Urea

About: Urea is a research topic. Over the lifetime, 21394 publications have been published within this topic receiving 382444 citations. The topic is also known as: carbamide & carbonic acid diamide.

Preparation and properties of a double-coated slow-release and water-retention urea fertilizer.

Abstract: A double-coated, slow-release, and water-retention urea fertilizer (DSWU) was prepared by cross-linked poly(acrylic acid)-containing urea (PAAU) (the outer coating), polystyrene (PS) (the inner coating), and urea granule (the core). Elemental analysis results showed that the nitrogen content of the product was 33.6 wt %. The outer coating (PAAU) regulated the nitrogen release rate and protected the inner coating from damage. The slow-release property of the product was investigated in water and in soil. The possible mechanism of nitrogen release was proposed. The influences of PS coating percentage, temperature, water absorbency, and pH on the release of nitrogen were also investigated. It was found that PS coating percentage, temperature, and water absorbency had a significant influence on the release of nitrogen. However, the pH had no effect. The water-retention property of the product was also investigated. The results showed that the product not only had a good slow-release property but also excellent water-retention capacity, which could effectively improve the utilization of fertilizer and water resources. The results of the present work indicated that the DSWU would find good application in agriculture and horticulture, especially in drought-prone areas where the availability of water is insufficient.

Facile Microwave-Assisted Hydrothermal Synthesis of CuO Nanomaterials and Their Catalytic and Electrochemical Properties

Abstract: Copper oxides have been widely used as catalysts, gas sensors, adsorbents, and electrode materials. In this work, CuO nanomaterials were synthesized via a facile microwave-assisted hydrothermal process in Cu(CH3COO)2(0.1 M)/urea(0.5 M) and Cu(NO3)2(0.1 M)/urea(0.5 M) aqueous systems at 150 °C for 30 min. The formation processes of copper oxides were investigated, and their catalytic activities were evaluated by the epoxidation of alkenes and the oxidation of CO to CO2. Their electrochemical properties were compared as supercapacitor electrodes using cyclic voltammetry. Experimental results indicated that copper acetate solution could be hydrolyzed to form urchin-like architectured CuO, and the addition of urea accelerated this transformation. CuO nanoparticles were formed and aggregated into spheroidal form (CuO-1) in Cu(CH3COO)2/urea aqueous solution. Cu2(OH)2CO3 was formed as an intermediate, and then thermally decomposed into CuO nanorods (CuO-2) in the Cu(NO3)2/urea aqueous system. The synthesized cop...

Molecular Association in Solution: A Kirkwood−Buff Analysis of Sodium Chloride, Ammonium Sulfate, Guanidinium Chloride, Urea, and 2,2,2-Trifluoroethanol in Water

Abstract: Molecular association has been investigated as a function of solution composition for sodium chloride (NaCl), guanidinium chloride (GdmCl), ammonium sulfate ((NH4)2SO4), urea, and 2,2,2-trifluoroethanol (TFE) mixtures with water. A Kirkwood−Buff analysis of the available experimental data provided information concerning the degree of excess association of the various species in solution. The results indicate that increasing concentrations of NaCl have no effect on the excess self-association of water, while GdmCl, (NH4)2SO4, and urea slightly increase the excess self-association of water. The presence of TFE results in composition dependent effects with a strong increase in the self-association of water at low TFE concentrations. The consequences of these observations in the context of water structure making properties are discussed. The excess self-association of cosolvents (except urea) displayed an initial increase which proceeded through a maximum at low cosolvent concentration and then decreased stea...