Dissertations / Theses on the topic 'Layed double hydroxides'

Dan Beaty (1937-2002) was a prolific composer, pianist, researcher, educator, and writer. His large compositional output included chamber works, choral works, songs, orchestral pieces, electronic music, and keyboard works. Beaty was well versed in traditional Western music as well as the more avant-garde and perplexing idioms of the twentieth century. Beaty's compositions reflect the many fascinating, if not always popular, musical trends of his time. His music encompasses styles from serial to jazz, shows compositional influences from Arnold Schoenberg to Indonesian music, and demonstrates thought-provoking and highly intellectual craftsmanship. This document explores several of Beaty's songs through a discussion of the composer's life and compositional process. Songs included in this document are Three Weeks Songs, October, November, A Sappho Lyric, Love Song, That Night When Joy Began, and War Lyrics. This document was written to accompany the author's DMA Lecture-Recital at the University of North Texas. Unfortunately, Beaty's vocal music was never published and is mostly unknown. One goal of the project was to initiate interest in Beaty's songs. Through this document, Lecture-Recital, and additional performances, considerable strides have been made to bring Beaty's songs to new audiences throughout the United States. In addition, the author has received permission from the Beaty family to publish Dan Beaty's songs.

Nanoparticles may affect secondary pollutants such as copper. Layer Double Hydroxides (LDH) are synthetically produced nanoparticles that adsorb copper via cation exchange. Pretreatment of copper test solutions with LDH nanoparticles followed by filtration removal of LDH nanoparticles demonstrated the smallest LDH aggregates removed the most copper toxicity. This was due to increased surface area for cation exchange relative to larger particle aggregates. Co-exposure tests of copper chloride and clay were run to determine if smaller clay particles increased copper uptake by D. magna. Coexposure treatments had lower LC50 values compared to the filtration tests, likely as a result of additive toxicity. LDH nanoclays do reduce copper toxicity in Daphnia magna and may serve as a remediation tool.

Hierarchical arrangement of biological composites such as nacre and bone containing high filler (ceramic) content results in high strength and toughness of the natural material. In this study we mimic the design of layered bone microstructure and fabricate an optimal multifunctional bio-nanocomposite having strength, toughness and corrosion resistance. Poly (butylene adipate-co-terephthalate) (PBAT), a biodegradable polymer was used as a substrate material with the reinforcement of LDH (Layered double hydroxide) as a nanofiller in different concentrations to achieve enhancement in mechanical properties as well as processing related thermostability. Corrosion resistance was increased by mimicking a layered structured which incorporated a tortuous diffusion path.

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Cálculos de primeiros princípios baseados na Teoria do Funcional da Densidade (DFT) foram utilizados para investigar propriedades estruturais e eletrônicas de Hidróxidos Duplos Lamelares (HDL) de composição Mg-Al-Tereftalato e Mg-Al-CO3 nas razões molares, x, de 0,25, 0,33 e 0,50. Foi feita uma análise estrutural, baseada na energia total com mapeamento angular do tereftalato (TA) e cálculos de RMN de carbono 13C, que demonstrou a existência de orientações preferenciais na região interlamelar. As diferenças de densidade de carga demonstraram maior transferência de carga das moléculas de água do que do ânion com as lamelas, sendo mais pronunciada em Mg-Al-TA com x = 0,50. O cálculo de ΔG de formação demonstrou que a síntese de Mg-Al-CO3 com x = 0,50 não é espontânea à temperatura ambiente, ao contrário do Mg-Al-TA. Apesar da relação entre as áreas ocupadas pelos ânion e moléculas de água por carga da lamela permitirem a acomodação na estrutura lamelar verificou-se que existe uma competição pelos sítios das lamelas. O resultado da otimização de geometria mostrou a preferência das moléculas de água formarem ligações de hidrogênio com as hidroxilas da lamela, que deslocam o carbonato no Mg-Al-CO3. Este íon passa então a adotar uma posição inclinada em relação à lamela, demonstrado pelos cálculos da energia de formação como sendo desfavorável. Foi simulada a desidratação do Mg-Al-TA e o acordo encontrado para a temperatura de desidratação reportada experimentalmente foi excelente. Foi observada uma modificação mensurável no deslocamento químico do 13C de um dos núcleos de carbono na nova orientação do TA na estrutura desidratada. A influência do cátion divalente nos HDL estudados foi verificada pela substituição do Mg2+ por Zn2+ ou Ni2+. Foram observadas diferenças nos parâmetros geométricos relacionadas à diferenças nos raios iônicos. A análise de carga de acordo com os critérios de Bader indicaram que as cargas dos átomos de oxigênio do TA e das moléculas de água não são alterados de forma significativa pelo tipo da cátion divalentes escolhido.
First principles calculations based on Density Functional Theory (DFT) were used to investigate the structural and electronic properties of Layered Double Hydroxides (LDH) of Mg-Al-terephthalate and Mg-Al-CO3 composition with molar ratios, x, of 0.25, 0.33 and 0.50. The structural analysis was based on total energy angular mapping of terephthalate (TA) and NMR calculations of carbon 13C, which demonstrated the existence of preferred orientations in the interlayer region. The charge density differences demonstrated greater load transfer of water molecules than the anion with the layer being more pronounced in Mg-Al-TA with x = 0.50. The calculated ΔG of formation demonstrated that the synthesis of Mg-Al-CO3 with x = 0.50 is not spontaneous at room temperature, unlike the Mg-Al-TA. Although the ratio between the areas occupied by the anion and water molecules per positive charge area permit the accommodation in the layer structure, it was found that there is a competition for the layer sites. The lower energy geometry optimization showed the preference of the water molecules to form hydrogen bonds with the hydroxyl groups of the layer, displacing the carbonate of Mg-Al-CO3. This ion then will adopt an inclined position regarding to the layer, shown by the Gibbs free energy formation to be unfavorable. The Mg-Al-TA dehydration reaction simulated found an excellent agreement with experimental values. A measurable change in the 13C chemical shift of the carbon nuclei was verified in the new position of the TA in the dehydrated structure. The influence of divalent cation was verified by substitution of Mg2+ by Zn2+ or Ni2+. Differences were observed in geometric parameters related to differences in the ionic radii. Charge analysis based on Bader criteria indicated no significant variation in oxygen atoms of TA and water molecules by the type of divalent cation chosen.

碩士
萬能科技大學
環境工程研究所
104
The possibility of removing boron from wastewater by synthesizing Ca2+ and Al3+ layer double hydroxides (LDHs) in situ was investigated using the method of putting Ca2+ and Al3+ into wastewater. Effects of Ca/Al and Al/B molar ratio, reaction temperature, and reaction time on the removal efficiency of boron were examined. It was found that for the Ca-Al system, the boron can be efficiently removed from synthetic raw water. Moreover, larger Ca/Al and Al/B molar ratio, lower reaction temperature, and longer reaction time could induce higher boron removal efficiency. For the practical glass wastewater, although the removal performance of boron might be affected in the existence of other high charge anions (e.g., ), it still reached 60% under the best operation conditions, implying this method might have a great application potential for the real wastewater systems. However, how to reduce the amounts of high charge anions should be firstly overcome.

博士
國立中興大學
材料科學與工程學系所
103
In this work, the Poly(ethylene adipate) (PEA)/organically modified layered double hydrogen silicates(OLDH) nanocomposites were prepared by solution blending method. The structure and morphology of nanocomposites were investigated using X-ray diffraction and TEM analysis. The results show that OLDH layers were randomly dispersed in the PEA matrix. Dynamic mechanical analysis (DMA) data shows the storage modulus of the 0.5 wt% PEA/OLDH nanpcomposite is 961 MPa, which is 3.4 times higher than pure PEA. The thermal properties of PEA and PEA/OLDH nanocomposites were also observed by TGA instrument. The thermal stability of PEA/OLDH nanocomposites was significantly lower than that of pure PEA matrix. These results are probably due to the presence of Mg and Al metals in PEA/OLDH nanocomposites that cancatalyze the depolymerization or inter- and intra-molecular transesterification reactions of the PEA resulting in their worse thermal stability. Effect of OLDH on the crystallization behavior was investigated using a diffential scanning calorimetry (DSC) and polarized optical microscopy (POM). Isothermal crystallization results of PEA/OLDH nanocomposites show that addition of OLDH into PEA induced heterogeneous nucleation effect, thus increasing the crystallization rate and reducing the surface chain folding energy. Non-isothermal crystallization behaviors of the PEA and PEA/OLDH were also discussed in detail. The biodegradability of PEA and PEA/OLDH nanocomposites have been investigated using the enzymatic degradation method with Pseudomonas fluorescens lipase at pH 7.2 and 37℃. Biodegradable behavior and mechanism of PEA and PEA/OLDH nanocomposites were studied by using the Differential Scanning Calorimetry (DSC), X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Gel Permeation Chromatography (GPC) and weight loss measurement. Effects of OLDH contents on the degradation behavior of PEA were also explored. The weight loss results reveal that the slower degradation rate of nanocomposites by the addition of OLDH as compared to the pristine PEA sample. These results suggest that the OLDH nanofillers play a major role in enzymatic hydrolysis reaction. The degradation of PEA was mainly due to the barrier effect of nanofillers and the lower available surface for enzymatic hydrolysis. The degradation mechanism of PEA due to the enzymatic hydrolysis is a complex process involving different phenomena, the preferential enzymatic degradation of the amorphous regions as compared to crystalline ones. The SEM micrographs of PEA and PEA/OLDH nanocomposites shown the formation of holes is the result of degradation taking place in the polymeric surface.

碩士
萬能科技大學
環境工程研究所
102
The possibility of removing anions from wastewater was investigated by putting cations into wastewater. It was found that this method might have a great application potential for the real wastewater systems. However, how to reduce both the sludge amounts and the chemicals costs should be firstly overcome.

碩士
國立臺灣科技大學
化學工程系
107
Nowadays, Electrical vehicle and metal-air battery has blossomed and attracted various of attention among people and these technologies usually require high efficiency on water splitting reaction. Water splitting(H2O→H2+1/2 O2), ideally driven by solar power, is one of the most efficient and sustainable ways to produce molecular hydrogen(H2) and oxygen (O2) gases in high purity. If available, water splitting would have the potential to solve the global urgent energy needs of future societies without any environmental cost. Water oxidation also known as oxygen evolution reaction(OER), one half-reaction of water splitting, has long been the bottleneck due to its four proton-coupled electron-transfer process that requires such a high redox potential. Herein, we report a newly designed OER nanocatalyst, NiFe LDH(Layered Double Hydroxide) based electrochemical catalyst is decorated by CeOx (CeOx/NiFe LDH), to improve its site activity and further the whole catalyst activity. Ni and Fe are earth abundant elements and their product NiFe LDH has been proved as a new benchmark in OER. Meanwhile, having little activity in OER, CeO2, still could be a nice synergistic catalyst and accelerate the dispersion rate of oxygen in OER revealed from some literatures. In this work, we try to combine these two composites and investigate how partial reduced CeO2 affect the activity of NiFe LDH. The 6.28%CeOx /NiFe LDH derived from the hydrothermal method, has an excellent specific activity(1 A/cm2Ni2+/3+) under 0.1M KOH, almost 5 folds higher than pure NiFe LDH. The XPS results show that there is a strong electronic interactions between NiFe LDH and CeOx and it leads to an enhanced OER performance. The stability of this catalyst could also be good for its 94% retention under 1M KOH for 24h. Nevertheless, due to the structural damage in NiFe LDH from the second hydrothermal treatment, mass activity of this catalyst is less satisfying. To further optimize the mass activity, we developed a catalyst, synthesized by the microwave method(6.4%CeOx /NiFe LDH). In this case, both better mass activity(40.3 mA/mgNiFeLDH at 1.54VRHE ) and specific activity(0.33A/cm2) could be achieved. The XAS result reveals that the decoration by CeOx could decrease the coordination number between Ni-O and Ni-M, creating a more loose structure and larger amount of oxygen vacancies. Finally, 6.4%CeOx /NiFe LDH with enhanced activity and long-time stability was successfully prepared.

碩士
中原大學
環境工程學系
106
The LDHs consisted of metal ions with two and three valence electrons, and anions including NO3-、CO32- . In this study, Mg2+ and Al3+ with molar ratio 3:1 and anions are added to solution containing chromate under the various pH values to synthesize LDHs. The adsorption rates and adsorption capacity for chromate are evaluated. For the structural memory effect, the LDHs can be synthesized using hydrothermal method, and then calcine them under different temperatures. The calcined LDHs mixed with chromate solution. The changes in chromate concentration in given period are analyzed. The chromate concentration change was measured at different times, and the adsorption rate and the maximum adsorption capacity were also calculated. The results showed that the four adsorbents of LDHs, C300-LDHs, C400-LDHs and C500-LDHs were all in accordance with the Langmuir model. The maximum adsorption capacities were: 185.19 (mg / g), 222.22 (mg / g), and 285.71 (mg / g), 357.14 (mg/g). The kinetic adsorption is in accordance with Pseudo second order kinetics, and the adsorption effect is: C500-LDHs> C400-LDHs> C300-LDHs. The in-situ removes the removal effect of dichromate from water 0.024 mol Mg(NO3)2‧6H2O、0.008 mol Al(NO3)3‧9H2O、0.0672 mol NaOH、0.0044 mol Na2CO3 as the best dosage.

碩士
中興大學
土壤環境科學系所
95
Chlorinated phenoxyacetic acid herbicides, such as 2,4-dichlorophenoxyacetic acid（2,4-D）, are widely used for controling weeds. Due to its low pKa value of 2.73, 2,4-D exists as an anionic species in the environment and has high mobility in soils and can easily migrate to non-target area by leaching. Layered double hydroxides (LDHs) have high specific surface area and anionic exchange capacity (AEC), so they have high potential in immobilizing inorganic and organic anion contaminants in water. However the adsorption is not specific to 2,4-D, and the existences of other anions may lower the adsorption efficiency of LDHs for 2,4-D. A better understanding of the adsorption mechanisms of LDHs will be essential for selective removal of 2,4-D by LDHs from water. In this study, the effects of the positive charge density and nitrate orientation of LDHs on the adsorption of 2,4-D were investigated. Mg/Al-NO3 LDH with Al3+/(Mg2++Al3+) molar ratios of 1/3 (LDH3), 1/4 (LDH4), 1/5(LDH5) were synthesized and used as the adsorbents. The kinetic study showed that the adsorption could reach equilibrium in 10 minutes. Among the samples, LDH3 has the highest layer charge density and contains nitrate with an orientation perpendicular to the hydroxide sheets, so the maximum adsorption of 2,4-D on LDH3 was as high as 89% of its anionic exchange capacity. The 2,4-D adsorption of LDH3 occurred mainly through ion exchange for interlayer nitrate. On the contrary, LDH5 with a low 2,4-D adsorption capacity due to the low accessibility of 2,4-D to the interlayer space. The accessibility was restricted by the small basal spacing of LDH5 as a result of the parallel orientation of the interlayer nitrate with respect to the hydroxide sheet. Thus, the 2,4-D adsorption occurred mainly on the external surface of the material, and the maximum adsorption of 2,4-D on LDH5 was 16 ％ of its anionic exchange capacity. For LDH4 that contains interlayer nitrate with both parallel and perpendicular orientations, the adsorption characteristics was between those of LDH3 and LDH5, and the maximum amount of 2,4-D adsorbed on LDH4 was 66% of the anionic exchange capacity. The results of competitive adsorption revealed that the adsorptions of 2,4-D on LDH3 and LDH4 are less affected by the coexistences of other anions, such as Cl-、Br 、NO3-、HCO3-、SO42-, in solution. The kinetic adsorption curves of LDH3 and LDH4 in different temperatures had a good fit with pseudo-second order kinetic model. The rate of the adsorption of 2,4-D on LDHs increasing with temperature, and LDH3 required more activation energy to adsorb 2,4-D then LDH4. The results of this study suggested that LDH3 is a better adsorbent for removing 2,4-D from water.

碩士
國立中興大學
化學系所
107
A layered double hydroxide (LDH) material was prepared and coated onto the surface of glassy fiber as a sorbent of solid phase microextraction (SPME) to collect halo-phenols in aqueous samples by headspace sampling for GC-ECD analysis. The LDH material was prepared by mixing magnesium nitrate and aluminum nitrate in water homogeneously and adjusted the pH to 10, then reflux for 24 hrs at 100 oC. After washing with water to neutral and then by alcohol, the LDH was formed posterior to dry in an oven. The SPME-LDH sorbent was prepared by dip-coating a glassy fiber into a mixed solution of LDH and silicone adhesive several times and dried vertically. The effectiveness of LDH fiber preparation was identified their functional groups by FT-IR, and the surface was observed with SEM. A headspace sampling of halo-phenols from 10 mL aqueous sample in a 20 mL sampling-vial was examined. Factors affecting the sampling such as the pH and temperature of sample, stir-rate, salting-out effect, and extraction time were optimized. Results indicated that the sampling was optimal at pH 2.0, 30% NaCl addition, 1000 rpm stirring at 60 oC for 35 min. For desorption and analysis by GC-ECD, detections are linear in 0.05 - 7.5, 0.01 - 1.5, and 0.005 - 7.5 μgL-1 for trichlorophenol, tetrachlorophenol, tribromophenol and pentachlorophenol, respectively, with correlation coefficients (R2) in 0.9960 - 0.9978. Detection limits are in 1.3 - 14.6 ngL-1 and method detection limits are in 4.4 - 48.5 ngL-1. The method was used to analyze four halophenols in river water and in farm-soil samples, and no residuals of halophenols was found. When spiked standards in samples and analyzed by the method, the recoveries of halophenols were in 86.6 - 98.3% with RSD in 2.4 - 7.4 %, and in 86.6 - 98.5 % with RSD in 2.8 - 7.7 %, respectively. The prepared LDH absorbent for SPME sampling with advantages of easy preparation, thermal stability, low-costs, high-enrichment, no carry-over, and no organic solvent required. Thus, it is a simple, rapid, sensitive, inexpensive, and eco-friendly sample preparation method.

碩士
國立中興大學
材料科學與工程學系所
101
The cost of mild steel build concentrated sulfuric acid storage tanks is much lower than the abovementioned stainless steels. However, the carbon steel has higher corro-sion rates than stainless steels.The corrosion of mild steel in the industry by concentrat-ed sulfuric acid is a great concern.The study explored the environmental clean method of the adhesion on coated JIS G3131 mild steel. The JIS G3131 samples were treated in pH 0.3 Mg2+/ Cl-/ HCO3–/ CO32– aqueous at 70 ºC with CO2 being bub-bling into the above solution continuously, and then immersing it in pH 12.0 HCO3‐/CO32‐ aqueous at 70 ºC. An Mn–Fe–CO3 LDH film was thus formed on the JIS G3131.According to corrosion test in aqueous 0.85M H2SO4, the Mn–Fe–CO3 LDH film coated sample had a much higher the corrosion resistance than the raw material (JIS G3131). The corrosion potential (E(corr)) of the coated mild steel sample was -0.386 V Ag/AgCl and corrosion current density (Icorr) of the coated mild steel sample was 14.87 A/cm2. (The JIS G3131 mild steel had Ecorr~-0.468 Ag/AgCl , and Icorr~738.3 μA/cm2 )

碩士
國立中興大學
材料科學與工程學系所
103
The Mg alloy applications for the automotive industry have received attention due to its light weight. Furthermore, magnesium alloys have high specific strength and low density. However, it has a poor corrosion resistance, and strength decreased rapidly when a fire occurs. Therefore, this study will improve corrosion resistance and thermal properties of AZ91D by the thermal barrier-corrosion prevention spray coating. In this research, the CaCO3/Ca3(SiO4)O-base powder mixed with SiO2 and Mg-Fe LDH powder to form a paste which sprayed on the surface of magnesium alloy AZ91D. The result of corrosion test show that the corrosion current density of 16 wt. % SiO2 addition was 12 μA•cm-2, 20 wt. % LDH addition was 8 μA•cm-2. Both conditions had a much higher the corrosion resistance than the raw material (AZ91D). The adhesion of coating increased with the drying time. Furthermore, the thermal barrier-corrosion prevention spray coating has a low thermal diffusivity than AZ91D (16 wt. % SiO2 addition was 2.9 mm2/s, AZ91D was 24.42 mm2/s). After Coating, the density of sample was about 1.84 g/cm3, only slightly higher than AZ91D (the density of AZ91D was about 1.8 g/cm3).