Morphologically novel tungsten nanorods (WNRs) with the co-existence of two crystalline phases, α-W (thermodynamically stable) and β-W, were fabricated by glancing angle RF magnetron sputtering technique under various Ar pressures and flow rates. For these nanorods, a significant variation in their morphology and surface roughness was observed. These structures could be useful in a wide range of applications such as field emission, robust superhydrophobic coatings, energy, and medicine. 相似文献
Superhydrophobic surface was prepared by sol-gel method on aluminum substrate via immersing the clean pure aluminum substrate into the solution of zinc nitrate hexahydrate (Zn(NO3)2·6H2O) and hexamethylenetetraamine (C6H12N4) at different molar ratios and unchanged 0.04 mol/L total concentration, then heated at 95 °C in water bath for 1.5 h, subsequently modified with 18 alkanethiols or stearic acid. When the molar ratios of Zn(NO3)2·6H2O and C6H12N4 were changed from 10:1 to 1:1 the contact angle was higher than 150°. The best prepared surface had a high water contact angle of about 154.8°, as well as low angle hysteresis of about 3°. The surface of prepared films using Zn(NO3)2·6H2O and C6H12N4 composed of ZnO and Zn-Al LDH, and Al. SEM images of the film showed that the resulting surface exhibits different flower-shaped wurtzite zinc oxide microstructure and porous Zn-Al LDH. The special flowerlike and porous architecture, along with the low surface energy leads to the surface superhydrophobicity. 相似文献
The ligand solid angle approach has been successfully applied to the analysis of the catecholate complexes of Sb(III) and
Sb(V). The Sb(III) complexes possess an electron lone pair that influences their molecular structure but does not behave as
a classic “ligand” when intermolecular interactions are concerned. The Sb(III) complexes in solid state form numerous intermolecular
interactions that effectively increase metal shielding, and herein we analyze the effects of the lone pair of electrons on
the complex coordination geometry. In the five-coordinate R3CatSb(V) complexes (Cat = catecholate ligand, R = Ph, Me, Cl) the metal is shielded by 87(3)% and multiple intermolecular
contacts are observed. The central metal in the six-coordinate antimony(V) complexes R3CatSb(V) · L is shielded to the extent of 89(2)% and no strong attractive intermolecular interactions are detected in solid
state. Thus, the metal shielding in excess of 85% is required to prevent complex dimerization or additional ligation of the
central atom by a nucleophile. 相似文献
Stopped-flow apparatus coupled with a large variety of detection techniques is one of the most frequently used instruments to study rapid kinetics. With the recent technical advances of small angle scattering beam-lines and more particularly in the fields of electronics and detectors, the 10 last years have seen the development of combined stopped-flow and small angle neutron or X-ray experiments. Time resolutions of the order of 10 ms for X-rays to 100 ms for neutrons allow one to follow the very early stages of the sample formation. This review presents recent applications in the fields of soft matter and biology. The different studies reveal pathways and intermediate states during phase transitions, which are of fundamental importance to understand and control the properties at equilibrium. 相似文献
Contact angle and the wetting behaviour of solid particles are influenced by many physical and chemical factors such as surface roughness and heterogeneity as well as particle shape and size. A significant amount of effort has been invested in order to probe the correlation between these factors and surface wettability. Some of the key investigations reported in the literature are reviewed here.It is clear from the papers reviewed that, depending on many experimental conditions such as the size of the surface heterogeneities and asperities, surface cleanliness, and the resolution of measuring equipment and data interpretation, obtaining meaningful contact angle values is extremely difficult and such values are reliant on careful experimental control. Surface wetting behaviour depends on not only surface texture (roughness and particle shape), and surface chemistry (heterogeneity) but also on hydrodynamic conditions in the preparation route. The inability to distinguish the effects of each factor may be due to the interplay and/or overlap of two or more factors in each system. From this review, it was concluded that:
•
Surface geometry (and surface roughness of different scales) can be used to tune the contact angle; with increasing surface roughness the apparent contact angle decreases for hydrophilic materials and increases for hydrophobic materials.
•
For non-ideal surfaces, such as mineral surfaces in the flotation process, kinetics plays a more important role than thermodynamics in dictating wettability.
•
Particle size encountered in flotation (10-200 μm) showed no significant effect on contact angle but has a strong effect on flotation rate constant.
There is a lack of a rigid quantitative correlation between factors affecting wetting, wetting behaviour and contact angle on minerals; and hence their implication for flotation process. Specifically, universal correlation of contact angle to flotation recovery is still difficult to predict from first principles. Other advanced techniques and measures complementary to contact angle will be essential to establish the link between research and practice in flotation. 相似文献
Prediction of the rolling behavior of ships in irregular sea remains one of the most difficult problems in ship engineering. The present work facilitates solution of this problem by derivation of a model which is meaningful from the subject-specific point of view and can efficiently be analyzed with the path-integration method. The model is a single Itô’s stochastic differential equation for the rolling angle of a ship located at a fixed spatial point. The equation appears to be of the third order and nonlinear. It takes into account the elevation of stochastic traveling sea waves. The stochasticity of the elevation is allowed for by stationary stochastic velocity of the waves. The works also notes the picture for the multistability of the derived model. Improvement of capabilities of the methods for multistable nonlinear systems is included in directions for future research. 相似文献
Surface treatment procedures such as grinding and polishing are needed to provide the ceramic dental restorative materials with proper fitting and occlusion. The treated surfaces are customarily glazed to improve the strength and smoothness. Though smoothness and wetting of the dental surfaces are important to minimize bacterial plaque retention, influence of the surface treatment and glazing procedures on the final surface roughness and its correlation to wettability are overlooked.
In this work, effect of various treatment (diamond fraising, stoning, sanding and aluminum oxide and rubber polishing) and glazing (auto and overglazing) techniques on the final roughness and the resulting wettability of dental ceramic surfaces were investigated using scanning electron microscopy (SEM) observations and atomic force microscopy (AFM) scans, 75 scans per sample. The surfaces were characterized and assigned an average roughness measure, Ra. The wettability of the same surfaces was evaluated using micro-contact angle measurements (25 micro-bubbles placed on a grid on each surface) to correlate the final surface roughness and wettability.
The results show that overglazing prevails over surface irregularities from different treatment procedures and provides homegeneously smooth surfaces with mean Ra < 10 nm. It also produces uniformly wetted surfaces with low contact angles around 20°. The autoglazed surfaces are less smooth (mean Ra around 50 nm) and displays sporadic topographic irregularities. They display larger and less uniform contact angles ranging between 35° and 50°. The results suggest that overglazing should be preferred after surface treatment to obtain a smooth and well-wetted dental ceramic surface. 相似文献
The growth of highly functionalised poly allyl alcohol films by pulsed plasma polymerisation of CH2CHCH2OH on biomedical grade polyurethane has been followed by X-ray photoelectron spectroscopy (XPS) and contact angle measurements. Film thickness is observed to increase approximately linearly with plasma modification time, suggesting a layer-by-layer growth mode of poly allyl alcohol. Water contact angle measurements reveal the change in the surface free energy of wetting decreases linearly with plasma modification up to the monolayer point after which a constant limiting value of −24 mJ m−2 was attained. Films prepared at 20 W plasma power with a duty cycle of 10 μs:500 μs exhibit a high degree of hydroxyl (OH) retention with minimal fragmentation of the monomer observed. Increasing the plasma power up to 125 W is found to improve OH retention at the expense of ether formation generating films close to the monomer stoichiometry. Duty cycle plays an important role in controlling both film composition and thickness, with longer off times increasing OH retention, while longer on times enhance allyl alcohol film growth. 相似文献