本文選題：木材　切入點(diǎn)：熱掃描顯微鏡　出處：《南京林業(yè)大學(xué)》2016年博士論文　論文類型：學(xué)位論文

【摘要】：導(dǎo)熱特性是材料最重要的物理性質(zhì)之一。木材是典型的多孔材料,宏觀尺度測(cè)定的木材導(dǎo)熱特性是木材結(jié)構(gòu)中固、液、氣三相共同作用的結(jié)果。隨著木材微納加工及重組技術(shù)研發(fā)工作的開展,獲得微尺度下木材中固相物質(zhì)的導(dǎo)熱特性具有重要意義,同時(shí)微尺度分析木材中固相物質(zhì)的導(dǎo)熱特性對(duì)木材宏觀尺度下導(dǎo)熱特性的理解也具有重要作用。另一方面材料導(dǎo)熱特性由材料的結(jié)構(gòu)與性質(zhì)所決定,材料的結(jié)構(gòu)與性質(zhì)發(fā)生變化將引起材料導(dǎo)熱特性的變化,由此分析材料的導(dǎo)熱特性也是研究材料結(jié)構(gòu)與性質(zhì)的重要途徑。掃描熱顯微鏡技術(shù)(SThM)是微尺度研究材料導(dǎo)熱特性的有效手段。本論文主要通過使用SThM研究木質(zhì)基材料的微觀導(dǎo)熱物性,從微觀導(dǎo)熱特性的角度分析木質(zhì)基材料的微觀結(jié)構(gòu)特征。主要研究?jī)?nèi)容包括如下方面:第一部分重點(diǎn)研究木材細(xì)胞壁的微觀導(dǎo)熱特性。同時(shí)基于木質(zhì)材料微觀導(dǎo)熱特性的研究,分析木質(zhì)材料的微觀組成與結(jié)構(gòu)的特性,重點(diǎn)從熱物性的角度解釋細(xì)胞壁不同壁層的結(jié)構(gòu)特征。第二部分使用SThM技術(shù)從導(dǎo)熱特性角度研究膠粘劑樹脂和木材膠合界面的結(jié)構(gòu)特征,基于在微觀尺度木材與膠粘劑樹脂導(dǎo)熱特性的差異,分析了樹脂在木材細(xì)胞壁和細(xì)胞腔中的滲透作用,為木質(zhì)復(fù)合材料結(jié)合特性的研究建立新的技術(shù)途徑。第三部分結(jié)合光譜分析技術(shù)、X射線衍射技術(shù)、納米壓痕等技術(shù)嘗試將SThM技術(shù)引入到木材熱解的研究工作中,重點(diǎn)研究熱解后木材細(xì)胞壁的化學(xué)組成、微觀構(gòu)造及物性的轉(zhuǎn)變,分析熱解過程木材化學(xué)、物理及微觀構(gòu)造特性轉(zhuǎn)變的相互關(guān)聯(lián)性。通過本研究開拓了木質(zhì)材料微觀導(dǎo)熱特性的研究途徑,開發(fā)了基于導(dǎo)熱特性分析的木質(zhì)材料微觀組成與結(jié)構(gòu)的研究方法。本文獲得的主要研究結(jié)果歸納如下:(1)使用SThM研究橡木纖維細(xì)胞壁在橫切面導(dǎo)熱特性的結(jié)果表明,細(xì)胞壁S2層的導(dǎo)熱能力要明顯高于胞間層(CML)和角隅(CC);顯微拉曼技術(shù)研究結(jié)果顯示S2層的纖維素含量較高;X射線衍射研究獲得纖維素在S2層中以約11°的纖絲角近似平行于細(xì)胞軸向分布排列的結(jié)論。在S2層中熱量順纖維紋路方向傳遞;而CML和CC中木質(zhì)素含量高,且CML和CC的化學(xué)成分中呈雜亂分布排列,沒有規(guī)則的紋路方向,因此此區(qū)域相比較S2層導(dǎo)熱能力要低。使用SThM在木材徑向解剖面對(duì)細(xì)胞壁進(jìn)行掃描成像,結(jié)果顯示從徑向?qū)?xì)胞壁施加熱量后細(xì)胞壁的不同區(qū)域(S2、CC和CML)沒有表現(xiàn)出導(dǎo)熱能力的差異。造成上述結(jié)果的機(jī)理是木材細(xì)胞壁徑向施加熱量后熱量在S2層的傳遞垂直于木材的微纖絲方向,即熱量沿木材橫紋方向傳遞;同時(shí)CC,CML區(qū)域化學(xué)成分排列成無序狀態(tài),因此從徑向施加熱量后,細(xì)胞壁不同區(qū)域表現(xiàn)出的導(dǎo)熱能力近似一致。本部分可得出結(jié)論,造成木材細(xì)胞壁不同區(qū)域?qū)崽匦缘牟町愔饕怯捎诓煌瑓^(qū)域組成成分的空間排列特征造成。木材導(dǎo)熱在宏觀尺度表現(xiàn)出典型的各向異性,本部分SThM實(shí)驗(yàn)研究表明細(xì)胞壁由于其自身構(gòu)造特征,在微尺度其導(dǎo)熱特性也表現(xiàn)出了各向異性的特點(diǎn)。(2)使用SThM研究木質(zhì)復(fù)合材料膠合界面結(jié)構(gòu)特征,從微觀導(dǎo)熱特性角度分析木材細(xì)胞壁與添加納米纖維素的酚醛樹脂的結(jié)合特征。研究結(jié)果表明酚醛樹脂在微尺度下表現(xiàn)出的導(dǎo)熱能力要明顯低于木材細(xì)胞壁。納米纖維素纖絲、納米纖維素晶體添加到酚醛樹脂膠中對(duì)微尺度下膠粘劑的導(dǎo)熱物性沒有造成影響。由于膠粘劑與細(xì)胞壁導(dǎo)熱特性的差異,從膠粘劑過渡到木材細(xì)胞壁有一個(gè)明顯的SThM探針電流值由小到大的過渡區(qū)間,此區(qū)間包含了膠合界面區(qū)域中的膠粘劑與木材基質(zhì)相互影響的區(qū)域和兩相物質(zhì)直接接觸結(jié)合的界面區(qū)。通過SThM掃描圖像分析確定了過渡區(qū)間的長(zhǎng)度,添加了納米纖維素晶體的酚醛樹脂與細(xì)胞壁的區(qū)間長(zhǎng)度為1.92±0.32μm,而添加納米纖維素纖絲的酚醛樹脂與細(xì)胞壁的區(qū)間長(zhǎng)度為1.76±0.277μm,其中膠粘劑與木材基質(zhì)直接接觸的界面區(qū)長(zhǎng)度分別為0.73±0.144μm和0.7±0.092μm。SThM的測(cè)試結(jié)果顯示在膠合界面附近的木材細(xì)胞腔中發(fā)現(xiàn)了膠粘劑的不連續(xù)滲透,即膠粘劑在個(gè)別細(xì)胞腔中充分充填。而根據(jù)探針電流分析結(jié)果顯示,細(xì)胞腔中的膠粘劑與膠合區(qū)的純膠粘劑的導(dǎo)熱物性有差異,原因是充填到細(xì)胞腔中的膠粘劑與細(xì)胞腔中原有的充填物進(jìn)行了混合,充填物在膠粘劑中的摻雜造成了細(xì)胞腔中膠粘劑的成分與性質(zhì)有別于純膠粘劑。(3)使用SThM研究熱解過程中木材細(xì)胞壁結(jié)構(gòu)轉(zhuǎn)變特性,SThM研究結(jié)果表明隨著熱解溫度的提高,木材細(xì)胞壁的壁層結(jié)構(gòu)直到300℃都能觀測(cè)到,而在325℃的熱解后,細(xì)胞壁橫切面反應(yīng)出細(xì)胞壁壁層結(jié)構(gòu)已經(jīng)消失,整個(gè)細(xì)胞壁結(jié)構(gòu)成均一化。SThM圖像識(shí)別細(xì)胞壁不同壁層,主要是基于壁層的導(dǎo)熱物性差異。造成不同壁層熱物性差異主要原因又是在S2層中熱量順紋傳遞,而CML區(qū)域結(jié)構(gòu)排列無序?qū)е聦?dǎo)熱能力不及S2層。經(jīng)325℃熱解后,細(xì)胞壁的微纖絲定向排列結(jié)構(gòu)特征已經(jīng)消失,即熱量在S2層中已無順紋傳遞的條件。紅外光譜研究表明,熱解溫度達(dá)到325℃后木材細(xì)胞壁的化學(xué)成分中纖維素和半纖維素已經(jīng)基本熱裂解。拉曼光譜同樣表明325℃木材細(xì)胞壁各區(qū)域的化學(xué)成分結(jié)構(gòu)已呈現(xiàn)均一化。元素分析也證實(shí)熱解溫度由300℃上升到325℃后,木材中的元素含量發(fā)生重大變化。X射線衍射表明熱解溫度到325℃時(shí)反應(yīng)細(xì)胞壁微纖絲定向排列的衍射峰已經(jīng)消失。使用納米壓痕技術(shù)對(duì)細(xì)胞壁的微觀力學(xué)性能進(jìn)行測(cè)試,結(jié)果表明達(dá)到熱解溫度300℃時(shí)木材細(xì)胞壁的彈性模量發(fā)生重大變化。本部分研究表明在木材熱解過程中細(xì)胞壁物理性質(zhì)、微觀構(gòu)造和化學(xué)成分轉(zhuǎn)變具有很強(qiáng)的相關(guān)性,SThM技術(shù)可以有效的應(yīng)用到木質(zhì)材料微觀物性與結(jié)構(gòu)轉(zhuǎn)變的研究工作中。
[Abstract]:Thermal conductivity is one of the most important physical properties of materials. Wood is a typical porous material, wood thermal properties determination of macro scale is wood structure solid, liquid, gas phase interaction results. With wood micro nano processing and recombinant technology research and development work, it is of great significance to thermal conductivity of solid materials in micro scale wood in the meanwhile, the micro scale analysis also plays an important role in the thermal conductivity of solid wood material to understand thermal characteristics of wood macro scale. On the other hand, the material thermal properties are determined by the structure and properties of materials, structure and properties of materials change will lead to changes in thermal properties of materials, which is an important way to heat analysis properties of materials is also on the material structure and properties. Scanning thermal microscope technology (SThM) is an effective means to study the characteristics of micro thermal conductivity materials. This theory This paper mainly through the micro thermal properties using SThM of wood based materials, analysis of microstructure characteristics of wood based materials from the micro angle thermal properties. The main contents include the following aspects: the first focuses on the micro thermal properties of wood cell wall. At the same time, based on micro thermal properties of wood materials, microstructure and properties analysis the structure of wood materials, mainly to explain the structure characteristics of different wall layer of the cell wall from the thermal point of view. The second part is the use of SThM technology from the thermal properties of adhesive resin and wood bonding interface of structural features, differences in micro scale wood and adhesive resin thermal characteristics based on the analysis of the penetration of resin in wood cell cell wall and cavity, for wood composite materials combining with the characteristics of the establishment of a new approach to the third part of the combination of spectral analysis. Technology, X ray diffraction technology, nano indentation technology to introducing SThM technology to the research work of wood pyrolysis, chemical composition of wood cell wall of pyrolysis, change the microstructure of transitivity analysis, the pyrolysis process of wood chemistry, relationship of the change of physical properties and microstructure of micro thermal conductivity approaches. Wood materials development through the study on the development of the characteristic analysis method for thermal conductivity of wood materials based on micro composition and structure. The main results obtained in this paper are summarized as follows: (1) SThM of oak fiber cell wall in cross section shows that thermal conductivity of the thermal conductivity of cell wall layer was higher than that of S2 the cell layer (CML) and corner (CC); micro Raman spectroscopy study showed higher cellulose content in S2 layer; X ray diffraction of cellulose in the S2 layer to about 11 degrees The microfibril angle approximately parallel to the axial distribution of cells arranged. Conclusion in the S2 layer along the fiber texture direction of heat transfer; while CML and CC in high lignin content, and chemical composition of CML and CC in a random arrangement, ridge orientation with no rules, so this area compared to the S2 layer to low thermal conductivity. The use of SThM in the wood cell wall face radial anatomy imaging, results from different regions of the cell wall of radial cell wall after applying heat (S2, CC and CML) showed no difference in conductivity. The mechanism of causing these results is the wood cell wall heat transfer in heat applied radial microfibril the direction perpendicular to the wood of the S2 layer, the heat transfer along the wood grain direction; at the same time CC, CML regional chemical components are arranged in a disordered state, so the heat is applied from the radial, approximate conductivity of cell wall in different regions show Consistent. This part can be concluded, caused by differences in thermal properties of wood cell wall in different regions is mainly due to the different components of the spatial arrangement of regional characteristics. By wood heat conduction exhibit anisotropy typical on the macro scale, experimental study of this part of SThM showed that the cell wall due to its structural characteristics, its thermal properties in micro scale show the anisotropic characteristics. (2) using the characteristics of SThM research of wood composite bonding interface structure, from the perspective of micro thermal characteristic analysis of wood cell wall and adding nano cellulose phenolic resin bonding characteristics. The research results show that the thermal conductivity showed phenolic resin under micro scale was significantly lower than that of wood cell wall. Nano fiber, nano crystalline cellulose added to the thermal properties of micro scale adhesive phenolic resin without impact. The adhesive The difference of thermal conductivity and cell wall properties of the agent, the adhesive transition to the wood cell wall has an obvious transition interval SThM probe current value increases, the interval contains the interface region and two-phase material adhesive and wood matrix bonding interface in the area of mutual influence in direct contact with the transition interval length is determined. Through SThM image analysis, add the interval length and cell wall phenolic resin nano crystalline cellulose was 1.92 + 0.32 m, interval length and cell wall phenolic resin and nano cellulose fibrils was 1.76 + 0.277 m, of which the length of the interfacial area directly contact adhesive and wood matrix were 0.73 + 0.144 m and 0.7 + 0.092 m.SThM test results show that the adhesive is not found in the continuous penetration of the wood cell cavity near the interface bonding, the adhesive in the individual cells in the cavity filling According to the current probe points filling. Analysis results show that the thermal properties of adhesive and bonding area of cells in the cavity of pure adhesive has the difference, reason is filling the original adhesive and cell cavity filling into cells in the cavity were mixed, filling in the adhesive and the doping caused the composition and properties of adhesives in the cell cavity is different from the pure adhesive. (3) the wood cell wall structure using SThM on the pyrolysis process of transition, SThM results show that with increasing pyrolysis temperature, wood cell wall lining structure until 300 degrees can be observed, while in the pyrolysis of 325 DEG C, the reaction cross section of the cell wall a cell wall layer structure has disappeared, the cell wall structure into a normalized.SThM image recognition of different cell wall layers, is the main difference between thermal wall layer. Based on differences in wall thermal properties is the main reason In the S2 layer heat transfer along the grain, and the CML regional structure disorder lead to heat capacity is less than the S2 layer. By 325 DEG C after pyrolysis, microfibril orientation of cell wall structure characteristics have disappeared, the heat in the S2 layer has no grain transfer conditions. FTIR analysis showed that the chemical composition of cellulose pyrolysis temperature up to 325 DEG C after the wood cell wall and hemicellulose pyrolysis has been basically. Raman spectroscopy also shows that the chemical composition of wood cell wall structure 325 degrees each area has been normalized. Elemental analysis also confirmed that the pyrolysis temperature increased from 300 to 325 DEG C., element content in wood changed.X X-ray diffraction show that the diffraction peaks of the pyrolysis temperature to 325 DEG C when the reaction cell wall of microfibril orientation has disappeared. The micro mechanical properties of the cell wall using nanoindentation test results show that the pyrolysis temperature reached 3 The elastic modulus of wood cell wall at 00 C with significant changes. This part of the study showed that in the pyrolysis process of wood cell wall in physical properties, microstructure and chemical composition change has a strong correlation, SThM technology can be applied to study changes in the micro material of wood material and structure effective.

【學(xué)位授予單位】：南京林業(yè)大學(xué)
【學(xué)位級(jí)別】：博士
【學(xué)位授予年份】：2016
【分類號(hào)】：S781

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4 孫U，

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