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本文针对原有杨树常规杂交育种技术体系的不足,进行了四个方面的改进:将原有两种控制授粉技术-室外大树搭架法杂交和室内切枝水培法杂交改进为室外植株斜置法和室外切枝扦插法;通过借鉴棉农棉花育苗技术,总结了一个简易、经济、出苗率高的杨树播种育苗新技术-营养钵直播直移法;提出了芽保存率、苗期节间距、冠径比等几个新指标,丰富了杨树常规育种的选择指标体系;建立了基因库与试验林二元路线选择法。 相似文献
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Porous sol-gel glass of CaO-SiO2-P2O5 system with macropores larger than 100 μm was prepared by adding stearic acid as pore former when the sintering was carried out at 700 ℃ for 3 h. The sol-gel porous glass shows an amorphous structure. The diameter of the pore created by pore former varies from 100 to 300 μm, and macroporous glass has a narrow and small pore size distribution in mesoporous scale. The porosity and pore size ofmacroporous bioactive glass can be controlled. 相似文献
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用燃烧合成法制备纳米氧化锌 总被引:4,自引:0,他引:4
以尿素或三(羟甲基)氨基甲烷(THAM)为燃料,以硝酸锌为锌源和氧化剂,采用燃烧合成的方法制备了纳米氧化锌。由于反应物吸水,直接将它们混合就可以得到均匀的浆状先驱物;这种先驱物可以在电炉上加热点燃,得到蓬松的泡沫状纳米氧化锌。探讨了燃料和氧化剂配比对反应的影响,发现燃料过剩是自蔓延高温合成的必备条件。采用X-射线衍射、透射电镜以及比表面分析等方法对所制得的粉末进行表征。结果表明:燃烧法可以制备纳米氧化锌,具有简单,快速,便宜的优点。 相似文献
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聚L-乳酸(PLIA)是具有良好生物相容性和生物降解性的半结晶聚合物,其热稳定性较差,在加工中的热处理会造成材料严重降解,使其相对分子质量显著下降,机械性能明显降低。该文作者通过试验、分析,研究了加热时间和加热温度对提纯与未提纯PLLA降解的影响,并结合降解机理对其原因进行探讨。结果表明,当温度升高到180℃以上时,在aomin内PLLA的相对分子质量即减小一半;提纯后的PLLA模压最佳加热温度为185℃。 相似文献
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Shear-thickening rheological response of PCC/PEG suspensions 总被引:1,自引:0,他引:1
The steady and dynamic rheological behaviors of precipitated calcium carbonate (PCC) suspension in polyethylene glycol (PEG)
were investigated on a TA AR2000ex rheometer. Under steady shear consistency index K and flow exponent N of suspensions with different volume fractions were determined. The shear-thinning and the discontinuous shear-thickening
behavior were observed at different constant frequencies from 10 to 100 rad/s. The relationship between the complex viscosity
and the constant frequency were determined. As the volume fraction increases, flow exponent N shows a rapid increase, and it increases dramatically when the discontinuous shear-thickening takes place, while consistency
index K decreases. Dynamic oscillatory shear experiments were conducted at constant strain amplitude and constant frequency, respectively.
For the frequency sweep, the system shows viscous property in entire range of the frequency investigated, and the complex
viscosity shows discontinuous jump at a critical frequency of 10 rad/s. For the strain sweep, on the other hand, at low strain
the elastic modulus is strongly dependent on the strain, and the viscous modulus is independent of the strain. But at the
critical strain point both of the moduli show an abrupt jump and the system transits from elastic to viscous at a strain of
0.1. 相似文献
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HA-316L不锈钢纤维非对称功能梯度生物材料制备与显微组织 总被引:3,自引:0,他引:3
用低压热等静压方法在1100℃下制备了HA(ZrO2)-316L不锈钢纤维非对称FGM,其中316L不锈钢纤维含量按体积比20%→15%→10%→5%呈非对称梯度变化.并通过金相显微镜、SEM、EDXA分析了材料的微观结构和微区元素含量.结果表明,HA(ZrO2)-316L不锈钢纤维非对称FGM微观上表现为316L不锈钢纤维在FGM中呈无序、均匀分布状态,316L不锈钢纤维包裹于HA(ZrO2)基体中,两者结合紧密,界面表现为部分凹凸不平,316L不锈钢纤维与HA(ZrO2)基体紧紧的咬合在一起.在FGM基体中发生了微量的韧化相Fe元素扩散,韧化相316L不锈钢纤维不发生基体相Ca、P元素的扩散,基体与韧化相均相对独立,二者之间不发生任何化学反应.随着HA含量增加,HA(ZrO2)-316L不锈钢纤维复合材料的断裂韧性和弹性模量逐渐减小,体现了FGM中各梯度层的力学性能缓和设计.HA(ZrO2)-316L不锈钢纤维FGM中,分析认为,增韧机理主要为纤维拔出增韧和层间裂纹偏转增韧. 相似文献
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采用热压工艺制备了HA/316L粉非对称生物功能梯度材料(FGM)。HA/316L粉非对称生物FGM在宏观上呈现明显的梯度,微观上则表现出成分连续变化,且各成分分布均匀、弥散。在各梯度层内部及界面都没有裂纹及大孔洞出现,界面结合紧密。随着316L粉的含量增加,韧窝的数量逐渐增加,韧窝形貌由浅变深,边缘由尖锐逐渐变得圆滑,表明材料由脆性断裂向韧性断裂转化。纯HA梯度层为典型的脆性断裂,HA80/316L和HA60/316L梯度层表现为典型的晶间断裂,HA40/316L和HA20/316L梯度层断裂性质为晶间断裂中掺杂有韧性断裂,而316L梯度层则表现为典型的韧性断裂。316L粉的加入改变了HA/316L粉生物FGM各梯度层的断裂方式,从而提高了材料的力学性能。从整体上而言,HA/316L粉生物FGM主要增韧机制包括层间裂纹偏转增韧与裂纹偏转增韧。 相似文献