Papers by Keyword: LDH

Abstract: The main perspective of this paper is enhancing the physico-mechanical and protective characteristics of concrete. This was achieved by incorporation Layered double hydroxide (LDH) in mix design of concrete with different doses. The concrete specimens were prepared with LDH percentages (0.5, 1.0, 1.5, and 2) % by the cement weight. After the characterization of LDH, the prepared concrete specimens were investigated as follows: the workability and density of the fresh concrete, effect of the addition of LDH on the compressive strength of hardened concrete were determined. The protective performance of concrete was evaluated by determining water absorption, contact angle, and chloride permeability. The obtained results detected that the physico-mechanical and protective performance of concrete are enhanced gradually by the addition of LDH up to 1.5% as follows; concrete slump decreased from 110 mm for control sample (concrete without LDH addition) to 47mm for M3 sample (concrete with 1.5% LDH) by 57% decrease percent. Density of concrete with 1.5% LDH increased by 5% as compared with control sample. Compressive strength increased by 25% for concrete with 1.5% LDH as compared with controls one. On the same time experimental results demonstrated that both water absorption and chloride permeability were decreased by 20% & 43% respectively, meanwhile contact angle increased by 24% for the same comparative samples. After this percent (1.5%), LDH is agglomerate and therefore unable to disperse uniformly so the optimum calculated percent of LDH for enhancing concrete performance is 1.5%.

Abstract: Novel ordered Ultra thin Films (UTFs) based on the hybrid assembly of exfoliated Zn-Cr Layered double hydroxide (LDH) monolayers and typical dawson-type polyoxometalate (POM) anions α-P₂W₁₈O₆₂^6- (P₂W₁₈) were prepared by utilizing a layer by layer (LBL) technique. The structural integrity of the UTFs were characterized by ICP-AES, XRD, IR, UV/DRS, indicating that the Dawson structures remained intact in the hybrid compositions. The morphology and the thickness of the UTFs were evaluated via SEM. The visible light photocatalytic performances of the UTFs were tested in the degradation of aqueous azo dye Congo red (CR). The UTFs showed much higher photocatalytic activity than pure Zn-Cr-NO₃^- LDH, mainly attributed to the improved absorbance and response ability to the visible light.

Abstract: The novel TiO₂/graphene sheet (TiO₂/GSs) nanocomposites were synthesized using graphene oxide sheets and TiCl₃. All target composites were characterized by transmission electron microscopy (TEM), X-ray electron diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and energy dispersive X-ray spectra (EDX), and the surface areas were tested with the Brunauer-Emmett-Teller (BET) method. We studied the cytotoxicity of TiO₂/GSs nanoparticles on A549 cells by examining the influence of TiO₂/GSs on cell morphology and viability by methyl thiazolyl tetrazolium (MTT) assay. We also determined membrane integrity and apoptosis of A549 cells after different doses of TiO₂/GSs exposure by LDH assay and flow cytometry. Assay of A549 cell viability showed regular reductions with a time-and dose-dependent tendency after exposure to pure TiO₂, TiO₂/4.2wt% GSs and TiO₂/6wt% GSs for 24 hrs or 48 hrs. The LDH released and cellular apoptosis also had a dose-dependent effect, which was associated with the surface area of TiO₂/4.2wt% GSs. Our results provide essential knowledge of the acceptable biocompatibility of TiO₂/GSs nanocomposites, and only when cells were exposed at a high concentration (≥50 μg/mL), and for a prolonged period of time did TiO₂/GSs nanoparticles exhibit minimal cytotoxicity against A549 cells.

Abstract: A Mg–Al layered-double hydroxide (LDH) intercalated by sulphonato-salhen-chromium (III) complex was prepared and then used to the selective oxidation of benzyl alcohol by 30% H₂O₂. without any organic solvent, phase transfer catalyst or additive. The results revealed that the LDH hosted chromium complex exhibited much higher catalytic performance than its homogeneous analogue. Under the optimal reaction conditions, the highest conversion of benzyl alcohol reached 52.1%, with 100% of the selectivity to benzyldehyde.

Abstract: Object: The antioxidant dose-effect relationship and the mechanism of Xiongma Dripping Pills were study to explore the protective effects of oxidative damage in PC12 cells of different doses of Xiongma Dripping Pills containing serum. Method: Oxidative stress injury model of PC12 cells was established by peroxide hydrogen (H₂O₂), sodium nitroprusside (SNP), content and cell culture supernatant lactate dehydrogenase (LDH) and the liquid content of glutathione peroxidase (GSH-PX) were detected by chemical colorimetric determination. Results: There was a plasma concentration peaked in Xiongma Dripping Pills 8 times (6g•kg^-1) dose group, ferulic acid plasma concentration was 10.59 ± 2.92, the plasma concentration gastrodin 18.13 ± 4.63. H₂O₂ and SNP could cause injury in PC12 cells, and increased LDH leakage, reduce the content of GSH-PX (P<0.01). Gung Ma the Dripping Pills can reduce LDH leakage, increase the content of GSH-PX. Xiongma Dripping Pills 8-fold dose group content is the most significant.Conclusion: There was a significant protective effect on Xiongma Dripping Pills serum containing H₂O₂ and SNP induced oxidative damage of PC12 cells and its mechanism was relevant with clearing the free radicals, enhanceing antioxidant enzyme activity in vivo. There was the most significant effect on Xiongma Dripping Pills 8-fold dose group, and there was positive correlation on plasma concentration and pharmacological effects.

Abstract: A series of polystyrene (PS) nanocomposites with various concentration of organomodified Ni-Al LDH (3, 7 wt%) were synthesized by solvent blending method and the effect of Ni-Al LDH content on the thermal properties and degradation kinetics of PS/ Ni-Al LDH nanocomposites was examined. Thermogravimetric analysis (TGA) was employed to evaluate the thermal properties of the prepared PS nanocomposites with various content of Ni-Al LDH. The obtained TGA results reveal that the PS/Ni-Al LDH nanocomposites exhibits enhanced thermal stability when compared with pure PS and the thermal stability of the nanocomposites increase with an increase in the LDH content from 3 to 7 wt%. When 15% weight loss is selected as a point of comparison, the thermal decomposition temperature of the PS/Ni-Al LDH nanocomposite containing 7 wt% of LDH is about 28°C higher than that of pure PS. The thermal degradation kinetics of the nanocomposite materials are investigated using two kinetic models such as Flynn-Wall-Ozawa method and Friedman method. The improvement of thermal stability of the nanocomposites with increasing LDH content is also validated by increasing the activation energies.

Abstract: Magnesium alloys exhibit poor formability at room temperature because of their hexagonal close packed (hcp) structure. The grain refinement can improve its ductility and formability. Friction stir processing (FSP) is an emerging solid state surface modification technique that can produce homogeneous microstructure with fine-grains in a single pass. The effect of friction stir processing variables that can affect tensile strength and formability of magnesium AZ 31B alloy are studied. The formability of friction stir processed sheet was studied by limiting dome height (LDH) test in plane-strain deformation condition. The results indicate that the tensile properties and formability are improved by friction stir processing. The objective of the present work is to establish randomisation of texture to increase work hardening exponent by favourably orienting a large number of grains (texture) in AZ31 alloy to improve its stretch formability by promoting additional straining in thickness direction. Keywords: Friction stir processing, LDH, Formability, etc.

Abstract: Lamellar hydrotalcite (HT) was synthesized in the laboratory following combustion method. Tapai fueled HT was found to exhibit more orderly packed microstructure and was more crystalline in nature than its urea fueled counterpart, particularly at higher combustion temperature. The pore structure of tapai fueled HT resembled that of bottle neck with possibility of tapered with open-end that might also be present. The crystal size of tapai fueled HT was larger than urea fueled HT but greater size reduction was experienced by the former material, suggesting that more energy might have been supplied to the sample to disintegrate the particles, since tapai has higher and cleaner carbohydrate source than urea.

Abstract: PS/LDH nanocomposites were synthesized via in-situ polymerization technique using styrene monomer with toluene as a solvent. A series of LDHs (Mg-Al, Co-Al, Ni-Al, Cu-Al, Cu-Fe and Cu-Cr LDHs) was first prepared from their nitrate salts by co-precipitation method. The above prepared, pristine LDHs were organically modified using sodium dodecyl sulfate (SDS) to obtain organomodified LDHs (OLDH). Then, PS nanocomposites containing 5 wt.% OLDHs were prepared by in-situ polymerization method. The structural and thermal properties of LDHs and corresponding nanocomposites were characterized by X-Ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA). The absence of OLDH peak (003) in the XRD patterns of PS/OLDH nanocomposite confirms the formation of exfoliated nanocomposites. The presence of sulfate groups in the modified LDHs is confirmed by FTIR analysis. The appearance of new peaks in the FTIR spectra in the region of 3400-3500 cm^-1, 1670-1680 cm^-1 and 1200-1260 cm^-1 for O-H stretching, H-O-H vibration and stretching vibration of sulfate, respectively indicate the existence of LDHs in the PS/OLDH nanocomposites. The entire exfoliated PS/OLDH nanocomposites exhibit enhanced thermal stability relative to the pure PS. When 50% weight loss is selected as point of comparison, the decomposition temperature of nanocomposites is about 3-5^o C higher than that of pure PS.

Abstract: The objective of this work is to investigate the influence of LDH loading on the thermal stability and thermal degradation kinetics of the PP/Ni-Al LDH nanocomposites using thermogravimetric analysis (TGA) and to compare the results with that of the neat PP. For this, Ni-Al LDH was first prepared by co-precipitation method at constant pH using their nitrate salts and subsequently organically modified using sodium dodecyl sulphate (SDS) by regeneration method. A series of novel PP/Ni-Al LDH nanocomposites was then prepared with various amounts of LDH by melt intercalation method. The XRD results confirm the formation of exfoliated PP/LDH nanocomposites. PP/LDH nanocomposites exhibit enhanced thermal stability relative to the neat PP due to the presence of barrier effect of LDH lamellar layers and the thermal stability of the nanocomposites also increases with increase in the LDH loading. When 10% weight loss is selected as a point of comparison, the decomposition temperature of PP/LDH (5 wt %) nanocomposite is 15 oC higher than that of neat PP. The thermal degradation activation energy of the nanocomposites is determined via Coats-Redfern method and compared with that of neat PP. The improvement of thermal stability of PP nanocomposites is also confirmed by increasing the activation energies (Ea) and the integral procedural decomposition temperature (IPDT) compared with neat PP. Criado method is finally used to determine the degradation reaction mechanism of various samples.