Influence Of TiO2 Nanoparticles Research Articles

Influence of TiO2 nanoparticles on IMC growth in Sn–3.0Ag–0.5Cu–xTiO2 solder joints in reflow process

The influence of TiO2 nanoparticles on the growth kinetics of intermetallic compound (IMC) between Sn–3.0wt.% Ag–0.5wt.% Cu–xwt.%TiO2 (x=0, 0.02, 0.05, 0.1, 0.3, and 0.6) solder and copper substrate during reflow process has been investigated in this study. Scanning electron microscope (SEM) was applied to observe the microstructural evolution of the solder joints, to measure the thickness of the IMC layer, and to estimate the grain size of the IMC layer. The IMC phases were identified by energy-dispersive X-ray spectroscopy (EDX) and X-ray diffractometry (XRD). Results show that both the thickness and grain size of IMC decrease when TiO2 nanoparticles are added into the Sn–3.0Ag–0.5Cu solder system, and have a significant drop when the weight percentage of TiO2 nanoparticles is about 0.1wt.%. Beyond this amount, the thickness and grain size of IMC increase slightly. The growth exponents for both the IMC layers and grains are determined by curve-fitting to study the growth kinetics of IMC in the soldering reaction process. Results reveal that the growth exponents of the IMC layer range from 0.354 to 0.358, and those of the IMC grains range from 0.332 to 0.346, which suggests that the growth of the IMC layer is controlled by the combined kinetics process of atomic interdiffusion, interfacial reaction, and grain ripening. These data also show that Sn–3.0Ag–0.5Cu with about 0.1wt.% TiO2 nanoparticles solder system exhibits the smallest growth rate and gives the most prominent effect in suppressing IMC growth and refining IMC grain size. Based on the theory of adsorption, heterogeneous nucleation, and Ostwald ripening, a mechanism for retarding the IMC growth rate due to TiO2 nanoparticles addition is proposed.

Influence of TiO2 nanoparticles on thermal property, wettability and interfacial reaction in Sn–3.0Ag–0.5Cu–xTiO2 composite solder

The influence of TiO2 nanoparticles on thermal property, wettability, and interfacial reaction in Sn–3.0Ag–0.5Cu–xTiO2 (x = 0, 0.05, 0.1, and 0.6) lead-free composite solder was investigated in this study. Results show that the solidus temperatures of the TiO2-containing composite solder have no obvious change compared with TiO2-free solder. However, the liquidus temperatures of the TiO2-containing composite solders increase by 4.4 °C with an increase in amounts of TiO2 nanoparticles. The wetting angle of the composite solder decreases with the addition of TiO2 nanoparticles ranging from 0.05 to 0.1 wt%, while the spreading area increases. Based on the spherical cap model, the mathematical relation between the wetting angle and spreading area is analyzed. Scanning electron microscopy was used to observe the interfacial microstructure evolution of solder joints and to estimate the thickness of the intermetallic layer. Energy dispersive x-ray and x-ray diffractometry were used to identify the intermetallic compound (IMC) phases. Results reveal that both the thickness of IMCs and the size of Cu6Sn5 grains formed in the solder matrix decrease when TiO2 nanoparticles were added. It was also observed that some of the TiO2 nanoparticles are adsorbed on the surfaces of the scallop-like Cu6Sn5 grains. According to the adsorption theory, the surface energy of the Cu6Sn5 grains decreases with adsorption of TiO2 nanoparticles. Therefore, the diffusion of Sn and Cu atoms might be retarded, resulting in suppressing the growth of the IMCs layer.

1-D photonic crystals for photovoltaics

The paper presents the theoretical analysis of photonic structures with 1-D photonic crystals on both sides of the slab glass and the results of experimental research. Within the scope of theoretical analysis, using the 2x2 transfer matrix method, we have determined the spectral reflectivity and transmittance characteristics, and basing on the said characteristics, we have determined the influence of the number of bilayers on the maximum reflectivity and on the width of the main reflectivity peak. For the structure with four bilayers (SiO2/TiO2) we have obtained the maximum reflectivity of 0.933 for the wavelength λr = 505nm and full width at half maximum of the main reflectivity peak of FWHM=185nm.   Full Text: PDF References T.M.Razykov, C.S.Ferekides, D.Morel, E.Stefanakos, H.S.Ullal, H.M.Upadhyaya,"Solar photovoltaic electricity: Current status and future prospects", Sol. Energy 85, 1580 (2011)[CrossRef] B. Parida, S. Iniyanb, R. Goic,"A review of solar photovoltaic technologies", [CrossRef] Organic electronics, edited by Hagen Klauk, (Weinheim, WILEY-VCH Verlag GmbH & Co.KGaA,. 2006) E. Gondek, I.V.Kityk, A.Danel,"Some anthracene derivatives with N,N-dimethylamine moieties as materials for photovoltaic devices", [CrossRef] E.Gondek, Y.Djaoued, J.Robichaud, P.Karasiński, I.V.Kityk, A.Danel, K.J.Plucinski,"Influence of TiO2 nanoparticles on the photovoltaic efficiency of the ITO/PEDOT:PSS/fluorine copolymers/polythiophene: TiO2/Al architecture", J. Mater. Sci.: Mater Electron[CrossRef] R.Signerski, G.Jarosz,"Effect of buffer layers on performance of organic photovoltaic devices based on copper phthalocyanine-perylene dye heterojunction", Opto-Electron. Rev. 19, 468 (2011)[CrossRef] A.G.Imenes, D.R.Mills,"Spectral beam splitting technology for increased conversion efficiency in solar concentrating systems: a review", Sol. Energy Mater. Sol. Cells 84, 19 (2004)[CrossRef] A.Zhedi,"Review of modelling details in relation to low-concentration solar concentrating photovoltaic", Ren. Sust. Energy Rev 15, 1609 (2011)[CrossRef] B.C.Rowan, L.R.Wilson, B.S.Richards,"Advanced Material Concepts for Luminescent Solar Concentrators", [CrossRef] R.M.Almeida, L.M.Fortes, M.C.Gonçalves,"Sol–gel derived photonic bandgap coatings for solar control", Opt. Mater. 33, 1867 (2011)[CrossRef] E. Yablonovitch,"Inhibited Spontaneous Emission in Solid-State Physics and Electronics", Phys. Rev. Lett. 58, 2059 (1987)[CrossRef] G.V.Morozov, F.Placido, D.W.L.Sprung,"Absorptive photonic crystals in 1D", J. Opt. 13, 035102 (2011)[CrossRef] P.Karasiński, "Influence of aging and annealing on the properties of silica films produced with sol-gel method", Opt. Appl. 36, 389 (2006) P.Karasiński, E.Gondek, S.Drewniak, I.V.Kityk,"Nano-sized blue spectral shift in sol–gel derived mesoporous titania films", J. Sol Gel Sci. Techn. 61, 355 (2012)[CrossRef]

The influence of TiO2 nano-particles on bond strength of cold roll bonded aluminum strips

Abstract In the present work, cold roll bonding (CRB) process characteristics of AA1050 strips, such as bond strength, threshold deformation, undulation of peeling force, and peeled surface in the presence of TiO 2 nano-particles were carried out and compared to those of aluminum strip without particles. The bond strength was evaluated by the peeling test. The results indicated that when the reduction in thickness was increased, the peeling force of AA1050 strips was enhanced. It was found that the presence of TiO 2 nano-particles reduces the bond strength of layered strips when compared to layered pure aluminum for the same reduction in thickness applied through CRB process. When the reduction in thickness was increased, the undulation of average peeling force values was increased at constant particles content. Also, the strips without particles had lower undulation value as compared to the strips with titanium oxide particles. In addition, in the presence of titanium oxide, when the particles content was increased, the undulation of average peeling force values was decreased at constant reduction in thickness. On the other hand, by increasing the particles content, the average slope of bond strength curves was decreased and the threshold deformation was increased. Finally, it was found that the bond strength of AA1100/alumina/AA1100 strips was much more than that of AA1050/titanium oxide/AA1050. This was attributed to both the metal and particle type.

Influence of TiO2 nanoparticles on the photovoltaic efficiency of the ITO/PEDOT:PSS/fluorine copolymers/polythiophene: TiO2/Al architecture

Results of a study on the application of a copolymer of fluorine as acceptor and 1H-pyrazolo[3,4-b]quinoxaline as a donor in bulk heterojunction solar cells are given. To the best of our knowledge, 1H-pyrazolo[3,4-b]quinoxaline co-polymers were not applied in organic photovoltaic devices yet. Organic photovoltaic devices as well as devices of active layers with TiO2 nanocrystals of different crystallite size were investigated. The methods of polymer and TiO2 nanocrystllites synthesis are presented and their physical properties are given. The fabricated photovoltaic structures possess high values of U oc voltage as as well as relatively high parameters of I sc currents. The maximally achieved parameters corresponded to open circuit voltage U oc = 1.13[V], and short current density Isc = 33.49[μA] under illumination 1,3 [μW cm−2], which correspond to energy conversion efficiency equal to about 0.80 %. The TiO2 nanocrystallites play a crucial role in the photovoltaics parameters.

Influence of TiO2 nanoparticles on cellular antioxidant defense and its involvement in genotoxicity in HepG2 cells

We investigated the effects of two types of TiO2 nanoparticles (<25 nm anatase, TiO2-An; <100 nm rutile, TiO2-Ru) on cellular antioxidant defense in HepG2 cells. We previously showed that in HepG2 cells, TiO2 nanoparticles are not toxic, although they induce oxidative DNA damage, production of intracellular reactive oxygen species, and up-regulation of mRNA expression of DNA-damage-responsive genes (p53, p21, gadd45α and mdm2). In the present study, we measured changes in mRNA expression of several antioxidant enzymes: catalase, superoxide dismutase, glutathione peroxidase, nitric oxide synthase, glutathione reductase and glutamate-cysteine ligase. As reduced glutathione has a central role in cellular antioxidant defense, we determined the effects of TiO2 nanoparticles on changes in the intracellular glutathione content. To confirm a role for glutathione in protection against TiO2-nanoparticle-induced DNA damage, we compared the extent of TiO2-nanoparticle-induced DNA damage in HepG2 cells that were glutathione depleted with buthionine-(S,R)-sulfoximine pretreatment and in nonglutathione-depleted cells. Our data show that both types of TiO2 nanoparticles up-regulate mRNA expression of oxidative-stress-related genes, with TiO2-Ru being a stronger inducer than TiO2-An. Both types of TiO2 nanoparticles also induce dose-dependent increases in intracellular glutathione levels, and in glutathione-depleted cells, TiO2-nanoparticle-induced DNA damage was significantly greater than in nonglutathione-depleted cells. Interestingly, the glutathione content and the extent of DNA damage were significantly higher in TiO2-An- than TiO2-Ru-exposed cells. Thus, we show that TiO2 nanoparticles cause activation of cellular antioxidant processes, and that intracellular glutathione has a critical role in defense against this TiO2-nanoparticle-induced DNA damage.

Crystallization Behaviour of TiO&lt;sub&gt;2&lt;/sub&gt; Nanoparticle Reinforced Polypropylene

Composites of isotactic polypropylene (iPP) with different TiO2 nanoparticle loads (0.5 vol.%, 2 vol.% and 4 vol.%) were compounded by optimized twin screw extrusion. The crystallization behaviour of these semicrystalline nanocomposites was examined by differential scanning calorimetry (DSC), scanning electron microscope (SEM) and polarized optical light microscope (POM) combined with a hot stage module to pursue in-situ the structure development. Wet chemical etching was applied to highlight morphological details like spherulites and lamellar structures for SEM observations. An obvious influence of TiO2-nanoparticles on the crystallization could be verified.

Thermal properties of PMMA/TiO2 nanocomposites prepared by in‐situ bulk polymerization

AbstractThe surface of anatase TiO2 nanoparticles, obtained by the controlled hydrolysis of titanium tetrachloride, was modified by 6‐palmitate ascorbic acid. The surface modified TiO2 nanoparticles were dispersed in methyl methacrylate and mixed with a appropriate amount of poly(methyl methacrylate) to obtain a syrup. The nanocomposite sheets were made by bulk polymerization of the syrup in a glass sandwich cell using 2,2′‐azobisisobutyronitrile as initiator. The molar masses and molar mass distributions of synthesized poly(methyl methacrylate) samples were determined by gel permeation chromatography. The content of unreacted double bonds in synthesized samples was determined by 1H NMR spectroscopy. The influence of TiO2 nanoparticles on the thermal stability of the poly(methyl methacrylate) matrix was investigated using thermogravimetric analysis and differential scanning calorimetry. The synthesized samples of poly(methyl methacrylate) have different molar mass and polydispersity depending on the content of the surface modified TiO2 nanoparticles. The values of glass transition temperature of so prepared nanocomposite samples were lower than for pure poly(methyl methacrylate), while the glass transition temperature of samples preheated in inert atmosphere was very similar to the glass transition temperature of pure poly(methyl methacrylate). The thermal stability of nanocomposite samples in nitrogen and air was different from thermal stability of pure poly(methyl methacrylate). POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers