松香包膜尿素的释放特性研究

以松香为成膜物质,制备了一系列的包膜尿素,利用扫描电子显微镜研究了包膜尿素的表面形貌,用浸泡溶解法表征了所得包膜尿素的释放特性,讨论了包覆量与操作条件对包膜尿素释放特性的影响。结果表明,松香是一种优良的尿素包膜材料,包覆量在5%以上时,松香包膜尿素具有显著缓释性能,包覆量越大,缓释效果越好。     

大颗粒包膜尿素控释肥在冬小麦上的施用效果

在河南驻马店砂姜黑土区及延津潮土区对大颗粒包膜尿素控释肥（CRU）在冬小麦上的施用效果进行了研究.结果表明：相同氮素用量时,大颗粒包膜尿素控释肥比普通尿素（BU）增产,即在100％用量、75％用量及50％用量相比时,驻马店试验增产率为5.7％、10.26％、13.5％,延津试验增产率为3.3％、11.7％、10.4％,增产效果显著.大颗粒包膜尿素控释肥的比表面积较小,可以大量节省包膜材料,减少土壤污染.     

Al/NiO复合粒子的制备与表征

以N i(NO3)2.6H2O和CO(NH2)2为主要原料,通过均匀沉淀法,90℃恒温12 h,异相成核,在片状金属铝粉表面包覆一层N i2CO3(OH)2,制备出包覆式复合粒子A l/N i2CO3(OH)2。将复合粒子在马弗炉中400℃恒温灼烧2 h,制备出了A l/N iO复合粒子。通过SEM、XRD及粒度测试等分析方法,对复合粒子的形貌、晶体结构及粒径进行了表征。     

Particle dimensions in polystyrene/polyethylene blends as a function of their melt viscosity and of the concentration of added graft copolymer

Apparent particle dimensions in blends of low density polyethylene (PE) and polystyrene (PS) made by mixing in the molten state have been measured and have been shown to depend on the viscosity of the mixed system. At a certain shearing rate small particles of the dispersed polymer are obtained if the polymer in excess has a high viscosity. At a higher concentration however this effect is counteracted completely if the dispersed phase has a low viscosity and thus lowers the overall viscosity. Coalescence is affected in the same way and the size of the particles increases greatly with increasing concentrations. If a highly viscous polymer is dispersed in a low viscosity polymer matrix relatively large particle sizes will be found at the preset shearing rate mentioned above. With increasing concentration of the highly viscous dispersed phase the particle size decreases due to the increasing viscosity. This effect is counteracted by coalescence leading to a relatively slow increase of particle size with concentration. Addition of surfactants such as graft copolymers based on PS and PE leads to smaller particle sizes as expected.     

Urea particle coating for controlled release by using DCPD modified sulfur

The shell of sulfur coated urea was easily cracked due to sulfur being friable. Sulfur was modified with dicyclopentadiene (DCPD) to increase its strength and abrasion resistance. SEM images showed that the micro-structure of modified sulfur was denser and more uniform than pure sulfur. The strength of modified sulfur increased with the DCPD/S ratio. Experiments of urea particle coating with sulfur and modified sulfur were carried out in a fluidized bed coater. The shell of coated urea particles with modified sulfur was more compact than that with pure sulfur. The modification retarded the sulfur phase transformation from monoclinic to orthorhombic, avoiding the crack formation in the coating shell of sulfur. The modified sulfur coated urea particles can be produced with thinner shell and higher strength, and had better controlled release properties.     

Effect of prilled urea and modified urea materials on yield and quality of geranium (Pelargonium graveolens L. Her.)

Two field experiments were conducted to study the effect of prilled urea, neem cake coated urea, dicyandiamide treated urea and urea supergranules applied to a perennial aromatic herb, geranium (Pelargonium graveolens L. Her'.) grown on a sandy loam soil. Application of nitrogen increased the biomass and essential oil yields. Neem cake coated urea significantly increased the yields over prilled urea. There was no residual effect of N levels and N carriers. The concentration and quality of essential oil were not influenced either by levels or carriers of N.     

Coalescence behaviour of gas bubbles in aqueous solutions of n-alcohols and fatty acids

Coalescence frequency and coalescence times of bubble pairs formed on two adjacent capillary tubes were determined in aqueous solutions of n-alcoho and fatty acids. The results show, that coalescence times of bubbles are proportional to the surface excess concentration of the solute. Coalescence ti increase with the polarity of the hydrophilic group of the solute, its chain length and the bubble size. Coalescence frequency decrease drastically fro 100% to 0% at a distinct solute concentration. The transition in coalescence behaviour occurs, if the coalescence times becomes greater than the availa contact times of the bubbles. The transition concentration therefore decreases with increasing rate of bubble formation.     

Effect of rates and sources of nitrogen application on yield and nutrient uptake of Citronella Java (Cymbopogon winterianus Jowitt)

Two field experiments were conducted for two crop cycles each of two years (1985–87 and 1986–88) on an entisols to study the effect of rate and sources of N application on yield and nutrient uptake of Citronella Java (Cymbopogon winterianus Jowitt). Fresh herbage and essential oil yields were significantly influenced by application of N up to 200 kg ha^–1 yr^–1, while tissue N concentration and N uptake increased only to 150 kg N ha^–1. The oil yields with Neem cake coated urea (urea granules coated with Neem cake) and urea super granules were 22 and 9% higher over that with prilled urea and urea supergranules were significantly increased up to 200 kg N ha^–1 while with Neem cake coated urea, response was observed only to 150 kg N ha^–1! Estimated recovery of N during two years from Neem cake coated urea, urea supergranules and prilled urea were 38, 31 and 21%, respectively.     

COATING OF UREA WITH AN AQUEOUS POLYMERIC SUSPENSION IN A TWO-DIMENSIONAL SPOUTED BED

In this work, a process of coating of urea with polymeric film was developed and analyzed experimentally in a two-dimensional spouted bed. An experimental design was utilized to investigate the effects of operational variables, e.g., air flow rate, air temperature, atomizing air pressure and coating suspension flow rate, on the efficiency of the process, particles growth, particles growth kinetics and physical properties. The results showed that the efficiency of the process and particle growth characteristics were strongly influenced by the operational variables. Coating of the polymeric suspension of Eudragit® improved up to four times the moisture holding capacity of coated urea in relation to uncoated urea. The bulk density, grain size and sphericity were found to be independent of operational conditions.     

Fe3O4水基磁流体的制备及其分散性能研究

采用共沉淀法制备了纯Fe3O4纳米粒子,分别用高氯酸、四甲基羟胺和油酸/十二烷基苯磺酸钠为表面活性剂对其进行表面处理后分散在水中,得到了3种水基磁流体,对这3种磁流体的浓度及稳定性进行了测定。实验结果显示:酸性、碱性和中性水基磁流体中Fe3O4的浓度分别为4.8%、5.8%和8.1%,其中中性水基磁流体中粒子的分散性能最佳;经过离心后,3种水基磁流体中的粒子均产生了沉降,且酸性和碱性磁流体中的粒子比中性磁流体中的粒子沉降的多。在此基础上,对影响粒子分散稳定性的机理进行了初步探讨。     

Synthesis of Nickel Sulfide Powders by Thioacetamide in the Presence of Urea

Additions of urea were found to increase the yield of nickel sulfide formation from acidic solutions of thioacetamide. Two precipitation mechanisms were identified: hydrolysis and direct reaction between nickel and thioacetamide. Hydrolysis-controlled precipitation is evident with low initial pH. The direct reaction is dominant at high initial pH. Nucleation proceeds by a direct reaction between nickel and thioacetamide. The role of urea in precipitation of nickel was found to be twofold. Urea increases the rate of thioacetamide decomposition, thus increasing the concentration of H₂S form. Secondly, decomposition increases the pH of the solution, which in turn increases the relative concentration of S⁼ ions. Agglomeration of particles was more evident in the powders obtained in the presence of urea.     

可生物降解PBAT包膜尿素缓释肥料的制备与性能研究

以可生物降解PBAT为包膜材料,通过循环流化床工艺制备一系列PBAT包膜尿素缓释肥料,并对制备工艺进行了优化;通过扫描电镜观察包膜肥料表面形态特征,分析缺陷形成原因;通过水中静置法测试PBAT包膜尿素缓释肥料的缓释性能,测定缓释曲线,样品的初期释放率为20%~50%,第28天的累积释放率为70%~90%。     

Electrorheological properties of poly(o-anisidine) and poly(o-anisidine)-coated silica suspensions

Poly(o-anisidine) (PANs) and PANs-coated silica particles were prepared by oxidative polymerization of o-anisidine using ammonium persulphate in the absence and presence of silica particles, respectively. The entire surface of the silica particles was completely covered with PANs polymerized using low concentration of o-anisidine. The effects on the electrorheological behavior of surface modification of the silica particles coated with PANs were studied under oscillatory shear. Electrorheological properties of PANs and PANs-coated silica particle suspensions were found to exhibit higher performance in nonaqueous solutions than those of silica particle suspensions even at high temperatures.     

调理剂对醇酸树脂包膜尿素缓释性能的影响

以颗粒尿素为核心,醇酸树脂为膜材料,淀粉、高岭土、硅藻土、松香、氧化钙等为调理剂,制备了一系列不同膜厚度的包膜尿素。利用水浸泡法考察了调理剂种类及包覆量对包膜尿素的缓释性能的影响,并利用SEM对包膜尿素的表面及界面进行了观察。结果表明,醇酸树脂是一种良好的膜材料,实验所选用的几种调理剂中以高岭土的效果最好,淀粉的效果最差;粒尿素膜的包覆量的增加,缓释性能也逐渐加强。     

一种生物有机无机掺混肥料的生产与应用

介绍一种生物有机无机掺混肥料的原料组成、生产过程,以及其田间应用试验效果。该肥料由自制的包硫氮钾肥与颗粒增产菌剂、颗粒有机氮肥、高分子包膜尿素、大颗粒氯化钾、颗粒磷酸二铵及颗粒微肥（硫酸锌或硼砂）掺混而成,具有改良土壤、刺激作物生长、营养全面、养分利用率高的优势。其花生田间试验与施普通复混肥（15—15—15）比,增产率达14．2％。     

Fabrication of Machinable Silicon Carbide-Boron Nitride Ceramic Nanocomposites

SiC/BN nanocomposite powders with the microstructure of micrometer-sized SiC particles coated with nanometer-sized BN particles were prepared via a chemical reaction, which used a mixture of boric acid (H₃BO₃) and urea (CO(NH₂)₂) as reactants coated on the surface of the SiC particles to react under a nitrogen-gas atmosphere. The results of XRD, TEM, and SAED studies showed that the coating layer (BN) was composed mostly of amorphous and nanometer-sized BN particles at the reaction temperature of 850°C. When the nanocomposite powders were hot-pressed at 1850°C, machinable SiC/BN ceramic nanocomposites with fine grain size and homogeneous microstructure were fabricated. The composite that contained 20 wt% BN exhibited high strength (the three-point bending strength was 588.4 ± 26.8 MPa) and excellent machinability.     

包醛酶淀粉吸附性能的研究

本文介绍了肠溶制剂包醛酶淀粉在尿素溶液中的吸附性能，以及溶液的浓度，ｐＨ值，吸附剂用量对吸附性能的影响。结果表明，包醛酶淀粉的吸附速度大于包醛氧淀粉，吸附容量大约是包醛氧淀粉的４倍，当溶液ｐＨ〈４时，随着ｐＨ值减小，对溶液中尿素的吸附力迅速降低。     

Silver coating of spindle- and filament-type magnetic particles for conductive adhesive applications

Spindle-type hematite and magnetite particles and nickel filaments have been coated uniformly with silver by using chemical reduction. The effects of the reaction time and the concentration and nature of the reducing agent on the particle coatings were investigated at constant temperature. The reaction time had a pronounced effect on the nature of the coated surface layer. Coated and core particles were examined by scanning electron microscopy (SEM) and energy-dispersive X-ray analysis (EDAX). The electrical properties of the particles were also characterized. The conductivity of nickel filaments which can be oriented under a magnetic field for anisotropic electric conduction increased from 302 to 877 S/cm at 3.5 kPa pressure when coated with silver.     

Storage stability and solubility of poly(urea‐formaldehyde) microcapsules containing A‐olefin drag reducing polymer

Microcapsules containing α‐olefin drag reducing polymer were prepared by in situ and interfacial polymerization with urea, formaldehyde, and styrene as shell materials, respectively. IR spectrums of prepared shells indicated the formations of poly(urea‐formaldehyde) and polystyrene in the microencapsulating process. The morphologies of uncoated particles and microcapsules were observed by scanning electron microscopy (SEM) which proved that the α‐olefin drag reducing polymer particles were effectively coated. For the purpose of determining the stability of microcapsules in transportation and storage, the static pressure experiment was carried out and lasted for 6 months. In this process, microcapsules with polystyrene as shell material stuck together after 3 months; however, those with poly(urea‐formaldehyde) kept the state of particles. The thermal characteristics of uncoated particles (core), poly(urea‐formaldehyde) (shell), and microcapsules with that as shell material were characterized by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) which proved that thermal stable temperature of microcapsules containing α‐olefin drag reducing polymer with poly(urea‐formaldehyde) as shell material was below 225°C, and the mean heat absorbed by microcapsules in the temperature increasing process was 1.5–2.0 W/g higher than that by cores. The evaluation of drag reducing rate of microcapsules showed that the microencapsulating process had no influence on the drag reduction of α‐olefin drag reducing polymer. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

聚氨酯包膜尿素的制备

用异氰酸酯与聚氧化丙烯二醇(PPG)合成聚氨酯,再以其包裹尿素制成聚氨酯包膜尿素.采用比色法绘制聚氨酯包膜尿素的缓释曲线,讨论了异氰酸酯与羟基摩尔比(NCO/OH)、包膜率、反应方式、异氰酸酯、PPG分子量对包膜尿素缓释性能的影响.结果发现,以丙酮为溶剂,NCO/OH为1.1,在50～60℃的水浴温度下,PPG-300...