Experimental Investigation and Numerical Simulation for Corrosion Rate of Amorphous/Nano-Crystalline Coating Influenced by Temperatures

A high-velocity oxygen fuel (HVOF) system was employed to prepare a Fe49.7Cr18Mn1.9Mo7.4W1.6B15.2C3.8Si2.4 amorphous coating on mild steel. The electrochemical behavior of the resultant coatings, namely as-sprayed coating and vacuum heat-treated coating (at 650 °C and 800 °C), were investigated in a 3.5% NaCl solution at variable temperatures using scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, optical microscopy (OM), and XRD diffraction. Moreover, COMSOL Multiphysics version 5.5 software were employed for predicting the galvanic corrosion of amorphous material immersed in an aqueous NaCl solution, using the software finite element kit. The experiments demonstrated that the coatings’ pitting resistance was significantly affected by temperature. The results also showed that temperature affected the pitting corrosion rate and changed the shape of the pits. However, the changes were not as extreme as those observed in stainless steel. Furthermore, there was no significant difference between the as-sprayed coating and the vacuum-heat-treated coating at 650 °C. At low NaCl concentrations at and temperatures below the critical pitting temperature, the resulting pits were significantly small with a hemisphere-like. By contrast, at a higher NaCl concentration at 70 °C, particularly in the case of heating at 650 °C, the pits appearing on the Fe-based amorphous coating were vast and sometimes featured a lacy cover.

Shear-Coated Linear Birefringent and Chiral Cellulose Nanocrystal Films Prepared from Non-Sonicated Suspensions with Different Storage Time

Nanocelluloses are very attractive materials for creating structured films with unique optical properties using different preparation techniques. Evaporation-induced self-assembly of cellulose nanocrystals (CNC) aqueous suspensions produces iridescent films with selective circular Bragg reflection. Blade coating of sonicated CNC suspensions leads to birefringent CNC films. In this work, fabrication of both birefringent and chiral films from non-sonicated CNC suspensions using a shear-coating method is studied. Polarization optical microscopy and steady-state viscosity profiles show that non-sonicated CNC suspensions (concentration of 6.5 wt%) evolve with storage time from a gel-like shear-thinning fluid to a mixture of isotropic and chiral nematic liquid crystalline phases. Shear-coated films prepared from non-sonicated fresh CNC suspensions are birefringent, whereas films prepared from suspensions stored several weeks show reflection of left-handed polarized light. Quantification of linear and circular birefringence as well circular dichroism in the films is achieved by using a Mueller matrix formalism.

Mesomorphic Behaviour and DFT Insight of Arylidene Schiff Base Liquid Crystals and Their Pyridine Impact Investigation

A new series of Schiff base liquid crystal have been prepared and studied. Schiff bases of p-alkyl aniline derivatives and 4-phenyl pyridine-4′-carbaldehyde were prepared. The terminal alkyl groups substituting aniline are of varied chain length, namely C8, C12 and C14. The structures of the compounds were elucidated by 1H NMR and 13C NMR. The mesomorphic thermal and optical characteristics of the samples were determined via differential thermal analysis (DSC) and polarization optical microscopy (POM). All compounds exhibit enantiotropic dimorphic mesophase behaviour, referred to as smectic X1 (SmX1) and smectic X2 (Sm A). Experimental results obtained for the mesophases were correlated with density functional theory (DFT) theoretical calculations. The results of the new series are further compared to two series of compounds bearing pyridine (two ring Schiff bases) and biphenyl, respectively, in their mesogens. The series of compounds of one pyridine ring are generally not mesomorphic. The results indicate that the alkyl chain length has a strong impact on the mesomorphic characteristics and thermal stabilities of the different mesophases. As a trend, the temperature ranges of both of smectic mesophases of all compounds are higher in new compounds bearing the 4-phenyl pyridine moiety. In addition, the total mesophase range is generally higher in the new compounds when compared to their biphenyl analogues. Finally, theoretical DFT calculations were performed to illustrate the experimental finding of the mesomorphic behaviour in terms of the molecular geometry and aromaticity, π–π stacking and LOL-π.

Micro-structural Investigations on Oppositely Charged Mixed Surfactant Gels With Potential Dermal Applications

Dicarboxylic amino acid-based surfactants (N-dodecyl derivatives of -aminomalonate, -aspartate, and -glutamate) in combination with hexadecyltrimethylammonium bromide (HTAB) form a variety of aggregates. Composition and concentration dependent mixtures may exhibit liquid crystal, gel, precipitate and clear isotropic phases. Liquid crystalline patterns were identified by polarization optical microscopy and fluorescence microscopy. FE-SEM studies reveal porous and flower like morphology. Phase transitions and weight loss depend on composition where thermotropic behaviors were revealed through differential scanning calorimetry and thermogravimetric analyses, respectively. Systems comprising more than 60% HTAB demonstrate shear-thinning behavior. Gels cause insignificant toxicity to human peripheral lymphocytes and irritation to mouse skin; they do not display the symptoms of cutaneous irritation, neutrophilic invasion and inflammation (erythema, edema, and skin thinning). Gels also exhibit antibacterial effect on Staphylococcus aureus, a potent causative agent of skin and soft tissue infections, suggesting its possible application as vehicle for dermatological drug delivery.

Uses of Building Stones in Architectural Elements of El Kantara Town, Biskra (Algeria).

<p> </p><p><strong>Abstract-</strong> The preservation and conservation of historical and cultural built heritage is necessary to preserve the history of cities and the identity of populations. Built heritage is a cultural asset whose preservation and protection is essential to any society. Building stones are one of the most widely used construction materials throughout history. Normally, building stones come from the vicinity of where they are used, which ensures the integration of the built heritage with its surroundings. Due to their decay, building stones need to be preserved and conserved.</p><p>El Kantara, formerly Calceus Herculis, is an oasis located 52 kilometers north of Biskra, Algeria. It is characterized by its rich history with alternation of different civilizations: Roman, Muslim and French. El Kantara is an example of vernacular architecture that uses building materials provided by the local environment. Due to the mountainous nature of El Kantara, building stones have been one of the most used materials since the Roman period.</p><p>Our research is based on Dachra Dhahraouia as a case study. It is one of three villages in El Kantara and the oldest core of the city. It was founded around the 7th century by a group of families who had arrived to this place during the Muslim conquests because of its strategic location and its position, on the heights overlooking the El Haï valley and the palm grove. When the French settled in El Kantara and created their village, the name Dachra Dhahraouia changed to Red Village because of its red earth color.</p><p>Dachra Dhahraouia is a protected area (May 6, 2013). It is considered a model of authentic Arab-Berber architecture, for its type of construction, its doors, its alleys, the organization of its houses, its traditional materials and its architectural character in harmony with nature, traditions and customs. The building stones are used in houses, in foundations of historic walls, in entrance steps in public spaces as benches and in steps of stairs. They are also used in the fence wall of the old cemetery.</p><p>The aim of this paper is to study the different existing building stones used in architectural elements of Dachra Dhahraouia. In order to achieve the purpose of this study, six samples (5 × 5 × 5 cm) of the different stone types were tested from different houses and public spaces. Polarization optical microscopy and X-ray diffraction techniques were used for petrographic characterization. Bulk density, porosity, color and ultrasound propagation wave measurements were used for petrophysic characterization of the heritage stones.</p><p> </p><p>The most-used building stone found in Dachra Dhahraouia is a limestone, used in foundations, fence walls and in steps of stairs. Quartzite valley pebbles are used just in the foundations. Dolomite is also part of the building stones used in public spaces as pavements. Also, ashlars from the Roman period are reused in entrance steps and in the foundations of some houses.</p><p> </p><p><strong>Index Terms-</strong> building stones. architectural elements. El Kantara. Heritage.</p>

PRODUCTION OF CELLULOSE NANOCRYSTALS BY HYDROLYSIS IN MIXTURE OF HYDROCHLORIC AND NITRIC ACIDS

In this work, cellulose nanocrystals (CNC) have been produced by hydrothermal method in a mixture of hydrochloric and nitric acids in molar ratios of 8:2, 7:3, 6:4 and 5:5. Hydrolysis of sulphate cellulose in the mixtures of nitric and hydrochloric acids was conducted in a sealed thick-walled stainless steel vessel with a teflon insert for 3 h at 110 °С. Properties of CNC have been characterized by applying different methods: elemental analysis, thermogravimetric analysis, IR spectroscopy, polarization optical microscopy, scanning electron microscopy, and dynamic light scattering. Yield of CNC, size and charge of the CNC particles, degree of polymerization, temperature of thermal destruction have been determined, and morphology of the CNC samples has been characterized. The highest CNC yield (32%) has been observed at a 7:3 ratio of nitric and hydrochloric acids. It has been established that the CNC particles are spherical and have an average size of 60-80 nm. An assumption has been made that presence of a strong oxidant (nitric acid) may cause hydrolysis of both amorphous and crystalline (in part) regions of cellulose, which affects the final shape of the CNC particles. It has been shown that the hydrolysis in a mixture of nitric and hydrochloric acids causes an oxidation of primary hydroxyl groups of the cellulose pyranose ring and formation of surface carboxyl groups. The CNC aqueous suspensions demonstrate high colloidal stability due to a rather high surface charge. It is noted that the CNC thermal stability is much higher than that of the CNC samples obtained by the standard sulfuric acid hydrolysis: the temperature of thermal destruction increases by 130-148 °С.

RELEASING OF ACETYL HEXAPEPTIDE-3 USING A LECITHIN BASED LIQUID CRYSTAL SYSTEM

One of the promising areas of application of liquid crystal systems for medicine and cosmetics is the development of matrices for drug delivery. A relatively new technology for this is the use of lecithin-based liquid crystal systems, in which the smallest droplets of the aqueous phase are stabilized not by ordinary emulsifiers, but by a network of bilayers of surfactants, like those that make up the lipid barrier. In this regard, the lecithin / water / propylene glycol /vaseline oil system, which is non-toxic and biodegradable, was obtained and investigated. By finding the minimum interfacial tension of lecithin at the boundary of the water-propylene glycol mixture / mineral oil, the necessary concentrations of the components of the aqueous phase were selected. Phase diagram was received. The liquid crystal region was studied by the method of polarization-optical microscopy. It was determined that in this area the system self-organizes with the formation of a lamellar mesophase. The results of the study of the phase behavior of lyotropic liquid-crystal systems with incorporated substances contribute to an understanding of the processes of their delivery and to solving the problem of release, since the supermolecular structure is destroyed during the phase transition and the active substance is released. In this regard, acetyl hexapeptide-3, which is an analogue of botulinum toxin and widely used in cosmetics and medicines, was introduced into the system, and UV spectra of the peptide were obtained. With the use of the Franz diffusion cell, the release of acetylhexapeptide-3 through a cellophane membrane was investigated. The quantitative characteristics of the introduction of the peptide into the complex were established. Its prolonged action is shown when passing through the membrane. This system can be used as a basis for the transport of peptides into skin cells.

Chemical, Mineralogical, and Refractory Characterization of Kaolin in the Regions of Huayacocotla-Alumbres, Mexico

In the present work, the chemical, mineralogical, refractory, and microstructural characterizations of kaolinites from the Huayacocotla-Alumbres region, which is between Veracruz and Hidalgo border, by X-ray diffraction (XRD), polarization optical microscopy (POM), scanning electron microscopy (SEM), refractoriness proof (pyrometric cone equivalent), and thermogravimetric analysis (TGA) were carried out. The analysis by POM showed that the kaolinization degree in this region is variable due to the presence of primary minerals, such as plagioclase, feldspar, and quartz. Additionally, hydrothermal alteration of the epithermal type was determined by oxidation of sulfides (pyrite and galena) and chlorite association. With the X-ray diffraction technique, andalusite and kaolinite were identified as the majority phases in Huayacocotla and quartz was identified as the majority phase in Alumbres. The minority phases, such as dickite, kaolinite, and cristobalite, were observed in both zones. The SEM technique was useful in the determination of the morphology of kaolinite and impurities of Na, Mg, K, and Fe of the complex clay illite-andalusite-dickite group. Thermogravimetric analysis was useful to discover the decomposition temperature and reveal the significant difference between 400 and 800°C, which showcases the greatest mass loss due to dehydration and carbonates decomposition. The mullite phase was detected at approximately 1000°C in the kaolin samples. The refractoriness tests were important to determine the stability temperature of kaolin, which is between 1300 and 1600°C. This stability temperature makes it feasible to use the kaolin as a refractory material for both low and high temperatures. The variables that affect the kaolin stability temperature were determined by principal components with the XLSTAT free program.

Growth and Magneto-Optical Properties of Bi-Substituted Lutetium Iron Garnet Films

Epitaxial (Lu,Bi)3(Fe,Ga)5O12 films were grown on GGG (111) orientated and GGG(100) orientated substrates by the LPE method over a wide temperature range. Epitaxial growth, surface morphology, chemical composition as well as magneto-optical properties of the films were investigated by ESEM, TEM, AFM, EDAX, and polarization optical microscopy. The magnetic anisotropy of the films, lattice mismatch as well as Bi concentration in the films is also discussed. The films exhibit in-plane or out-of-plane magnetization, depending on growth temperatures. The Bi concentration in the grown films and saturation magnetization field also exhibit a dependence on growth temperatures. When the film is very thin, its coercivity will increase and the orientation of magnetization transits from out-of-plane to in-plane.