Increasing Hydroxyl Content Research Articles

Enhancing Slurry Stability and Surface Flatness of Silicon Wafers through Organic Amine-Catalyzed Synthesis Silica Sol.

The stability of slurries used for chemical mechanical polishing (CMP) is a crucial concern in industrial chip production, influencing both the quality and cost-effectiveness of polishing fluids. In silicon wafer polishing, the conventional use of commercial neutral silica sol combined with organic bases often leads to slurry instability. To address this issue, this study proposes organic amines-specifically ethanolamine (MEA), ethylenediamine (EDA), and tetramethylammonium hydroxide (TMAOH)-as catalysts for synthesizing alkaline silica sol tailored for silicon wafer polishing fluids. Sol-gel experiments and zeta potential measurements demonstrate the efficacy of this approach in enhancing the stability of silica sol. The quantitative analysis of surface hydroxyl groups reveals a direct correlation between enhanced stability and increased hydroxyl content. The application of the alkaline silica sol in silicon wafer polishing fluids improves polishing rates and enhances surface flatness according to atomic force microscopy (AFM). In addition, electrochemical experiments validate the capability of this polishing solution to mitigate corrosion on silicon wafer surfaces. These findings hold significant implications for the advancement of chemical mechanical polishing techniques in the field of integrated circuit fabrication.

Synthesis and Characterization of Co-Doped Fly Ash Catalyst for Chalcone Synthesis

A series of solid base fly ash hybrid materials were synthesized by doping alkali, alkaline earth metals with nitrogen, separately using co-precipitation process, combined with surfactant incorporating method. The catalysts were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and photoluminescence spectroscopy. Results revealed that the co-doped hybrid materials are highly stable with particle size in the range of 40-60 nm. The surface basicity of fly ash was upraised by increased hydroxyl content by doping with alkali, alkaline earth metals with nitrogen. The basicity of hybrid material was measured by liquid phase, solvent free, single step condensation of 4-chlorobenzaldehyde and acetophenone giving higher conversion rate and selectivity of desired product chalcone. This conversion showed that the fly ash based hybrid material has sufficient basic site, responsible for the catalytic activity

Effects of TeO2 and CaCl2 network modifiers on the Er3+:4I11/2→4I13/2 transition in fluoroaluminate multi-component glasses

We investigated thermal and fluorescence properties of Er3+ doped fluoroaluminate multi-component glasses modified by TeO2 and CaCl2. A better thermal stability with a higher ΔT (98 °C) was obtained for the TeO2 modified sample, which had a high radiative transition probability (Arad) of the Er3+: 4I11/2→4I13/2 transition. In addition, under 980 or 808 nm excitation, the Er3+ 2.7 µm emission intensity of the TeO2 modified sample decreased owing to its increased hydroxyl content induced by TeO2 modifiers. Excellent mid-infrared fluorescence along with a longer lifetime (3.48 ms) were observed in the glass tuned by CaCl2. The CaCl2 modified sample exhibited higher stimulated absorption and emission cross sections, obtained using the Füchtbauer-Ladenburg and McCumber formulas. Moreover, the strong effect of hydroxyl on the mid-infrared fluorescence properties was systematically analyzed. The oxygen network modifiers in the fluoroaluminate multi-component glass provide improved thermal properties, while the AlF3-based glasses with chlorine network modifiers have larger potentials for applications in the mid-infrared region.

Feasibility study on corrosion protection of steel bar in a self-immunity system based on increasing OH− content

In this paper, a kind of novel ethyl cellulose (EC)/calcium hydroxide microcapsule to establish a self-immunity system based on increasing hydroxyl content for the reinforced concrete is proposed. The capacity for lifting the threshold value of [Cl−]/[OH−] in this system is feasibly evaluated. Different dosages of microcapsules are placed in the sodium chloride solution with a concentration of 3.5wt% to characterize the corrosion protection by means of linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS). The working mechanism of this system consists of the chemical triggering (capsule shell) and releasing (capsule core) processes when a microcapsule is exposed a decreasing pH condition, and the release of core materials in turn restores the alkaline environment against steel bar depassivation. The test results of environmental scanning electron microscopy (ESEM) equipped with texture element analysis microscopy (TEAM) reveal that the capsule shell sensible to the [Cl−]/[OH−] ratio forms an excellent low-pH trigger mechanism. In addition, the electrochemical experiment indicates the chloride-induced corrosion intensity of a steel bar can be monitored with the decreasing Icorr and more negative Ecorr, which is further observed by the pitting characteristics of steel bars.

Fabrication of hierarchically structured rutile TiO2 nanorods on mica particles and their superhydrophilic coating without UV irridiation

In this work, we report a facile strategy to fabricate hierarchical rutile TiO2 thin film on mica substrates through hydrolysis of TiCl4 ethanolic solution in water. Scanning electron microscopy (SEM) and transmission electron microscope (TEM) analysis reveal that the rutile TiO2 film is composed of nanorods and nanoparticles. The nanorod crystals grew along the [101] direction, forming predominantly exposed {110} facets. Interestingly, rutile TiO2 coated mica particles can be directly applied as a general kind of building blocks to construct large-area super hydrophilic surfaces without UV irradiation by the simple spin-coating technique. The superhydrophilicity originates from the combination of the special rough structures of hierarchical nanorods and nanoflowers and the increased hydroxyl content caused by calcinations. More importantly, this property is very stable for half a year and could be used in self-cleaning surfaces.

Probing substrate effects on relaxation dynamics of ultrathin poly(vinyl acetate) films by dynamic wetting of water droplets on their surfaces

The dynamic wetting of water droplets on ultrathin poly(vinyl acetate) (PVAc) films supported by substrates with tunable surface hydroxyl group content was investigated at room temperature. The jumping angle of water droplets on the ultrathin PVAc films decreased with increasing hydroxyl content on the substrate surface, while a smooth evolution of the water droplet contacting line emerged for the film supported by a substrate with 100% hydroxyl groups. The critical thickness of ultrathin PAVc films, through which the interfacial effect from substrate chemistry on the dynamic wetting of water droplets on their surfaces will disappear, was measured by this novel method and the results showed that the critical thickness increased from ∼35 nm to ∼75 nm with increasing hydroxyl content from 41% to 100% on the substrate. This relationship between critical thickness and hydroxyl content was attributed to the intensities of the hydrogen bonds, resulting in lower chain mobility at the interface and a higher elastic modulus of the whole ultrathin film. This study demonstrates that the dynamic wetting of a liquid droplet on ultrathin polymer films is very sensitive and effective to access their mechanical properties, relaxation behavior and those properties affected by the substrate surface chemistry.

Synthesis and characterization of novel solid base catalyst from fly ash

A new type of solid base catalyst was synthesized by chemical and thermal activation of fly ash, collected from Thermal Super Power Station situated in Kota, Rajasthan, India. The chemical activation was carried out by 50wt.% NaOH followed by thermal activation at 450°C. The modified physiochemical property of solid base fly ash (SBFA) was determined by X-ray diffraction, FT-IR spectroscopy, Scanning Electron Microscopy, N2 adsorption–desorption studies and Flame Atomic Absorption Spectrophotometry. The results reveal that the catalyst is nano-crystalline in nature with crystallite size 11nm and particle size in the range 840nm to 6.95μm. The surface basicity and therefore, catalytic activity in SBFA was originated by increased hydroxyl content as compared to fly ash, suggesting that the catalyst possess higher surface active sites. The basicity of the catalyst was measured by liquid phase, solvent free, single step condensation of benzaldehyde with cyclohexanone giving higher conversion (>70%) and selectivity (>80%) of desired product α,α′-dibenzylidenecyclohexanone. This excellent conversion shows that the catalyst has sufficient basic sites both on the surface and in the bulk, responsible for the catalytic activity. Furthermore, this catalyst may replace conventional environmentally hazardous homogeneous liquid bases making an ecofriendly; solvent free, solid base catalyzed process. The application of fly ash to synthesize a solid base catalyst finds a noble way to utilize this abundant waste material.

Low Temperature Heat Capacity of High Purity Silica Glasses in Magnetic Field

Based on the temperature response of a relaxation type calorimeter, the heat capacity of vitreous silica has been determined between 0.35 K and 30 K and in magnetic fields up to 8 T, for several high purity glasses with different hydroxyl contents and native defects. It is found that the heat capacity of synthetic silica glasses without native defects is composed of contributions due to phonons and intrinsic low-energy excitations, which are unaffected by magnetic fields. A thermodynamically consistent description of the low-energy excitations can be given in terms of the tunneling state (TS) model. The intrinsic value of the TS density of state for vitreous silica is determined to be \(\bar P\) = 0.92 · 1045J−1m−3 and increases with increasing hydroxyl content. The superlinear temperature dependence of the heat capacity found to be valid down to 15 mK is phenomenologically described by a minimal energy splitting of Δ0,min/kB ≈ 2 mK. Magnetic contributions to the specific heat observed in Suprasil W are interpreted as excited triplet states of native point defects and have been investigated in fields up to 8 T.

The study of poly(styrene-co-p-(hexafluoro-2-hydroxylisopropyl)-?-methylstyrene)/poly(ethylene oxide) blends

Different hydroxyl content poly(styrene-co-p-(hexafluoro-2-hydroxylisopropyl)-α-methylstyene) [PS(OH)-X] copolymers were synthesized and blends with 2,2,6,6-tetramrthyl-piperdine-1-oxyl end spin-labeled PEO [SLPEO] were prepared. The miscibility behavior of all the blends was predicted by comparing the critical miscible polymer–polymer interaction parameter (χcrit) with the polymer–polymer interaction parameter (χ). The micro heterogeneity, chain motion, and hydrogen bonding interaction of the blends were investigated by the ESR spin label method. Two spectral components with different rates of motion were observed in the ESR composite spectra of all the blends, indicating the existence of microheterogeneity at the molecular level. According to the variations of ESR spectral parameters Ta, Td, ΔT, T50G and τc, with the increasing hydroxyl content in blends, it was shown that the extent of miscibility was progressively enhanced due to the controllable hydrogen bonding interaction between the hydroxyl in PS(OH) and the ether oxygen in PEO. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 2312–2317, 2004

Effect of hydrolyzed surface layer on the cytotoxicity and chemical resistance of a low fusing porcelain

Objectives. The objectives of this study were to verify the formation of a hydrolyzed surface layer on Duceram LFC and to determine its effect on the cytotoxicity of the porcelain as measured by cellular activity and concentrations of leached ionic species. Methods. Specimens were fabricated from dentin porcelain by a vibration blotting technique. Half of the specimens underwent accelerated aging by subjecting them to the standard test for hydrolytic resistance (ISO 6872). Fibroblast cell cultures were placed in direct contact with specimens. Cell viability was assessed using succinic dehydrogenase activity. Chemical resistance was determined by leaching specimens with a continuous flow of deionized water and measuring the concentrations of soluble ions in the leachates. Porcelain surface topography was examined using atomic force microscopy, and Fourier transform infrared spectroscopy was used to detect the composition of the surface layer. Results. Hydrolyzation treatment created a smooth texture on the porcelain surfaces but did not result in a hydrolyzed surface layer with increased hydroxyl content. There was a decreased alkali ion content in the surface layer of hydrolyzed specimens. Mean cellular SDH activities for non-hydrolyzed and hydrolyzed porcelain were 75±7 and 80±5% of Teflon ® controls, respectively. Only sodium ions were present in significant concentrations in collected leachates. The sodium concentration decreased over the initial 4.5 h of leaching. Significance. The changes in surface layer texture and composition as the result of the aging treatment had little effect on the cytotoxicity and chemical resistance of Duceram LFC. The results suggest that Duceram LFC would pose no biocompatibility risk even after extended exposure to the oral environment. These data also provide baseline material properties to be used in future studies of the effects of porcelain additives.

Adsorption of Poly(vinyl butyral) in Nonaqueous Ferrite Suspensions

The adsorption of poly(vinyl butyral) (PVB) on NiCuZn ferrite powder in binary solvent systems of 1-butanol and toluene has been investigated. The adsorption isotherms of different PVB's on ferrite powder from various solvent mixtures follow closely the Langmuir monolayer types and can be explained by adsorption competition between solvents and PVB. A relatively poor solvent for PVB increases its adsorption on ferrite powder and thus improves the dispersion of the powder in the nonaqueous suspension. The adsorbance of PVB increases with increasing hydroxyl content in PVB suggesting that PVB is bonding strongly to the protruding surface hydroxyl groups on ferrite powder.

Structure‐property relationship of HTPB‐based propellants. II. Formulation tailoring for better mechanical properties

AbstractThere has been a constant endeavor to improve the mechanical properties of hydroxylterminated polybutadiene (HTPB) ‐based composite solid propellants. A systematic study has been conducted on different batches of HTPB resins with varying molecular weights and hydroxyl values. Propellant formulation experiments were conducted wherein the ratio of chain extender to crosslinker was systematically varied, with a view to achieve the maximum possible strain capability and moderately high tensile strength, keeping all other parameters constant. The influence of increasing hydroxyl content from trimethylolpropane at the expense of hydroxyl content from butanediol, on the mechanical properties of the finished propellant, has been depicted on 3‐dimensional graphs. The isoproperty lines, plotted as a triangular chart with the percentage hydroxyl contents from the three constituents, can be used to arrive at the suitable formulation for a specified application depending upon the OH value of the resin. HTPB resins with high molecular weight, low functionality, and low hydroxyl value require higher levels of trifunctional curing agent and higher NCO / OH ratios to obtain outstanding mechanical properties, especially elastic properties, compared to low molecular weight, high functionality resins. The impact of hard and soft segment domain structure on the mechanical behavior of the cured systems is more pronounced in the low molecular weight resin formulations due to the higher hard segment content compared to those attainable in high molecular weight resin formulations. © 1993 John Wiley & Sons, Inc.

Sugars decrease the thermal denaturation and aggregation of arachin

The effect of three sugars D‐xylose, D‐glucose and D‐sucrose (with increasing hydroxyl content) on the thermal denaturation and protein‐protein interactions of arachin at pH 3.6 were studied by various physicochemical techniques. These included gel melting temperature, turbidity, electrophoresis, viscosity, u.v. difference, fluorescence and circular dichroic measurements. Sugars decreased the heat‐induced aggregation of arachin as shown by the gel melting temperature, turbidity and electrophoretic measurements. Arachin became more compact in the presence of sugars as shown by the reduced viscosity, u.v. difference and fluorescence spectral measurements. Far u.v.‐CD spectral measurements suggested that sugars increase the ordered structure. Viscosity and spectral measurements also showed that heating and cooling in the presence of sugars at pH 3.6 decrease the thermal unfolding of arachin. The effectiveness of the sugar to bring about all the described changes increased with its hydroxyl content. The preventive effect of sugars on the thermal denaturation and aggregation of arachin probably arises from their capacity to strengthen the intra‐protein hydrophobic and hydrogen bonding.