共查询到19条相似文献,搜索用时 312 毫秒
1.
2.
3.
4.
5.
6.
7.
大多数材料在被拉往一个方向时,另一方向就会变薄,这类似于橡皮筋被伸展时的表现.不过,一种被称为"巴基纸"的碳纳米管在伸展时可增加宽度,在均匀压缩时长度和宽度均可增加. 相似文献
8.
9.
阐述了小麦秸秆焚烧、堆放产生的污染环境问题及其危害,分析了小麦秸秆污染控制困难的原因,提出了采取因地制宜利用、综合管理、改造农业机械功能等方面的防治对策。 相似文献
10.
11.
12.
用电子自旋共振波谱仪研究麦秸中的自由基 总被引:7,自引:0,他引:7
借助于电子自旋共振波谱仪研究了紫外光、温度、胶粘剂和机械加工对麦秸中自由基的影响。结果表明:反映麦秸自由基特征量的g因子与木材的g因子具有相同的数值。机械加工对木材及麦秸中自由基的影响相似,麦秸被加工越细小,其自由基含量越高,但麦秸的自由基含量要明显低于木材,麦秸形态变化后自由基的比例也明显低于木材,外界温度变化可以影响麦秸的自由基浓度,100℃之前,此影响不显著,100℃后,麦秸的自由基浓度明显上升,紫外光的照射对麦秸自由基浓度有影响,随着紫外光照射时间的延长,麦秸中自由基浓度逐渐增加,但增中值不大,并趋于稳定,麦秸中的自由基与胶粘剂之间可以发生利用,麦秸与秸中自由基浓度逐渐增加,但增加值不大,并趋于稳定。麦秸中的自由基与胶粘剂之间可以发生作用,麦秸与脲醛树脂胶反应后,其自由基含量略有减小。而麦秸与异氰酸酯反应后,其自由基含量有较大程度的降低。 相似文献
13.
14.
We compared the chemical composition of wood fibres and fibre surfaces of several eucalypt species and hybrids originating
from various growth sites in South Africa. The objective was to test for differences in chemical surface composition due to
genetics or site with the ultimate aim to facilitate a tailor-made supply of wood for pulping that results in an optimal blend
of fibres that can be pulped together with similar yields. This, however, requires a sound knowledge of the fibre properties.
The surface functionality on the single fibre level is a key property, because it determines how good inter-fibre bonding
will be when paper is formed, which depends amongst other fibre properties on the amount of free hydroxyl groups that are
available and therefore on the cellulose content on the fibre surface. The cellulose and lignin content on the fibre surface
were determined with chemical force microscopy, a variation of atomic force microscopy. Since the general bulk composition
of the fibre and the surface composition might differ, both parameters were determined. We found significant differences in
the cellulose and lignin content on fibre surfaces, with regard to genotype and site, respectively. In some, but not all,
cases, the surface composition of wood fibres followed the bulk composition, and differences were generally more pronounced.
Differences due to genotype were significant, especially with regard to the surface lignin content—but variation due to site
was also distinctly recognisable. This variation in surface functionality could be the reason why some pulpwood blends result
in a lower pulp yield and different quality. 相似文献
15.
16.
研究表明黑荆木材1—3年生密度为0.59—0.65g/cm3,5—10年生为0.72g/cm3;1—7年生木材成分变化不大,纤维素在45%以上,半纤维素在25%以下,木素在21%以下。比较6年生黑荆木材及其KP、CTMP的纤维形态,纤维长度在0.76mm以上的,木材为72.04%、Kp为72.22%、CTMP为82.58%;平均纤维长度木材为0.856mm、KP为0.845mm、CTMP为1.165mm;纤维宽度在12一24μm,木材为92.62%、KP为92.86%、CTMP为34.63%;平均纤维宽度木材为15.6μm、KP为15.8μm、CTMP为30.7μm;长宽比木材为54.9、KP为53.3、CTMP为37.9。 相似文献
17.
蒸汽爆破-乙醇蒸煮两步法预处理对麦秆结构的影响 总被引:1,自引:0,他引:1
对麦秆采用先蒸汽爆破后乙醇蒸煮的两步法进行预处理,研究预处理对麦秆组分及结构变化的影响。蒸汽爆破过程实验条件选取200 g绝干麦秆,压力1.75 MPa和时间3.5 min。乙醇预处理过程选取80 g蒸汽爆破麦秆(绝干),55%乙醇,两者固液比1∶5(g∶mL),温度170℃、时间30 min。通过高效液相色谱法测定,预处理最终产物组分中半纤维素降低89%左右,木质素降低35%左右。采用红外光谱、纤维形态分布分析及SEM分析对预处理过程中麦秆结构变化情况进行研究,结果表明:蒸汽爆破过程破坏了半纤维素酯键连接且半纤维素降解非常明显,但对纤维素链结构影响和降解作用相对较低;麦秆经过蒸汽爆破预处理后,纤维平均长度明显降低,而平均宽度却显著增加;再经乙醇预处理后纤维平均长度基本保持不变,但平均宽度降低;经两步预处理后麦秆纤维的天然物理结构由紧密到蓬松,纤维束呈松散状态且纤维表面基本无碎片附着物,利于后续加工利用。 相似文献
18.