We explore the lithographic limits of lamellae-forming PS-b-PMMA block copolymers by performing directed self-assembly and pattern transfer on a range of PS-b-PMMA materials having a full pitch from 27 to 18.5 nm. While directed self-assembly on chemical contrast patterns was successful with all the materials used in this study, clean removal of PMMA domains and subsequent pattern transfer could only be sustained down to 22 nm full pitch. We attribute this limitation to the width of the interface, which may represent more than half of the domain width for materials with a critical dimension below 10 nm. With the limit of pattern transfer for PS-b-PMMA set at ∼11 nm, we propose an integration scheme suitable for bit patterned media for densities above 1.6 Tdot/in(2), which require features below this limit. Directed self-assembly was carried out on chemical contrast patterns made by a rotary e-beam lithography system, and pattern transfer was carried out to demonstrate fabrication of large area (up to 25 mm-wide annular band of circular tracks) nanoimprint templates for bit patterned media. We also demonstrate compatibility with hard disk drive architecture by fabricating patterns with skewed radial lines with constant angular pitch and with servo patterns that are needed in hard disk drives to generate a radial positional error signal (PES).

According to the dielectric design, a new kind of rare-earth (RE)-doped TiO 2 particle was synthesized by means of sol-gel technique for use in electrorheological (ER) fluids. A distinct enhancement in the yield stress under dc electric field was found by using such particles, when compared with that of pure TiO 2 . The yield stress of typical cerium-doped TiO 2 suspension was about 5.0 kPa at 3 kV/mm and 7.0 kPa at 4 kV/mm, which were 10 times higher than that of a pure TiO 2 suspension. The yield stress showed a marked dependence on RE-doping degree. Substitution of 10 mol % cerium or 8 mol % lanthanum for Ti could obtain the highest yield stress. These were well explained by the dielectric measurements that showed an increase in the dielectric loss and the dielectric constant at low frequency and their regular change with rare earth content. The lattice distortion and defects in the TiO 2 crystal caused by substitution for Ti with large-radius RE ions may be responsible for the obvious improvement noted above.

Here we introduce a simple low-cost yet robust method to realize spontaneously wrinkled morphologies on spherical surfaces. It is based on surface chemical oxidation of aqueous-phase-synthesized polydimethylsiloxane (PDMS) microspheres in the mixed H2SO4/HNO3/H2O solution. Consequently, curvature and overstress-sensitive wrinkles including dimples and labyrinth patterns are successfully induced on the resulting oxidized PDMS microspheres. A power-law dependence of the wrinkling wavelength on the microsphere radius exists. The effects of experimental parameters on these tunable spherical wrinkles have been systematically investigated, when the microspheres are pre-deposited on a substrate. These parameters include the radius and modulus of microspheres, the mixed acid solution composition, the oxidation duration, and the water washing post-treatment. Meanwhile, the complicated chemical oxidation process has also been well studied by in-situ optical observation via the microsphere system, which represents an intractable issue in a planar system. Furthermore, we realize surface wrinkled topographies on the whole microspheres at a large scale, when microspheres are directly dispersed in the mixed acid solution for surface oxidation. These results indicate that the introduced wet surface chemical oxidation has the great potential to apply to other complicated curved surfaces for large-scale generation of well-defined wrinkling patterns, which endow the solids with desired physical properties.

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TiO 2 is very important electrorheological (ER) material due to its high dielectric constant. But its weak ER activity is amazing. We report here a novel approach to enhance the electrorheological activity of TiO 2 by doping it with chromium (Cr) ion. X-ray diffraction shows that the material possesses the anatase phase when the Cr/Ti molar ratio is smaller than 10%, while phase separation appears upon further increasing the Cr/Ti molar ratio. X-ray photoelectron spectroscopy shows that Cr 6+ and Cr 3+ are codoped in TiO 2 crystal and induce a shift of the binding energy of TiO 2 . Rheological experiments show that Cr-doping significantly enhances the ER activity of TiO 2 . The yield stress τ E of a typical 10 mol % Cr-doped TiO 2 suspension is about 2.3 and 7.0 kPa at 4 kV/mm when the volume fraction is 18% and 34%, respectively. The ER efficiency ((τ Eτ 0 )/τ 0 ) of a typical Cr-doped TiO 2 suspension is about 280 (10.55 s -1 ) at 3 kV/mm, which is 18 times higher that of pure TiO 2 suspension. Especially, the yield stress shows a marked dependence on Cr doping degree, and ER activity tends to decline with phase separation when the doping degree is higher than 10 mol %. On the basis of the structure analysis and dielectric and conduction measurements, we attribute the enhancement of ER activity of TiO 2 to the improvement in the dielectric and conduction properties, induced by the activated internal structure, including defect and impurities of TiO 2 due to doping with different valent Cr ions.

Black liquor is a major wastewater generated from the pulping process that has a detrimental impact on the environment. This work assessed the potential of black liquor to be an inexpensive resource of alkali catalyst in supercritical water gasification of coal through thermodynamic analysis and experimental study. The experiments were performed in a fluidized-bed reactor at 550°C and 25 MPa, and the products were characterized by gas chromatography, X-ray fluorescence, X-ray diffraction, and gas chromatography-mass spectrometry. In the gasification of coal and black liquor mixtures, the presence of coal can improve the H 2 production under the equilibrium state. Both the inherent alkalis and lignin in black liquor played a role of improving the gasification efficiency of coal. The alkalis also accelerated the water−gas shift reaction and increased the H 2 fraction. The high total mixture concentration inhibited the gasification, and the reactor was plugged with a concentration of 25 wt %. The presence of black liquor fixed more sulfur in the solid residues, but it aggravated the corrosion of the 316 SS reactor. The aqueous product mainly contained alkylphenols, cyclopentanone, and their derivatives. A simple influencing mechanism of lignin on coal gasification was proposed: the decomposition of lignin prior to coal can generate some phenolic compounds, which can promote the extraction of the substances coated outside the coal particle and favor the further reaction between the coal and water.

To enhance electrorheological (ER) activity by improving interfacial polarization, we prepared a new mesoporous Cr-doped TiO2 ER material by a copolymer-templated sol-gel method. The material was characterized by differential scanning calorimeter and thermogravimetric (DSC-TG) analysis, Fourier transform infrared (FT-IR), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption, and X-ray photoelectron spectroscopy (XPS) techniques. The ER activity was studied by the rheological curve and yield stress under an electric field. The results showed that the mesoporous Cr-doped TiO2 ER material possessed a high surface area over 200 m2/g and a crystalline anatase pore wall doped by different valent Cr ions. The ER activity of mesoporous Cr-doped TiO2 was higher than that of nonporous Cr-doped TiO2. The yield stress and ER efficiency of the mesoporous Cr-doped TiO2 ER suspension was 3 times as high as that of the nonporous Cr-doped TiO2 ER suspension, 7 times as high as that of the mesoporous undoped TiO2 ER suspension, and 20 times as high as that of the nonporous pure TiO2 ER suspension. Furthermore, the ER activity of mesoporous Cr-doped TiO2 showed a dependence on surface area, and the high porosity or surface area samples showed higher ER activity. The dielectric spectra analysis showed that the mesoporous Cr-doped TiO2 ER suspension possessed a significantly larger interfacial polarizability compared with the nonporous Cr-doped TiO2 ER suspension, and the regular change of polarizability with surface area or porosity was in accordance with the change of ER activity with surface area or porosity. The improvement of dielectric properties or polarization could well explain the enhancement of the ER activity of mesoporous Cr-doped TiO2.

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