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Preparation and Characterizations of Tantalum Pentoxide (Ta2O5) Nanoparticles and UV-Curable Ta2O5-Acrylic Nanocomposites
(2010-08-05)
Huang, Heh-Chang
;
Hsieh, Tsung-Eong
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Tantalum pentoxide (Ta2O5) nanoparticles with the sizes in the range of 20-50 nm were prepared via a chemical route in which the oleic acid (OLEA) was adopted as the surfactant for the synthesis process. X-ray diffraction (XRD) revealed the as-synthesized Ta2O5 transforms from amorphous to hexagonal and ortho-rhombic structures at the temperatures of 700 degrees C and 750 degrees C, respectively, illustrating the suppression of recrystallization temperature of Ta2O5 due to the particle size reduction. UV-curable nanocomposites containing the Ta2O5 nanoparticles and acrylic matrix were also prepared. Thermogravimetry analysis (TGA) found an about 10-20 degrees C improvement on the 5% weight-loss thermal decomposition temperatures (T(d)s). Dielectric measurement showed that the dielectric constant of nanocomposite increases with the increase in the filler loading without severe deterioration of dielectric loss. The increment of dielectric constants was ascribed to the addition of high-dielectric inorganic fillers as well as the presence of interfacial polarization at the organic/inorganic interfaces. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 117: 1252-1259, 2010
Mechanical properties of nanocomposites with functionalized graphene
(2016-11)
Lee, Ming-Wei
;
Wang, Tai-Yuan
;
Tsai, Jia-Lin
;
機械工程學系
;
Department of Mechanical Engineering
The research investigated the thermal and mechanical properties of graphene/epoxy nanocomposites. Pristine graphene and functionalized graphene were used as nano-reinforcement in the nanocomposites. The graphene loadings employed in the nanocomposites were 0.1, 0.3, 0.5, and 1.0wt%. The functional groups grafted on the functionalized graphene were characterized through Fourier transform infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Results indicated that two kinds of functional groups are grafted on the functionalized graphene surfaces: one contains only COOH group and the other contains both COOH and NH2 groups. Moreover, from mechanical and thermal testing, it was found that the nanocomposites with functionalized graphene demonstrate better mechanical and thermal properties than those with pristine graphene. The graphene containing NH2 and COOH functional groups exhibits superior mechanical and thermal properties than the graphene with only COOH functional group. In addition, Young\'s modulus and thermal conductivity of the nanocomposites increase as the graphene loading increases. However, the fracture toughness and tensile strength of the nanocomposites attain peak values when the functionalized graphene loading is 0.1wt%. The effects of the functional groups on the mechanical and thermal properties of nanocomposites were elaborated using molecular dynamics (MD) simulation. It was revealed that the interfacial thermal conductance and normalized interaction energy increase between the functionalized graphene and epoxy matrix, which may be responsible for the enhanced mechanical properties in the functionalized graphene/epoxy nanocomposites.
Enhanced Magnetocaloric Effect Driven by Interfacial Magnetic Coupling in Self-Assembled Mn3O4-La0.7Sr0.3MnO3 Nanocomposites
(2015-12-09)
Vandrangi, Suresh K.
;
Yang, Jan-Chi
;
Zhu, Yuan-Min
;
Chin, Yi-Ying
;
Lin, Hong-Ji
Magnetic refrigeration, resulting from the magneto caloric effect of a material around the magnetic phase-transition temperature, is a topic of great interest as it is considered to be an alternate energy solution to conventional vapor-compression refrigeration. The viability of a magnetic refrigeration system for magnetic cooling can be tested by exploiting materials in various forms, from bulk to nanostrucutres. In this study, magnetocaloric properties of self-assembled Mn3O4-La0.7Sr0.3MnO3 nanocomposites, with varying doping concentrations of Mn3O4 in the form of nanocrystals embedded in the La0.7Sr0.3MnO3 matrix, are investigated. The temperatures corresponding to the paramagnetic-to-ferromagnetic transitions are higher, and the values of change in magnetic entropy under a magnetic field of 2 T show an enhancement (highest being similar to 130%) for the nanocomposites with low doping concentrations of Mn3O4, compared to that of pure La0.7Sr0.3MnO3 thin films. Relative cooling power remain close to those of La0.7Sr0.3MnO3. The enhanced magnetic phase-transition temperature and magnetocaloric effect are interpreted and evidenced in the framework of interfacial coupling between Mn3O4 and La0.7Sr0.3MnO3. This work demonstrates the potentiality of self-assembled nanostructures for magnetic cooling near room temperature under low magnetic fields.
Characterizing vibration damping response of composite laminates containing silica nanoparticles and rubber particles
(2015-03-01)
Huang, Chien-Yang
;
Tsai, Jia-Lin
;
機械工程學系
;
Department of Mechanical Engineering
This research aims to characterize the damping properties of fiber/epoxy composites containing different degrees of silica nanoparticles and rubber particles. Conventionally, adding rubber particles into fiber/epoxy composites would lead to dramatic reduction of stiffness although the vibration damping could be improved accordingly. In order to enhance the damping properties of the fiber composites without sacrificing the stiffness, silica nanoparticles together with rubber particles were introduced into the epoxy resin through the sonication process. The epoxy resin was then treated as matrix and impregnated into the fiber layer by means of the vacuum hand lay-up process to form the composite laminates. The vibration damping as well as the flexural stiffness of the fiber composite was measured using the forced vibration technique together with the half-power method. In addition, the vibration damping of the composite laminates, consisting of silica nanoparticles and rubber particles, was characterized using the micromechanical analysis. The repeated unit cell with the fibers displaying randomly in the matrix was employed to represent the microstructures of the unidirectional composites. The loss factor as well as the moduli obtained from the micromechanical analysis were regarded as the effective properties homogenizing within the fiber composites. In conjunction with the modal shapes, the vibration damping of the composite laminates with stacking sequence of [0](10), [90](10), [+/- 45](2s), and [90/0](2s) was calculated using the finite element analysis. Experimental results indicated that with the incorporation of the silica nanoparticles together with the rubber particles, the reduction of flexural stiffness of fiber composites, especially for the [90](10) laminates, was diminished while the damping properties of laminates were improved. Moreover, it was found that the effect of the particles in the [0](10) laminates is relatively minimal. The vibration damping responses of composites laminates obtained using the micromechanical analysis together with the modal analysis exhibit an agreement with the experimental data.
探討粉體類奈米複合材料之機械性質
(2008)
蔡佳霖
;
Tsai Jia-Lin
;
國立交通大學機械工程學系(所)
本研究旨在提出連續微觀力學模型，來描述以奈米尺寸的二氧化矽(Silica)球體為內含物，聚亞醯胺(Polyimide)奈米複合材料的機械性質。為了建立穩定且適合的二氧化矽/具聚亞醯胺奈米複合材料，藉由分子動力學(Molecular dynamic)模擬，依序完成NVT系綜及NPT系綜分析。模擬過程中檢查位勢能的變化，當能量在平均值附近變動持續一段時間，則系統達到平衡，且此分子結構達到了能量最低的狀態。藉由分子動力學模擬，可以分別計算出奈米內含物及週遭基材 (Matrix) 間的非鍵結間距(Non-bonded gap)，及非鍵結能量(non-bonded energy)。假設單位化後的非鍵結能量 (非鍵結能量除上內含物的表面積)，與球形內含物及其週遭基材互相作用之間，存在相互關係。接著發展包含球形內含物、基材以及等效介面層的三相連續微觀力學模型，以描述奈米複合材料的行為。在微觀力學模型中，等效介面層的尺寸假設為非鍵結間距，且藉由線性彈簧模型，可將單位化非鍵結能量對應為等效介面層的勁度。另一方面，由分子動力學模擬，分別給予分子結構三個方向微小的位移場，可直接計算出楊氏模數。此結果將與為微觀力學模型的結果比較。除了分子模擬之外，將利用拉伸以及破壞實驗研究球形內含物的奈米複合材料的機械性質。考慮20nm、200nm及1m三種不同的球形內含物，以瞭解內含物尺寸對於奈米複合材料之機械性質的影響。最後，實驗結果將與分子模擬以及連續微觀力學模型計算的結果，相互對照及比較。
添加氮化硼以提升高分子奈米複合材料之熱傳導性質
(2012)
林宏洲
;
LIN HONG-CHEU
;
國立交通大學材料科學與工程學系（所）
高分子導熱材料因具易塑性、加工易等優勢，廣泛應用於各項電子封裝產品；故熱穩定性佳、導熱性能佳、電氣絕緣性佳、施工簡便之導熱高分子材料具有潛力發展為先進之導熱封裝膠。在高分子材料中添加六方平面晶體的氮化硼 (Boron Nitride) 可形成導熱效率佳的高分子奈米複合材料 (nanocomposites)。因氮化硼價格較昂貴，可混掺廉價之Al2O3 以降低成本。但添加過多氮化硼(或氧化鋁)時，雖可提高導熱效率卻降低了高分子的加工便利性，因此如何添加最適量的氮化硼 (Boron Nitride)及Al2O3 於封裝膠可使得高分子奈米複合材料 (nanocomposites)達到最佳導熱效率是本計畫的研究重點。關
探討粉體類奈米複合材料之機械性質
(2007)
蔡佳霖
;
Tsai Jia-Lin
;
國立交通大學機械工程學系(所)
本研究旨在提出連續微觀力學模型，來描述以奈米尺寸的二氧化矽(Silica)球體為內含物，聚亞醯胺(Polyimide)奈米複合材料的機械性質。為了建立穩定且適合的二氧化矽/具聚亞醯胺奈米複合材料，藉由分子動力學(Molecular dynamic)模擬，依序完成NVT系綜及NPT系綜分析。模擬過程中檢查位勢能的變化，當能量在平均值附近變動持續一段時間，則系統達到平衡，且此分子結構達到了能量最低的狀態。藉由分子動力學模擬，可以分別計算出奈米內含物及週遭基材 (Matrix) 間的非鍵結間距(Non-bonded gap)，及非鍵結能量(non-bonded energy)。假設單位化後的非鍵結能量 (非鍵結能量除上內含物的表面積)，與球形內含物及其週遭基材互相作用之間，存在相互關係。接著發展包含球形內含物、基材以及等效介面層的三相連續微觀力學模型，以描述奈米複合材料的行為。在微觀力學模型中，等效介面層的尺寸假設為非鍵結間距，且藉由線性彈簧模型，可將單位化非鍵結能量對應為等效介面層的勁度。另一方面，由分子動力學模擬，分別給予分子結構三個方向微小的位移場，可直接計算出楊氏模數。此結果將與為微觀力學模型的結果比較。除了分子模擬之外，將利用拉伸以及破壞實驗研究球形內含物的奈米複合材料的機械性質。考慮20nm、200nm及1m三種不同的球形內含物，以瞭解內含物尺寸對於奈米複合材料之機械性質的影響。最後，實驗結果將與分子模擬以及連續微觀力學模型計算的結果，相互對照及比較。
Synthesis and characterization of novel organic/inorganic hybrid polymers containing polyhedral oligosilsesquioxanes
(2005-01-01)
Xu, HY
;
Gao, XY
;
Guang, SY
;
Chang, FZ
;
應用化學系
Hybrid polymers, poly(vinyl pyrrolidone-co-isobutyl styryl polyhedral oligomeric silsesquioxanes)s (PVP-POSS) were synthesized by one step polymerization and characterized using GPC and DSC. Addition of POSS significantly increases the Tg of polyvinylpyrrolidone at a fair high POSS content and obtained high molecular weight polymers with very narrow molecular distribution. The POSS content in the resulted hybrids can be controlled by varying the POSS feed ratio.
Size effect on fracture behaviors of epoxy composites with micron and nano alumina particles
(2007)
Tzeng, Shi-Hua
;
Tsai, Jia-Lin
;
機械工程學系
;
Department of Mechanical Engineering
This research is aimed to fabricate the nano and micron particle reinforced composites as well as to understand the particulate size effect on the mechanical behaviors of the composites. The stiffness, strength and fracture toughness were investigated in this study. Spherical alumina particles with diameters of 5 microns and 10-20 nano meters were dispersed respectively into the epoxy resin using the mechanical mixer followed by the sonication. To measure the stiffness and strength of the composites, coupon specimens were prepared and then tested in tension. On the other hand, the fracture toughness was evaluated by performing three point bending tests on the single edge notch bending specimens. Experimental results revealed that the Young's modulus of composites basically is not affected by particulate size; while, the tensile strength of the composites containing nano particles is higher than that with micron particles. From the fracture tests, it was indicated that the composites containing nano particles possess superior fracture toughness than the composites with micron inclusions.
Organoclay effect on transverse tensile strength and in-plane shear strength of unidirectional glass/epoxy nanocomposites
(2007)
Tsai, Jia-Lin
;
Wu, Ming-Dao
;
機械工程學系
;
Department of Mechanical Engineering
This research focuses on the fabrication of glass fiber/epoxy organoclay nanocomposites as well as on the investigation of organoclay effect on transverse tensile strength and in-plane shear strength of the nanocomposites. To demonstrate the organoclay effect, three different loadings of organoclay were dispersed respectively in the epoxy resin using a mechanical mixer followed by sonication. The corresponding glass/epoxy nanocomposites were produced by impregnating dry glass fiber with organoclay epoxy compound via a vacuum hand lay-up procedure. For evaluating transverse tensile strengths, the unidirectional coupon specimens were prepared and tested in the transverse direction. Results indicate that with the increment of organoclay loadings, the glass/epoxy nanocomposites demonstrate higher transverse tensile strength. On the other hand, the in-plane shear strengths were measured from [+/- 45] laminates. It is revealed that when the organoclay loadings increase, the in-plane shear strength of glass/epoxy nanocomposites also increases appropriately. Scanning Electron Microscopy (SEM) observations on the failure surfaces indicate that the increasing characteristics in transverse and in-plane failure stresses may be ascribed to the enhanced fiber/matrix bonding modified by the organoclay.

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