Papers by Keyword: Size Distribution

Abstract: Metal direct writing in semi-solid slurry is an innovative technology to realize low-cost printing of load-bearing parts in contrast to laser-based additive manufacturing. However, it is challenging to achieve near net-forming of 3D parts in the current stage because of the out of controlled microstructure and hence the unstable macro extrusion of the used semi-solid slurry. Here, mixed powder remelting (MPR) is introduced to actively design the characteristics of solid phases, i.e., solid fraction, shape factor, and size distribution. Specifically, high-melting-point pure Al powder served as the dispersed solid phases in the liquid phase that transformed from Al-Si alloy powder after remelting, leading to hypoeutectic Al-Si semi-solid slurry. The effectiveness of this approach was experimentally examined and kinetically modelled, to prepare semi-solid slurry with pre-set microstructure. The improved extrusion stability of semi-solid slurry can be anticipated, and it is universal for manufacturing of metal matrix composites slurry.

Abstract: Heterogeneous metal complex catalyst such as Zinc glutarate (ZnGA) and Zinc-Ferum Double Metal Cyanide (Zn-Fe DMC) have been shown to improve reactivity for alternating copolymerization using CO₂ and epoxides. However, there are not lot of studies that have been done to study the effect of different parameter such as time and temperature on the catalytic activities of ZnGA and Zn-Fe DMC. ZnGA was treated with toluene while Zn-Fe DMC catalyst was treated with (complexing agent) tert-butanol. The main focus of this study is to synthesize ZnGA and Zn-Fe DMC at different parameter where the catalysts were produced at a variety of temperatures (50,60,70 °C) and reaction times (3h & 9h). Three different zinc-ferum ratios (1:4, 1:6, and 1:8) were developed for the Zn-Fe DMC catalyst to compare the effect of iron as metal and zinc on the active site. The catalyst was characterized using Fourier-transform infrared spectroscopy (FTIR) to determine their functional elements and Brunauer–Emmett–Teller analysis (BET) for surface characterization and pore size. The effects of reaction parameters such as time and reaction temperature were investigated using this catalyst in an auxiliary-batch reactor. FTIR result shows that GA was successful incorporation into ZnO and the production of ZnGA catalysts. The presence of typical functional groups in the Zn–Fe DMC catalysts was also confirmed. The surface area and pore volume of ZnGA increases as the temperature and reaction time increases while Zn-Fe DMC the surface area and pore volume decrease as the ratio increases. These surface-modified catalysts can generate high-molecular-weight polymers, which benefits both the environment and industry.

Abstract: Products from an arc discharge between various conducting materials (copper-copper, graphite-graphite, natural graphite and their combination) in water and air have been studied. The SEM and SEM-EDS analysis, and the BET analysis on products from discharges were done as well identifying their size distribution. There are two essential types of product taken in investigation as (i) pure metallic particulates, and (ii) specific structures of materials. The visual properties of nano-sized products formed in two media at different current are compared. In products obtained in air, tiny spherical particulates of size in nano-order are observed repeatedly, as well ordinary nano-sized particulates as ones in water. The main visual feature of the particulates formed in air is their existence in deposition in which they are separated by itself. Plenty of individual scrolling sheets of graphite layer of enormous size frequently encounter in soot on electrodes.

Abstract: This study investigates the influence of aqueous solution molarity on the structural characteristics of zinc oxide (ZnO) grown by hydrothermal method. From the X-ray diffraction (XRD) patterns of the ZnO nanostructures, the diffraction peaks confirm the ZnO hexagonal wurtzite type crystalline structure. To investigate the structural properties of ZnO structures in more detail, we analyze the XRD line profiles of the samples by Warren-Averbach model. Based on the model, the diffraction intensity of the XRD is calculated in Fourier space and the information on the size distribution can be derived. Observing the calculated nanostructure size distribution of the samples, we can see that the breadth of the size distribution function decreases then increases with increasing molarities. Furthermore, the theoretical analyzed results are verified by photoluminescence (PL) measurements and the scanning electron microscope (SEM) images.

Abstract: Products formed in the discharge region of the DC arc between graphite electrodes in water were studied. Whereas one of them was grown on a cathode and kept whole, the other is arose by erosion of electrodes in powder form and sank or floated in the surrounding water. The structure of the products was studied by SEM and SEM EDX analysis. The whole parts grown on the cathode were made up three different components: (i) almost spherical tiny particulates; (ii) long and narrow linear parts; and (iii) macro particulates of gigantic size. We have identified the size distributions and the number densities for these component parts in the sample as well their mechanical features. The powder samples included bulk particulates of carbon sheets and linear structures, like a thread. The study shows that the long linear structures in the powder sample are formed by the scrolling of carbon layers whereas the ones deposited are formed by a growth mechanism

Abstract: The properties of Ti-43Al-9V-Y alloy powders, which were produced by cold crucible melting and argon gas atomization, were investigated. The results showed that the size of the powders was normal distribution in a range of 10-210μm. The powders possessed a near perfectly spherical shape. The microstructure of the powders was composed of dendritic and cellular crystal grains, and the dendritic crystal grains decreased in finer particles. The X-ray diffraction result indicated that there were two main phases, α2 and B2 in the powders, and the amount of B2 phase increased as the particle size decreased. In addition, the oxygen and nitrogen contents were below 1000ppm and around 140ppm, respectively.

Abstract: Various sizes SiO₂ colloidal particles in the size range of 260-950 nm were synthesized by the stöber method by adjusting the amount of ammonia from 9.0 ml to 3.0 ml while keeping 20.0 ml tetraethyl orthosilicate (TEOS), 125.0 ml ethanol, 6.0 ml ammonia and 18.0 ml distilled water fixed. In addition, X-ray diffraction (XRD) and scanning electron microscopy (SEM) were employed to analyze the crystallinity and morphology of the synthesized SiO₂ colloidal particles; the XRD result show that the SiO₂ colloidal particles are amorphous at room temperature; the SEM results demonstrated that the amount of ammonia could have significant effects on the size, size distribution and sphericity of the SiO₂ colloidal particles. SiO₂ colloidal particles were resulted with good monodispersity when the amount of ammonia was in the range of 6.0-90 ml, while SiO₂ colloidal particles with double size distribution were obtained when the range is 3.0-4.5 ml; on the other hand, SiO₂ spheres were resulted with good sphericity when the ammonia is in the range of 6.0-7.5 ml.

Abstract: The ultrafine and nano particles compared to larger particles are gaining high importance because of their vulnerable effects to environment and human health causing respiratory problems, cardiovascular disease, and various types of cancers leading to premature death [1]. WHO report points out that approximately, two thirds of the global burden of disease due to urban outdoor air pollution is mostly from the developing countries in Asia (Cohen et al. 2004)[2]. By number, nearly all of the particles emitted by a diesel engine are nanoparticles which are also true for gasoline engines [3]. This is addressed by new UN Regulations by introducing the emission norms for diesel and GDI vehicles for particle number and PM_2.5 as 6 x 10 ¹¹ and 4.5 mg/km respectively [4]. However, other S.I. engines like CNG, even though they look clean as there is no visible smoke but emitting large number of particles is necessary to investigate. This research paper focuses on characterization of ultrafine and nano particle emissions from CNG vehicle on Indian driving cycle and it covers experimental Investigation to identify the significance of different operating phases viz. idling, acceleration, deceleration and cruising for their contributions to particle number and size distribution pattern over urban as well as on extra urban part of the cycle. CNG passenger car shows large peak of PN emissions during cold starting phase at the beginning of the test cycle which is almost twice that of diesel vehicle. However, this concentration peak will decrease near to 25% on light operating loads during urban part of the cycle, but during acceleration and cruising operation on extra urban cycle under heavy load the PN emissions from CNG car are higher in magnitude. The particles emitted from CNG buses are too small to contribute to PM₁₀ as they are of ultrafine and nano size range.

Abstract: This article selected a typical office as the research object to study the effects of smoking on indoor particles. It analyzed the indoor particle characteristics in different conditions. It also compared the indoor particle characteristics in two different environments: opened-window and closed-window. The results indicate that, smoking has significant impacts on the mass and number concentrations of indoor particles. The particles with size of less than 1μm are significantly influenced. Opened-window mainly influences the indoor particles less than 2.5μm and it is beneficial for the disperse of the indoor particles.

Abstract: The combined blowing process of metallurgical multiphase reactor was simulated by water modeling. The effects of operation conditions on dispersed phase size distribution were studied and an empirical formula was obtained. Based on the law of additive codimensions, the interface areas under different operation conditions were calculated by means of box counting and projection relationship. The results show that the frequency of dispersed phase with certain granularity level are in a certain proportion to its size level, and the dispersed phase areas are influenced by the top and bottom combined blowing.