ALBERT

Description: Nickel aluminate is a transition metal oxide with spinel structure with potential applications as catalysts and sensors. Both applications benefit from high specific surface areas as well as chemical stoichiometry control. However, a systematic approach to understand synthetic parameters affecting stoichiometry and agglomeration of nickel aluminate nanoparticles is still lacking. In this work, co-precipitation using direct and reverse strikes and polymeric precursor techniques were comparatively studied to address this problem. While the polymeric method could deliver stoichiometric spinel, the samples were highly agglomerated exhibiting low surface area. Both co-precipitation procedures produced smaller sizes and less agglomerated nanoparticles as compared to the polymeric precursor, but for the reverse-strike, Ni 2+ preferentially formed a soluble complex with ammonia and led to nickel deficient nanoparticles. Stoichiometric (1 mol NiO:1 mol Al 2 O 3 ) nanocrystalline nickel aluminate was only achieved when using controlled excess Ni 2+ . The normal-strike lead to more stoichiometric compositions without need for excess cations, but the obtained nanoparticles were less homogeneous and showed smaller surface areas as compared to the reverse-strike method.

Description: SummaryThirty-four soils from the Rothamsted Experiments were exhaustively cropped with ryegrass in the glasshouse. The concentration and yield of potassium in ryegrass tops and the potassium intensity in the soil were measured every 4 weeks, after harvesting the grass.The change in K-intensity of soils, rich in potassium, with exhaustion differed from that of ‘poor’ soils. This change was related to the rate of change of the cumulative K-yield. The rate of change of soil K-intensity demarcated periods of intense and limited exhaustion and partial recovery of the soil during cropping.The cumulative K-yield of ryegrass was very significantly related to the K-intensity of the uncropped soil; the ‘16-week’ yield was slightly better related than the ‘60-week’ yield. For Park Grass soils, the relationship was improved by allowing for variations in soil pH.The K-intensity of all soils, with or without manuring, decreased to nearly 10-3 (M)½ in (AR)0 units after 16 weeks cropping, although large differences in K-yield persisted until much later.K-buffer capacity per unit clay content of the soil, measured by a laboratory method, was inversely related to the K-intensity of the uncropped soil. The K-buffer capacities of soils rich in potassium, measured in laboratory and glasshouse experiments, were significantly related, but were unrelated for ‘poor’ soils. The K-buffer capacity (laboratory method) of Rothamsted soils with different manurial treatments was only very approximately related to the cumulative K-yield.Less K was taken up from all Rothamsted soils given nitrogen fertilizer in the field and their K intensities were also smaller than the corresponding soils without ‘N’. Field liming of acid soils decreased their K-intensity and increased their K-buffer capacity, presumably because more potassium was removed by the field crop.A rapid method is suggested for measuring potassium intensities of soils.

Description: SUMMARYTwenty-six soils from different parent materials were exhaustively cropped with ryegrass in the glasshouse. Soil and crop measurements revealed inter-relationships similar to those observed with Rothamsted soils (Part I) generally, except that 12 of 20 soils, ‘poor’ in K (as defined by the K intensity of the uncropped soil and the change in soil K intensity with cropping), gave patterns of K uptake by the ryegrass crop similar to those of soils ‘rich’ in K. This indicates that these soils contain some K reserves not differentiated from those accumulated by K-manuring in Rothamsted by laboratory measurements.The cumulative K yield of ryegrass was very significantly related to the K intensity of the uncropped soil. The relationships were improved slightly by allowing for differences in soil pH and organic carbon content. The cumulative K yields at 16 weeks and at 60 weeks were better related to the total clay (