Size analysis of the chips generated during abrasive machining of granite in relation to productivity and efficiency parameters

ABSTRACT

Characterization of particulate samples is widely used in many industrial applications including abrasive machining. Regarding granite machining with diamond-segmented circular sawblades, there is seemingly little or no published material on the size characterization of the generated chip particles in relation to productivity and efficiency of the process. The work described in this paper attempts to fill this gap in the literature. With this aim, a granite workpiece material was subjected to a series of sawing tests. Cutting depth and feed rate were varied at different levels to produce three different test designs leading to 10 different material removal rates ranging from 60 to 240 cm²/min. Particle sizing of the chips generated at each individual removal rate were quantitatively determined by means of image-processing system. Also, specific energy and process forces were determined at each employed removal rate. The general trends observed on the whole showed that the size and size distribution of the generated chips changed as a function of material removal rate, specific energy, and process forces. More importantly, despite the complexity of the process, it was found that a particular mean chip size can be designated corresponding to near-optimum machining conditions in terms of process productivity and efficiency.     

One-Dimensional Cobalt(II) and Zinc(II) Succinato Coordination Polymers with Nicotinamide: Synthesis, Structural, Spectroscopic, Fluorescent and Thermal Properties

Cobalt(II) and zinc(II) succinato (suc) coordination polymers with nicotinamide (nia), {[Co(μ-suc)(H₂O)₂(nia)₂] · 2H₂O} _n (1) and {[Zn(μ-suc)(H₂O)₂(nia)₂] · 2H₂O} _n (2) have been synthesized and characterized by elemental analyses, magnetic moments, IR and TG-DTA. Single-crystal X-ray analyses of 1 and 2 reveal that these complexes are isostructural and crystallize in triclinic space group Complexes 1 and 2 are 1-D coordination polymers, in which the metal(II) ions exhibit an octahedral geometry with two suc, two nia and two aqua ligands. The nia ligand is N-bonded, while the suc ligand bridges the metal centers through the carboxylate groups. The 1D chains are further assembled to form 3D networks by strong N–H···O and OW–H···O hydrogen bonds. IR spectra confirm the coordination modes of both suc and nia ligands, while TG-DTA data are in agreement with the crystal structures. Fluorescent analysis in the solid state shows that all complexes display intraligand (π–π*) emissions of nia.     

Thermal conductivity of MgO-C refractory ceramics: Effects of pyrolytic liquid and pyrolytic carbon black obtained from waste tire

In the present study, thermal conductivity and mechanical properties of MgO-C refractory ceramic bricks were investigated. Pyrolytic liquid and pyrolytic carbon black obtained from pyrolysis of waste tires were used as a resin and carbon source, respectively. The pyrolysis of the tires was conducted in a fixed bed reactor at the temperature of 500?°C with a 15?°C/min heating rate under nitrogen flow (0.5?lt/min). Before using in MgO-C refractory ceramic blends, pyrolytic products were purified with the acidic extraction methods which resulted in 61and 66?wt%. decreases in sulfur and ash contents in pyrolytic carbon, respectively. After this treatment of pyrolytic liquid, the sulfur content was reduced by 24?wt%. Eight different blends of MgO-C refractory ceramics consisting of different pyrolytic product contents were prepared, pressed, and tempered at 250?°C, and then characterized in terms of porosity, thermal conductivity, and density. The mechanical behavior of the samples was tested using a three-point bending test. Archimedes test was employed to determine the porosity and density. Surface properties of the bricks were analyzed by scanning electron microscopy (SEM). The obtained results were compared with a reference consisting of graphite and resin. The results revealed that mechanical and thermal properties of the developed bricks were highly sensitive to the porosity and the carbon source as well as the type of binder.     

A three-dimensional silver(I) coordination polymer involving a new bridging mode of saccharinate

A three-dimensional silver(I)-saccharinato (sac) coordination polymer [Ag₂(μ-sac)₂]_n has been synthesized and characterized by elemental analysis, IR and single crystal X-ray diffraction. The silver(I) ions are doubly bridged by the imino N and carbonyl O atoms of two sac ligands, leading to a dimer [Ag₂(μ-sac)₂] with a very short Ag–Ag contact of 2.8622(6) Å. The dimeric units are linked by unique Ag–C_sac (η¹) bonds into two-dimensional ladder-like layers, which are further assembled into a three-dimensional network by weak Ag?O(sulphonyl) and π(sac)?π(sac) interactions. Complex 1 is the first example of a polymeric network involving the η¹ Ag–C bonds. In addition to the new coordination mode of sac, the IR spectrum and thermal properties of the complex were discussed.     

GaInNAs-based Hellish-vertical cavity semiconductor optical amplifier for 1.3 μm operation

Hot electron light emission and lasing in semiconductor heterostructure (Hellish) devices are surface emitters the operation of which is based on the longitudinal injection of electrons and holes in the active region. These devices can be designed to be used as vertical cavity surface emitting laser or, as in this study, as a vertical cavity semiconductor optical amplifier (VCSOA). This study investigates the prospects for a Hellish VCSOA based on GaInNAs/GaAs material for operation in the 1.3-μm wavelength range. Hellish VCSOAs have increased functionality, and use undoped distributed Bragg reflectors; and this coupled with direct injection into the active region is expected to yield improvements in the gain and bandwidth. The design of the Hellish VCSOA is based on the transfer matrix method and the optical field distribution within the structure, where the determination of the position of quantum wells is crucial. A full assessment of Hellish VCSOAs has been performed in a device with eleven layers of Ga_0.35In_0.65N_0.02As_0.08/GaAs quantum wells (QWs) in the active region. It was characterised through I-V, L-V and by spectral photoluminescence, electroluminescence and electro-photoluminescence as a function of temperature and applied bias. Cavity resonance and gain peak curves have been calculated at different temperatures. Good agreement between experimental and theoretical results has been obtained.     

In situ compatibilization of PEN/LCP blends by ultrasonic extrusion

In situ compatibilization of immiscible blends of PEN and thermotropic LCP was achieved by the ultrasonically‐aided extrusion process. Ultrasonically‐treated PEN underwent degradation, leading to a decrease of its viscosity. Viscosity of LCP was unaffected by ultrasonic treatment. Because of reduced viscosity ratio of PEN to LCP at high amplitude of ultrasonic treatment, larger LCP domains were observed in molding of the blends. LCP acted as a nucleating agent, promoting higher crystallinity in PEN/LCP blends. Ultrasonically‐induced copolymer formation was detected by MALDI‐TOF mass spectrometry in the blends. Ultrasonic treatment of 90/10 PEN/LCP blends improved interfacial adhesion in fibers spun at intermediate draw down ratios (DDR), improving their ductility. The lack of improvement in the mechanical properties of fibers spun at high DDR after ultrasonic treatment was attributed to the disturbance of interfacial copolymer by high elongation stresses. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011.     

Analysis of energy transfer and ternary non-covalent filler/matrix/UV stabilizer interactions in carbon nanofiber and oxidized carbon nanofiber filled poly(methyl methacrylate) composites

Ternary non-covalent interactions between carbon nanofibers (CNFs), oxidized carbon nanofibers (ox-CNFs), poly(methyl methacrylate) (PMMA) chains, and benzotriazole-containing UV stabilizers were analyzed using Fourier-transform infra red spectroscopy (FTIR), time-resolved fluorescence emission spectroscopy, and fluorescence lifetime imaging microscopy. The results indicated that PMMA chains form hydrogen bonds both with ox-CNF fibers and the UV stabilizer molecules. It was also determined that UV stabilizers strongly interact with CNF particles via π-π interactions. The extent of π-π and hydrogen bonding interactions was determined to be lower between ox-CNF particles and UV stabilizers due to less perfect graphitic structure of the former. The morphology of the composites indicated that the hydrogen bonds between PMMA chains and ox-CNF particles resulted in highly improved state of filler dispersion in ox-CNF/PMMA composites.     

Asymmetric Supercapacitors Based on Graphene/MnO2 Nanospheres and Graphene/MoO3 Nanosheets with High Energy Density

Asymmetric supercapacitors with high energy density are fabricated using a self‐assembled reduced graphene oxide (RGO)/MnO₂ (GrMnO₂) composite as a positive electrode and a RGO/MoO₃ (GrMoO₃) composite as a negative electrode in safe aqueous Na₂SO₄ electrolyte. The operation voltage is maximized by choosing two metal oxides with the largest work function difference. Because of the synergistic effects of highly conductive graphene and highly pseudocapacitive metal oxides, the hybrid nanostructure electrodes exhibit better charge transport and cycling stability. The operation voltage is expanded to 2.0 V in spite of the use of aqueous electrolyte, revealing a high energy density of 42.6 Wh kg^?1 at a power density of 276 W kg^?1 and a maximum specific capacitance of 307 F g^?1, consequently giving rise to an excellent Ragone plot. In addition, the GrMnO₂//GrMoO₃ supercapacitor exhibits improved capacitance with cycling up to 1000 cycles, which is explained by the development of micropore structures during the repetition of ion transfer. This strategy for the choice of metal oxides provides a promising route for next‐generation supercapacitors with high energy and high power densities.     

Evaluation of fresh state,rheological properties,and compressive strength performance of cementitious system with grinding aids

Grinding aids (GA) affect the fresh and hardened state properties of cement systems in addition to the economic and ecological advantages they provide. Nevertheless, there is not enough information in the literature regarding the effect of GA utilization on the rheological properties of cementitious systems. In this study, the effect of different types of GA utilization on the grinding efficiency, setting time, and physical properties of cement and rheological properties of cement paste was investigated. Besides, adsorption of the water-reducing admixture (polycarboxylate ether [PCE]) to the cement containing GA was investigated by total organic carbon analysis. According to the results, regardless of the type of GA, while the grinding efficiency was positively affected by GA utilization in cement, the adsorption degree of PCE, some fresh and rheological properties of the mixtures were negatively affected. With the use of GA, an increase was observed in the early age compressive strength of mortar mixtures. Consequently, the properties of cementitious systems containing GA should be taken into consideration to assess GA performance in addition to the grinding efficiency.     

Friction and wear behaviors of reciprocatingly extruded Al–SiC composite

This study focuses on the friction and wear behaviors of reciprocatingly extruded Al–SiC composites. To increase the strength of metal matrix composites and refine the grains of the matrix some deformation processes can be applied, such as reciprocating extrusion (RE). For this reason, RE was carried out on a 6061 Al matrix by a SiC (20 μm) reinforced composite one. The billets were extruded under a pressure of 17.5 MPa at 573 K with a 10:1 extrusion ratio. The reciprocating extrusions were carried out by using up to 15 passes.