Diffusion of water in palm leaf materials

Diffusion of water into plant materials is known to decrease their mechanical strength and stiffness but improve formability. Here, we characterize water diffusion through areca palm leaf-sheath—a model plant material, with hierarchical structure, used in eco-friendly foodware. The diffusion process is studied using mass gain measurements and in situ imaging of water transport. By treating the areca sheath as homogeneous ensemble, and incorporating effects of material swelling due­ to water absorption, a factor typically neglected in prior studies, the diffusion coefficient D w for water is estimated as (6.5 ± 2.2) × 10 −4 mm 2 s −1 . It is shown that neglecting the swelling results in gross underestimation of D w . Microstructural effects (e.g. fibre, matrix) on the diffusion are characterized using in situ imaging of the water transport at high resolution. The observations show that the water diffuses an order of magnitude faster in the matrix (8.63 × 10 −4 mm 2 s −1 ) than in the fibres (7.19 × 10 −5 mm 2 s −1 ). This non-uniformity is also reflected in the swelling-induced strain in the leaf, mapped by image correlation. Lastly, we vary salt concentration by controlled additions of NaCl and note a non-monotonic dependence of the diffusion on concentration. Implications of the results for improving foodware manufacturing processes and product life are discussed.

Dandelion pappus morphing is actuated by radially patterned material swelling

Plants can generate motion by absorbing and releasing water. Such motion often facilitates reproductive success through the dispersal of seeds and fruits or their self-burial into the soil. Asteraceae plants, such as the dandelion, often have a hairy pappus attached to their fruits to allow them to fly and in many cases, these can open and close depending on moisture levels to modify dispersal. Here we demonstrate the relationship between structure, composition and function of the underlying hygroscopic actuator. By investigating the structure and properties of the actuator cell walls we have identified the mechanism by which the dandelion pappus closes and developed a structural computational model that can capture observed pappus closing. This model was used to explore the contribution of differential material domains in the actuator function and the critical design features. We find that the actuator relies on the radial arrangement of vascular bundles and surrounding tissues including cortex and the floral podium around a central cavity. This allows heterogeneous swelling in a radially symmetric manner to co-ordinate precise movements of the pappus hairs attached at the upper flank. This actuator is a derivative of bilayer structures, but is radial and can synchronise the movement of a planar or lateral attachment. The simple, material-based mechanism presents a promising biomimetic potential in robotics and functional materials.

Pharmacognostic analysis of Salvia hispanica L. seeds

The aim. The aim of this work was to conduct a microscopic and phytochemical study of the seeds of chia (Salvia hispanica L.). Materials and methods. Chia seeds were examined macroscopically and microscopically. To study the qualitative composition of the main groups of biologically active substances, histochemical, microchemical and chemical reactions were used. Hydroxycinnamic acids were identified by paper chromatography. To obtain a lipophilic extract, a Soxhlet apparatus and an exhaustive chloroform extraction method were used. The study of the quantitative content of fatty acids was carried out by gas chromatography. The content of polysaccharides in the raw material was determined by the gravimetric method. According to the SPhU method, the raw material swelling index was determined. Results. The main macro- and microscopic features of chia seeds have been established. Histochemical reactions, microchemical reactions made it possible to establish the presence of mucus and fatty oils in chia seeds. With the help of chemical reactions, the presence of flavonoids in the raw material was established. The quantitative content of fatty oils is 24.0±1.2 %. The content of water-soluble polysaccharides in the whole raw material was 4.01±0.07 %, in the crushed raw material - 5.04 ± 0.05 %. As a result of determining the swelling index, it was found that this indicator for the whole chia seeds was 20, and for the crushed ones – 17. The content of hydroxycinnamic acids in the chia seeds was 1.07±0.03 %. 9 fatty acids have been identified, among which linoleic acid predominates in terms of content. Conclusions. The presence and quantitative content of mucus, fatty oils, water-soluble polysaccharides, flavonoids, hydroxycinnamic acids, fatty acids was confirmed in the seeds of chia (Salvia hispanica L.). The obtained data can be used to develop regulatory documentation for chia seeds in order to use this raw material in pharmacy and medicine

16Cr-19Ni steel swelling at dose rates from 1×10-8 to 1.6×10-6 dpa/s

The article presents the first data on EK-164ID steel swelling after operational irradiation in a fast nuclear reactor in the temperature range of 370–630 °C and maximum damaging doses of 66–77 dpa. The dose accumulation rate along the cladding tubes made of this material was 1×10-8–1.6×10-6 dpa/s. The swelling was determined by the hydrostatic weighing method with an error of no more than 0.5%. The results obtained were analyzed depending on the irradiation parameters and in comparison with the 16Cr-15Ni grade material. The objectives of the study were to estimate the characteristic values of the maximum swelling temperature and dose as well as to calculate the average material swelling rate at the working temperature of irradiation, the incubation period for the onset of swelling, and the stationary swelling rate. It was found that the tube samples, characterized with austenite grain sizes of 9–12 µm before irradiation, have an average swelling rate of 0.035–0.05 %/dpa after reaching the maximum damaging doses of 66–77 dpa (at a rate of (1–1.5)×10-6 dpa/s) and not more than 0.035%/dpa at doses less than 20 dpa (at a rate of 5×10-7 dpa/s). The characteristic maximum swelling temperature of the studied material is in the range of 430–500 °C. The characteristic maximum swelling dose is in the range of 61–72.5 dpa or 70–80% of the maximum accumulated dose. The incubation stationary swelling period for the material is 30 dpa. The stationary swelling rate is 0.1% /dpa. The radiation resistance characteristics of the studied material have an advantage over those for 16Cr-15Ni grade cladding materials under similar irradiation conditions and a similar structural state, which inherits grain sizes of 9–14 μm during the tube processing.

Improvement of Strength Parameters of Foam Ceramics for Energy-Efficient Enclosing Structures

Studies of the influence of vibration impact on the strength of foam-ceramic raw material, produced on the basis of chemically modified natural silicites, are presented. The natural oscillation frequencies of mineral particles are established, taking into account their size, density and ultimate shear stress of raw suspensions. It is shown that the coincidence of the natural and forced oscillations of the particles leads to an increase in the thixotropic effect. Using the technology of a controlled «sol-gel» transition in the structure of raw material, swelling under the influence of vibration load, samples of the material were obtained with a higher-quality macrostructure without the use of binders. Indicators of compressive strength and average density of raw and ceramics are given.

Experimental Investigation on Micro-Groove Manufacturing of Ti-6Al-4V Alloy by Using Ultrasonic Elliptical Vibration Assisted Cutting

The micro-groove structure on the planar surface has been widely used in the tribology field for improving the lubrication performance, thereby reducing the friction coefficient and wear. However, in the conventional cutting (CC) process, the high-quality, high-precision machining of the micro-groove on titanium alloy has always been a challenge, because considerable problems including poor surface integrity and a high level of the material swelling and springback remain unresolved. In this study, the ultrasonic elliptical vibration assisted cutting (UEVC) technology was employed, which aimed to minimize the level of the material swelling and springback and improve the machining quality. A series of comparative investigations on the surface defect, surface roughness, and material swelling and springback under the CC and UEVC processes were performed. The experimental results certified that the material swelling and springback significantly reduced and the surface integrity obviously improved in the UEVC process in comparison to that in the CC process. Furthermore, for all the predetermined depths of the cut, when the TSR (the ratio of the nominal cutting speed to the peak horizontal vibration speed) was equal to one of twenty four or one of forty eight, the accuracy of the machined micro-groove depth, width and the profile radius reached satisfactorily to 98%, and the roughness values were approximately 0.1 μm. The experimental results demonstrate that the UEVC technology is a feasible method for the high-quality and high-precision processing of the micro-groove on Ti-6Al-4V alloy.

Theoretical and Experimental Investigations of Tool Tip Vibration in Single Point Diamond Turning of Titanium Alloys

The material swelling effect in single point diamond turning (SPDT) causes ragged materials on a machined surface which slows down the movements of tool tip vibration, and acts as a simple impacted pendulum system with a damping effect and displays a single twin peak in fast Fourier transform (FFT). Due to the low elastic modulus and low thermal conductivity of titanium alloys, the material swelling effect of titanium alloys in SPDT is much more serious than that of traditional metals. For this reason, the tool tip vibration in SPDT of titanium alloys is expected to be different from previous reports. In this study, apart from the demonstration of the original single twin peak induced from the material swelling effect by the main cutting motion, we reported recently that there exists another twin peak induced by secondary material swelling arising from the movement of tool tip vibration in the SPDT of titanium alloys. The additional twin peak was located at the right side of the original twin peak in FFT, displaying two twin peaks in the frequency domain of cutting force and suggesting the existence of another tool tip vibration system with a new damping factor in the SPDT of titanium alloys. Combining the effects of primary and secondary material swelling, the new dynamic model with the modified damping factor of tool tip vibration system are developed, which surface roughness of the machined titanium alloys in SPDT was predicted in higher accuracy by using the new model. The FFT of cutting force, surface roughness, and surface profile were provided in this article for the experimental validations.

MAINTENANCE OF FILTRATION AND CAPACITIVE RESERVOIR PROPERTIES DURING TEMPORARY ISOLATION

The article provides the analysis of factors affecting the reservoir properties (filtration and capacity) during repair works. It is revealed that the maintenance of filtration and capacitive reservoir properties is ensured by high-quality blocking and unblocking the reservoir, as well as by prevention of clay material swelling. Solution of these problems is possible through proper selection of the bridging agents (nature, type and fractional composition) used in the blocking composition, and various functional additives (salts, polymeric reagents and surfactants). Furthermore, the reasons of clay minerals swelling and various ways to prevent this process are analyzed. It is determined the peculiarities of clay minerals structure are essential for their properties, and in particular, their ability to swell.