Search Results (42)

Global resource consumption continues to grow each year, exerting increasing pressure on their availability. This trend could lead to a shortage of raw materials in the coming years. Aware of the risks associated with this situation, the European Union has implemented policies and strategies aimed at diversifying its supply sources, including waste recycling. In this context, the present study was conducted with the objective of developing innovative processes to concentrate valuable metals present in the non-recovered fractions of waste electrical and electronic equipment (WEEE). Three types of samples were studied: washing table residues (WTRs), printed circuit boards (PCBs), and powders from cathode-ray tube screens (CRT powders). Several separation techniques, based on the physical properties of the elements, were implemented, including electrostatic separation, magnetic separation, and density and gravity-based separations. The results obtained are promising. For WTRs and PCBs, the recovery rates of targeted metals (Cu, Al, Pb, Zn, Sn) reached approximately 91% and 80%, respectively. In addition to these metals, other valuable metals, present in significant quantities, deserve further exploration. Regarding CRT powders, the performances are also encouraging, with recovery rates of 54.7% for zinc, 57.1% for yttrium, and approximately 71% for europium. Although these results are satisfactory, optimizations are possible to maximize the recovery of these critical elements. The techniques implemented have demonstrated their effectiveness in concentrating target metals in the treated fractions. These results confirm that recycling constitutes a viable alternative to address resource shortages and secure part of the supplies needed for the European Union’s industry. Full article

Waste electrical and electronic equipment (WEEE) is a continuously growing concern, with issues arising from intensive resource consumption and the environmental and human impacts being caused by inadequate practices. The purpose of this study is to evaluate the impacts of end-of-life management options generated by Information Technology (IT) and telecommunication equipment in Romania during the period of 2018–2021 from a sustainability point of view, including environmental aspects, such as greenhouse gas emissions (GHG) and energy consumption, economic aspects, considering workforce earnings and revenues collected for the public budget, and social impacts through job creation. To achieve the main objective, a two-step methodology is used, with one step to determine the relevant quantities of WEEE generated by the subcategories of IT and telecommunication equipment, using the European Union’s WEEE Calculation Tool based on two approaches, WEEE reported in Eurostat (Scenario 1) and apparent consumption (Scenario 2), and a second step to evaluate the environmental, economic, and social impacts of the WEEE management system by applying Waste Reduction Model (US EPA WARM). Regarding the six WEEE categories evaluated, in both scenarios, Flat-Panel Displays is the category with the lowest environmental impact and highest economic and social benefits, while, on the opposite side, the Cathode-Ray Tube (CRT) category displays the highest environmental impact and lowest economic and social benefits. Full article

Rare earth is an important strategic resource and a key mineral resource for global competition. As the depletion of primary rare-earth resources increases, a great number of rare-earth secondary resources, such as waste phosphor powder collected from fluorescent lamps, cathode-ray tubes, and other luminescent materials, continue to be generated and accumulated. How to achieve the low-carbon extraction and green and efficient utilization of these resources has become an urgent problem to be solved. In recent years, preliminary enrichment methods, such as flotation, magnetic separation, and adsorption, chemical methods, such as acid leaching and alkaline fusion, external-field-enhanced methods (including mechanical activation, microwave and oxidant, green solvent, etc.), and solvent extraction have been used for the separation and extraction of rare-earth elements (REEs), such as Y, Eu, Ce, Tb, La, and Ga, from waste phosphors. In this article, we systematically summarized the research progress of commonly used separation and extraction methods for REEs in waste phosphor powders, analyzed the advantages, disadvantages, and existing problems of different methods, and proposed potential directions for future research. Full article

In this study, the vitrification of asbestos-cement waste (ACW) and glass cullet from cathode-ray tubes (CRTs) was performed. The resulting product of vitrification from the abovementioned waste was used as the reinforcing phase in a composite with the AA7075 alloy matrix. The composite was made by means of the FSP (friction stir processing) method. The main aim of this work was to determine whether the product of the vitrification can be utilized as the reinforcing phase in the composite. The tests show that introducing the vitrification product into the composite matrix increases both the hardness of the material and its wear resistance. The composite was characterized by a 39% higher hardness and 30.4% higher wear resistance compared to the initial AA7075 alloy. The changes in the properties were caused by strong refinement of the grains, but primarily by the presence of the hard particles of the reinforcing phase in the composite matrix. This research demonstrates that vitrified material, thanks to its properties, can constitute a full-value reinforcing material that can ultimately replace more expensive engineering materials in composites. Full article

The carbon nanotube cold cathode has important applications in the X-ray source, microwave tube, neutralizer, etc. In this study, the characteristics of carbon nanotube (CNT) electron gun in series with metal-oxide-semiconductor field-effect transistor (MOSFET) were studied. CNTs were prepared on a stainless steel substrate by chemical vapor deposition and assembled with a mesh gate to form an electron gun. The anode current of the electron gun can be accurately regulated by precisely controlling the MOSFET gate voltage in the subthreshold region from 1 to 40 µA. The current stability measurements show the cathode current fluctuation was 0.87% under 10 h continuous operation, and the corresponding anode current fluctuation was 2.3%. The result has demonstrated that the MOSFET can be applied for the precise control of the CNT electron gun and greatly improve current stability. Full article

Field emission is an important work mode for electron sources, and carbon nanotubes (CNTs) have been extensively studied for their good emission properties. It is well known that the parameters of the grid deeply influence the field emission performance of CNTs, a relationship that requires further elucidation. Therefore, in this study, the relationship between the grid aperture ratio and electron transmittance was studied through simulations and experiments. This study’s results indicate that the electron transmittance improved as the grid aperture ratio increased. Meanwhile, electron beam spot simulations and imaging experiments indicate that an increased grid aperture ratio will expand the cathode electron divergence, leading to a larger electron beam spot size. These results demonstrate that there is a trade-off in maintaining the grid aperture ratio between high electron transmittance and relatively small electron beam spot size, and the optimum grid aperture ratio is between 75% and 85%. These results will provide a reference for the design and optimization of X-ray tubes and other electron sources. Full article

LiNi_0.9Mn_0.1−xAl_xO₂ (NMA) (x = 0.01, 0.03, 0.05) cathodes were synthesized via the co-precipitation method and continued with the calcination process in a tube furnace at 750 °C under flowing oxygen gas for 12 h. X-ray diffraction (XRD) revealed a well-formed and high-purity phase with a hexagonal structure. LiNi_0.9Mn_0.07Al_0.03O₂ (NMA 973) had the best electrochemical performance with the lowest redox peak separation, the smallest charge transfer resistance (71.58 Ω cm⁻²), the highest initial specific discharge capacity of 172 mAh g⁻¹ at 0.1C, and a capacity retention of 98% after 100 cycles. Under high current density at 1 C, NMA 973 had excellent specific discharge capacity compared to the other samples. The optimal content of Mn and Al elements is a crucial factor to obtain the best electrochemical performance of NMA. Therefore, NMA 973 is a promising candidate as a cathode for high-energy-density lithium-ion batteries. Full article

In this study, the possibility of applying the hyperspectral imaging (HSI) technique in the Short-Wave InfraRed (SWIR) spectral range to characterize polymeric parts coming from Waste from Electric and Electronic Equipment (WEEE) is explored. Different case studies are presented referring to the identification of (i) plastic flakes inside a mixed waste stream coming from a recycling plant of monitors and flat screens, (ii) different polymers inside a mixed plastic waste stream coming from End-Of-Life (EOL) electronic device housings and trims, (iii) contaminants (i.e., metals) in a mix of shredded plastic particles coming from a recycling line of electrical cables, and (iv) brominated plastics in mixed streams constituted by small appliances (i.e., cathode-ray tube televisions and monitors). The application of chemometric techniques to hyperspectral data demonstrated the potentiality of this approach for systematic utilization for material characterization, quality control and sorting purposes. The experimental findings highlight the feasibility of employing this method due to its user-friendly nature and quick detection response. To increase and optimize WEEE valorization avoiding disposal in landfills or incineration, recycling-oriented characterization and/or quality control of the processed products are fundamental to identify and quantify substances to be recovered. Full article

This paper presents an alternative way to recycle cathode ray tube glass waste, together with fly ash and kaolin, into new glass ceramic materials. The samples were obtained using three firing temperatures: 700, 800, and 900 °C. The effect of the fly ash/CRT waste ratio upon the materials’ firing shrinkage, apparent density, apparent and total porosity, chemical stability, and compression strength was investigated. The firing shrinkage used as a dimensional stability parameter, a firing shrinkage range between 2.19–8.18%, was positively influenced by the waste mix amount. The apparent density of the obtained materials is positively affected by the heat treatment temperature, rising from 2.09 to 2.93 (g·cm⁻³), while the apparent porosity decreases with the increase of the firing temperature from 6.08 to 2.24 %. All the studied glass ceramics show very good chemical stability and complete immobilization of the Pb²⁺ and Ba²⁺ ions in the glass ceramic matrix. The compression strength of the sintered materials ranges between 1.42–11.83 (N·mm⁻²), being positively influenced by the kaolin amount and negatively influenced by porosity. The obtained results confirm the viability of the proposed alternative to use CRT waste and fly ash together with kaolin to obtain glass ceramic materials that can be used for outdoor paving applications. Full article

Carbon nanotubes (CNTs) show significant advantages in the development of cold cathode X-ray tubes due to their excellent field emission performance; however, there are still some problems, such as short lifetime and the low emission current of large-area CNTs. In this paper, a front-grid carbon nanotube array model was established, and the electric field intensity near the tip of the CNTs’ electric field enhancement factor was analytically calculated. A simulation model of a CNT three-dimensional field emission electron gun was established by using computer simulation technology (CST). The effects of grid wire diameter, grid aperture shape, and the distribution of grid projection on the cathode surface on the cathode current, anode current, and electron transmission efficiency were analyzed. The aperture ratio was used to evaluate the grid performance, and the simulation results show that the ideal aperture ratio should be between $65\%$ and $85\%$. A grid structure combining a coarse grid and a fine grid was designed, which can make the electric field intensity around the grid evenly distributed, and effectively increased the cathode emission current by $24.2\%$ compared with the structure without the fine grid. The effect of grid aperture ratio on the electron transmission efficiency was tested. The simulation results and optimized structure can provide a reference for the grid design of cold cathode emission X-ray tubes. Full article

This paper reported a study based on the application of SWIR (shortwave infrared) spectroscopy to assess the presence of brominated flame retardants (BFRs) in plastic scraps coming from an e-waste stream composed by CRT (i.e., cathode-ray tube) monitors and televisions. An X-ray fluorescence (XRF) analysis was performed on plastic scraps to determine the presence and content of bromine (Br). The presence in plastic waste-flow streams, fed to or resulting from a recycling process, of individuals characterized by high concentrations of Br does not allow their use as secondary raw materials, imposing the need for an ad hoc separation processes. Chemometric methods were adopted for setting up models able to discriminate Br content. In more detail, principal component analysis (PCA) was used as an exploratory tool, while partial least squares (PLS) and locally weighted regression based on PLS regressions (LWRPLS) were used as multivariate regression models to test the ability of the spectra to predict Br content. The LWRPLS, showing an R_p² of about 0.9, demonstrates the ability of this algorithm to establish a good correlation between the spectral signatures of plastic scraps and their Br content. Full article

In this study, the photocatalytic effect of TiO₂ (1 wt. % and 3 wt. %) deposited on the surface of sintered cathode ray tube glass was examined, as well as its effect on an E. coli strain (BL21(DE3)). DTA analysis indicated the sintering temperature for samples to be 820 °C while scanning electron microscopy (SEM)showed an intimate contact and a strong interface between the support and photocatalyst. Near-ambient pressure X-ray photoelectron spectroscopy (NAP-XPS) was employed to establish the chemical and bonding environment of the samples. The investigations of the bacterial viability were conducted using flow cytometry, a specific cellular viability assay, while bacterial growth was measured using the turbidimetric method. The experimental results show the influence of the TiO₂ concentration on the bacterial inactivation process: higher concentrations (3% wt.) have a bactericidal effect in the long term, whereas lower concentrations (1% wt.) render them inactive for a shorter time in the exponential growth stage. The preliminary results were used to calculate the efficiency of microbial inactivation and the parameters of the kinetics of inactivation using ANOVA software. The results indicate that this material could be an effective solution for water disinfection. Full article

We present results for the production of highly charged ions in a rippled electron beam propagating in a multi-section drift tube with different electrostatic potentials in an axial magnetic focusing field. The inner-shell ionization of target atoms by electron impact occurs in local ion traps formed at the electron-beam crossovers. The utmost electron current density achieved is assessed at ~10 kA/cm${}^2$. The successive ionization of cathode materials and working substances such as xenon and bismuth was investigated as a function of the confinement time. The characteristic X-ray radiation from ions including Ir${}^{62+}$, Ce${}^{48+}$, Xe${}^{46+}$, and Bi${}^{60+}$ was detected. It is shown that it is possible to extract highly charged ions from local ion traps for a certain geometry of the drift tube structure and a certain distribution of the electric potentials. Full article

Microtube-like porous carbon (MPC) and tube-like porous carbon–sulfur (MPC-S) composites were synthesized by carbonizing milkweed pappus with sulfur, and they were used as cathodes for lithium–sulfur batteries. The morphology and uniformity of these materials were characterized using X-ray powder diffraction, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy with an energy-dispersive X-ray analyzer, thermogravimetric analysis, and X-ray photoelectron spectrometry. The electrochemical performance of the MPC-S cathodes was measured using the charge/discharge cycling performance, C rate, and AC impedance. The composite cathodes with 93.8 wt.% sulfur exhibited a stable specific capacity of 743 mAh g⁻¹ after 200 cycles at a 0.5 C. Full article

Many researchers have reported on the preparation and characterization of thin films. The prepared thin films could be used in lasers, cathodic ray tubes, solar cells, infrared windows, ultraviolet light emitting diodes, sensors, supercapacitors, biologic applications, and optoelectronic applications. The properties of these thin films strongly depend on the deposition techniques. Throughout the years, many investigations into the production of various types of thin films (by using the successive ionic layer adsorption and reaction (SILAR) method) were conducted. This method attracts interest as it possesses many advantages when compared to other deposition methods. For example, large area depositions could be carried out in any substrates at lower temperatures via inexpensive instruments; moreover, a vacuum chamber is not required, it has an excellent growth rate, and the unique film properties could be controlled. In this work, metal sulfide, metal selenide, metal oxide, and metal telluride were deposited on substrates by using the SILAR method. According to the findings, both thick and thin films could be synthesized under specific conditions during the experiment. Additionally, the results showed that the number of deposition cycles, rinsing times, immersion times, and concentrations of the precursors affected the crystallinities, grain sizes, film thicknesses, surface roughness, and shapes of the obtained films. These films could be used in solar cell applications with high power conversion efficiency due to the appropriate band gap value and high absorption coefficient value. Full article