Irregular Particle Size Research Articles

The effect of processing parameters on amorphous carbon nitride layer properties

Surface morphology, deposition rate (DR), bonding composition, structural, optical and electrical properties of pulsed laser deposited amorphous carbon nitride (a-CN x ) layers using camphoric carbon (C 10H 16O) target precursor as a function of substrate temperatures (STs), laser fluences (LFs) and target to substrate distances (TSDs) are reported. At fixed LF and TSD, surface roughness, particle density and particle size increase, whereas the DR decreases with higher ST. When the TSD and ST are fixed, surface roughness, particle density, deposition rate and nitrogen (N) content increase, whereas particle size decreases with higher LF. While when the LF and ST are fixed, decreasing TSD results in an increase in the irregular small particle size, particle density, surface roughness, DR and N content. The N content in a-CN x layers is found to increase with higher ST up to 400 °C and decrease thereafter. While the increase of LF and decrease of TSD result in an increase in the N content. We found that the amorphous structure of a-CN x layers and the ratio of sp 2 trihedral component to sp 3 tetrahedral component are strongly dependent on ST, LF and TSD. The a-CN x layers with high N content have relatively high electrical resistivity.

A series of NiMo/Al 2O 3 catalysts containing boron and phosphorus : Part I. Synthesis and characterization

In this work, a series of nickel–molybdenum, nickel–molybdenum–boron and one nickel–molybdenum–phosphorus catalysts were prepared by incipient wetness impregnation method. Calcination temperature, nickel, molybdenum and boron concentrations in γ-Al 2O 3 were varied from 450 to 600 °C, 1.8 to 3.1 wt.%, 10.6 to 13.2 wt.% and 0.5 to 1.7 wt.%, respectively. Nickel–molybdenum–phosphorus catalyst was prepared using 2.7 wt.% phosphorus. All catalysts were thoroughly characterized. The catalyst containing 10.6 wt.% Mo and 2.4 wt.% Ni in γ-Al 2O 3 gave maximum BET area of 211 m 2/g. In these catalysts, the molybdenum oxides were present predominantly as polymolybdate and tetrahedral form. Addition of boron to NiMo/Al 2O 3 caused an increase in weak acid centers, whereas phosphorus caused the formation of acid centers with intermediate strength. Also, addition of boron caused the formation of crystalline B 2O 3 and MoO 3 on the catalyst surface, evident from both XRD and SEM analyses. Whereas addition of phosphorus caused the formation of irregular particle size and agglomeration on the catalyst surface, evident from SEM-EDS analysis. New Lewis and Brönsted acid sites on the catalyst surface were observed from FTIR analysis because of the addition of boron and phosphorus to NiMo/Al 2O 3.

Influence Of Deposition Parameters On The Structural, Optical And Electrical Properties Of Amorphous Carbon And Amorphous Carbon Nitride Films Grown By Pulsed Laser Deposition Using Camphoric Carbon Target

The role of laser fluence (LF) and target to substrate distance (TSD) on the surface morphology, deposition rate, composition, structural, optical and electrical properties of amorphous carbon (a-C) and amorphous carbon nitride (a-CN x ) films deposited by Xe-Cl excimer pulsed laser deposition is reported. At fixed TSD, the surface roughness, particle density and deposition rate increase, whereas the particle size decreases with higher LF. When the LF is fixed, TSD decreases resulting in an increase in the irregular small particle size, particle density, surfaces roughness and deposition rate. We found that the amorphous structure of a-C and a-CN x films is strongly dependent on the LF and TSD. The a-CN x films with high deposition rate have relatively high nitrogen content and high electrical resistivity.

Synthesis of lead zirconate titanate from an amorphous precursor by mechanical activation

Many of the chemistry-based processing routes for functional ceramics inevitably involve calcining the chemical-derived precursors at an intermediate/high temperature, in order to form the designed ceramic phase. This is very undesirable, although widely used, as the calcination can result in an extensive degree of crystal growth and particle coarsening at the calcination temperature and therefore ruins almost all the advantages offered by the chemistry-based processing routes, such as an ultrafine particle size and high sintering-reactivity. Using a specifically designed PZT precursor prepared by co-precipitation, it is demonstrated that the precursor-to-ceramic conversion can alternatively be realized by mechanical activation. In this connection, a single phase, nanocrystalline perovskite PZT powder has been successfully derived from an amorphous hydroxide precursor by mechanical activation. The resulting PZT powder was well dispersed, and the particle size was in the range of 30–50 nm, as observed using the scanning electron microscopy and transmission electron microscopy. This is in contrast to the poor particle characteristics, represented by very coarse and irregular particle and agglomerate sizes, for the powder derived from calcination at 750°C. The activation-triggered PZT powder was sintered to a density of 97.6% theoretical density at 1150°C for 1 h. Sintered PZT ceramic exhibits a dielectric constant of 927 at room temperature and a peak dielectric constant of ∼9100 at the Curie point of 380°C when measured at the frequency of 1 kHz.

Development of metal-resin composite restorative material. Part 3. Flexural properties and condensability of metal-resin composite using Ag-Sn irregular particles.

Powder-liquid type metal-resin composites, using Ag-Sn irregular particles as the filler, 4-META as coupling agent and UDMA + TEGDMA as resin matrix, were experimentally prepared under 9 different conditions (three different particle sizes and three different filler contents). The flexural strength and flexural modulus were measured. Three different irregular particle size MRCs without redox-initiator at 94% filler content, as well as amalgam, conventional hybrid composite and Ag-Sn spherical particle MRC were evaluated for condensability. The flexural strength of the Ag-Sn irregular particle MRC was significantly influenced by both the filler particle size and filler contents (p < 0.01). It increased when either the filler content increased or the particles size decreased. The highest flexural strength (97.6 MPa) was obtained from the condition of particles size < 20 microns and 94% filler content. The flexural modulus was significantly influenced by filler content and it increased with increasing filler content. The condensability of the Ag-Sn irregular particle MRC was lower than that of amalgam but much higher than presently available conventional composites and spherical particle MRC.

Aminated Phyllosilicates Synthesized via a Sol−Gel Process

Three analogous phyllosilicates were synthesized via a sol−gel process from the reaction of magnesium ions with aminated trialkoxysilanes in an aqueous basic medium at 373 K. The inorganic−organic hybrids obtained, designated as SILMgx (x = 1−3) are related to [3-aminopropyl]-, [N-(2-aminoethyl)-3-aminopropyl]-, and [(10-amino)-4,7-diazanonyl]trimethoxysilane, respectively. The elemental analysis of these hybrids gave the following C/N ratios: 3.1, 2.5, and 2.4. Thermal analysis data showed 50.7, 56.2, and 58.0% weight losses for the same sequence of hybrids. However, the thermal stability decreased in the order SILMg1 > SILMg2 > SILMg3. The surface areas of these matrixes are <2.0 m2 g-1 and X-ray diffraction patterns gave lamellar distances of 1745, 2063, and 2323 pm for SILMgx (x = 1−3). The infrared data indicated the existence of a phyllosilicate structure with absorption at 540 cm-1, which is associated with vibration of the Mg−O group. 29Si NMR showed the presence of three silicon species: T1, T2, and T3 in the inorganic−organic backbone structure. The photomicrographs obtained by scanning electron microscopy showed in all cases well-formed particles that have irregular shapes and particle sizes.

Effect of phosphate ion on filtration characteristics of solids generated in simulated high level liquid waste

The effect of phosphate ion on the filtration characteristics of solids generated in a high level liquid waste was experimentally examined. Addition of phosphate ion into the simulated HLLW induced the formation of phosphate such as zirconium phosphate and phosphomolybdic acid. The filtration rate of zirconium phosphate abruptly dropped in the midst of filtration because of a gel-cake formation on the filter surface. The denitration of the simulated HLLW contained zirconium phosphate improved the filterability of this gelatinous solid. The filtration rates of denitrated HLLW decreased with increase of the phosphate ion concentration, since the solids formed by denitration had irregular particle size and configuration in the simulated HLLW with phosphate ion. To increase the filtration rate of denitrated HLLW, a solid suspension filtration tester was designed. The solid-suspension accelerated the filtration rate only in the simulated HLLW with more than 1500 ppm phosphate ion concentration. Under this condition, the simple agitation can easily suspend the constituent solids of filter cake in the solution and a much higher filtration rate can be obtained because the filter cake is continuously swept from the filter surface by rotation of propellers.

Phase Transformation as a Function of Particle Size in Nanocrystalline Zirconia

ABSTRACTBulk zirconia undergoes a pressure-induced transformation from a (low pressure) monoclinic phase to a high pressure tetragonal phase, at around 3GPa (above 900K). We have studied the structures of zirconia nanoparticles formed by plasma-spraying an organo-metallic precursor. Inspection of the particles in the TEM reveals that they adopt one of two distinct crystal structures, depending upon their size. The smallest particles have the tetragonal structure, while larger ones are monoclinic. Interpolation of the data reveals a critical size above which the monoclinic structure is stable. Upon annealing, the zirconia particles coarsen and the small tetragonal particles transform to the monoclinic structure at about the critical size. Coarsening under these conditions produces irregular particle size distributions. We estimate that the surface-stress induced internal pressure in the tetragonal nanoparticles can be as high as 5 GPa and the corresponding surface stress is about 6N/m.

Distribution of zinc, lead, cadmium and copper between different size fractions of sediments II. The Krka River Estuary and the Kornati Islands (Central Adriatic Sea)

The levels of zinc, cadmium, lead and copper in different grain-size fractions of recent sediments, collected from the Krka River Estuary and the Kornati Islands during October 1983, were determined. The distributional patterns of these metals mainly depended on the textural characteristics of the sediment. The clay/silt size particles contained the highest amounts of zinc, cadmium and lead. Copper exhibited an irregular particle size distribution. In general, the contents of copper in different grain-size fractions and their distribution throughout the area seemed to be influenced by biological activities. In the coastal region, the concentrations of cadmium in the coarse particles (>63 μm) appeared to coincide with the quantities of carbonate present in the sediments. A significant enrichment of lead was observed in the lower part of the Krka River Estuary and in coastal regions with intensive ship traffic. Sediment collected near an industrial waste outflow was found to be enriched with zinc, lead and copper of anthropogenic origin.