Explore the vast range of titles available.

The amount of energy used to break rock is of interest in mine-to-mill operations to minimize energy consumption during blasting at the mine site and comminution at the processing plant. In this research, a direct energy measurement was made using high-velocity impact to cause breakage of long granite cores, and to study the energy dissipation along the entire bar length. The results show the formation of three zones of damage-fragmentation, fracture and elastic - that have been characterized in 3D using X-ray tomography. The fragmentation zone of the granite bars was studied in detail to describe the particle size distribution and the particle shape characteristics. The experimental energy dissipation in the fragmentation zone was found to be in close agreement with the expected energy calculated from the Bond work index (BWI) equation [1] when the anisotropic granite particles in the fragmentation zone are defined by length rather than by sieve size. The results increase our understanding of rock breakage and energy consumption and may find future applications in mine-to-mill operations.

In this study, cupric oxide (CuO) nanoparticles were synthesized via sonochemical method. The samples were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscope, and transmission electron microscopy. The spherical CuO nanoparticles were dispersed in sodium hexametaphosphate under sonication (25 kHz) to analyze the particle size distribution and UV absorption spectra. Using these absorption spectra, we further examined the CuO nanoparticle to explore the possibility of using them as a material for applications such as solar cell and textile production.

Purpose – The purpose of this paper is to explore the use of binder jetting to fabricate high-purity copper parts. The ability to fabricate geometrically complex copper shapes would have implications on the design and manufacture of components for thermal management systems and structural electronics. Design/methodology/approach – To explore the feasibility of processing copper via binder jetting, the authors followed an established material development process that encompasses powder selection and tuning process parameters in printing and thermal cycles. Specifically, the authors varied powder size and sintering cycles to explore their effects on densification. Findings – Three differently sized copper powders were successfully printed, followed by sintering in a reducing atmosphere. It was found that a 15-μm-diameter powder with a sintering cycle featuring a 1,080°C maximum temperature provides the most dense (85 per cent) and pure (97 per cent) final copper parts of the parameters tested. Research limitations/implications – Due to powder-based additive manufacturing techniques’ inherent limitations in powder packing and particle size diameter, there are difficulties in creating fully dense copper parts. To improve thermal, electrical and mechanical properties, future work will focus on improving densification. Originality/value – The paper demonstrates the first use of binder jetting to fabricate copper artifacts. The resulting copper parts are denser than what is typically found in binder jetting of metal powders (without infiltration); significant opportunity remains to further optimize the manufacturing process by introducing novel techniques to tailor the material properties for thermal/electrical applications.

An in-depth understanding of the gravity flow behaviour of broken ore is beneficial to improving the ore recovery in sublevel caving mines. In this study, granular dolomites were used as an analogue to experimentally explore the effect of the physical properties of fragments on the gravity flow behaviour of broken ore. Five groups of granular dolomites were prepared first. Then, the particle size, particle size distribution, and particle morphology (e.g., sphericity, circularity, and fractal dimension) in each group were measured following the standard particle morphology test. After that, the angle of repose and the isolated extraction zone (IEZ) of each group were determined by performing funnel and isolated draw experiments, respectively. The experimental results highlighted the insubstantial effect of particle size and the significant effect of particle morphology on the angle of repose and isolated extraction zone of granular dolomite. It was found that a wider particle size distribution yielded an isolated extraction zone with a nonuniform shape and a smaller mass drawn because of the percolation of finer particles and the jamming of larger particles. Further, a linear negative correlation was revealed between the repose angle and the IEZ mass. Establishing the relationship between the repose angle and the IEZ shape would be of great significance. In this regard, the findings of this study can aid a preliminary analysis.

Changes in particle granulometry could lead to significant changes in a soil’s behavior, making an understanding of micro-scale granulometry essential for practical applications. Changes in particle size, shape, and particle size distribution could result from a combination of applied normal and shearing stresses, which can in turn influence further response of the material. This study explored particle breakage during both compressive and shear loading under typical stresses. A deeper understanding of the phenomenon requires distinguishing broken and unbroken grains at the particle scale. Dynamic Image Analysis (DIA) was therefore employed to quantify changes in particle granulometry in two sands, a siliceous Ottawa sand and a calcareous sand known as Fiji Pink. Pre-sorted specimens having similar size, granulometry, and particle size distributions were tested using both oedometric and direct shear tests having the same aspect ratio, facilitating a direct comparison of the effects of shearing and compression on similar materials having different mineralogy. A breakage index was used for prognosis of particle breakage at key reference diameters. During oedometric tests, grain breakage was limited in both sands at stresses up to 1.2 MPa, but it increased significantly during direct shear tests. A conceptual model was proposed to explain the particle breakage mechanism during shear, at four key phase points representing (1) maximum compaction, (2) transition from compaction to dilative behavior, (3) maximum shear stress, and (4) peak test strain. In addition, a loading intensity framework was adopted to explain the relative roles of normal and shearing stresses on particle breakage. An increase of fines in soil during shearing was also observed and related to two sources: coarser grain abrasion and finer particle crushing. The vulnerability of grains with more anisotropic shapes was also observed. The loading intensity framework suggested that attrition of particle diameter could be divided into two phases, with a transitional critical loading intensity that appeared constant for each sand. For Ottawa sand, abrasion was the primary mechanism observed, causing a significant increase in Aspect Ratio ( AR ) and Sphericity ( S ) for finer grains. For Fiji sand, a transition from abrasion to attrition was noted, leading to limited sphericity decrease for the largest particles. Finer particles cushioning larger Fiji sand particles are more prone to breakage, resulting in increased AR and S . Finally, test results were used to propose a simple hyperbolic model to predict evolution of the particle size distribution during shear, for sands. The model was also verified using published data on grain evolution during shear of a different sand, not employed in its development.

The decomposition of supersaturated solid solution in the Cu–0.06 wt% Zr alloy has been investigated. Upon aging of the initially quenched alloy the homogeneous precipitation of particles is dominating. The decomposition begins from the precipitation of a metastable copper–zirconium phase, the particles of which have the shape of nanodimensional disks. An increase in the aging temperature results in the formation of coarser rodlike particles of the Cu 5 Zr equilibrium phase. Aging of the deformed alloy is characterized by the predominance of the heterogeneous precipitation of particles at subboundaries and dislocations, and the decomposition begins at a lower temperature. The particle size is less by an order of magnitude than that in the quenched state. The precipitation of nanodimensional particles at dislocations retards the formation of recrystallization centers.

The objective of this research, was to investigate the pullout behavior of straight high-strength steel fibers embedded in different ultrahigh-performance concretes with a compressive strength ranging from 190 MPa to 240 MPa. Particular attention was placed on obtaining matrixes with high packing density, to enhance the physicochemical bond with the embedded fiber. The parameters investigated included the use of different sand ratios, silica fume and glass powder with different mean particle sizes, different superplasticizers, and the addition of hydrophilic or hydrophobic nanosilica particles. Thus, by tailoring the matrix composition, significantly different bond stress versus slip-hardening behaviors were achieved. This is atypical for straight smooth steel fibers, which are normally characterized by a bond-slip softening behavior. Microscopical studies revealed that scratching and delaminating of the brass-coated fiber surface by fine sand and by abrading matrix particles is one reason for this phenomenon, and help explain the maximum equivalent bond strength observed of up to 20 MPa.

In the current study, an attempt is made to synthesize copper tungstate (CuWO 4 ) nanoparticles via a large-scale and facile sonochemical method with the aid of copper (II) nitrate and sodium tungstate dihydrate in an aqueous solution. Besides, three polymeric surfactant agents such as polyvinylpyrrolidone, polyethylene glycol, and polyvinyl alcohol were used to investigate their effects on the morphology and particle size of CuWO 4 . XRD, SEM, EDS, and UV–Vis spectroscopy were employed to characterize structural, morphological, and optical properties of CuWO 4 nanoparticles. According to the vibrating sample magnetometer result, CuWO 4 nanoparticles indicated a paramagnetic behavior at room temperature. In addition, methyl orange was chosen as a dye water pollution to evaluate its degradation by as-synthesize copper tungstate under ultraviolet light irradiation. Furthermore, the photocatalysis results reveal that the maximum decolorization of 75 % for methyl orange occurred with CuWO 4 nanoparticles in 90 min under ultraviolet light irradiation.

To investigate the role of particle size on the oxidation, bioavailability, and adverse effects of manufactured Cu nanoparticles (NPs) in soils, we exposed the earthworm Eisenia fetida to a series of concentrations of commercially produced NPs labeled as 20‐ to 40‐nm or <100‐nm Cu in artificial soil media. Effects on growth, mortality, reproduction, and expression of a variety of genes associated with metal homeostasis, general stress, and oxidative stress were measured. We also used X‐ray absorption spectroscopy and scanning X‐ray fluorescence microscopy to characterize changes in chemical speciation and spatial distribution of the NPs in soil media and earthworm tissues. Exposure concentrations of Cu NPs up to 65 mg kg−1 caused no adverse effects on ecologically relevant endpoints. Increases in metallothionein expression occurred at concentrations exceeding 20 mg kg−1 of Cu NPs and concentrations exceeding 10 mg kg−1 of CuSO4 Based on the relationship of Cu tissue concentration to metallothionein expression level and the spatial distribution and chemical speciation of Cu in the tissues, we conclude that Cu ions and oxidized Cu NPs were taken up by the earthworms. This study suggests that oxidized Cu NPs may enter food chains from soil but that adverse effects in earthworms are likely to occur only at relatively high concentrations (>65 mg Cu kg−1 soil).

The complexes derived from reaction of copper(II) salts (Cl − , Br − , CH 3 COO − and SO 4 −2 ) 2-(3-Amino-4,6-dimethyl-1 H -pyrazolo[3,4-b]pyridin-1-yl)acetohydrazide were prepared and characterized. Different standardized instruments were used for obtaining the required data (spectral method UV–Vis., IR, 1H-NMR, mass spectra) magnetic susceptibility and thermogravimetric analysis TGA were performed. The electronic spectral data and magnetic moment values proved that all the copper complexes have octahedral geometry. CuO nanoparticles with 15.5 nm of particle size have been synthesized via solid state thermal decomposition using these copper (II) complexes as new precursors. Surface morphology of the synthesized CuO nanoaprticles were investigated by Ultraviolet visible light spectroscopy (UV–Vis), X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscopy. The photocatalytic activity of CuO nanoparticles was assessed toward photocatalytic degradation of MB dye and the results exhibited 97 % efficiency with degradation rate of 0.018 min −1 .