Current Topics and Emerging Issues in Materials Sciences Vol. 1

Nafion is a sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, which is an excellent material for fuel cell membranes. This widely used copolymer has been investigated for decades, but it has been hardly considered as a sensitive layer to organic vapours, but only as a conductor of electricity. However, its sensitive properties make it an interesting material for sensor applications. Indeed, the mass production of this material open new developments to design reliable and cheap sensors, useful for military, industrial and medical applications. In this work, we study Nafion (and eventually other ionomers) physical and transport response when it enters in contact with ketone vapours, on the perspective to design new chemical sensors, more compact and cheaper.

This work shows the possibility to employ sulfonated tetrafluoroethylene-based fluoropolymer-copolymer, commercially known as Nafion, as a sensible layer on sensors to detect organic solvents such as ketones. The detection and evaluation of ketone corpuses is very important for multiple applications on medicine, specially to detect and evaluate Diabetes Mellitus from the breath of patients. Nafion is a very stable copolymer, easily available and relatively inexpensive. This allows us to envision the possibility of having cheap and reliable sensors to detect vapours of these substances based on this copolymer. The main result of the present work is that; Nafion can protonate gaseous ions from organic solvents, such as acetone and similar substances, which modify its electrical properties, presenting a differentiated behavior according to the chemical nature of these substances, which could lead to their identification, designing an electrical nose, because each behaviour is a fingerprint of the substance to detect. Then this material can be used in the design of electrical sensors, which can be low-cost, reliable, and chemically stable, representing an excellent alternative to ceramic sensors.

Ti-TiO₂-rGO composite structures synthesized in microwave-assisted hydrothermal conditions were successfully obtained by in-situ deposition of reduced graphene oxide (rGO) on Ti foil. The aggregation of graphene layers is prevented by microwave-assisted hydrothermal treatment due to the fast and uniform heating mode, which represents the main advantage of using this method for synthesis of the composite structures. Within this research, TiO₂ crystallin layer was growth in a controlled atmosphere consisting of a mixed flow gas (95%Ar and 5 %O₂) at 500°C by thermal oxidation of Ti foil in the presence of 0.5 M hydrofluoric acid. Investigations such as X-ray diffraction, UV-VIS analysis, and SEM morphology were used to analyze the structural, optical, and morphological characteristics of the composites. The I-V measurements of the Ti-TiO₂-rGO composite structures were performed in forward bias with an applied voltage between -3 V and +3 V, and a step rate of 10 mV/s. Furthermore, the electrochemical behavior was studied using cyclic voltammetry in a 1M KNO₃ supporting electrolyte with 4 mM K₃Fe(CN)₆ to ascertain the electroactive surface area and apparent diffusion coefficient. The charge transfer resistance was investigated by electrochemical impedance spectroscopy in 0.1 M Na₂SO₄ supporting electrolyte and frequency range between 100 kHz and 0.1 Hz, to confirm the rGO role on the electrode surface. In conclusion, this study provided new insights into the development of high-performance and cost-effective Ti-TiO₂-rGO structures both for the development of electrochemical electrodes and gas sensors.

The purpose of this research is to examine current procurement and inventory management practices and to improve inventory policies for the central warehouse and industrial depot. The primary goal of material procurement and inventory management in healthcare organizations is to reduce supply costs while maintaining patient care quality. In general, there are two ways to keep supply levels stable: Joint procurement and direct purchase from the point of use. In the case of joint procurement, the related point of use will place an order with the central warehouse. The alternative way is for each department to place the order directly with the supplier. To keep the service running, new order policies must be implemented. In the present investigation, we define a performance metric, the supply-demand ratio, to assess the efficiency of inventory management and procurement processes.  The easiest way is to set up a high inventory level to avoid and shortage. The new strategy allows for a significant reduction in holding expenses, idle stock, and space usage while still maintaining service levels.

Nanowear and viscoelasticity were evaluated to study the nanotribological properties of lubricant films of Z-tetraol, D-4OH, and A20H on diamond-like-carbon protective layers, including their retention and replenishment properties. For A20H and thick Z-tetraol-coated disks, the disk surface partially protrudes, and the phase lag (tan \(\delta\) ) increases with friction. Good replenishment enables the lubricant to reflow and cover areas depleted after sliding contact between the head and disk. The retention and replenishment of lubricants depend on their interactions with the diamond-like carbon (DLC) film on the surface of the disk. This result is consistent with replenishment of the lubricant upon tip sliding. For the D-4OH-coated disk, the tan \(\delta\) value decreases with tip sliding, similar to the case for the unlubricated disk. The durability of the lubricant-coated magnetic disks was then assessed using friction tests with increasing and decreasing loads. Regardless of the load, the unlubricated disk's friction force quickly increases after about 30 reciprocating cycles. By plotting the friction coefficient's relationship with the load and reciprocating cycle number, the lubrication state can be calculated. There are four categories in which the friction coefficient can be placed. In addition, the changes in the friction coefficient were mapped with respect to the lubrication state, emphasizing four distinct areas of lubricant behavior. The lowest friction area constitutes fluid lubrication. The second area constitutes the transition to mixed lubrication. The third area constitutes boundary lubrication. The highest friction of the fourth area results from surface fracture. The boundary lubricating area of the A20H lubricant was wide, because of its good retention and replenishment properties.

The dependence of macro-mechanical properties of consolidated body on crystalline phase composition, dimensions, form, distribution in matrix, and form factor plays an important role in materials science and, more broadly, in long-term operation of work-pieces in industry. While working in responsible fields of technology of ceramics and ceramic composites the above referred properties are attributed extremely great role with the view of durability and endurance at the terms of heavy mechanical loads. The crystalline phase plays the most important role in mechanical strength or deformation of any material when describing the resistance of any concrete type work-piece. It is crucial in the correlative explanation of materials mechanics and matrix properties. The role of a macro- and micro-structural component, specifically the crystalline phase, in the transition of stable states of materials into meta-stable states is extremely important in our case because the destruction of ceramic materials and composites will give us an exhaustive response to the role of macro- and micro-mechanical properties of materials.Our research aims to develop a formula for the dependence of macro-mechanical properties of ceramic and ceramic composites on crystalline phase, the most powerful component of their structure, which will allow theorists and practitioners to correctly select and develop technologies and technological processes.

On the basis of the study of micro- and macro-mechanical properties of ceramics and ceramic composites and the morphology of crystalline phase and the analysis of the study we determined and created parameters of the formula.

When the work-piece is thoroughly destructed, the formula covers macro-mechanical properties:  mechanic at bending at three and four-point load, mechanic at contraction; among morphological characteristics: composition of crystalline phase and their spreading in matrix, their sizes, form factor; correlative dependence of the above listed properties. A completely new definition of the factor of crystalline phase spreading in matrix is proposed.

The developed formula is of consolidated nature and can be used in ceramic material and ceramic composites technology. The formula will assist practitioners in correctly planning and carrying out all positions of technology of work-piece production, carrying out the most responsible thermal treatment process of technology of work-piece production, and determining the correlation between mechanical and matrix properties of materials.

Preparation of new metal alloy coatings capable of protecting steel from corrosion is a major objective of electrochemical deposition and functional galvanotechnics. A growing interest of researchers in alloys electrodeposition is mainly caused by the cost-effectiveness of metal coatings due to inexpensive and eco-friendly electrolytes used.  In that regard, of particular interest was the possibility of obtaining manganese alloys characterized by high anti-corrosion performance with suitable mechanical properties. Manganese, a metal with high negative standard potential (-1.18V, SHE) is chemically active and easily reacts with air oxygen and moisture. Despite their high effect, electrocoatings of pure manganese are fragile and in case of impact are easily removed from a steel surface to get protected from corrosion. To decrease chemical activity and brittleness of manganese, it is alloyed with metals of lower negative standard potential, e.g. with Cu, Zn and others.

The goal of present research is obtaining of high quality coating of Mn-Cu-Zn alloy, determination of parameters of electrolysis, electrolyte composition, effect of cathodic current density on chemical composition, morphology and structure of coatings. Also, corrosion tests of electrodeposited alloys are studied.

Mn-Cu-Zn alloys were electrodeposited from sulphate bath, containing citrate or EDTA and their mixtures as complexing ligands. The impact of bath composition and deposition parameters on alloy composition, cathodic current efficiency, structural and electrochemical properties was investigated. At a higher current density structural and electrochemical properties was investigated. At a higher current density ( \(\geq 37.5 \mathrm{~A} \mathrm{dm}^{-2}\) ) a uniform surface deposit of \(\mathrm{Mn}-\mathrm{Cu}-\mathrm{Zn}\) was obtained. Optimal \(\mathrm{pH}\) of electrolyte \(\left(0.3 \mathrm{~mol} / \mathrm{dm}^3 \mathrm{Mn}^{2+}+0.6 \mathrm{~mol} / \mathrm{dm}^3\left(\mathrm{NH}_4\right)_2 \mathrm{SO}_4+0.1\right.\)\(\mathrm{mol} / \mathrm{dm}^3 \mathrm{Zn}^{2+}+0.005 \mathrm{~mol} / \mathrm{dm}^3 \mathrm{Cu}^{2+}+0.05 \mathrm{~mol} / \mathrm{dm}^3 \mathrm{Na}_3 \mathrm{Cit}+0.15 \mathrm{~mol} / \mathrm{dm}^3 \mathrm{EDTA} ; \mathrm{t}=30^{\circ} \mathrm{C} ;\)\(\mathrm{t}=30^{\circ} \mathrm{C} ; \mathrm{T}=20 \mathrm{~min}\) ) for silvery, nonporous coating of \(\mathrm{Mn}-\mathrm{Cu}-\mathrm{Zn}\) alloy was within 6.5-7.5; coating composition: \(71-83 \% \mathrm{Mn}, 6-7.8 \% \mathrm{Cu}, 11.5-20 \% \mathrm{Zn}\), current efficiency up to \(40 \%\). XRD patterns revealed \(\mathrm{BCT}\) (body centred tetragonal) y-Mn solid phase solution (lattice constants \(a=2.68 Å ; c=3.59 Å\) ). Corrosion tests on deposited alloys were carried out in an aerated \(3.5 \% \mathrm{NaCl}\) solution. The corrosion current density (icor) of the electrodeposited alloys on carbon steel was 10 times lower than corrosion rate of pure zinc and manganese coatings. Triple alloy coatings corrosion potential (Ecorr \(=-1140 \mathrm{mV}\) vs. \(\mathrm{Ag} / \mathrm{AgCl}\) ) preserved negative potential value longer (more than three months) compared to carbon steel substrate \(\left(E_{\text {corr }}=-670 \mathrm{mV}\right.\) vs. \(\left.\mathrm{Ag} / \mathrm{AgCl}\right)\). Tafel polarization curves of \(\mathrm{Mn}-\mathrm{Cu}-\) \(\mathrm{Zn}\) alloy coatings in aerated \(3.5 \% \mathrm{NaCl}\) solution did not exhibit typical passivation behavior, which can be described by the formation of low solubility of adherent corrosion products on the alloy surface. Corrosion testing on Mn-Cu-Zn electrocoating in a chlonine environment demonstrates that it is the best cathodic protective coating for a steel product.

This chapter deals with the preparation, properties, electrochemical and electrical conductivity behaviour of carbides. Zirconium carbide (ZrC) was synthesized by a simple sol–gel method using zirconium n-propoxide, acetic acid, and saccharose as carbon source. The sol-gel processing of materials offers several potential advantages over conventional methods. The most important are improved properties regarding the specific microstructural features. The chapter presents the synthesis of ZrC powders by the sol-gel method.  When heat-treated at 900ºC under flowing argon flow, gels transformed into intimately mixed amorphous raw powder. Further heat treatments above 1200, 1300, 1500ºC led to the formation of zirconium carbide with some dissolved oxygen in the lattice. The potential window and the electrochemistry of standard redox reactions have been investigated in 1 M KCl solution at a scan rate of 50 mV s^-1using cyclic voltammetry in the potential region of -1 to 1.4 V. Electrochemical parameters of the carbide using organic electrolyte have been studied by cyclic voltammetry and electrochemical impedance spectroscopy. Electrical conductivity as a function of temperature in the range of 50-950ºC is also investigated.

This study aims to address the drawbacks by reviewing prominent alternative materials that have the potential to replace standard aggregate such as granite for pavement wearing course. A well-designed road must be able to deliver strong initial skid resistance and sustain it over the pavement's service life. This is one of the criteria for a well-designed road. Skid resistance is the capacity of the pavement surface to generate sufficient friction when a moving rubber tire of a vehicle passes through it. Locally accessible building materials have a tendency to polish under traffic and provide insufficient friction, therefore they frequently do not meet traditional pavement criteria. The performance of the skid resistance of the road surface changes based on the shape, size, and gradation of the aggregate in the pavement mixture of the surface to be worn, as well as environmental and traffic conditions. According to the results of this study, environmental factors such as seasonal fluctuations, aggregate choice, and pavement textures affect skid resistance. Furthermore, it has been demonstrated that recycled materials, such as steel slag, exhibit excellent strength and endurance, making them higher quality than natural aggregates.

Determination of the correlation of characteristics of consolidated body with content, size, distribution in matrix and shape factor of porous phase. The goal of the following paper is to determine formula for correlation between characteristics of ceramics and ceramic composite materials and porous phase, which is the weakest part of material. This will allow theorists and practicists to correctly choose and improve technologies and technical processes. According to the study and analysis of micro- and macrostructural, micro-and macromechanical of ceramics and ceramic composite materials, parameters of the formula was determined. Formula contains macromechanical properties. When detail is completely decomposed: mechanics on bending by three or four-point load, mechanics on shrinking, breaking, impact resistance. Morphologic characteristics: Porous phase content in the matrix and its distribution, size, shape factor of pores. Correlation of given factors with others structural characteristics, such as: crystal and glass phases. Novel determination of pore distribution factor is given. Created formula has collective nature and using it allows researchers and practicists to correctly plan and precisely preform all the positions of the technological production.

Herein, the synthesis of polyurethane-based aerogels is described. Then, these materials are characterized and the influence of different catalyst contents in the formulations on the final properties is studied. Tunable thermal conductivities are reached by changing the catalyst amount, since this factor also has a strong effect on the aerogel nanostructures. Thus, thermal conductivity values ranging from 11.7 to 24.2 mW/mK can be obtained, reaching the most insulating value for polyurethane aerogels in the literature. Finally, the stiffness and elasticity of these materials was evaluated by mechanical compression experiments. The elastic modulus followed a clear trend with the catalyst concentration, and, therefore, with the porous structure obtaining values from 0.13 to 6.32 MPa. Thus, in this work, the structure-properties relationship of these materials has been explored, achieving the production of super-insulating materials with tailorable stiffness in combination with optical transparency leading to on-demand applications. The exceptional insulation of silica aerogels was reached at the same time that their general brittleness was improved while keeping good transparency to visible light (85 %, 650 nm) becoming promising materials.