Corrosion inhibition of mild steel in sulphuric acid using a bicyclic thiadiazolidine

The inhibitory effect of 3a,6a-diphenyltetrahydro-1H-imidazo [4,5-c] [1, 2, 5] thiadiazole-5(3H)-thione 2,2-dioxide (TTU) on the corrosion behaviour of mild steel in 0.5 M H₂SO₄, at (30 ± 0.5) °C was studied by gravimetric, potentiodynamic polarization, electrochemical impedance spectroscopy, and scanning electron microscopy measurements. The effect of inhibitor concentration on the corrosion rate, surface coverage and inhibition efficiency is investigated. Results show that TTU exerts a strong inhibiting effect on mild steel corrosion and acts as a cathodic-type inhibitor. TTU does not affect the mechanism of the cathodic reaction while the anodic reaction mechanism changes upon addition of the inhibitor. Possible mechanistic pathways for the inhibition process are proposed. The inhibition efficiency of TTU may be due to either the adsorption of inhibitor molecules building a protective film or the formation of an insoluble complex of the inhibitor with metal cations. TTU adsorption obeys the Langmuir model.     

Antibacterial and antifungal dressings obtained by photochemical deposition of silver nanoparticles

The antimicrobial activity of silver against a wide spectrum of bacteria, fungi and viruses is known since antiquity. Silver has been used as topical antimicrobial agent in the treatment of wounds since many years and advanced silver‐based dressings have been designed so far. The aim of this study was the development of low‐cost antibacterial and antifungal dressings through the surface modification of conventional cotton gauzes. Different percentages of silver were deposited on textile substrates by adopting an innovative silver deposition technique based on the photochemical deposition of silver nanoparticles. The uniformity of the coating and the distribution of the silver clusters on the surface were evaluated by scanning electron microscopy (SEM). The amount of silver was quantified by thermogravimetric analysis (TGA) and the presence of metallic silver nanoparticles was also assesses through UV–Vis–NIR with integrating sphere and energy dispersive X‐ray spectroscopy EDX. The effectiveness of the silver treated textile was verified on different microorganisms, namely Escherichia coli, Staphylococcus aureus, Pseudomonas p43 and Candida albicans derived from a clinical isolate. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40326.     

Carbon nanotube/polymer nanocomposites: A study on mechanical integrity through nanoindentation

Carbon nanotubes (CNTs) are under intense investigation in materials science owing to their potential for modifying the mechanical proprieties of their composites. In this work, nanomechanical and nanotribological properties of polymer composites, reinforced with multiwall carbon nanotubes (MWCNTs) and single wall carbon nanotubes (SWCNTs), have been studied using the nanoindentation and nanoscratch technique. In particular, three different epoxy resins reinforced using several percentage of two different types of MWCNTs have been studied (range 0–7 wt%). Another resin was reinforced using MWCNTs (range 0–2.5 wt%) and SWCNTs (range 0–5 wt%) as fillers. Hardness and elastic modulus using nanoindenter instrument have been evaluated, while the coefficient of friction of the nanocomposites is obtained using nanoscratch. The results show an evident dependence with the percentage of CNTs. For all types of resins, an optimum in nanomechanical properties is found at intermediate levels of CNTs filling. POLYM. COMPOS., 36:1432–1446, 2015. © 2014 Society of Plastics Engineers     

Electronic structure,optical properties,and lattice dynamics in atomically thin indium selenide flakes

The progressive stacking of chalcogenide single layers gives rise to two-dimensional semiconducting materials with tunable properties that can be exploited for new field-effect transistors and photonic devices. Yet the properties of some members of the chalcogenide family remain unexplored. Indium selenide (InSe) is attractive for applications due to its direct bandgap in the near infrared, controllable p- and n-type doping and high chemical stability. Here, we reveal the lattice dynamics, optical and electronic properties of atomically thin InSe flakes prepared by micromechanical cleavage. Raman active modes stiffen or soften in the flakes depending on which electronic bonds are excited. A progressive blue-shift of the photoluminescence peaks is observed for decreasing flake thickness (as large as 0.2 eV for three single layers). First-principles calculations predict an even larger increase in the bandgap, 0.40 eV, for three single layers, and as much as 1.1 eV for a single layer. These results are promising from the point of view of the versatility of this material for optoelectronic applications at the nanometer scale and compatible with Si and III-V technologies.      

Colloidal Bi2S3 Nanocrystals: Quantum Size Effects and Midgap States

Among solution‐processed nanocrystals containing environmentally benign elements, bismuth sulfide (Bi₂S₃) is a very promising n‐type semiconductor for solar energy conversion. Despite the prompt success in the fabrication of optoelectronic devices deploying Bi₂S₃ nanocrystals, the limited understanding of electronic properties represents a hurdle for further materials developments. Here, two key materials science issues for light‐energy conversion are addressed: bandgap tunability via the quantum size effect, and photocarrier trapping. Nanocrystals are synthesized with controlled sizes varying from 3 to 30 nm. In this size range, bandgap tunability is found to be very small, a few tens of meV. First principles calculations show that a useful blueshift, in the range of hundreds of meV, is achieved in ultra‐small nanocrystals, below 1.5 nm in size. Similar conclusions are envisaged for the class of pnictide chalcogenides with a ribbon‐like structure [Pn₄Ch₆]_n (Pn = Bi, Sb; Ch = S, Se). Time‐resolved differential transmission spectroscopy demonstrates that only photoexcited holes are quickly captured by intragap states. Photoexcitation dynamics are consistent with the scenario emerging in other metal–chalcogenide nanocrystals: traps are created in metal‐rich nanocrystal surfaces by incomplete passivation by long fatty acid ligands. In large nanocrystals, a lower bound to surface trap density of one trap every sixteen Bi₂S₃ units is found.     

Biochemical indicators of nutritional status and dietary intake in Costa Rican Cabécar Indian adolescents

The purpose of this study was to determine the blood levels of selected nutritional status indicators and the dietary intake of Costa Rican Cabécar Indians aged 10 to 16 years. The results showed that 65% of the adolescents had an adequate body mass index (BMI) for their age, and 32% had a BMI < 5th percentile. Likewise, the study revealed a high prevalence of anemia (57%), deficient serum folate levels (54%), deficient vitamin B12 levels (31%), and subclinical vitamin A deficiency (10%). Additionally, the youngsters had elevated prevalences of high triglyceride levels (77%), borderline high-density lipoprotein (HDL) cholesterol levels (46%), homocysteine levels > 10 micromol/L (29%), and homozygous mutation of methylenetetrahydrofolate reductase (MTHFR) (49%). The diet was poor, being high in saturated fat and low in polyunsaturated fat, fiber, and several micronutrients. The dietary intakes of more than 55% of the adolescents did not meet 50% of the estimated average requirements (EAR) for zinc, vitamin A, vitamin C, vitamin B12, vitamin B2, and folate. Furthermore, a high prevalence of parasitosis was found (68%). Our results show an adolescent Cabécar population with a mosaic of nutritional deficiencies and cardiovascular risk factors.     

On the thermoeconomic approach to the diagnosis of energy system malfunctions: Part 1: the TADEUS problem

This work is the first part of a wider project aiming at demonstrating the capabilities offered by the thermoeconomic approach to the diagnosis of malfunctions in energy utility systems (TADEUS problem). The final goal is to create a common basis of work for people interested in applying thermoeconomics to identify malfunctions and to evaluate their effects on the overall plant performance. The main issues to be addressed when performing a diagnosis of energy system malfunctions using a thermoeconomic approach are summarized. A combined cycle power plant is proposed to demonstrate the practical feasibility of the thermoeconomic approach. An overview of its operation characteristics, thermodynamic design properties and control strategy is given in Part 1, and a comprehensive model is described for further use as common basis to illustrate the various diagnosis approaches either by the authors or third parties. Possible component malfunctions and main theoretical aspects of the thermoeconomic approach are presented in Part 2. The paper shows at which level of detail the analysis of physical and technical characteristics of the plant should be performed, how to develop a design and off-design model suitable for malfunction analysis, how to analyse and define component malfunctions and how to interpret and use thermoeconomic variables and indexes.     

Time-resolved thermal lens and thermal mirror spectroscopy with sample-fluid heat coupling: a complete model for material characterization

This work presents a theoretical study of a heat transfer effect, taking into account the heat transfer within the heated sample and out to the surrounding medium. The analytical solution is used to model the thermal lens and thermal mirror effects and the results are compared with the finite element analysis (FEA) software solution. The FEA modeling results were found to be in excellent agreement with the analytical solutions. Our results also show that the heat transfer between the sample surface and the air coupling fluid does not introduce an important effect over the induced phase shift in the sample when compared to the solution obtained without considering axial heat flux. On the other hand, the thermal lens created in the air coupling fluid has a significant effect on the predicted time-dependent photothermal signals. When water is used as fluid, the heat coupling leads to a more significant effect in both sample and fluid phase shift. Our results could be used to obtain physical properties of low optical absorption fluids by using a reference solid sample in both thermal lens and thermal mirror experiments.     

The Transmission Line for the SPIDER experiment

The 100 keV Ion Source Test facility – Source for the Production of Ions of Deuterium Extracted from RF plasma (SPIDER) – is aimed to test the full scale prototype of the Ion Source for the ITER 1 MeV Neutral Beam Injector (NBI). The SPIDER facility requires the construction of a High Voltage Deck (HVD) and of a High Voltage Transmission Line (TL) respectively to host the Ion Source Power Supplies system polarized at 100 kV and to carry the power and signal conductors to the beam accelerator.In already existing NBI systems with beam energy above 100 keV, the TL is realized with the SF₆ Gas Insulated Line technology. In the SPIDER TL case, the presence of a large inner conductor (half meter diameter), would make the pressurized TL a complex and costly component; therefore a free air insulated solution has been proposed. The paper focuses on the design of this TL, which has to host inside the complex high potential (100 kV) inner electrode a number of power and measuring conductors and has to minimize the Electro Magnetic Interferences (EMI) produced by the frequent grids breakdowns.Finite Element (FE) analyses have been performed to verify the configuration from the electrostatic point of view, to evaluate EMI screening effectiveness and to assess the impact of the relatively high thermal dissipation of power conductors located inside the high potential electrode. Moreover, an experimental test campaign has been carried out on a TL mockup to validate the TL electrostatic configuration under DC voltage. Finally, the paper reports on the status of procurement activities for the Transmission Line.