapes of these breccia bodies, together with signs of magma/water interactions, suggest their origin from rootless explosions. Their extension through the complete thickness of the lava, as well as their distribution in the lava flow were earlier documented by geophysical survey (Štainbruch 2019), whose results are re-interpreted in this contribution (Fig. 4). Another effect of the lava/water interaction is represented by “sunburn” decomposition (spheroidal decomposition of the rock; Fig. 5a). The development of the spheroidal cracks seems to be restricted to the glass-containing groundmass (Fig. 5b). As the sunburn decomposition develops mainly at the base, around the rootless craters, and less frequently on the top of the lava. It seems that these irregular features reflect gentle hydration of glass-containing rock, similarly to perlitic cracks in silicic lavas (e. g., McPhie et al. 1993). Subsequently to cracking, the glass tends to analcime recrystallization (Fig. 5c, d), enhancing the decomposition of the rock. Pyroclastic deposits exposed in two small abandoned quarries near Razová and Karlovec, respectively, were interpreted as tuffites (mixed volcano-sedimentary deposits) in the past. Despite that these deposits contain abundant fragments of basement greywackes, the fragments display no signs of rounding or sorting (Fig. 6). Poorlysorted clast-supported deposits well correspond to the near-vent ballistic accumulation of phreatomagmatic eruption. At Karlovec, predominance of the finer-grained facies with diagonal bedding suggests that these rocks originated by base-surge deposition. The potential source of the phreatomagmatic eruption can be found in the circular depression underneath Velký Roudný (Fig. 1b, c), as supported by a magnetic anomaly (Fig. 7). The phreatomagmatic character of the volcanic activity possibly results from an eruption through a lake dammed by the Bílčice lava of the Velký Roudný scoria cone (Fig. 8).

Oblique angle co-deposition of nanocolumnar tungsten thin films with two W sources: Effect of pressure and target current

Two series of tungsten thin films are sputtered on silicon and glass substrates by oblique angle co-deposition technique with an original configuration. Two opposite distinct tungsten targets are simultaneously used, both tilted with an oblique angle of 80°. The growth is performed at low (0.33 Pa) and high (1.5 Pa) argon sputtering pressure and the current intensity applied to the targets varies between 50 and 250 mA. The effect of these deposition parameters on the films microstructure and electrical properties is investigated by scanning and transmission electron microscopy, X-ray diffraction and pole figures, and van der Pauw method. Due to self-shadowing effect, all tungsten sputtered thin films are porous and columnar. At low pressure, the columnar tilt angle β can be tuned with the target current intensity until obtaining vertical columns. X-ray diffraction and pole figure analyses point out a A15 crystal structure (β-W) and a uniaxial fiber texture with a <100> growth direction. In contrast, tungsten thin films deposited at high pressure present a cauliflower structure and are poorly crystallized. Both deposition parameters also affect the films electrical resistivity and anisotropy. These behaviors are discussed and linked to the microstructure and crystallography.

Evaluation on the microhardness of Ni-TiO2 nanocomposite coatings on AISI 1022 substrate

The surface strength and performance of the material depends mainly on the appropriate coating techniques and also on the selection of the appropriate process parameters. From in this, electroplating is broadly used to protecting the material's surface and hence increases the life of industrial components. The present study pulse electrodeposition of Ni-TiO2 nanocomposite coating was developed on the surface of AISI 1022 Carbon Steel from watts bath. Such nanocoatings greatly enhanced the better hardness, wear and corrosion resistance in the automotive industry. The present work purpose to examine the influence of the coating process parameters on the microhardness (MH) of Ni-TiO2 nanocomposite coating on AISI 1022 Carbon Steel with the aid of response surface methodology (RSM). The Pulse frequency (Hz), Current density (A/cm2) and Duty cycle (%) parameters are considered and integrated into the RSM three factors and three level orthogonal arrays to determine the optimized condition for improved hardness of the coating. The contribution of the coating parameters was studied with the help of analysis of variance (ANOVA). The result revealed frequency: 20 Hz, current density: 0.2 A/cm2 and duty cycle: 30% coated specimen uniformly distributed cauliflower structure than compared to the frequency: 30 Hz, current density: 0.2 A/cm2 and duty cycle: 20%. To explore that uniformly coated specimen EDX, field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD) respectively.

Feasible study on poly(Pyrrole-co-Pyrrole-3-Carboxylic Acid)-modified electrode for detection of 17β-Estradiol

Preparation and characterizations of poly(pyrrole-co-pyrrole-3-carboxylic acid) (PPYPA) film on the surface of screen printed carbon electrode (SPE) has been discussed in the manuscript. Different ratios of monomer for PPYPA preparation will be applied to determine 17β-estradiol using cyclic voltammetry. The SPE was modified with PPYPA film using an electrodeposition method and followed by the immobilization of 75mer aptamer specifically binding to 17β-estradiol as a model study. The materials were characterized by cyclic voltammetry, Fourier transform infrared, electrochemical impedance spectroscopy and scanning electron microscopy. The redox peak potential was found to be at 0.13 V and 0.26 V. The appearance of cauliflower structure in the SEM image which indicates PPYPA film was formed on SPE. Moreover, PPYPA/SPE exhibited a lower charge transfer resistance (Rct) compared to bare SPE indicates a good conductivity of film. Our study shows that 3:1 ratio between PPY and pyrrole-3-carboxylic acid provided highly active surface area for the immobilization of 75mer aptamer for 17β-estradiol detection.

Investigation of recently discovered common green opals from Anosy (Madagascar)

The physical, chemical and gemological properties of recently discovered common green opals from Anosy (South-Eastern Madagascar) have been investigated using different analytical methods such as standard optical and gemological analyzes, X-ray powder diffraction (XRPD), Scanning Electron Microscopy (SEM), Micro-Raman Spectroscopy and Laser Ablation Microprobe (LA-ICP-MS). Anosy opals have a yellowish green color with a light yellowish rim, translucent / opaque diaphaneity with greasy luster, red oxide spots and are inert to long and short wavelength UV radiation (366–254 nm). The values for refractive index and specific gravity range between 1.435–1.460 and 2.03-2.07, respectively. According to XRPD and Raman analyses, the opals are CT type with tridymite more abundant than cristobalite and also contain clay minerals (saponite). Iron and, subordinately, V and Cu appear the main chromophores that determine the green-yellowish color, while Ni and Cr are very subordinate. Other detected trace elements are Mg, Al, Ca, K, and Na. The high contents of Ba are noteworthy since this element is rarely reported in opals worldwide. SEM observations show three types of structures already observed in the CT opals: homogeneous and very fine microspheres, lepispheric cauliflower structures and globular aggregates of different sizes formed by laminae.

Optimization of Ni-B coating bath and effect of DMAB concentration on hardness and wear

In this study, reducing agent amount, stabilizer amount, coating bath temperature and stirring speed parameters were examined for optimization of electroless Ni-B coatings, and the effect of reducing agent amount on hardness and wear of the coating was investigated. The pH of the electroless Ni-B coatings made for 1 h was set to 6, nickel chloride (NiCl2.6H2O) as the nickel source, sodium acetate (C2H3NaO2) as the complexing agent, thiourea as the stabilizer (CH4N2S) and DMAB ((CH3)2NBH2) as the reducing agent was used in the coatings. The bath parameters were varied as; the amount of reducing agent (2 g/L, 3 g/L and 4 g/L), coating bath temperature (65°C, 70°C and 75°C), stabilizer amount (0.5 mg/L, 1 mg/L, and 2 mg/L) and stirring speed (250, 300 and 350 rpm). After determining the optimum conditions, the effects of the amount of reducing agent on the coating were examined. Scanning Electron Microscopy (SEM), X-ray diffractometer (XRD), Vickers nano-hardness test and tribometer were used for characterization of coatings. In the optimization studies, it was observed that the coating morphology was in the form of cauliflower and columnar structures were formed in the cross-section images. According to optimization results on the morphologies, the samples which compact and free-crack have been investigated phase structure, hardness and tribology properties. In XRD analysis, coatings produced with different amounts of reducing (DMAB) are amorphous as-deposited, after annealed at 400°C for 2 h, nickel borides (Ni2B and Ni3B) phases are formed and increased the preferential orientation (111) of the nickel crystal plane. The effect of DMAB concentration on coating was examined in as-deposited condition and post annealing. The formation of nickel borides after annealing increases the hardness. The effect of DMAB concentration on the coating after annealed was examined and it was observed that the wear resistance of the dense and homogeneously dispersed sample in the coating matrix was more perfect than other samples. Consequently, hardness (850 HV), coefficient of friction (0.37) and wear rate (2.92 × 10−7 mm3/Nm) of B2 sample which free-crack and compact was obtained. These results indicate a high strengthen B2 sample produced with 3 g/L DMAB concentration and 70°C bath temperature could utilize in a harsh medium.

Organic Surfactant Assisted Polypyrrole Materials as Effective Chemiresistive Gas Sensors for VOCs and Toxic Gas Detection

Surfactant assisted PPy materials are explored as efficient gas sensors for VOCs and toxic gases in the present work. Polypyrrole nanostructures were prepared by chemical oxidative polymerization using various sulfonic acids as surfactants between 0-5 °C. The effect of sulfonyl group on PPy was confirmed by FT-IR spectrum analysis. Doping of sulfonic acid has a strong effect on morphology of polymer blends which displayed the amorphous, globular, cauliflower, flakes and compact sheet like structures observed in the surface morphology. The conductivity of doped PPy observed to be dependent on the nature of dopant and its doping level. The electrical conductivity was observed to enhance by an order in magnitude on the addition of organic surfactants from 0.1 to 2.0 M. The pristine PPy shows high % response of 93% and 70% only for NH3 and Cl2 respectively. But different surfactant doped PPy were found to be highly sensitive for most of the VOCs and toxic gases which emerged as efficient sensor materials for fast response and recovery at the lowest level of 5 ppm.

Electrolyte Transfer at a Liquid-Solid Polypyrrole Interface Quantified By in Situ X-Ray Reflectometry

In situ characterization of the electrochemical (EC) intercalation mechanism of ions in conductive polymer films is one of the most important aspects in the development of novel organic supercapacitors. Compared to atomic force microscopy and quartz microbalance measurements, synchrotron-based in situ X-ray reflectometry (XRR) allows deeper and more detailed insights into electrically controlled transfer processes of electrolytes across liquid-solid interfaces. The low roughness of the layer system to be investigated, which is required for XRR, is a particular challenge: Electrochemically deposited polypyrrole (PPy) films naturally possess a rough surface, the typical cauliflower structure. In the present study, PPy was deposited on a silicon crystal with a fast-varying voltage to obtain a PPy film with a very smooth surface, which led in parallel to a significantly denser film, which also increases the XRR contrast. This 30 nm thin PPy film was measured in situ in a 0.1M HClO4 environment with XRR at different voltage levels between -0.2 and +0.5V vs Ag/AgCl and the film thickness and electron density were determined. A linear and reversible change in thickness and electron density was measured, which is typical for the potential-dependent intercalation process of anions. The number of electrons transferred across the electrolyte-PPy interface was determined from the change in thickness and electron density, from which the transport of matter was derived. The correlation with the electrically measured transferred charge resulted in a ratio that was significantly below the expected value for exclusive anion exchange. Considering all present and available matter, it can be deduced that proton transport partially compensates for the charge and that 2-3 water molecules per incorporated perchlorate anion are removed from the film. Fast XRR measurements on the same PPy film during applied cyclovoltammetry showed two intervals of different behavior of the PPy film: In the higher voltage range anion intercalation dominates, the PPy film shows a very high pseudo-capacity due to its high density, while in the lower voltage range proton exchange starts and reduces the pseudo-capacity. Electrochemical impedance spectroscopy confirmed these results: Above the transition of these two voltage ranges, the conductivity of the PPy film increases dramatically due to the intercalation of perchlorate anions. With the presented synchrotron-based, in situ EC-XRR setup the film thickness, the electron density, and the change of both, as well as the pseudo-capacitance and conductivity as a function of the applied voltage can be measured simultaneously on ultra-thin electrochemical polymer films. Especially for the development of new electrochemical systems this is a highly potent measurement technique for in situ characterization.