Role of chromium in anomalous behaviour of the passive layer in Ni-Cr-Mo alloys in 1M HCl solution

This work seeks to understand the underlying mechanism involved in passivity of Ni-Cr-Mo alloys in a less concentrated HCl solution (1M) by systematically varying contents of Cr and Mo solutes in model Ni-Cr-Mo alloys. Corrosion behaviour was evaluated based on potentiodynamic polarisation tests carried out in conjunction with electrochemical impedance and x-ray photoelectron spectroscopies of passive films that formed on alloys during their exposure to the HCl solution. Results have shown that an increase in Mo alone is not sufficient to improve the corrosion resistance of the alloys at lower concentrations of HCl. Optimum concentrations of Cr and Mo solutes have been found to be in the vicinity of ~17 wt.% Cr and ~19 wt.% Mo for superior corrosion resistance of the alloys. This was attributed to the protection of the Cr2O3 layer as a consequence of the enrichment of Mo6+ ions in the passive film in 1M HCl solution.

The effect of deproteinization methods on the properties of glucosamine hydrochloride from shells of white leg shrimp (Litopenaeus vannamei) and black tiger shrimp (Penaeus monodon)

ABSTRACT: The effect of methods to remove protein content on the properties of glucosamine hydrochloride from the shells of white leg shrimp (Litopenaeus vannamei) and black tiger shrimp (Penaeus monodon) was investigated. Chitin from shrimp shells was obtained by demineralization in 6% HCl for 12h, deproteinization by two different methods (first group soaked in 8% NaOH for 36h and second group treated in Alcalase enzyme at the concentration of 0.2% for 36h). Two group samples were converted to glucosamine hydrochloride by soaking in 36.76% HCl solution for 5h at 85 °C. The results of fourier transform infrared spectroscopy (FTIR), solubility and recovery yield analysis showed that deproteinization methods did not significantly affect the properties of glucosamine hydrochloride. However, glucosamine hydrochloride from white leg shrimp shells contained higher recovery yield and solubility than black tiger shrimp shells.

The Effect of Hydrochloric Acid Solution and Glycerol on The Mechanical, Hydrate Properties and Degradation Rate of Biofilm from Ripe Banana Peels

Banana peel is a biomass waste that has not been utilised optimally, despite its high starch content. Moreover, starch has potential as a raw material for biofilm or edible film production. This research focused on using the starch content from the mature banana peel to create a biofilm. Starch was extracted from the banana peel; then, it was hydrolyzed with a variation of hydrochloric acid solution (HCl) of 0.5 M (0, 2, 4 %-v/v Starch). Glycerol (0, 20, 40 %-w/w starch) was used as a plasticizer. It was found that the formulation of 4%-v/v HCl solution and glycerol 20%-w/w resulted in the highest biofilm’s tensile strength of 4.18 MPa. However, the elongation break percentage achieved the best result at 20,2% when the formulation of 0%-v/v HCl solution and 40%-w/w glycerol was applied. Increasing HCl solution and glycerol was proven to improve the biofilm’s solubility in the water, where 47.9% solubility was attained in the formulation of 40%-w/w glycerol and 4%-v/v HCl solution. The degradation rate of biofilm in the soil was measured using zero- and first-order kinetic rates. The zero-order resulted in the best model with a half-life time (t1/2) between 73 to 108 days.

Mechanical and Durability Properties of Cementless Concretes Made Using Three Types of CaO-Activated GGBFS Binders

This study examined the mechanical and durability properties of CaO-activated ground-granulated blast-furnace slag (GGBFS) concretes made with three different additives (CaCl2, Ca(HCOO)2, and Ca(NO3)2) and compared their properties to the concrete made with 100% Ordinary Portland Cement (OPC). All concrete mixtures satisfied targeted air content and slump ranges but exhibited significantly different mechanical and durability properties. The CaO-activated GGBFS concretes showed different strength levels, depending on the type of additive. The added CaCl2 was the most effective, but Ca(NO3)2 was the least effective at increasing mechanical strength in the CaO-activated GGBFS system. The OPC concrete showed the most excellent freezing–thawing resistance in the durability test, but only the CaO-activated GGBFS concrete with CaCl2 exhibited relatively similar resistance. In addition, the chemical resistance was significantly dependent on the type of acid solution and the type of binder. The OPC concrete had the best resistance in the HCl solution, while all CaO-activated GGBFS concretes had relatively low resistances. However, in the H2SO4 solution, all CaO-activated GGBFS concretes had better resistance than the OPC concrete. All concrete with sulfate ions had ettringite before immersion. However, when they were immersed in HCl solution, ettringite tended to decrease, and gypsum was generated. Meanwhile, the CaO-activated GGBFS concrete with CaCl2 did not change the type of reaction product, possibly due to the absence of ettringite and Ca(OH)2. When immersed in an H2SO4 solution, ettringite decreased, and gypsum increased in all concrete. In addition, the CaO-activated concrete with CaCl2 had a considerable amount of gypsum; it seemed that the dissolved C-S-H and calcite, due to the low pH, likely produced Ca2+ ions, and gypsum formed from the reaction between Ca2+ and H2SO4.

Anthocyanin content in grains of barley and oat accessions from the VIR collection

Background. Barley (Hordeum vulgare L.) and oat (Avena sativa L.) are grain crops belonging to one of the main sources of food and forage in the Russian Federation. They contain proteins, various groups of vitamins, fats, carbohydrates, β-glucans, minerals and different bioloactive compounds, including anthocyanins. Recently, much attention has been given to anthocyanins due to their various valuable properties. Therefore, the grain of barley and oat is a potentially promising economic product and a component of functional nutrition. The aim of this work was to estimate the content of anthocyanins in barley and oat accessions with different pigmentation of kernels and lemma. Materials and methods. 32 barley and 11 oat accessions were studied by spectrophotometry. Anthocyanins were extracted from barley and oat kernels with a 1% HCl solution in methanol. Results and discussion. As a result of the study, accessions and varieties with the highest content of anthocyanins were identified: for barley these are k-15904 (China), k-19906 (Mongolia), k-18709 (Japan), k-18723, k-18729 (Canada), k-17725 (Turkey) belonging to var. violaceum; k-29568 (Japan) – var. densoviolaceum; k-8690 (Ethiopia) – var. griseinigrum; k-28205 (Germany) – var. nudidubium; and for oat these are k-15527 (A. ayssinica Hochst. var. braunii Koern., Ethiopia) and k-15245 (A. strigosa Schreb. subsp. brevis var. tephera Mordv. ex Sold. et Rod., Poland). Conclusion. The obtained results demonstrated that the VIR collection includes accessions with potential value for the development of varieties with an increased anthocyanin content, which can be used as functional food products.

Durability Investigation of Sulfur and Traditional Concrete within Aggressive Environments

An experimental study was conducted to evaluate durability (compressive strength and mass loss%) in the modified sulfur concrete within aggressive environments. The modified sulfur concrete was prepared by adding recycled polymeric and filler materials that showed a noticeable enhancement for modified sulfur concrete characteristics. A durability comparison between modified sulfur concrete and traditional concrete was investigated at normal and aggressive environments (10% HCl and 3% NaCl). A cuboid shape with size (50 × 50 × 50mm) was used in this research to investigate the durability of both modified sulfur and traditional concrete. The modified sulfur concrete characteristics revealed high stable structure than traditional due to preventing a process of crystallization of sulfur that modified with polymer and fillers. The compressive strength was 10.87 – 22.5% increased for modified sulfur concrete compared to the traditional concrete at the normal environment. In the aggressive environments, the modified sulfur concrete illustrated high resistance strength compared to the traditional concrete. The comparison revealed a significant impact for 10% HCl and 3% NaCl on the traditional concrete. The compressive strength decreased between (88.78 – 96.17) % for traditional concrete compared to modified sulfur concrete in 10% HCl solution and (84.25 – 95.06) % in 3% NaCl solution. Furthermore, mass loss % of the modified sulfur concrete indicated high resistance compared to the traditional concrete in both 10% HCl and 3% NaCl solutions.

Study on the Perspective of Mechanical Properties and Corrosion Behaviour of Stainless Steel, Plain and TMT Rebars

In the present research, the effects of various alloying elements and microstructural constituents on the mechanical properties and corrosion behaviour have been studied for four different rebars. The microstructures of stainless steel and plain rebar primarily reveal equiaxed ferrite grains and ferrite-pearlite microstructures, respectively, with no evidence of transition zone, whereas tempered martensite at the outer rim, followed by a narrow bainitic transition zone with an internal core of ferrite-pearlite, has been observed for the thermomechanically treated (TMT) rebars. The hardness profiles obtained from this study display maximum hardness at the periphery, which decreases gradually towards the centre, thereby providing the classical U-shaped hardness profile for TMT rebars. The tensile test results confirm that stainless steel rebar exhibits the highest combination of strength (≈755 MPa) and ductility (≈27%). It has been witnessed that in Tafel plots, the corrosion rate increases for all the experimental rebars in 1% HCl solution, which is well expected because the acid solutions generally possess a higher corrosive environment than seawater (3.5% NaCl) due to their acidic nature and lower pH values. However, all the experimental results obtained from Tafel and Nyquist plots correlate well for both 1% HCl and 3.5% NaCl solutions.