Papers by Keyword: Ultrafine

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: By using a surface treatment agent on the surface of calcium carbonate, discussed the variation of the specific surface area of the calcium carbonate during the grinding process, determined the added amount and added time of the dispersing agent, and researched on the grinding effect. According to the changes about the specific surface area of the grinding calcium carbonate particles, compared with the different effects that added the uniform dispersant and added the corresponding needs dispersant, had the particle size relationship followed the change of the specific surface area, reach to the purpose that refine the particle size and get a narrower particle size distribution.

Abstract: A new synthetic technology of Strontium carbonate with high gravity is introduced in this paper. We got ultrafine SrCO3 powders with Sr(NO3)2 and NaCO3 or CO2 as raw material by high gravity method. We studied flows, the rotating speed, additives and CO2 as the reactants on the morphology of strontium carbonate. The results show that the presence of additive-free, we got rod-like structure of strontium carbonate. Added EDTA, we got a good dispersion of spherical particles of narrow particle size distribution. The presence of EDTA, the average particle size of spherical particles decreases with the speed increases. CO2 alternative Na2CO3 as the reactants, the presence of additive-free, we got the bundle structure of strontium carbonate. The presence of EDTA, we got spherical particles, but the particle dispersion is not well, gathered together.

Abstract: The ultrafine CeO2 powder was prepared using NH4HCO3 as precipitation agent. The effects of six drying methods, such as room-temperature drying、common oven drying、microwave drying、organic solvent displacement drying、freeze drying、vacuum drying, on hard agglomerates and physical property of CeO2 were studied. The results showed that freeze drying is more effective to prevent the ultrafine CeO2 powder from hard agglomerates. The ultrafine CeO2 powder with small mean particle size and uniform distribution and large specific surface area，was obtained by freeze method.

Abstract: Slagging coal gasifiers operate at temperatures as high as 1650°C in a reducing environment so that combustion chambers are lined with high chromia refractories. The quality of these refractories applied on IGCC should be a key factor that affects the entire cost of electric power production. In this study, low cost chromia-alumina castables were chosen as candidate refractories for IGCC. To enhance the workability of chromia-alumina castables, ultrafine alumina powder was added to improve the workability. It’s proved that the specific surface area and particles size distribution of ultrafine powders in matrix part greatly affect the flow values and microstructures.

Abstract: Ultrafine pulverization technology was applied for producing apple pomace powder, and the physical-chemical properties of the ultrafine powder including fluidity, water solubility, water holding capacity, fat binding capacity, and solubility of total phenolics and sugars were investigated. Results suggested that ultrafine pulverization had distinct effect on surface properties of apple pomace powder. With decreasing the size of apple pomace powder, the flow behavior and water solubility were improved, and the dissolubility of total phenolics and sugars increased significantly, while the water holding capacity and fat binding capacity decreased. These results would provide useful insight for exploiting the potential applications of apple pomace ultrafine powder in functional foods as well as extracting polyphenols and polysaccharides for commercial practices.

Abstract: Using La₂O₃ and Co(NO₃)₂•6H₂O as raw material, ultrafine perovskite-type oxides LaCoO₃ was prepared by Supercritical Fluid Drying Technology and Sol-Gel method. The prepared materials’ crystal structure and morphology were characterized by TG-DTA、XRD、FT-IR and TEM. The photocatalytic activity of ultrafine LaCoO₃ powders was evaluated by degradation of methyl orange (MO) solution under 15W UV light irradiation. The results show: At 250°C , the amorphous ultrafine La-Co particles with the size less than 10 nm can be obtained by Supercritical Fluid Drying Technology. At 850°C , the size of the particles increased to 15-35nm, the nanocrystalline LaCoO₃ had a perfect rhombohedral perovskite structure. At 900°C , the crystalline phases of the lanthanum-cobalt mixed oxides were LaCoO₃ and La₂O₃, and the amorphous component is Co₂O₃, the presence of lanthanum affects the crystallization of cobalt oxides. The LaCoO₃ has excellent photocatalytic activities and 100% MO solution was decolorized only after 4h.

Abstract: Effect of plane strain machining parameters such as rake angle and cutting velocity on the formation of ultra-fine structure in several materials has been studied. The microstructure and hardness of chips generated by machining were characterized by optical microscopy, scan electron microscopy and hardness tester respectively. The experimental results indicated that chip materials with ultra-fine grained and high hardness can be produced with more negative tool rake angle at some lower cutting velocity. The rake angle has more important effect on the formation of ultra-fine grain chips than cutting velocity. The rake angle for getting chips of obvious refined and significant hardened is different for different materials respectively. While the temperature of shear plane and tool-chip interface are increased with the increasing cutting velocity which alleviates the increase of hardness produced by decreasing rake angle.

Abstract: Ammonium aluminium carbonate hydroxide (AACH), with a small quantity of γ-AlOOH, was synthesized through solid-state reaction at room temperature using AlCl3·6H2O and NH4HCO3 as raw materials and polyethylene glycol (PEG-10000) as the dispersant. After calcined at 1100°C for 1.5h, α-Al2O3 powders with primary particle sizes of 20~30nm were obtained. The crystal phase, particle size and morphology of the high-purity ultrafine α-Al2O3 were characterized. The results showed that a small quantity of γ-AlOOH in the AACH decomposed and formed crystal seeds. The presence of crystal seeds reduced the nucleation activation energy and therefore reduced the phase transformation temperature.

Abstract: Ultrafine cerium-doped GSAG phosphor powders are prepared by a solution combustion process using glycine and urea as fuel. Single-phase cubic GSAG:Ce crystalline powder is obtained by calcining the as-synthesized amorphous materials at 800oC and no intermediate phase is observed. Transmission electronic microscope morphology shows that the resultant GSAG:Ce powders have uniform size and good homogeneity. The photoluminescence spectra of Ce3+ substituted for Ce3+ in GSAG has been measured on samples calcined at 1000oC.