Effect of different concentration of rapeseed‐oil‐based polyol and water on structure and mechanical properties of flexible polyurethane foams

Flexible polyurethane foams (FPURFs) with varied concentration of water from 3.2 to 4.2% and rapeseed oil based polyol (ROP) in the range of 13–22% in polyol premix were obtained. Effects of changes in polyurethane (PUR) formulation on the foaming process and mechanical properties of FPURFs were analyzed. It was found that the change of water content in PUR formulation influences its foaming process. Higher water content in the PUR formulation increases the growth velocity and the temperature of reaction mixture. In the case of foams modified with ROP, an opposite effect can be observed, where higher content of that component resulted in overall downturn of the foaming process and decreases of registered temperature inside the foams core. An addition of ROP beneficially influences on foams cellular structure favoring creation of finer cells. Such modification of PUR formulation with ROP increased apparent density, reduced hardness, and resilience of flexible foams. What is more the support factor of FPURFs with ROP was higher in comparison to the reference foam. Along with higher water content in the PUR formulation, apparent density and hardness has decreased and foams ability to absorb energy has been increased. © 2015 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2015 , 132, 42372.     

Al2O3–B4C–Al Composite Material Systems via Pressureless Infiltration Methods

Modification of the Al₂O₃–Al system's chemistry via the addition of B₄C is described and is shown to result in fully dense structures via wetting techniques at high temperatures, without the need for pressure-assisted infiltration. The relationships between the surface area of boron carbide and alumina powders, the effectiveness of infiltration, the material chemistry following infiltration, and the resulting mechanical properties of Al₂O₃–B₄C–Al composites are evaluated. Additional approaches, including the incorporation of aluminum metal powder as an additional wetting agent before infiltration, are described in conjunction with a variation of both the surface areas and the volumetric ratios of inert Al₂O₃ to reactive B₄C phases. These methods can provide the means to achieve low-cost metal matrix composites in both vacuum and argon infiltration environments, and represent an approach that enables the generation of articles with complex geometries, requiring minimal secondary finishing treatment.     

Spiral of hatred: social effects in Internet auctions. Between informativity and emotion

An auction platform is a dynamic environment where a rich variety of social effects can be observed. Most of those effects remain unnoticed or even hidden to ordinary users. The in-depth studies of such effects should allow us to identify and understand the key factors influencing users’ behaviour. The material collected from the biggest Polish auction house has been analyzed. NLP algorithms were applied to extract sentiment-related content from collected comments and to measure informativity. Emotional distance between negative, neutral and positive comments has been calculated. The obtained results confirm the existence of the spiral-of-hatred effect but also indicate that much more complex patterns of mutual relations between sellers and buyers exist. The last section contains a several suggestions which can prove useful to improve trustworthiness of users’ reports and security of an auction platform in general.     

Femtosecond resonance enhanced CARS for background-free detection of organic molecules

We study the coherent excitation profile (CEP) of resonance enhanced femtosecond CARS in a model system zinc phthalocyanine in a polymer film host as a prospective technique for detection and identification of molecular species in ambient environments. A new method of suppressing the non-resonant FWM background is demonstrated. Transform theory is applied to calculate CEP based on the absorption spectrum, and good agreement between theory and experiment is obtained.     

Sustainable development and happiness in nations

 Environmental sustainability indicators are studied with a particular emphasis on the relation with measures of happiness in nations. Environmental sustainability indicators measure success in transition toward a sustainable economic system where development must also improve quality of environment and quality of life. Traditional indicators of sustainable development are focused on economic, environmental and social measures of development. A link between sustainable development indicators and quality of life is often difficult to see for the individual. Here a new strategy is presented, which aims to explore relation between sustainability and happiness in order to promote sustainable development. An important question whether sustainable development in the interest of future generations requires a happiness sacrifice from the part of the current generation is being addressed, and apparently no sacrifices in happiness are required, as it is possible to design strategies, which improve happiness and sustainability simultaneously.     

Microstructure Development in Low-Antimony Oxide-Doped Zinc Oxide Ceramics

The grain growth of ZnO ceramics sintered with low additions of Sb₂O₃ (<500 ppm of Sb) was investigated. Additions of Sb<250 ppm resulted in a coarse-grained microstructure with large ZnO grains (55–70 μm), much larger than the grain size of ZnO ceramics without any Sb₂O₃ addition (45 μm). The addition of 500 ppm of Sb resulted in a fine-grained microstructure with an average ZnO grain size of about 12 μm. The results are explained by an inversion-boundary (IB) -induced grain-growth mechanism. The grain-growth exponent has a value of about 2 as long as the grains containing IBs grow at the expense of IB-free grains. It increases to about 4 after the IB-containing grains impinge on each other, and achieves values above 10 for additions of 500 ppm of Sb when IBs nucleate in nearly all the ZnO grains so that grains with IBs prevail in the microstructure at an early stage in the grain-growth process.     

Effect of different rapeseed-oil-based polyols on mechanical properties of flexible polyurethane foams

Two rapeseed-oil-based polyols were synthesized by partial epoxidation of the double bonds in fatty acid chains and overall opening oxirane rings by using diethylene glycol. Flexible polyurethane foams with varied isocyanate index and modified by partial substitution of petrochemical polyether triol with rapeseed-oil-derived polyols were obtained. Bio-polyols: Polyol I and Polyol II differed in functionalities (2.5 and 5.2, respectively) and hydroxyl values (114 and 196 mg KOH/g, respectively). Influence of the bio-polyols on mechanical properties, resilience, apparent density, and cellular structure of synthesized foams was investigated. Compression properties were examined and compared via determining compression values and compression stress—strain characteristics, as well as tensile strength and elongation at break were estimated. Foams modified with Polyol I had higher values of resilience and elongation at break than those with Polyol II, while higher tensile and compression strength and superior cell structure were observed in the case of foams modified with Polyol II. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Freeze Casting: From Low-Dimensional Building Blocks to Aligned Porous Structures—A Review of Novel Materials,Methods, and Applications

Freeze casting, also known as ice templating, is a particularly versatile technique that has been applied extensively for the fabrication of well-controlled biomimetic porous materials based on ceramics, metals, polymers, biomacromolecules, and carbon nanomaterials, endowing them with novel properties and broadening their applicability. The principles of different directional freeze-casting processes are described and the relationships between processing and structure are examined. Recent progress in freeze-casting assisted assembly of low dimensional building blocks, including graphene and carbon nanotubes, into tailored micro- and macrostructures is then summarized. Emerging trends relating to novel materials as building blocks and novel freeze-cast geometries—beads, fibers, films, complex macrostructures, and nacre-mimetic composites—are presented. Thereafter, the means by which aligned porous structures and nacre mimetic materials obtainable through recently developed freeze-casting techniques and low-dimensional building blocks can facilitate material functionality across multiple fields of application, including energy storage and conversion, environmental remediation, thermal management, and smart materials, are discussed.     

High efficiency laser photothermal excitation of microcantilever vibrations in air and liquids

Photothermal excitation is a promising means of actuating microscale structures. It is gaining increased interest for its capability to excite atomic force microscopy (AFM) microcantilevers with wide frequency bandwidth in liquid environments yielding clean resonance peaks without spurious resonances. These capabilities are particularly relevant for high speed and high resolution, quantitative AFM. However, photothermal efficiency is low, which means a large amount of laser power is required for a given mechanical response. The high laser power may cause local heating effects, or spill over the cantilever and damage sensitive samples. In this work, it is shown that by simply changing from a probe with a rectangular cross-section to one with a trapezoidal cross-section, the photothermal efficiency of an uncoated silicon cantilever can be increased by more than a order of magnitude, and the efficiency of a coated cantilever can be increased by a factor of 2. This effect is demonstrated experimentally and explained theoretically using thermomechanical analysis. Results are shown for both air and water, and for normal bending and torsional oscillations.