臺灣博碩士論文加值系統

本論文分為兩個部份,第一部份探討自燃法中時-空混沌燃燒波前
的定量(characterization of spatiotemporal chaos in SHS).我們對
於2Al+Cr2O3+xAl2O3--->2Cr+(1+x)Al2O3系統,在稀釋程度不同的條件下,
擷取其波前位置與時間關係的資料,利用Karhunen-Loeve procedure將所
獲得龐大的波前資料,壓縮成資料量小,但具有高準確度的一組時序向量.
並以此計算其correlation dimension做為混沌動態的定量.並由以全體波
前位置數據所計算出的fractal dimension明顯大於以局部數據所計算而
得的結果顯示,本系統的混沌燃燒波是與時間及位置同時相關的.
第二部份是探討以自燃法大量製備碳化矽(large-scale combustion
synthesis of silicon carbide).由於碳化矽的反應放熱量不是很高,實
驗中發現其軸向燃燒波前傳遞距離不遠(約6mm).因此我們嘗試壓製大小
為12cmx12cmx0.5cm的反應物薄片,以一排火口構成的乙炔-氧燄噴槍預熱
一分鐘後反應之,發現以研磨60分鐘的矽(<44 micron meter)與碳黑(<2
micron meter)之混合粉末,加入8wt.%PVA所壓製而成的反應物薄片,其SHS
反應情形良好.所得產物並以XRD及SEM分析其成份與結構.對產物薄片幾個
不同位置取樣之後測其產率,介於95%~100%之間.

The thesis contains two parts. The first part describes
thecharacterization of spatiotemporal chaos in SHS.
Spatiotemporally chaoticpulsating waves in the thermite reaction
2Al+Cr2O3+xAl2O3--->2Cr+(1+x)Al2O3for various degrees of
dilution were quantified experimentally. We use a statistical
tool called Karhunen-Loeve (K-L) procedure to compress this
large wavefront data to a small vector time series for analysis
with a greataccuracy. We compute correlation dimension to
quantify the chaotic dynamics.Results showed fractal dimension
obtained by the spatiotemporal data was muchlarger than those
obtained by the localized wave data. This shows that spatio-
temporal chaos is more adequate to be characterized by analyzing
the entirewavefront data using the proposed method in this
paper. The second part studies the possibility to large-
scale production ofsilicon carbide by the combustion synthesis.
Due to the low heat of formationof silicon carbide, we found
that the maximal wave propagating distance inaxial direction was
around 6 mm and that there was no limitation on the
radialdirection. Base on this finding, we try to make large but
thin reactant sheets(dimension: 12 cm x 12 cm x 0.5 cm) from
ground powders of silicon (<44 micronmeter), carbon black
(<2micron meter) and 8wt.% PVA. Reactant sheets were burn by an
oxy-acetylene torch in the air to carry out reactions. The
combustedproducts were analyzed by the XRD and the SEM, and
yields of different partsof products were determined. The XRD
analysis showed the products were mainlybeta-SiC. Yields were
ranged from 95% to 100% depending on the spatial locations of
products.