Physical Measurements

The standard characterization of CMR thin films consists of resistance measurements versus temperature in zero field and under an applied magnetic field, by using the four probe technique and also in magnetization measurements. Results pertaining to strain effects will be discussed in the next section. Several groups focused their studies on the surface 84 86 . Extensive thin film surface studies were performed using two complementary techniques atomic force microscopy and magnetic force...

Effects Of Ultrasound 21 Physical Effects of Ultrasound

Intensive sonication of liquids can generate cavitation bubbles. The bubbles collapse violently, and in doing so, generate high temperatures and pressures within the gaseous contents. There are three different theories about cavitation the hot spot, the electrical, and the plasma theory. The most popular one is the hot-spot theory. Thus, it has been experimentally shown that the cavitational collapse creates drastic conditions inside the medium for an extremely short time generating...

References

Yamauchi, J. Appl. Phys. 64, 6044 (1988). 2. K. Suzuki, A. Makino, A. Inoue, and T. Masumoto, Mater. Trans., JIM 32, 93 (1991). 3. M. Knobel, D. R. dos Santos, I. L. Torriani, and R. S. Turtelli, Nanostruct. Mater. 2, 399 (1993). 4. A. Danzig and N. Mattern, Phys. Status Solidi A 147, 335 (1995). 5. B. G. Kim, J. S. Song, H. S. Kim, and Y. W. Oh, J. Appl. Phys. 77, 5298 (1995). 6. M. L. Fdez-Gubieda, I. Orue, F. Plazaola, and J. M. Barandiar n, Phys. Rev. B 53,...

SBA2 P63mmc Fm3m

SBA-2 was first synthesized by Stucky's group in 1995 by using Gemini surfactant C H2 +1N+(CH3)2(CH2)sN+ (CH3)3 (Cn_s_i) 10 . Based on powder XRD results, the material was believed to consist of discrete supercages in a hexagonal close-packed (hcp) arrangement and the space group was determined to be P63 mmc. The unit cell dimensions are a 6 nm and c 10 nm which can be tuned by changing Figure 5. TEM image of 3D porous single crystal of Cr2O3 synthesized using SBA-15 as a template which has...

Superlattices

Thin film methods offer a powerful and versatile technique for growing new structures, as previously seen for example in cuprates. This is due to strain effects that can stabilize structures which do not exist under classical conditions of pressure and temperature. For example, various metastable perovskites, which cannot be formed in bulk or can only be prepared under high pressure, such as BiMnO3 110 , YMnO3 119 , and atomically ordered LaFe0.5Mn0.5O3 153 , are synthesized via a pulsed laser...

In Superhard Nanolayered Composites

CNx MeN (Ti, Zr) The idea of this type of nanolayered composite originated from numerous attempts to synthesize carbon nitride ( -C3N4) in the crystalline state, which was predicted to have a hardness higher than that of diamond 4, 5 . Pseudomorphic stabilization between two nanolayers having a similar structure to -C3N4 was proposed 535-537 . The faces of TiN(111) and ZrN(111) were expected to be the best stabilizers because of the good lattice match between TiN(111) or ZrN(111) and -C3N4...

Double and Triple Perovskites A3Mn2O7 and A4Mn3O10

Although the majority of studies have been done on simple perovskites AMnO3, colossal magnetoresistance also occurs in (La, A)3Mn2O7 (A Ca, Sr). These compounds belong to the Ruddlesden-Popper phases whose general formula is A +1B O3b+1 (see Fig. 4). Two parents of this family were synthesized in thin film form with n 2 and n 3. Films of La2-2xCa1+2xMn2O7 (x 0.3) were deposited on (001)-MgO by single-target magnetron sputtering 56,57 . The c-axis oriented films of La2-2xSr1+2xMn2O7 (x 0.4) can...

Microstructural Characterization

An important part of the recent developments corresponding to nanostructured materials is related to those obtained by controlled crystallization, either by annealing the amorphous single phase or by decreasing the cooling rate from the liquid of metallic systems. Typically, in these nano-structures, precipitate sizes range between 5 and 50 nm embedded in an amorphous matrix with nanocrystal volume fractions of 10 to 80 , which means particle densities of 1022 to 1028 m-3. We present the most...

Mesoporous Solids

Another closely related field that has been developed by Gedanken and co-workers is the sonochemical coating of submicron ceramic spheres (silica, alumina, and zirconia) by a large variety of nanoparticles. This was done by synthesizing the ceramic spheres by conventional techniques (like the Stobber method for silica particles). The spheres were then introduced in the sonication bath, mixed with the solution of the precursor, and the ultrasonic radiation was passed through the solution for a...

Nanocrystalline HardAmorphous Matrix Nanocomposites

Nc-MenN a-Si3N4 (Me Ti, W, V) The synthesis and properties of Si3N4 TiN composite coatings have been the subject of scientific and technological interest. The first efforts to co-deposit silicon nitride and titanium nitride were undertaken in the 1980s 588-592 . The TiN Si3N4 composite coatings were prepared by chemical vapor deposition (CVD) from SiCl4+TiCl4+NH4 +H2 588-592 and TiCl4 SiH2Cl2 NH3 593 at a low pressure of 1.33-10.7 kPa and a relatively high temperature of 1050-1450 C, which is...

Info

The UV absorption of the dendrimers 1 in spincoat films is somewhat broader as in solution, and the maximum is shifted by about 10 nm to longer wavelengths. Both effects point to an increased intermolecular interaction. Prolonged irradiation of the films with 350 nm leads in all cases to a complete or almost complete disappearance of the long-wavelength band. The simultaneous FT-IR measurement reveals the disappearance of the band at 955 m-1, which corresponds to the typical out-of-plane...

General Principles of Micromagnetics

Classical (zero-temperature) micromagnetics describe magnetic materials in a nanometric lengthscale where each discretization unit is represented by a large magnetic moment that could be described in a semiclassical approximation, i.e., no quantum effects are taken into account. The principle of micromagnetics is due to Brown 107 who derived the micromagnetic equations for the equilibrium properties. The method consists in discretizing the magnetic film in finite differences 108-110 or finite...

H

Generally speaking, when the applied field is reduced from the saturation value, the competitive effects of magnetic exchange and magnetostatic interactions and the random magnetocrystalline anisotropy lead to magnetization ripple when the magnetization deviates locally from its saturation value 112, 128, 129 . Figure 14 supposes to simulate a hysteresis cycle of a permalloy-based thin film and a standard Kerr-microscopy image. The ripple formation and its changes through the hysteresis cycle...

Nanostructured Lipid Carriers

SLNs produced by high-pressure homogenization at elevated temperature hot homogenization technique are formed during the cooling process of the hot o w emulsion as mentioned above. To summarize occurring disadvantages, the immediate formation of a perfect crystal or formation during the long-term storage can cause drug expulsion. To avoid this, a less ordered lipid matrix with many imperfections is desirable for better accommodation of the drug, especially to avoid drug expulsion during...

Reduction of Protein Adsorption

Albumin is a model protein commonly used to study the protein-resistance properties of surfaces 53 . A 15fold reduction of albumin adsorption was found with PEG-coated PEG-PLA nanospheres compared to PLA ones 54 . Similar albumin-rejecting abilities were observed in the case of PLGA nanospheres surface modified by adsorption of PEG-PLA diblock copolymers 55 . Fibrinogen was used as a model blood protein to test the efficacy of the PEG coating on PEG-PACA nanospheres 49 . After freeze-fracture,...

Strengthening Mechanisms

The hardening mechanism of nanocomposites should be more complicated 165, 385, 386 than that in coarse-grained polycrystalline materials. The hardness of nanocomposites is most precisely approximated by the Hall-Petch equation, but currently there is no agreement on the strengthening mechanism of nanocomposites. A few strengthening models of nanostructured materials at nanoscale thicknesses of the bilayer repeat period below the Hall-Petch breakdown were proposed Orowan mechanism 344, 387-393 ,...

Optical Absorption

Another way to probe the electronic properties of SWNTs is through their optical absorption spectra. This technique is based on the well known phenomenon of light absorption Figure 14. Resonant Raman spectra in the tangential mode G mode obtained using three different laser excitation energies, for SWNT samples produced by CO disproportionation at 950 C. Reprinted with permission from 88 , J. E. Herrera et al., J. Nanotech., in press. American Scientific Publishers. by a chromophore group...

Sol Gel and Spray Pyrolysis

Chemical deposition has been widely used to prepare oxide films, such as ferroelectrics and semiconductor films 37 , since it is a fast and cost-efficient preparation method. In nebulized spray pyrolysis, a solution containing the organic derivatives of the relevant metals in a suitable solvent is nebulized by making use of a CMR transducer. The nebulized spray is slowly deposited on a solid substrate at a relatively low temperature, with sufficient control of the rate deposition to yield the...

Using Non Alkoxide Precursor

However, this problem can be overcome by using the cheap, commercially available non-alkoxide precursors, namely SnCl4, without further purification or modification. Following procedures are generally followed to prepare pure and modified SnO2 thin films by means of sol-gel technique utilizing non-alkoxide precursors. In the first method 5, 13, 14 , tin tetrachloride SnCl4 is first dissolved in propanol or any other alcohol forming a solution of tin compounds...

Synthesis Of Nanocrystalline SnO2 Via Solgel

Two sol-gel synthesis routes or precursors are generally used for producing SnO2 thin films first is the hydrolysis of tin alkoxide 8, 34, 74, 75 and the second is the hydrolysis of tin IV chloride 5, 6, 9-19, 21-26, 29, 30, 33, 37, 76 . SnO2 thin films can also be prepared from an aqueous SnO2 sol, which is synthesized via tin IV chloride hydrothermal treatment 16 . Semiconductor SnO2 gas sensor can be fabricated into three types of devices i sintered block 12, 16, 19 , ii thick film 27, 28 ,...

Characterization Of Solgel Coated SnO2 Thin Films

Typical SEM micrograph of nanocrystaUine SnO2 thin film coated on a Pyrex glass substrate is shown in Figure 4 77 . The SnO2 thin film appears to be relatively smooth. At some locations, few cracks are observed on the film surface, which are characteristic features of the sol-gel dip-coated thin films. Typical broad-scan XPS spectrum, within the B.E. range of 0-1100 eV, obtained for the nanocrystalline SnO2 thin film dip-coated on the Pyrex glass substrate is shown in Figure 5a 77 , which...

Sol Gel Spin Coating Process

Spin-coating is used for many applications where relatively flat substrates or objects are coated with a thin layer of material. In spin-coating, Figure 1, the material, in the form of a stable sol, to be made into coating is deposited onto the substrate surface and spun off to leave a uniform layer. There are four key stages in the sol-gel spin-coating process, Figure 2 3 1 Stage 1 This step involves the deposition of the sol onto the substrate surface, Figure 2. This can be done using a...

Advantages of Sol Gel Process

Sol-gel technique, as a method for synthesizing thin- or thick-film gas sensor, offers several advantages 1, 2 i The sol-gel technique is simpler and cheaper than others, ii it allows an easy coating of large and complex shaped substrates if the angles are not too sharp , iii the process is inexpensive with respect to the initial investment of the production plant and the running cost, iv it produces no perturbations of devices in the case of deposition on top, v it offers easy control of film...

Hall Petch Strengthening Mechanism

The experimental Hall-Petch relationship applied to hardness shows that the hardness of microcrystalline materials increases with a decrease in the average diameter of the grains 328-332 where d is the average diameter of the grains, H is the hardness, H0 is the hardness of the monocrystal when d x gt , and kH is the Hall-Petch intensity constant. Extrapolation of the Hall-Petch relationship to nanostruc-tured materials should show a much higher hardness than that of coarse-grained materials...

Opsonins and Dysopsonins

Immediately after intravenous administration, the nano-particles encounter hundreds of different plasma proteins. A protein layer begins to form within seconds at the nano-particles' surface after contact with blood. The adsorption of plasma proteins that are capable to interact with receptors on the MPS cells, thus promoting the particle uptake by these cells, is called opsonization. The complement is considered to be one of the main opsonins involved in the uptake of intravenously...

Disadvantages of Sol Gel Process

The sol-gel process has a few limitations, too. The real application of this synthesis route for the serial devices needs efforts in R amp D. Much work and time are needed in optimizing the stability of the sol, the durability, and the reproducibility of the results for the production of sensor devices. Moreover, the alkoxide precursors are generally costlier. In spite of these disadvantages, the sol-gel process has been proven to be a highly applicable and industrially viable process for...