NaH
PO
-MnO
-PbO
-Pb vitroceramics were studied usinginfrared (IR), ultraviolet-visible (UV-Vis) and electron paramagnetic resonance (EPR) spectroscopies to understand the structural modifications as ...potential candidates for electrode materials. The electrochemical performances of the NaH
PO
-MnO
-PbO
-Pb materials were investigated through measurements of cyclic voltammetry. Analysis of the results indicates that doping with a suitable content of MnO
and NaH
PO
removes hydrogen evolution reactions and produces a partial desulphatization of the anodic and cathodic plates of the spent lead acid battery.
There is growing interest in the opportunities regarding construction and demolition wastes, such as glass and metal powders, for developing a circular economy and their transformation into new ...materials. This management and recycling of construction and demolition waste offers environmental benefits and conservation of natural resources. In this paper, new magnetic composite materials were prepared by wet chemical synthesis methods using crushed glasses and iron and steel waste powders as raw materials. The prepared iron–silicate composites were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) analysis, infrared (IR), ultraviolet–visible, and electron paramagnetic resonance (EPR) spectroscopy, and magnetic measurements. The XRD data confirm the formation of varied crystalline phases of the iron ions. The presence of the Fe3O4 crystalline phase was detected in the composites containing the iron waste powders. The inspection of the SEM micrographs revealed slightly better homogeneity for the composite material containing larger amounts of iron waste and heterogeneous morphology with cracks and random crystallinity for the composite doped with steel waste. By doping with different contents of iron or steel waste powder, structural modifications in the silicate network and the formation of new bands in the IR spectra were evidenced. The UV-Vis spectra were characterized by the absorption peaks for both the tetrahedral and octahedral geometries of the Fe3+ ions and the octahedral coordination of the Fe2+ ions with oxygen anions. The EPR data show resonance lines with g ~2, 4.3, and 6.4, corresponding to the Fe3+ ions. Using hysteresis curves, the superparamagnetic properties of the iron–silicate composites were evidenced.
In recent years, natural materials are becoming a valid alternative to traditional sound absorbers due to reduced production costs and environmental protection. This study explores alternative usage ...of sheep wool as a construction material with improved sound absorbing properties beyond its traditional application as a sound absorber in textile industry or using of waste wool in the textile industry as a raw material. The aim of this study was to obtain materials with improved sound-absorbing properties using sheep wool as a raw material. Seven materials were obtained by hot pressing (60 ÷ 80 °C and 0.05 ÷ 6 MPa) of wool fibers and one by cold pressing. Results showed that by simply hot pressing the wool, a different product was obtained, which could be processed and easily manipulated. The obtained materials had very good sound absorption properties, with acoustic absorption coefficient values of over 0.7 for the frequency range of 800 ÷ 3150 Hz. The results prove that sheep wool has a comparable sound absorption performance to mineral wool or recycled polyurethane foam.
This study evaluated the potential of incorporating TiO2 nanoparticles (NT) into cementitious composites to provide self-cleaning and self-sanitising properties, as well as the partial replacement of ...natural aggregates with recycled glass (RGA), ceramic brick (RBA), granulated blast furnace slag (GBA), and textolite waste (RTA) from electronic equipment on these properties. Based on the research results, the addition of NT to cementitious composites led to a significant reduction in contact angle, which means an increase in surface hydrophilicity. At the same time, Rhodamine B stain fading was highlighted, with the degree of whiteness recovery of NT composites exceeding that of the control by up to 11% for natural aggregate compositions, 10.6% for RGA compositions, 19.9% for RBA compositions, 15% for GBA compositions, and 13% for RTA compositions. In a mould-contaminated environment, it was shown that the introduction of NT allowed the material to develop a biocidal surface capacity which is also influenced by the nature of the aggregates used. Furthermore, the study revealed that, under controlled conditions, certain recycled waste aggregates, such as textolite, promoted mould growth, while others, such as brick and slag, inhibited it, highlighting not just the effect of the addition of NT, but also the significant influence of the aggregate type on the microbial resistance of cementitious composites. These improvements in the performance of cementitious composites are particularly advantageous when applied to prefabricated elements intended for the finishing and decorative surfaces of institutional (schools, administrative buildings, religious structures, etc.) or residential buildings.
Starting from the context of the principles of Sustainable Development and Circular Economy concepts, the paper presents a synthesis of research in the field of the development of materials of ...interest, such as cementitious composites or alkali-activated geopolymers. Based on the reviewed literature, the influence of compositional or technological factors on the physical-mechanical performance, self-healing capacity and biocidal capacity obtained was analyzed. The inclusion of TiO2 nanoparticles in the matrix increase the performances of cementitious composites, producing a self-cleaning capacity and an anti-microbial biocidal mechanism. As an alternative, the self-cleaning capacity can be achieved through geopolymerization, which provides a similar biocidal mechanism. The results of the research carried out indicate the real and growing interest for the development of these materials but also the existence of some elements still controversial or insufficiently analyzed, therefore concluding the need for further research in these areas. The scientific contribution of this study consists of bringing together two apparently distinct research directions in order to identify convergent points, to create a favorable framework for the development of an area of research little addressed so far, namely, the development of innovative building materials by combining improved performance with the possibility of reducing environmental impact, awareness and implementation of the concept of a Circular Economy.
Cobalt-chromium (Co-Cr) alloys are the most widely used materials for removable and fixed dental prosthetic frameworks. The fitting accuracy between these components in dental prosthetic frameworks ...assembles (DPFAs) is largely influenced by the manufacturing method. This study presents a novel manufacturing method that combined two common techniques for obtaining one single framework: casting of Co-Cr inserts on top of parts previously manufactured by selective laser melting (SLM) of Co-Cr powder (CoM). Horizontal (
= 4) and vertical (
= 3) surfaces were microscopically analyzed (
= 770 count sum). The results revealed a high precision of the process and high fitting accuracy between the hybrid frameworks. The average distance measured between the frameworks in joined position was 41.08 ± 7.56 µm. In conclusion, the manufacturing of Co-Cr alloys DPFA using the CoM method reduced the deformation of hybrid frameworks and improved the joining accuracy between them.
New composite materials based on sawdust as reinforcing material and polyurethane foam as a binder agent, exhibiting sound absorbing proprieties, have been obtained. Due to the sound-absorbent ...proprieties exhibited by these type of materials, 11 new composite systems have been obtained varying the type and the size of sawdust particles, the percentage of binder and the thickness of material. The sound absorption properties of the new obtained materials are directly correlated with the composition, the thickness of materials as well as the air gap samples and the rigid wall. In addition, the morphological and thermal conductivity proprieties and the mechanical ones, of the new obtained materials, were carried out.
•New composite materials with improved sound absorbing proprieties were obtained.•Sound absorbent proprieties are correlated with the sawdust nature and dimension.•The air spaces trapped in the structure lead to additional acoustic absorption.
Waste from information technology (IT) and telecommunication equipment (WITTE) constitutes a significant fraction of waste from electrical and electronic equipment (WEEE). The presence of rare metals ...and hazardous materials (e.g., heavy metals or flame retardants) makes the necessary recycling procedures difficult and expensive. Important efforts are being made for Waste Printed Circuit Board (WPCB) recycling because, even if they only amount to 5–10% of the WITTE weight, they constitute up to 80% of the recovered value. This paper summarizes the recycling techniques applicable to WPCBs. In the first part, dismantling and mechanical recycling techniques are presented. Within the frame of electro-mechanical separation technology, the chain process of shredding, washing, and sieving, followed by one or a combination of magnetic, eddy current, corona electrostatic, triboelectrostatic, or gravity separation techniques, is presented. The chemical and electrochemical processes are of utmost importance for the fine separation of metals coming from complex equipment such as WPCBs. Thermal recycling techniques such as pyrolysis and thermal treatment are presented as complementary solutions for achieving both an extra separation stage and thermal energy. As the recycling processes of WPCBs require adequate, efficient, and ecological recycling techniques, the aim of this survey is to identify and highlight the most important ones. Due to the high economic value of the resulting raw materials relative to the WPCBs’ weight and composition, their recycling represents both a necessary environmental protection action, as well as an economic opportunity.
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