Simone Taraborelli, Simone Failla, Diletta Sciti
et al.
The impact of high-energy milling using WCCo media on the pressureless sintering and properties of TiB2 was studied. After 30 mins of milling, samples sintered at 2200 °C achieved a high relative density (>98 %) and a fine mean grain size (<2 µm). In the microstructure WxBy phases, often containing Co, were observed at triple points, due to contamination from the milling media. Moreover, core-rim structures with multiple rims were detected: the cores consisted of pure TiB2 grains, the rims were (TixWy)B2 solid solutions. The core-rim formation was significantly more pronounced compared to a reference sample of the same powder mixture densified by hot pressing at 1900 °C. The hardness reached 23 GPa, comparable to the hot-pressed sample, while the fracture toughness remained within 4.8–5.1 MPa·m1/2 up to 1000 °C. The strength was approximately 350–400 MPa up to 1000 °C, declining sharply at higher temperatures due to W-containing impurities. Thermal diffusivity and conductivity were similarly impacted by these impurities.
In addition to static loads, structural glazing joints in glass and facade construction in many regions are subject to extraordinary effects such as earthquakes. Seismic actions are characterized by a randomly recurring and dynamic load that affects the structural behavior of the viscoelastic material. Publications on the load-bearing behavior and design of structural glazing joints against seismic loading have not systematically considered these effects. In this paper, relevant parameters influencing the seismic loading of structural glazing joints are determined, evaluated, and narrowed down to areas of practical relevance as part of a theoretical stress analysis.
On this basis, extensive experimental investigations of the low-cycle fatigue behavior of structural glazing joints are presented. Cyclic stress-strain curves are determined and compared with quasi-static reference tests to describe the basic low-cycle fatigue behavior. The influence of the previously determined parameters on the cyclic load-bearing behavior can thus be determined and presented. These investigations provide an important basis for describing the behavior under typical seismic random loading. In particular, the type of load application caused by the different construction types of glass and facade buildings can be mentioned as a decisive influencing factor in addition to the frequency of building construction. The results provide a first important contribution to the modeling and design of structural glazing joints against earthquake effects. Within the framework of the IGF project "RISIKO", further extensive scientific investigations will be carried out on this basis in order to develop a design model for structural glazing joints in disaster scenarios.
The rapid development of miniaturization and refinement of modern electronic components has led to higher requirements for nanosized powders. The barium strontium titanate (Ba1-xSrxTiO3, BST) nanopowders with fine grains, uniform particle size and high purity have broad application prospects. Herein, BST nanopowders were synthesized via nonhydrolytic sol-gel method and the effects of different processing parameters on structure were investigated systematically by using X-ray diffraction, transmission electron microscopy, laser particle size analyser and thermogravimetric mass spectrometry. In the first step, different dispersants, dispersant concentration and calcination temperature were selected for synthesis of Ba0.6Sr0.4TiO3 powder to find optimal conditions. In the second step, these optimal conditions were used to synthesize BST powders, but different (Ba+Sr)/Ti and Ba/Sr molar ratios were used to find those that can enable preparation of single phase cubic perovskite powder. Therefore, this study showed how the processing parameters can be systematically tuned with the idea to obtain ultra-fine single phase BST nanoparticles.
The paper analyses the transition from a linear economy paradigm to a circular economy model in the textile industry, which is one of the most polluting industries in the world. The linear model involves a large consumption of raw materials and generates waste, while the circular economy model focuses on the regeneration of raw materials and recycling. This includes the 5 R's of textile waste management: rethink, reduce, reuse, recycle, and reintroduce. The circular economy is characterized by close cycles, in which waste is minimized or converted into valuable inputs. Textile recycling process can be mechanical, thermal, chemical and biological. A series of recycling methods for different fiber-based materials: cotton, wool, synthetic, which are proposed in scientific papers is presented, contributing to the promotion of a zero-waste world.
Claudia Voigt, Eric Werzner, Robert Fritzsch
et al.
The pressure drop of a ceramic foam filter is an important characteristic indicating the resistance to fluid flow through the filter. Filtration experiments have shown that filtration efficiency increases with decreasing functional pore size. However, this improvement comes at the cost of a higher pressure drop. Furthermore, trials with increased roughness of filter struts showed an improved filtration behavior. Comparing the influence of these filter properties on the filter efficiency is of high interest in terms of filtration per pressure drop. Therefore, the sensitivity of the pressure drop with respect to surface roughness needs to be known. In the study, the pressure drop of ceramic foam filters was measured for different functional pore sizes, porosities, and surface roughness in a water-based test facility at NTNU in Trondheim, Norway. The flow velocity was varied in the range of 0.6–80 cm/s, allowing the determination of the Darcy and non-Darcy permeability coefficients.
Abstract A two‐step process, including the premetallization of the SiC ceramic by Ag‐26.7Cu‐4Ti+B4C and the followed brazing with the Al‐based filler alloy, was developed to join 2219 aluminum alloy and the metallized SiC. The influence of metallization temperature and the B4C addition on the microstructure and mechanical properties of the joint was analyzed. The reaction products of Ti and B4C were detected in the brazing seam, such as Ti2B, TiC and graphite. With increasing of metallization temperature and B4C addition content, the shear strength of joint first increased and then decreased. The joint shear strength reached 14.0 MPa when SiC metallized with Ag‐26.7Cu‐4Ti+1%B4C at 930°C for 10 min, which showed that appropriate addition of B4C in Ag‐26.7Cu‐4Ti metallization layer could regulate the coefficient of thermal expansion difference between 2219 aluminum alloy and SiC to relieve the residual stress and improve the shear strength of their brazed joint.
Urban soils and streams contaminated with heavy metals have grown ubiquitous around the world throughout the industrialization age, severely reducing the quality and diversity of life. Industrial waste, such as chemical-releasing factories, is one of the primary anthropogenic sources of heavy metal contamination in soil and water bodies. To analyze the impact of industries to heavy metal contamination, the study assessed the soil quality along the heavy metals polluted river Ng'ombe near the battery recycling plant in Dar es Salaam, Tanzania's commercial city. The research looked at three heavy metals (Cu, Pb, and Zn) in a total of eight samples. Soils were found contaminated with both metals i.e., Copper, Lead, and Zinc at 4.68, 4.08 mg/L and, 5.79, respectively. Based on the soil samples taken surrounding the industry, it is possible to establish that the industry contributes significantly to the contamination in the soil and river Ng'ombe stream. Pb contamination was found to be fairly equally distributed across the area (2 to 6 mg/kg), as opposed to Zn (0.8 to 17 mg/kg) and Cu (0.04 to 19 mg/kg), which were shown to vary greatly on soil samples obtained around the area. Different pollution indices including geo-accumulation index, Potential contamination index, Contamination factor, Pollution load index and Modified degree of contamination were also used to investigate the impact of soil contamination, and all of them revealed that industrial discharges were an influence. However; study found the levels to be in permissible limit, but still, it exposes the community to cumulative consequences of metals bioaccumulation.
Marcelo Daniel Barros, Dachamir Hotza, Rolf Janssen
Abstract Ceramic laminates were produced by thermal pressing of pure alumina (Al2O3) and TiO2‐MnO‐doped alumina (d‐Al2O3) tapes and subsequently sintered at temperatures ranging from 1100 to 1250°C. The diffusion of dopants through the interface was investigated by optical (OM), scanning electron (SEM) microscopy, nanoindentation, and energy‐dispersive X‐ray spectroscopy (EDS) together with scanning transmission electron microscopy. Temperature‐dependent dopant diffusion and porosity profiles were, respectively, observed investigating the microstructure. For d‐Al2O3, the average grain size, hardness, and Young's modulus were higher when compared to pure alumina, while the dopants diffusion zone presented intermediate values of these properties. The increase in sintering temperature resulted in higher values of hardness and Young's modulus in both layers. A further investigation showed a gradual decrease in grain size, hardness, and Young's modulus from the doped to the pure alumina layer, corresponding to a decreasing gradient in the dopants concentration in the Al2O3 layer with increasing distance from the interface. High concentrations of Mn and Ti were observed at triple points and grain boundaries, as well as within alumina grains.
Charles Prado Ferreira de Lima, Guilherme Chagas Cordeiro
The use of biomass ash is an environmentally friendly practice in the search for sustainable construction materials. This study aimed to produce pozzolanic ash from corn straw with a high amorphous silica content, low carbon content, and high specific surface area via controlled acid leaching, two-step burning, and grinding. The effect of pretreating corn straw on the properties of the material was assessed by comparative analysis with corn straw and rice husk ashes produced without acid pretreatment. To this end, characterization data, hydration heat, chemically bound water, and portlandite consumption in pastes, and mortar compressive strength were used to evaluate the pozzolanicity of the ashes. The results indicated that all the ashes exhibited pozzolanic behavior and that the leaching process significantly improved the physical and chemical properties of corn straw ash, with reduction in portlandite content. The calorimetric results showed a change in hydration kinetics with an increase in ash in the cement mixes. Moreover, the compressive strength of leached corn straw ash-based mortars was greater than that of the other mortars, primarily for high levels of cement replacement (20 and 30% by mass).
Nur Quratul Aini Ismail, Nor Kamilah Saat, Mohd Hafiz Mohd Zaid
There is a lack of reports where dry milling methods have been used in the preparation of varistor based ceramics. Dry milling methods have been demonstrated to be able to produce fine and homogeneous sample powders. Soda lime silica (SLS) glass powder have also been used as dopants in ZnO varistor ceramics. This work focuses on the effect of dry milling on the microstructural and electrical properties of ZnO0.98-x-SLSx-CoO0.02. The sample mixtures were prepared via a solid state method with x = 0.5, 1.0, 1.5, and 2.0 mol%. XRD managed to detect Zn2SiO4 as secondary phase in the sintered samples. The results show that the average grain size decreased from 26.1 to 21.6 µm and densities of the varistor samples increased as x increased. The varistor sample that was sintered at 1100°C and doped with 2 mol% SLS glass powder shows good electrical properties with nonlinear coefficient, (α) 6.97, breakdown voltage 261.1 V/cm and leakage current (JL) 4.87 µA/cm2.
Levels of contamination of three mining industrial zones in Irkutsk Oblast and Zabaykalsky Krai were revealed by means of geoecological and geochemical monitoring. Bulk contents and mobile forms of As in soils, stubs, bricks, and dumps of the mining and processing industry were defined. This allowed revealing features of chemical composition of technogenic substrates for the purpose of a choice of a way of their neutralization. The possibility of chemical immobilization of mobile ionic forms of As in natural and man-made objects by treatment with alkaline reagents was studied. X-ray diffraction (XRD) analysis revealed pharmacolite CaHAsO4·2H2O, calcium arsenate Ca3(AsO4)2, and segnititePb(Fe3+)3AsO4(AsO3OH)(OH)6 that are formed in the obtained solid insoluble precipitates. Formation of new solid insoluble compounds indicates the chemical binding (immobilization) of arsenic-containing compounds and the irreversibility of the process. This allows us to offer an effective way of fixing toxic agents to reduce migration in the environment by stabilizing immobilized forms. Experiments with the use of lignin sludge ash (accumulated waste of the closed Baikal pulp and paper mill) for the neutralization of arsenic-containing waste of mining and metallurgical industries were carried out. Application of modified coal sorbing agents for the sorption of residual mobile forms of As (after treating with an alkaline reagent) allows achieving a decrease in its concentrations to the TLV standard for a hazardous substance. NoritRO 3520 is the most effective sorbing agent. The results are of high applied importance for the implementation of the method of chemical immobilization of mobile ion forms of As in technogenesiszones.
Alba E. Díaz‐Álvarez, J. Francos, Beatriz Lastra-Barreira
et al.
The rapid growth of the biodiesel industry has led to a large surplus of its major byproduct, i.e. glycerol, for which new applications need to be found. Research efforts in this area have focused mainly on the development of processes for converting glycerol into value-added chemicals and its reforming for hydrogen production, but recently, in line with the increasing interest in the use of alternative greener solvents, an innovative way to revalorize glycerol and some of its derivatives has seen the light, i.e. their use as environmentally friendly reaction media for synthetic organic chemistry. The aim of the present Feature Article is to provide a comprehensive overview on the developments reached in this field.
: Concept maps of chemistry can be obtained from thesaurus of chemistry. Analysis of information in the field of chemistry is done at graduate level, based on comparing and analyzing chemistry dissertations by using these maps. Therefore, the use of thesaurus for analyzing scientific information is recommended. Major advantage of using this method, is that it is possible to obtain a detailed map of all academic researches across all branches of science. The researches analysis results in chemical science can play a key role in developing strategic research policies, educational programming, linking universities to industries and postgraduate educational programming. This paper will first introduce the concept maps of chemistry. Then, emerging patterns from the concept maps of chemistry will be used to analyze the trend in the academic dissertations in chemistry, using the data collected and stored in our database at Iranian Research Institute for Information Science and Technology (IranDoc) over the past 10 years (1998-2009).
Bibliography. Library science. Information resources
Nepveu Manuel, Neele Filip, Delprat-Jannaud Florence
et al.
In this paper, we present an overview of the SiteChar workflow model for site characterisation and assessment for CO2 storage. Site characterisation and assessment is required when permits are requested from the legal authorities in the process of starting a CO2 storage process at a given site. The goal is to assess whether a proposed CO2 storage site can indeed be used for permanent storage while meeting the safety requirements demanded by the European Commission (EC) Storage Directive (9, Storage Directive 2009/31/EC). Many issues have to be scrutinised, and the workflow presented here is put forward to help efficiently organise this complex task.
Three issues are highlighted: communication within the working team and with the authorities; interdependencies in the workflow and feedback loops; and the risk-based character of the workflow. A general overview (helicopter view) of the workflow is given; the issues involved in communication and the risk assessment process are described in more detail. The workflow as described has been tested within the SiteChar project on five potential storage sites throughout Europe. This resulted in a list of key aspects of site characterisation which can help prepare and focus new site characterisation studies.
Chemical technology, Energy industries. Energy policy. Fuel trade