Sensors from Electrospun Nanostructures

Nanotechnology exerts a significant influence on materials science, providing new insights into the design of functional materials. One of the most studied areas of nanotechnologies is that of nanofibres, characterised by high specific volume, chemical activity and volume-dependent physical processes. The most promising method of producing nanofibres with various morphologies and functionalities from different materials is electrospinning, where high voltage is applied between the spinneret and the collector to the charged polymer solution (or melt) to draw polymer filaments. This chapter reviews the main electrospinning techniques for producing nanofibres from polymers, provides an overview on the influence of the spinning solution characteristics, the process parameters and the working environment on the process and highlights the many applications of electrospun nanofibres in the field of sensors. Latest advances in this field and the prospects for obtaining new electrospun nanofibre sensors are discussed

Mathematical Modeling of the Relation between Electrospun Nanofibers Characteristics and the Process Parameters

Electrospinning, the most favorable process of obtaining nanofibers, is capable of processing solution or melt polymers, ceramic materials or metals in many morphological variants, thus providing diverse functionalities. The chapter reviews the main ways in which nanofibers’ characteristics can be influenced by solution parameters, process parameters and ambient conditions, afterwards focusing on the role of some of the most significant electrospinning parameters (applied voltage, flow rate, nozzle to collector distance) on the diameter of the nanofibers. Experimental studies to model the influence of process parameters in the case of electrospinning polyetherimide solutions are presented. Response surface methodology and MATLAB simulation software have been used to obtain the mathematical models that indicate the most favorable parameters

THE ROLE OF THE URBAN ENVIRONMENT IN IMPLEMENTING THE CIRCULAR ECONOMY IN ROMANIA

In the present paper we analyzed the position of the Romanian urban environment in the process of implementing the circular economy, with the correlations and interdependences between the phenomena and demo-economic processes and the forms for the application of the circular economy. The poor implementation of the circular economy in the urban areas in Romania is conditioned by the low level of income, the expenditure, the consumption expenditure and the degree of low urbanization, the low level of labour productivity, etc., and by the psychology of the decision makers that is still not adjusted to the requirement to make the best choices for sustainable development of the economic system. We have highlighted the correlations between: the municipal waste recycling rate and the resource productivity in Romania; the total income of the population in the urban areas of residence in Romania and the waste recycling rate; the total average expenditure per person in urban areas and the municipal waste recycling rate; the monthly average consumption expenditure per person, in urban areas and municipal waste recycling rate; the employed population rate in urban areas and the municipal waste recycling rate; the urban population living in the 41 counties of Romania and Bucharest and the municipal waste recycling rate

Dynamics Control of the Complex Systems via Nondifferentiability

A new topic in the analyses of complex systems dynamics, considering that the movements of complex system entities take place on continuum but nondifferentiable curves, is proposed. In this way, some properties of complex systems (barotropic-type behaviour, self-similarity behaviour, chaoticity through turbulence and stochasticization, etc.) are controlled through nondifferentiability of motion curves. These behaviours can simulate the standard properties of the complex systems (emergence, self-organization, adaptability, etc.)

Fractional Factorial Design Study on the Performance of GAC-Enhanced Electrocoagulation Process Involved in Color Removal from Dye Solutions

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Measuring the Electrical Properties of MWNT-PA6 Reinforced Nanocomposites

The paper studies the electrical properties of polyamide 6- (PA6-) carbon nanotubes (CNTs) nanowebs, obtained through electrospinning. Three different treatments (chemical, mechanical, and mixed) were applied to the CNT in order to prepare the electrospinning solutions. For each treatment, the CNT content was different: 0.5%, 1%, 1.5%, and 2%. The electrical volume and surface conductivity of the obtained samples were studied by measuring their electrical volume and surface resistance. Homemade plate electrodes were used. The samples were also analyzed using a scanning electron microscope (SEM) and an atomic force microscope (AFM). Defects were found on the extremities: solvent traces, flat fibers, and beads. The mixed treatment seems too aggressive and it is not recommended. The AFM analysis gave values for roughness and profile height (Ra and Rz): extreme values were obtained for the chemically and mechanically treated samples. Next, a pristine PA6 sample was used to compare the influence of the CNT content on the electric behavior of the samples. By increasing the pressure on the specimens, the volume resistivity decreased exponentially, while the surface resistivity showed no significant changes, independently of the CNT content. The obtained behavior proves a great potential of the MWNT-PA6 reinforced nanocomposites for sensor applications