Higher Fine Fraction Research Articles

Preparation of Dispersed Copper(II) Oxide Nanosuspensions as Precursor for Femtosecond Reductive Laser Sintering by High-Energy Ball Milling.

This contribution demonstrates and discusses the preparation of finely dispersed copper(II) oxide nanosuspensions as precursors for reductive laser sintering (RLS). Since the presence of agglomerates interferes with the various RLS sub-processes, fine dispersion is required, and oversized particles must be identified by a measurement methodology. Aside from the established method of scanning electron microscopy for imaging individual dried particles, this work applies the holistic and statistically more significant laser diffraction in combination with dynamic image analysis in wet dispersion. In addition to direct ultrasonic homogenization, high-energy ball milling is introduced for RLS, to produce stable nanosuspensions with a high fine fraction, and, above all, the absence of oversize particles. Whereas ultrasonic dispersion stagnates at particle sizes between 500 nm and 20 μm, even after 8 h, milled suspension contains a high proportion of finest particles with diameters below 100 nm, no agglomerates larger than 1 μm and a trimodal particle size distribution with the median at 50 nm already, after 100 min of milling. The precursor layers produced by doctor blade coating are examined for their quality by laser scanning microscopy. The surface roughness of such a dry film can be reduced from 1.26 μm to 88 nm by milling. Finally, the novel precursor is used for femtosecond RLS, to produce homogeneous, high-quality copper layers with a sheet resistance of 0.28Ω/sq and a copper mass concentration of 94.2%.

Use of the Heterocypris incongruens bioassay for assessing ecotoxicity of soils containing the anionic surfactant sodium lauryl ether sulphate (SLES)

The production and consumption of surfactants are constantly increasing, and huge amounts are found in the environment as contaminants. Surfactants are widely used in domestic and industrial applications, including in tunnel-mechanized excavation of large-scale infrastructures (e.g. highways and railways). In the latter case, the commercial products are foaming agents containing the anionic surfactant sodium lauryl ether sulphate (SLES). Foaming agents are necessary for enhancing Tunnel Boring Machine-Earth Pressure Balance (TBM-EPB) performance. Consequently, there are SLES concentrations in excavated soils of which large quantities can have harmful effects on biota. SLES toxicity in the aquatic environment is well known; on the contrary, knowledge of its effects on soil organisms is quite limited. In order to better understand SLES ecotoxicity in soil, the standardized bioassay (ISO 14371:2012) with the crustacean Heterocypris incongruens, living in the soil–water interface, was used. The lethal concentrations of standard SLES (LC15: 120; LC50: 140 mg/L, respectively) and of three common commercial products used as foaming agents (LC50 varying from 275 to 3810 mg/L) were evaluated. Subsequently, the crustacean acute and sub-chronic effects (mortality and growth inhibition) were assessed in seven different excavated soils conditioned with various commercial products. In addition, SLES concentrations in each soil and in their soil water extract were also determined. Mortality was not recorded in soils conditioned with foaming agents; however, a growth inhibition (c.a. 61.6 %) was found for soils with a high fine fraction and conditioned with high amounts (≥2 L/m3 soil) of foaming agents. H. incongruens proved to be an appropriate bioassay for assessing the possible effects of high SLES concentrations in soil, especially when this surfactant is bound to soil.

ENGINEERING PROPERTIES OF LATERITIC SOIL IN OTUN AREA, EKITI STATE, NIGERIA

Lateritic soils at Otun Ekiti, Ekiti state, southwestern Nigeria were investigated with respect to their geotechnical properties and their suitability for subgrade and sub – base construction materials. Four disturbed lateritic soil samples (sample A, B, C and D) were selected for the various laboratory techniques. The grain size analyses, the specific gravity tests, the atterberg limit tests, compaction, California bearing ratio and shear box tests were carried out on the samples. The grain size analysis shows that sample A is gravelly silt-clayey sand. Sample B is silt – clayey gravel composition. Sample C is gravelly silt-clayey while Sample D is silt-clayey gravel. Atterberg consistency limit test indicate that sample A has 30.0%, liquid limit 19.5% plastic limit, 10.5% plasticity index, 9.1% shrinkage limit. Sample B has liquid limit of 27.0%, 16.2% plastic limit, 10.8% plasticity index and 7.4% shrinkage limit. Sample C has a liquid limit of 32.4%, plastic limit of 15.6%. It has a plastic index of 16.8%, Shrinkage limit of 9.7% while Sample D has a liquid limit of 36.2%, plastic limit of 17.7%. It has a plastic index of 18.5% and 11.1% as shrinkage limit. Thus, the soil is classified to be intermediate plasticity which can be used for sub – grade and sub – base materials. The soil samples are above the activity (A) line in the zone of intermediate plasticity (CL) which suggests that they are inorganic soils. Based on engineering use chart, the workability as construction engineering is good to fair particularly as erosion resistance in canal construction. However, the high shrinkage limit may also reduce erosion in this area because of cohesion of the plastic clay material. The California Bearing Ratio (CBR) values are within 2 – 3% (mean = 2.75%) and 2 - 4% (mean = 2.75%) in sample A and sample B respectively while California Bearing Ratio (CBR) of 2 - 4% (mean = 2.75%) and 2 – 3% (mean = 2.75%) in sample C and sample D respectively. This implies that the materials can be used as a sub-grade to base course material for support of flexible pavements. The compaction tests for the optimum water content for sample A is 15.0% and 13.0% for standard and modified proctor respectively. The standard and modified proctor for sample B is 15.0% and 14.0% respectively. The compaction tests for the optimum water content for sample C and D is 15.0% and 14.0% for standard and modified proctor respectively. The compaction tests for Sample A indicate a higher fine fraction and thus a higher optimum moisture content while sample B, C and D has higher coarse fraction with lower optimum moisture content. The cohesion falls within 70-90Kpa (mean = 79Kpa) and the angle of internal friction ranges from 260 - 320 with mean of 280 for standard and modified compaction energies respectively. The results obtained from geotechnical analysis suggest that the soil is good to fair as erosion resistance in canal construction because of its high bearing capacity and it can also be used as sub – grade and base course in road construction. Keywords: Lateritic soil, Construction, Erosional and Geotechnical.

Repetitive land application of urban sewage sludge: Effect of amendment rates and soil texture on fertility and degradation parameters

The agricultural reuse of urban sewage sludge in degraded croplands has seen a wide acceptance for biowaste recycling and for the improvement of soil fertility. However, soil degradation and health issues may arise from the fact that sludge addition causes chemical and biological contamination if mismanaged. To closely monitor the long term soil-sludge interactions, a field study was conducted over a three-year period under a semi-arid climate. More precisely, changes in topsoil properties were assessed in 4-m2 uncropped plots amended with sludge rates equivalent to 0, 40, 80 and 120 t ha−1 year−1 for two soil textures: soil A (sandy loam) and soil S (sandy). Results showed that all studied parameters changed significantly in a dose-dependent manner for both soils as compared to untreated controls. As such, sludge addition improved consistently TOC, N, P and K content up to soils treated with 120 t ha−1 year−1. The enhancement of soil nutrient status impacted positively on biological properties, including microbial biomass and soil enzyme activities (dehydrogenase, protease and phosphatase). However, the variation of soil properties was more important in soil A characterized by a higher fine fraction thus stronger retention capacity. Accordingly, XRD analysis of soil A revealed several identifiable peaks representing kaolinite and illite clays in contrast to soil S. Unexpectedly, high to excessive sludge doses of 80 and 120 t ha−1 year−1 did not provoke soil degradation after three repeated annual amendments. In fact, pH values in both soils remained within neutral to alkaline range (7.76–8.63); total heavy metals (Cu, Zn, Ni and Pb), soil salinity and fecal coliforms were all below threshold values for contaminated soils.

Velocity Profiles in the Shallow Lunar Subsurface Deduced from Laboratory Measurements with Simulants

AbstractTo provide a basic model for future lunar explorations, the compressional (P) and shear (S) wave velocity profiles in the shallow lunar subsurface are deduced from the velocities in a lunar soil simulant called FJS-1. The P-wave and S-wave velocities in several types of samples derived from FJS-1 were measured by laboratory bender element tests to examine the effect of confining stress, void ratio, and fine fraction content. Because of its high fine fraction content, FJS-1 exhibited remarkably lower velocities than other materials, although they were similar in terms of dependence of the confining stress and void ratio. Based on the test results, empirical equations for deriving the velocities of FJS-1 were proposed as functions of confining stress and void ratio. The equations were then used to deduce the P-wave and S-wave velocities in the shallow lunar subsurface. Two sets of continuous velocity profiles up to a depth of 60 m were estimated and found to be in agreement with existing velocity da...

A novel use of friability testing for characterising ribbon milling behaviour

Dry granulation using roll compaction (DGRC) has been increasingly adopted in the pharmaceutical industry due to its unique advantage of not requiring liquid binder and a subsequent drying process. However the DGRC process presents also some challenges, in particular, a high fine fraction generated during the milling stage significantly limits its application. Although the fines produced can be recycled in practice, it may lead to poor content uniformity of the final product. At present there is a lack of mechanistic understanding of milling of roll compacted ribbons. For instance, it is not clear how fines are generated, what are the dominant mechanisms and controlling attributes and whether any measurement technique can be used to characterise ribbon milling behaviour. Therefore, the aim of this paper was to assess whether ribbon milling behaviour can be assessed using some characterisation methods. For this purpose, friability was evaluated for ribbons made of microcrystalline cellulose (MCC) powders using a friability tester that was originally developed for characterising the tendency of pharmaceutical tablets to generate small pieces while being abraded. Granules were also produced by milling of the ribbons and their size distributions were measured. The correlation between the fine fraction of the granules with ribbon friability was then explored. It was found that there was a strong correlation between ribbon friability and the fine fraction of granules generated during milling. This implies that friability tests can be performed to characterise ribbon milling behaviour, and ribbon friability provides a good indication of the fraction of fines generated during ribbon milling.

Systematic evaluations regarding interparticular mass transfer in spheronization

Pellets are frequently used in pharmaceutical applications. The extrusion-spheronization process is a well-established technique used to produce pellets of a spherical shape and narrow size distribution. In this process, cylindrical extrudates are transformed into spherical pellets by spheronization. Most established mechanisms consider only breakage and deformation to explain pellet formation. An interaction between the rounding extrudates via adhesion of fine particles was not considered for many years.This study deals with the evolution of pellet properties over time during the spheronization process in order to quantify the influence of pellet interactions on their properties. Therefore the most important pelletization aids (MCCI, MCCII and κ-carrageenan) were investigated using acetaminophen as a model drug and lactose as a filler. In the first seconds of the spheronization process, a high fine fraction was seen which decreased during the process. Simultaneously, the material transferred between the pellets increased. However the fine fraction is not high enough to explain the mass transfer; therefore a direct transfer between the pellets was assumed. The pelletization aid has a huge influence on the amount of mass transferred. Whereas κ-carrageenan leads to a quite low mass transfer of 15%, MCCI and MCCII show higher values up to 25%.

Additives for lubricants containing poly(tetrafluoroethylene). Part 1: Synthesis and rheological characterization

This article describes the synthesis of dispersions consisting of irradiated poly(tetrafluoroethylene) (PTFE) micropowder in an ester oil (Synative ES TMP 05) and presents their results of the characterization in terms of stability and rheology. The degree of PTFE micropowder in the dispersion was gradually increased from 10 wt% to 25 wt%. In addition, two additives based on phosphoric acid were used to study whether they are able to affect the properties of the dispersion with the lowest concentration of PTFE micropowder. The amount of irradiated PTFE micropowder affects the stability against separation. The dispersion with the lowest concentration of PTFE micropowder (10 wt%) showed the highest stability due to the pronounced high fine fraction of PTFE particles (Ø: 0.2–0.5 µm). On the other hand, the PTFE/oil dispersions with higher concentrations own a distinctive amount of greater particles (Ø: 0.3–3.0 µm), suggesting a negative influence on the stability of the dispersions. Nevertheless, these dispersions can stabilize themselves by these structures.

SPATIAL AND TEMPORAL VARIATIONS IN INTER-TIDAL ANIMAL DISTRIBUTION AT LANGEBAAN LAGOON, SOUTH AFRICA

Summary Spatial and temporal changes in the distribution of food organisms potentially available to curlew sandpipers Calidris ferruginea at Langebaan Lagoon (33 °S, 18 °E) are described for the period February 1974—March 1975. The inter-tidal benthic fauna at sandy sites showed spring and autumn peaks in biomass and numbers. The fauna was dominated by the gastropod Assiminea globulus, which comprised 62,5% of the total biomass. A Production: Biomass ratio of 4,96 was found for this species, and 1,36 for the amphipod Urothoe grimaldi. The fauna at sites containing macrophytes (Spartina, Zostera, Arthrocnemum) showed winter peaks in biomass and numbers. Classification and ordination confirmed the discreteness of macrophyte and non-macrophyte sites, each having its own characteristic benthos. There was a positive correlation between the distribution of benthos and sediment parameters at the different sites, macrophyte sites having a higher fine fraction and organic content.