bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gelation Point In Borosilicate Sols From Rheological
Experiments
Authors: Surapanani Srinivas , Mullins Michael E. , Morrison Faith , Cornilsen Bahne C. 
Published: April 2011

ABSTRACTDynamic oscillatory experiments are used to monitor the gelation of the
borosilicate systems prepared through the sol-gel process from metal
alkoxides. The rheological experiments show that tan δ = G”/G’ is
independent of frequency at the gel point in agreement with the results of
others on organic gelling systems. The dynamic moduli at the gel point
followed power-law behavior with respect to frequency. The power-law
exponent is found to be ∼0.70. The apparent fractal dimension, dp, of the
network cluster at the gel point is determined. The dF values for
the samples ranged from 2.5 to 3.8 depending on the final structure of the
evolved products at the gel point. The large values (dF > 3)
exclude a simple geometric interpretation of the results. The effect of
processing parameters, such as composition of reactants and temperature, on
the resulting microstructures near the gel point is discussed.
Pillaring of Layered Double Hydroxides With Cage-Like
Polysilicates: a Possible New Class of Base Catalysts or Catalyst
Precursors
Authors: Fyfe Colin A. , Fu Guoyi , Grondey Hiltrud 
Published: April 2011

ABSTRACTPillaring of highly basic layered double hydroxides
(MgnAl(OH)2n+2Cl, n=2–5) with octameric
polysilicate (Si8O208-) has been achieved via a direct ion exchange route.
Experimental Studies On Diffusion Of Liquids In Porous
Glass
Authors: Shao Yong , Koone Neil , Zerda T. W. 
Published: April 2011

ABSTRACTDiffusion coefficients of water and cyclohexane in porous sol-gel glass of
average pore diameter 2.9 nm were obtained using a radioactive tracer
technique. This information was applied to calibrate the membrane in the
diaphragm cell which was subsequently used to measure the diffusion
coefficients for cyclohexane, acetone, toluene, acetonitrile, and
chloroform. Results for cyclohexane were compared with computer simulation
of molecular motion of cyclohexane in a model cylindrical pore of diameter
2.9 nm. Translational motion of polar liquids inside the pores was found to
be faster than that of neutral, not wetting solvents.
Synthesis, Structure and Magnetic Properties of Some New
Metal(II) Phosphonates: Layered
Fe(C2H5PO3).H2O,
α-Cu(C2H5PO3) and
Co(t-C4H9PO3).H2O, Tubular
β-Cu(CH3PO3)
Authors: Bujoli Bruno , Le Bedeau J. , Payen C. , Palvadeau P. , Rouxel J. 
Published: April 2011

ABSTRACTFe(II)C2H5PO3. H2O has been prepared via
prolonged reaction between iron oxychloride and ethylphosphonic acid in
acetone, in a sealed tube. The lamellar structure is very similar to that of
previously reported divalent metal phosphonates M(II)(RPO3).
H2O (M= Mg, Mn, Ni, Zn). The compound shows sign of 2D
antiferromagnetic correlations above the Néel temperature Tn=24K
and a weak ferromagnetic behavior is observed below TN. We also
report on the preparation methods and the crystal structures of two new
anhydrous copper phosphonates
a-Cu(II)(C2H5PO3), and
β-Cu(II)(CH3PO3) which exhibits an original tubular
three-dimensional structure. The reactivity of bulky phosphonic acids is
also described, with the case of
Co(II)(t-C4H9PO3).H2O.
Cross-Condensation Reactions in an Organically Modified Silica
Sol-Gel
Authors: Prabakar S. , Assink R. A. , Raman N. K. , Brinker C. J. 
Published: April 2011

ABSTRACTHigh resolution 29Si NMR has been used to study the extent of
cross condensation taking place in a hybrid organic/inorganic sol-gel
system. Tetraethoxysilane (TEOS) and methyltriethoxysilane (MTEOS) sol-gels
were chosen for this purpose. The sols were prepared by acid catalyzed
hydrolysis of TEOS and MTEOS with a H2O/Si ratio of 0.3.
29Si NMR shows signals due to both self-condensation and
cross-condensation between TEOS and MTEOS. Resonance assignments were made
by comparing the positions and intensities of peaks in the spectra of single
and multicomponent systems. It was found that, within experimental error,
the self- and cross-condensation rates are equal and that extensive
molecular level mixing takes place during the early stages of the
reaction.
Pore Morphology Study of Silica Aerogels
Authors: Hua D.W. , Anderson J. , Hæreid S. , Smith D.M. , Beaucage G. 
Published: April 2011

ABSTRACTSilica aerogels have numerous properties which suggest applications such as
ultra high efficiency thermal insulation. These properties relate directly
to the aerogel's pore size distribution. The micro and meso pore size ranges
can be investigated by normal small angle x-ray scattering and possibly,
nitrogen adsorption. However, the measurement of larger pores (> 250 Å)
is more difficult. Due to their limited mechanical strength, mercury
porosimetry and nitrogen condensation can disrupt the gel structure and
electron microscopy provides only limited large scale structure information.
The use of small angle light scattering techniques seems to have promise,
the only hurdle is that aerogels exhibit significant multiple scattering.
This can be avoided if one observes the gels in the wet stage since the
structure of the aerogel should be very similar to the wet gel (as the
result of supercritical drying). Thus, if one can match the refractive
index, the morphology can be probed. The combination of certain alcoholic
solvents fit this index matching criteria. Preliminary results for the gel
network (micron range) and primary particle structure (nanometer) are
reported by using small angle light scattering and ultra-small angle x-ray
scattering. The effects on structure over the length scale range of <1 nm
to >5 μπι under different conditions (precursors, pH, etc.) are
presented. The change in structure of an aerogel during isostatic compaction
to 228 MPa (to simulate drying from wetting solvents) are also
discussed.
Effects of Deposition Temperature and Thermal Treatment on the Structure of C60 and C70 Films
Authors: Rusakova I. , Hamed A. , Hor P.H. 
Published: April 2011

ABSTRACTC60 and C70 polycrystalline thin films, prepared by sublimation of powders onto carbon holey film substrates held at temperatures Ts of 40 and 200 °C, were investigated at room temperature using conventional and high resolution TEM. A strong dependence of grain size on Ts is observed. We obtain a mean grain size ˜25 nm for both C60 and C70 films when using Ts = 40 °C, but this size is ˜250 nm for C60 and ˜130 nm for C70 when using Ts = 200 °C. In all cases, however, an fc.c. structure with a high density of planar defecTs, twins and stacking faulTs, is observed. When a C60 film grown at Ts = 40 °C was annealed for several hours at only about 250 °C in vacuum, recrystallization took place, with grains as large as 250 nm now being present in the film. A condition to observe this recrystallization seems to be that the powder used to grow the film must be dried for long enough periods of time to minimize the amount of solvent residues.
Plasmons in C60, Carbon Onions and Carbon Tubes
Authors: Östling Daniel , RosÉn Arne , Apell Peter , Mukhopadhyay Gautam 
Published: April 2011

ABSTRACTAfter the discovery of the C60 molecule a lot of attention has been given to its optical and collective properties. The latest development in fullerene related research was the synthesis of coaxial carbon sheets called carbon or nano tubes and also spherical concentric graphitic shells called carbon onions. With a model describing the collective dynamics of electrons we may gain insight in the physics of the collective resonances. Based on a simple equation of motion for the induced density in a carbon particle we demonstrate the existence of a rich spectrum of collective resonances for both carbon onions and carbon tubes.
Quantitative In Situ Growth Measurements of Chlorine-Activated Homoepitaxial Diamond Cvd
Authors: Pan Chenyu , Margrave John L. , Hauge Robert H. 
Published: April 2011

ABSTRACTIn situ quantitative studies of the effects of substrate temperature, methane and chlorine flow rates on homoepitaxial diamond growth rates on (110) surfaces in a chlorine-activated diamond CVD reactor have been carried out using a Fizeau interferometer. The temperature dependence of diamond growth rates was found to display three distinct growth activation energies, ranging from 9±2 kcal/mol in the substrate temperature of 750-950°C, to 3.2±0.2 kcal/mol in the temperature range of 300-650°C, followed by 1.2±0.2 kcal/mol in the temperature range of 102-250°C. Atomic hydrogen is believed to be the dominant activating species in the highest temperature range, and atomic chlorine is believed to be the dominant species in the lower temperature regions. Studies of the methane flow effect on diamond growth rates revealed a linearity, indicating that the diamond growth rate was of the first order in methane flows. Diamond growth rates were also found to increase linearly with the chlorine flow. At high chlorine flow rates, however, an accelerated diamond growth rate was observed. Discussion is given to explain the observed results.
Strain and Impurity Content of Synthetic Diamond Crystals
Authors: Mccormick T. L. , Jackson W. E. , Nemanich R.J. 
Published: April 2011

ABSTRACTSamples of diamond crystals produced under various high pressure, high temperature conditions were studied using both micro photoluminescence and Raman spectroscopy. The 0.3 - 0.6 mm sized samples exhibited various levels of inclusion content, impurity content and strain. Photoluminescence studies revealed the presence of nitrogen in three forms. The 1.945 eV, 2.15 eV and 2.46 eV zero phonon lines and their associated sidebands were detected. The ratios between forms of impurities and their integrated intensities varied between samples. Variations in the distribution of the nitrogen forms were seen between regions of high and low strain birefringence patterns.
Novel Carbon Fibers by Laser Assisted Chemical Vapor Deposition (Lcvd)
Authors: Wallenberger Frederick T. , Diefendorf R. Judd , Frischknecht Kyle D. , Nordine Paul C. 
Published: April 2011

ABSTRACTChemically pure carbon fibers with small fiber diameters and high growth rates were obtained by laser assisted chemical vapor deposition (LCVD) using high reactor pressures and a unique rate control mechanism. Depending upon growth conditions and gases, these fibers were either flexible (elastic), brittle (thickened) or graphitic (strong). The elastic carbon fibers were uniform and appear to represent a novel form of carbon. The reactants were acetylene, ethylene or methane, and the reaction pressures ranged from 1.9 to 7.5 bar. The highest fiber growth rate was 0.33 mrn/s, and the lowest fiber diameter was 10 μm.
Thermal Stability Studies of Diamond-Like Carbon Films
Authors: Parmeter John E. , Tallant David R. , Siegal Michael P. 
Published: April 2011

ABSTRACTThin films of amorphous carbon/hydrogen, also known as diamond-like carbon or DLC, are of interest as an economical alternative to diamond in a variety of coatings applications. We have investigated the thermal stability of DLC films deposited onto tungsten and aluminum substrates via plasma CVD of methane. These films contain approximately 40 atom % hydrogen, and based on Auger spectra the carbon in the films is estimated to be approximately 60 % sp3 hybridized and 40 % sp2 hybridized. Thermal desorption, Auger, and Raman measurements all indicate that the DLC films are stable to 250–300° C. Between 300 and 500° C, thermal evolution of hydrogen from the films is accompanied by the conversion of carbon from sp3 to sp2 hybridization, and Raman spectra indicate the conversion of the overall film structure from DLC to micro-crystalline graphite or so-called “glassy” carbon. These results suggest that DLC of this type is potentially useful for applications in which the temperature does not exceed 250° C.
Hardness Measurements on Anode and Cathode Mounted, Plasma Deposited Amorphous Hydrogenated Carbon
Authors: Lin Shu-Han , Feldman Bernard J. , Li Dong , Chung Yip-Wah , Wong Mingshow , Sproul William D. 
Published: April 2011

ABSTRACTWe have measured the microhardness of various amorphous hydrogenated carbon thin films that were grown on both the anode and the cathode of our plasma deposition system. We observe no difference in microhardness between films with the same optical bandgap, whether grown on the cathode or on the anode. We conclude that the ion bombardment during cathode growth does not contribute to the hardness of the films. In contrast, we observe a large variation in microhardness as a function of optical bandgap. We conclude that it is increasing hydrogen concentration, found primarily in the clusters and not in the crosslinks, that decreases the hardness of our films. Finally, we observe that the addition of nitrogen to our films does not change the microhardness; again, the hardness is primarily determined by the hydrogen concentration.
Influence of Silicon Incorporation on the Properties of Hard a-C:H Films
Authors: Neto A.L. Baia , Santos R.A. , Freire F.L. , Beyer W. , Camargo S.S. 
Published: April 2011

ABSTRACT- Results on the properties of silicon incorporated hard a-C:H films deposited on the cathode of a glow discharge decomposition system using methane and silane gaseous mixtures are reported. Obtained samples showed an increased deposition rate, high hardness comparable to that of a-C:H, and a large decrease of the internal stress upon silicon incorporation. The structure of the samples seems to be similar to diamond-like a-C:H, as revealed by the total hydrogen content, infrared absorption and hydrogen effusion experiments. Our results indicate that the observed reduction of residual internal stress may be attributed to a less compact material and/or to a smaller density of voids containing hydrogen in comparison to pure a-C:H.
Pressure-Enhanced Interdiffusion in Amorphous Si/Ge Multilayers: Implications for Defect-Mediated Diffusion
Authors: Theiss Steven D. , Spaepen F. , Aziz M. J. 
Published: April 2011

AbstractWe have studied the pressure-dependence of the interdiffusion rate in amorphous Si/Ge multilayers. Samples were annealed in an externally-heated diamond anvil cell at 693 K at pressures ranging from 0 to 3.1 GPa. Interdiffusion rates were determined by ex situ x-ray diffraction measurements of the decay of the artificial Bragg peaks associated with the multilayer periodicity. Scaling experiments were performed to factor out the effects of concentration and time dependence in the diffusivity. All samples showed a consistent increase in diffusivity with applied pressure, characterized by a negative activation volume ranging from −44±3 to −37±2 percent of the atomic volume of Si for films ranging in average Si composition from 25 to 71 percent, respectively. These results are consistent with a model for diffusion in amorphous Si and Ge based on dangling bond migration.
Amorphous SIC-N Coatings: Its Properties and Applications
Authors: Yee Andrew L. , Ong Hockchun , Xiong Fulin , Chang R. P. H. 
Published: April 2011

AbstractLaser ablation has been used to deposit a:SiC-N films from a CVD SiC target. Depositions were carried out either in vacuum or in a nitrogen ambient ranging from 10 to 100 mT. The mechanical properties of the films versus nitrogen background pressure were assessed using nanoindentation and surface acoustic wave measurements. Deflected optical beam testing, pull testing and atomic force microscopy were used to determine film stress, film-substrate adhesion and film roughness, respectively. The optical properties were also characterized as a function of nitrogen back pressure using spectroscopic ellipsometry which determined refractive indices and predicted film compositions. Fourier transform infrared spectroscopy determined the bonding structures in the films, and finally Rutherford backscattering spectroscopy measurements were also performed. Based on the best mechanical and optical properties, the optimum film deposition conditions were obtained. It was observed that with an increase in nitrogen background pressure, oxygen content in the film, in the form of SiOx, increased significantly affecting the overall properties of the a:SiC-N films.
Modelling and Measurements of Stress-Controlled Interdiffusion in Multilayered Amorphous Alloys
Authors: Yang F. L. , Shih W. C. , Greer A. L. 
Published: April 2011

AbstractThe decay of X-ray satellite intensities is used to measure interdiffusion in amorphous Ni55Zr45 multilayers as a function of repeat distance, time and temperature. The data are compared to analytical expressions and a numerical simulation based on the analysis of Stephenson for stress effects. It is concluded that stress effects are very strong and that the analysis fits them quantitatively in a system such as a-Ni-Zr with marked diffusional asymmetry.
Temperature Dependence of the Intrinsic Stress and Biaxial Modulus of Plasma Deposited Silicon Nitride and Silicon Oxynitride Films
Authors: Harding David R. , Ogbuji Linus T. 
Published: April 2011

AbstractThe intrinsic stress and biaxial modulus of thin films of amorphous silicon nitride (0.5μm) and silicon oxynitride (1.5 to 2.5 μm) were measured following deposition (Ts=260 to 610°C), and then at discrete intervals throughout an annealing cycle. The biaxial modulus and intrinsic stress of the silicon nitride films increased from 110 GPa and 130 MPa, respectively, to 180 GPa and 680 MPa as the deposition temperature increased from Ts=340°C to Ts=610°C. The elemental composition was unaffected by the deposition temperature. Annealing at 1100°C increased the intrinsic stress to ≃ 1.8 GPa, as nitrogen and hydrogen were lost. Films with “near-stoichiometric” compositions (SiN1.1; H = 12 at.%) did not crack.Adding oxygen to form silicon oxynitride lowered both the biaxial modulus (20–30 GPa) and the intrinsic stress (−50 to 100 MPa). All the silicon oxynitride compositions (SiO0.3N1.0 to SiO1.7N0.5) were unstable when annealed above the deposition temperature (260°C). Films grown using mostly nitrous oxide (R = N2O/(N20+NH3) < 0.5) oxidized at 350°C to form silica. Simultaneously, the biaxial modulus and intrinsic stress increased to 100 GPa and 170 MPa, respectively. Films grown from mostly ammonia (R <0.5) lost nitrogen and hydrogen and cracked when the temperature exceeded the deposition temperature by 40 to 90°C. The stress induced by the elemental loss was ≃ 600 MPa.
Mechanical Stresses During Solid State Amorphization of Zr/Co Multilayers
Authors: Moske M. , Samwer K. 
Published: April 2011

AbstractThin film structures of crystalline Zr and Co, deposited in UHV, are investigated by bending beam technique and by X-ray diffraction. During isothermal annealing and interdiffusion reaction of the thin film double layer and multilayer packages large compressive stresses are generated while an amorphous ZrCo-phase is formed. This can, at first hand, be understood in terms of the Kirkendall effect where Co atoms, as the main moving species, lead to a volume increase of the film beyond the Co interface. The observed change in Zr lattice spacing in accordance with the evolution of mechanical stress indicates that the compressive stress is built up particularly within the Zr layer due to the solution of Co in Zr grains during the initial amorphization reaction. Film structures, having Co already present in the crystalline Zr layer after film deposition, show a decrease in reaction kinetics combined with a lower stress level, indicating that the interdiffusion reaction is depending on the stress state in the Zr grains. At late stages of annealing in high vacuum a sudden increase of additional compressive stress is observed, which could be attributed to the oxidation of Zr, very likely due to the formation of diffusion paths for oxygen through the Co (cap-) layer (Kirkendall voids). Such oxidation behavior was not observed with samples measured in situ in UHV directly after film deposition.
Emission of a Half-Rectangular Dislocation Loop from the Surface of a Compositionally Graded Epilayer
Authors: Zhang Tong-Yi 
Published: April 2011

AbstractWhen a half-rectangular perfect or partial dislocation loop is emitted from the surface of a strained epilayer, the optimum dislocation shape occurs at a saddle point of the total energy profile as a function of the dislocation width and length. The activation energy and the optimum shape are calculated for either a compositionally graded or uniform epilayer. The results indicate that 1) dislocation emission is more difficult in a compositionally graded layer than in a compositionally uniform layer; and 2) the ratio of threading dislocation density to mismatch dislocation density is lower in a compositionally graded layer than in a compositionally uniform layer. Theoretical results agree with experimental observations [1,2].
In Situ Measurement of Young’s Modulus and Residual Stress of Thin Electroless Nickel Films for Mems Applications
Authors: Roy S. , Furukawa S. , Miyajima H. , Mehregany M. 
Published: April 2011

AbstractThis paper reports in situ measurement of Young’s modulus and residual stress of electroless nickel films through the use of microfabricated nickel test structures, including electrostatic microactuators and passive devices. The test structures are fabricated in a new surface micromachining process, termed “nickel surface micromachining”, using electroless plated nickel as the structural layer and polysilicon as the sacrificial layer. Subsequent to fabrication, lateral resonant-type electrostatic microactuators of different geometries are resonated by electrical excitation. Using the measured resonant frequencies and knowledge of the device geometry, the Young’s modulus of the film is determined. The passive electroless nickel microstructures deform upon completion of the fabrication process due to residual stress in the film. Measurement of this deformation in conjunction with an appropriate mechanical model is used to determine the residual stress in the films.
Nanohardness Measurements on Thin Films
Authors: Upadhyaya K. R. , Saimoto S. , Timsit R. S. 
Published: April 2011

AbstractNanohardness measurements have been carried out on barrier-type anodic aluminum oxide films grown on super-purity aluminum and on a 600 nm thick Al-1wt%Cu blanket film deposited on a silicon wafer. This work was performed using a custom-built displacement-controlled apparatus. The anodic oxide films range in thickness from 20 to 100 nm. The material systems investigated correspond respectively to hard-film/soft-substrate and soft-film/hard-substrate combinations. The experimental evidence suggests that indentation of anodic films begins when the penetration-depth is approximately 1/5th the film thickness. There is also evidence that the measured hardness for Al-1wt%Cu film stems largely from the thin film material when the probing depth does not exceed approximately 1/5th the film thickness. Beyond this depth the substrate influences the film deformation behaviour and the measured hardness gradually reaches the hardness of the substrate material. The oxide films on aluminum show unexpected deformation properties.