Smooth Outer Surface Research Articles

Microencapsulation of a Model Oil in Wall System Consisting of Wheat Proteins Isolate (WHPI) and Lactose

Microencapsulation allows for the entrapment, protection, and delivery of sensitive and/or active desired nutrients and ingredients as well as biologically-active agents. The microencapsulating properties of wall solutions (WS) containing 2.5–10% (w/w) wheat proteins isolate (WHPI) and 17.5–10% (w/w) lactose were investigated. Core-in-wall-emulsions (CIWEs) consisting of the WS and soy oil were prepared at a wall-to-core (W:C) ratio ranging from 25:75 to 75:25 (w/w). Microcapsules were prepared by spray-drying the CIWEs. The CIWEs had a mean particle diameter smaller than 0.5 µm and surface excess that ranged from 1.59 to 5.32 mg/m2. In all cases, microcapsules with smooth outer surfaces that exhibited only limited surface indentation were obtained. The core, in the form of protein-coated lipid droplets, was embedded throughout the wall matrices. In all but one case, core retention was higher than 83%, and in 50% of the cases, it was higher than 90%. Core retention was significantly influenced the composition of the WS and by W:C ratio (p < 0.05). Except for two cases, microcapsules exhibited very limited core extractability. The microencapsulation efficiency was >90% and was influenced, to a certain degree, by the composition of the CIWEs. Results indicated the potential for utilizing wall systems consisting of WHPI and lactose as effective and highly functional microencapsulating agents in food and related applications.

Preparation of Covalently Crosslinked Sodium Alginate/Hydroxypropyl Methylcellulose pH-Sensitive Microspheres for Controlled Drug Release

Due to their biocompatible and eco-friendly properties, natural polymers have attracted significant attention as controlled drug delivery carriers. In this paper, a facile method is presented for preparing pH-sensitive microspheres via acidic esterification between sodium alginate (SA) and hydroxypropyl methylcellulose (HPMC). The resulting microspheres were characterized by scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FT-IR), and thermogravimetric analysis (TGA). To evaluate the potential applications of microspheres as a drug carrier, the controlled release of a model drug—diclofenac—was examined. The SEM analysis revealed that the microbeads were spherical with a relatively smooth outer surface and porous inner network structure. The drug release experiments indicated that the cumulative release of diclofenac was less than 1% in an acidic medium, whereas it was close to 100% within 3 h in a pH 6.8 phosphate buffer saline solution. These results demonstrated that the SA/HPMC microspheres are promising candidates as pH-sensitive drug delivery system.

Synthesis and optimization of polyurethane microcapsules containing [BMIm]PF6 ionic liquid lubricant

Polyurethane (PU) microcapsules containing [BMIm]PF6 as a lubricant have been fabricated by interfacial polymerization. The stabilizing effect of 10 kinds of emulsifiers towards [BMIm]PF6 ionic liquid have been delineated. A Pickering emulsion stabilized by lignin showed the best emulsification effect on highly viscous [BMIm]PF6. The types and reactivities of monomers have an important influence on the formation of microcapsules. Three kinds of isocyanate (IPDI, MDI, TDI) were reacted with diamines or diols to prepare the PU microcapsules in this work. The optiaml [BMIm]PF6@PU microcapsules were obtained when using IPDI and TETA as monomers, under conditions of 5,000 rpm emulsifying rate, 0.5 wt% concentration of lignin Pickering emulsion, and a 3:1 mass ratio of [BMIm]PF6/IPDI. The synthesized microcapsules have a regular and compact spherical structure, smooth outer, and inner surfaces with a mean diameter of 43 ± 15 µm, and a thickness of 3.8 µm. The core content of [BMIm]PF6@PU microcapsules was determined as >70%, and the initial decomposition temperature was 300 °C. The [BMIm]PF6 ionic liquid shown excellent lubricating property, ultralow friction coefficient (decreased by 72.7%) and wear rate (decreased by 160 times) were obtained by embedding 30 wt% microcapsules into epoxy compared with pure epoxy.

Thrombus on the inflow cannula of the HeartWare HVAD: an update.

The HeartWare HVAD (Medtronic, Minneapolis, MN) is a continuous-flow left ventricular assist device (LVAD) approved by the FDA in 2012 as a bridge to transplant in patients with end-stage left ventricular heart failure. The current inflow cannula has a smooth outer surface near the inflow edge and a sintered collar of titanium microspheres near the pump. A previous case series of HVAD patients bridged to transplant revealed thrombus on the outer surface of the inflow cannula in 8 of 8 patients, predominantly at the smooth-sintered interface, that was associated with a clinical stroke rate of 12.5%. Cases of HVAD devices removed at the time of heart transplant were identified in the surgical pathology database. The gross and microscopic findings were reviewed along with clinical data. A total of 22 patients with 24 HVAD implants diagnosed with dilated cardiomyopathy (13 patients), ischemic heart disease (4 patients), lymphocytic myocarditis (2 patients), hypertrophic cardiomyopathy (2 patients), and congenital valvular disease (1 patient) were included. Two patients received two HVADs to provide biventricular support. All patients received post-implantation anti-coagulation with an INR goal of 2 to 3. Gross pathologic examination revealed thrombi on the outer aspect of the HVAD inflow cannula in 23 of 24 devices (96%). The inflow cannula of the one device that did not develop thrombus was positioned such that the smooth-sintered interface was buried in the ventricular myocardium and not in contact with blood in the ventricular chamber. Complications during the period of device support included 9 thromboembolic events (41%) including 6 ischemic strokes (27%), 2 intracoronary thromboembolic events and 1 splenic infarct. Patients suffered strokes 4 to 174 days (mean 82) after HVAD placement and had thrombus on the inflow cannula ranging in size from 0.1-2.5 cm (axial), 0.4-4.5 cm (circumferential) and 0.1-0.5 cm (thickness). Histologic evaluation revealed bland, partially organized thrombi without evidence of infection. Other complications included driveline infections (9%), non-driveline related bacteremia (9%) and hemorrhage (5%). We report here an extension of our original study to a total of 22 patients with 24 HVAD implants who were all successfully bridged to transplant. We validate the very high prevalence of thrombus around the HVAD inflow cannula, associated with a clinical thromboembolic event in over a third of the patients, the majority of which were strokes. The nidus for thrombus formation appears to be the smooth-sintered interface of the HVAD inflow cannula.

Electrospun polymer bottle microresonators for stretchable single-mode lasing devices.

We report a simple electrospinning method to fabricate polymer bottle microresonators, which are doped with a lasing gain material and supported by electrospun polymer micro/nanofibers on a flexible grooved polymer substrate. The fabricated bottle microresonators have smooth outer surfaces and high quality. By using an interference light pump approach, single whispering gallery mode lasing is obtained, with a side-mode suppression factor over 20dB. By mechanically stretching the grooved substrate, tunability of the lasing peaks is demonstrated. Our method has the advantages of saving time and being low in cost and may have promising applications in stretchable lasing and sensing devices.

Structural design, fabrication and construction of the Armadillo vault

The Armadillo vault, exhibited at the 2016 Venice Architecture Biennale and commended at the 2017 Structural Awards, is a doubly curved, unreinforced, cut-stone, compression-only vault, constructed from 399 limestone blocks. The thickness of the stone varies from 8–12cm at the supports to 5cm at the peak. With a height of 4.4m and spans of over 15m, the structure has a thickness-to-span ratio half that of an eggshell. This paper describes the form-finding process and detailed structural analysis. Steel supports were designed to take the reaction thrusts of the vault and transfer them safely to both the ground and the internal steel tie system. The stone-cutting process for the limestone is also outlined, describing the rough-finished inner surface, which was patterned to follow lines of internal force flow, and the smooth flat outer surface. Finally, the process of erecting the formwork and falsework on site is also set out, including the process of decentring and the use of custom keystones.

Etched poly(ether ether ketone) jacket stir bar with detachable dumbbell-shaped structure for stir bar sorptive extraction

Development of stir bar sorptive extraction (SBSE) device with high stability and extraction efficiency is critical and challenging by date. In this work, etched poly(ether ether ketone) (PEEK) tube with high mechanical strength and large specific surface area was used as jacket for SBSE device. By etching with concentrated sulfuric acid, the smooth outer surface of PEEK become porous with plenty of micro holes, which was beneficial for coating of sorbents and significantly improved the extraction performance. After functionalized by bio-polydopamine method, strong hydrophobic p-naphtholbenzein molecular was immobilized onto the chemical resistant PEEK surface (PNB@E-PEEK) as stationary phase. We also firstly developed a simple detachable dumbbell-shaped structure for improving the workability of PEEK jacket stir bar. The dumbbell-shaped construction can eliminate the friction between stir bar and container, and the design of detachable structure make elution can be accomplished easier with small amount of organic solvent. It was interesting that the developed detachable dumbbell-shaped PNB@E-PEEK stir bar showed exceptional stability and extraction efficiency for SBSE enrichment of multiple analytes including several Sudan dyes, triazines, polycyclic aromatic hydrocarbons (PAHs), alkaloids and flavonoid. By coupling with high performance liquid chromatography-ultraviolet detection (HPLC-UV), PNB@E-PEEK stir bar based SBSE-HPLC-UV method was applied for the analysis of common Sudan dye pollutants. The method showed low limits of detection (0.02-0.03 ng/mL), good linearity (R2 ≥ 0.9979) and good reproducibility (relative standard deviation ≤ 7.96%). It has been successfully applied to determine three dye pollutants in tap and lake water.

Nepafenac loaded silica nanoparticles dispersed in-situ gel systems: Development and characterization

This research was aimed to develop and evaluate nepafenac loaded silica nanoparticles dispersed in-situ gel system for the improved treatment of ocular diseases. The blank silica nanoparticles prepared by stober’s process showed the particle size of 151 nm to 285 nm with the zeta potential of −19.6 to −31.9 mV. The nepafenac loaded silica nanoparticles were spherical in shape with smooth outer surface. The nepafenac loaded silica nanoparticles dispersed in poloxamer – chitosan in-situ gelling system showed gelling temperature of 32 °C with sustained release of nepafenac and higher permeation (58.79 μg) across the goat cornea than poloxamer – poloxamer (21.18 μg) in-situ gelling system. Hence the developed in-situ gelling system containing nepafenac loaded silica nanoparticle could be a promising tool for the topical delivery of drugs to the eye.

Osmotic contribution to the flow-driven tube formation of copper-phosphate and copper-silicate chemical gardens.

We have produced hollow copper-containing precipitate tubes using a flow-injection technique, and characterized their linear and volume growth. It is shown that the ratio of the volume increase rate to that of pumping is constant independent of the chemical composition. It is also found that osmosis significantly contributes to the tube growth, since the inward flux of chemical species dominates during the precipitate pattern formation. The asymmetric hydrodynamic field coupled with the inherent concentration and pH gradients results in different particle morphology on the two sides of the precipitate membrane. While the tubes have a smooth outer surface, the inner walls are covered with nanoflowers for copper phosphate and with nanoballs for copper silicate.

The first dinosaur egg from the Lower Cretaceous of Western Siberia, Russia

The Lower Cretaceous Ilek Formation in Western Siberia (Russia) has yielded various vertebrate fossils, including skeletal remains of dinosaurs. Here we report on a fragmentary theropod egg from the vertebrate locality Shestakovo 3 of the Ilek Formation in Kemerovo Province. We assign the specimen to the oogenus Prismatoolithus (oofamily Prismatoolithidae) as Prismatoolithus ilekensis oosp. nov., on the basis of the following unique combination of characters: ovoid-shaped egg; thin eggshell 300–330 μm thick; angustiprismatic morphotype; eggshell with three different layers; gradual transition between mammillary layer and prismatic layer; abrupt contact between prismatic layer and external layer; mammillary layer to prismatic layer to external layer thickness ratio is 1:3:0.6; prismatic layer with ill-defined squamatic texture; angusticanaliculate pore system; and smooth outer surface. Like other Early Creataceous Prismatoolithus, the egg of Prismatoolithus ilekensis oosp. nov. was laid by a small bodied theropod dinosaur (troodontid or primitive bird) and this taxonomic attribution is supported by results of our phylogenetic analysis. Prismatoolithus ilekensis oosp. nov. is the first Early Cretaceous ootaxon from Russia.urn:lsid:zoobank.org:act:734EAD40-86C3-488B-A61E-B5FF7378BC0E

00.06: Advances and development needs in the structural design of steel box girders for major bridges

ABSTRACTMajor cable‐supported bridges with a span exceeding 600m would not normally be feasible without a steel box girder to carry the traffic load. These box girders generally comprise a structural steel deck plate stiffened longitudinally by open or closed ribs and transversely by diaphragms. The stiffened deck plate supports the local wheel load and distributes it to the diaphragms from where it is transferred into the box girder. The stiffening ribs also increase the total cross‐sectional steel area and thereby contribute to the overall bending capacity of the box girder and finally, the stiffeners increase the resistance of the plate to buckling.This type of deck structure is generally called an “orthotropic bridge deck” due to the orthogonal nature of the stiffened deck plate and was first developed and utilised in 1950. The orthotropic steel deck is considerably lighter than a concrete slab in a composite girder and therefore makes longer span bridges possible, by reducing the self‐weight forces that would otherwise dominate. The self‐weight of the girder is a key driver in major bridge designs since it must be carried by all other bridge components, such as cables, towers, anchorages and foundations. The orthotropic steel girder is usually a fully closed box girder with all stiffening ribs placed inside the girder giving a smooth outer surface that is easy to paint and maintain. The interior of the closed box is often dehumidified without being painted giving an environmentally‐friendly fabrication that is safe to operate and maintain.However, the orthotropic steel deck is highly prone to fatigue meaning that the number of passing lorries, their axle/wheel configuration and total vehicle weight have a significant impact on the bridge deck design and fatigue life. The orthotropic deck therefore has higher fabrication costs when compared to conventional steel structures due to the high‐quality steel manufacturing and welding procedures that are necessary to achieve the required fatigue performance.The overall layout of an orthotropic bridge deck is basically unchanged since the 1960s, however the detailing has been refined considerably to a level where it is now seems difficult to improve it much further. However, the introduction of new materials e.g. sandwich steel deck structures in combination with new welding or gluing techniques could push box girder designs to new heights.

Influence of shell morphometry, microstructure, and thermal conductivity on thermoregulation in two tropical intertidal snails

AbstractTropical intertidal organisms tolerate large fluctuations in temperature and high desiccation rates when exposed during low tide. In order to withstand the short‐term heat stress, intertidal organisms adopt behavioral responses to maximize their survival. Our previous research showed that tropical littorinids found at the upper and lower intertidal shores in Singapore exhibited different behavioral adaptations during low tide. Most of the upper‐shore Echinolittorina malaccana kept a flat orientation, with the aperture against the substrate and the long axis of the shell towards the sun, whereas a majority of the lower‐shore individuals of Echinolittorina vidua stood with the edge of the aperture perpendicular to the substrate on the rocky shore during low tide. This prompted analyses of the shells of these two species to determine whether the differences in the shell morphometry, microstructure, and thermal conductivity of shells of E. malaccana and E. vidua were associated with their respective behavioral responses to thermal stress. Analyses of shell morphometry and thermal conductivity showed that shells of E. malaccana were more likely to minimize heat gain, despite having a higher thermal conductivity on the outer surface, due to their light‐gray, elongated shell. By contrast, the dark‐colored, globose shells of E. vidua probably gain heat more readily through solar radiation. Scanning electron microscopy images of the shells of both littorinid species further revealed that they have cross‐lamellar structure; however, only individuals of E. vidua showed the presence of disjointed rod layers and a pigmented inner shell surface. Individuals of E. malaccana had a rough outer shell surface with holes that inter‐connect to form water‐trapping channels that probably aid cooling. Individuals of E. vidua, however, had a smooth outer surface with rows of kidney‐shaped depressions as microsculptures which probably help to stabilize shell shape. In both Echinolittorina species, behavioral responses were used to overcome thermal stress during low tide that was associated with shell morphometry and shell thermal conductivity. Such combined adaptations increase survivability of the littorinids at their respective tidal levels.

Removal of p-chlorophenol from aqueous solutions by carbon nanotube hybrid polymer adsorbents

Aiming to remove chlorophenols from aqueous solution, carbon nanotube (CNT) hybrid polymer beads were fabricated via the phase inversion method, and were adopted as adsorbents to remove p-chlorophenol in this study. The CNT hybrid bead was composed of a smooth outer surface and hierarchical porous inner structure, with worm-like CNTs lying on/embedded in the polymer slices. The incorporation of CNTs in the polymer beads resulted in a dramatically improvement of the surface area. The adsorption kinetics and isotherms of p-chlorophenol from aqueous solutions on CNT hybrid adsorbents were studied, and the impacts of temperature and pH value on the adsorption were also explored. The adsorption capacity of CNT hybrid adsorbents towards p-chlorophenol was significantly superior to that of the neat polymer adsorbent and pristine CNT. And the CNT hybrid adsorbents also showed an outstanding separation performance from water treatment system after adsorption. The adsorption process of p-chlorophenol on CNT hybrid adsorbents was found to be an exothermic process, and physical adsorption was the predominant mechanism. The neutral p-chlorophenol molecule was a more effective form for adsorption than was the ionic form. The interaction between p-chlorophenol and the CNT hybrid adsorbents responsible for the adsorption was assumed mainly non-polar forces such as hydrophobic interactions and π–π electron coupling.

Facile synthesis of imidazole microcapsules via thiol-click chemistry and their application as thermally latent curing agent for epoxy resins

A novel method was developed to encapsulate 1-benzyl-2-methylimidazole (1B2MZ) to produce microcapsule-type latent curing agent using thiol-click reaction in an oil/water emulsion. The fabrication process was significantly simplified and required reaction time was greatly shortened due to the efficiency of click chemistry. In the oil phase, 1B2MZ was mixed with reactive monomers, 1,3,5-tri-2-propenyl-1,3,5-triazine-2,4,6 (1H, 3H, 5H)-trione (TTT) and tris[2-(3-mercaptopropionyloxy)ethyl] isocyanurate (TEMPIC) which would polymerize to result in polythioether shell of microcapsules by following a photoinitiated thiol-ene mechanism. Polyvinyl alcohol (PVA) aqueous solution acted as water phase. The whole reaction process lasted for 20 min, which was enough for almost full conversions of monomers. The generated latent curing agent had good spherical shapes with smooth outer surfaces and the mean diameter distributed in the range of 105.7 to 18.17 μm by adjusting PVA concentration or viscosity of oil phase. The curing behavior, kinetics and releasing mechanism of latent curing agent were studied by differential scanning calorimetry (DSC) and scanning electron microscope (SEM). This microcapsule-type latent curing agent had a long storage life for 30 days when mixed with epoxy resin at 20 °C, and the mixture could be cured at 100 °C within 1 h.

Fortification of Pasta with White Button Mushroom: Functional and Rheological Properties

Macaroni (pasta)—a popular extruded product prepared using durum wheat semolina is rich in complex carbohydrate, vitamin-B but deficient in proteins especially lysine and threonine leading to low biological value of the product. The present study was conducted to prepare a nutritionally enriched macaroni by supplementing semolina with white button mushroom. The fresh mushrooms are a rich source of proteins having most of the essential amino acids in good proportions, thus, can be a better option for nutritional enrichment of pasta with 10 to 30% supplementation. The mushroom fortified pasta showed better antioxidant activity of 11.14 percent as compared to 5.61% in control with phenol contents ranging from 0.559 to 0.660% with increased mushroom fortification. A gradual increase in moisture content, carbohydrates was also noticed with decreased crude fibre, crude protein, and fat as well. The SEM study and rheological properties showed the clear picture of protein network, a smooth outer surface, and significant increase in chewiness and springiness that resulted in a desirable mouthfeel during eating. Therefore, on the basis of sensory and rheological properties of mushroom supplemented pasta, the ratio of 80: 20 was found to be the best and thus optimized for development of nutritionally enriched macaroni.

Relaxor properties of barium titanate crystals grown by Remeika method

Barium titanate (BaTiO3, BT) crystals have been grown by the Remeika method using both the regular KF and mixed KF-NaF (0.6-0.4) solvents. Typical acute angle “butterfly wing” BT crystals have been obtained, and they were characterized using x-ray diffraction, scanning electron microscopy (including energy dispersive spectroscopy), conventional dielectric and acoustic emission methods. A typical wing has a triangular plate shape which is up to 0.5mm thick with a 10–15mm2 area. The plate has a (001) habit and an atomically smooth outer surface. Both K+ and F− solvent ions are incorporated as dopants into the crystal lattice during growth substituting for Ba2+ and O2− ions respectively. The dopants' distribution is found to be inhomogeneous, their content being almost an order of magnitude higher (up to 2mol%) at out surface of the plate relatively to the bulk. A few μm thick surface layer is formed where a multidomain ferroelectric net is confined between two≤1µm thick dopant-rich surfaces. The layer as a whole possess relaxor ferroelectric properties, which is apparent from the appearance of additional broad maxima, Tm, in the temperature dependence of the dielectric permittivity around the ferroelectric phase transition. Intense acoustic emission responses detected at temperatures corresponding to the Tm values allow to observe the Tm shift to lower temperatures at higher frequencies, or dispersion, typical for relaxor ferroelectrics. The outer surface of the BT wing can thus serve as a relaxor thin film for various electronic application, such as capacitors, or as a substrate for BT-based multiferroic structure. Crystals grown from KF-NaF fluxes contain sodium atoms as an additional impurity, but the crystal yield is much smaller, and while the ferroelectric transition peak is diffuse it does not show any sign of dispersion typical for relaxor behavior.

Cross‐Linked Sodium Alginate‐g‐poly(Acrylic Acid) Structure: A Potential Hydrogel Network for Controlled Delivery of Loxoprofen Sodium

AbstractA series of sodium alginate‐graft‐poly(acrylic acid) hydrogels (SA‐g‐pAA hydrogels) were synthesized with sodium alginate (SA) and acrylic acid (AA) in aqueous solution, ethylene glycol dimethacrylate (EGDMA) as a cross‐linker and ammonium peroxodisulfate (APS) as an initiator. Hydrogels were evaluated for thermal stability (TGA & DSC), revealing their higher strength toward thermal variation as compared to individual components. SEM micrographs show smooth and solid outer surface with a lack of porosity on it. FTIR results revealed the grafting reaction of AA on SA. Hydrogels were then evaluated for pH responsive behavior by equilibrium swelling ratio and swelling dynamics at low and high pH. Furthermore, these cross‐linked networks were also tested for the release of Loxoprofen sodium hydrate (LSH). Drug was loaded by diffusion method and showed pH‐dependent drug release characteristics. Korsmeyer–Peppas model is the best fit model to explain drug release from the cross‐linked network. Maximum swelling, drug loading, and release has been observed at pH 7.4. It is concluded that highly stable SA and AA based polymeric matrixes are developed. These polymeric matrixes have potential to be used as a carrier for controlled delivery of LSH.

Microcapsules Filled with a Palm Oil-Based Alkyd as Healing Agent for Epoxy Matrix.

One of the approaches to prolong the service lifespan of polymeric material is the development of self-healing ability by means of embedded microcapsules containing a healing agent. In this work, poly(melamine-urea-formaldehyde) (PMUF) microcapsules containing a palm oil-based alkyd were produced by polymerization of melamine resin, urea and formaldehyde that encapsulated droplets of the suspended alkyd particles. A series of spherical and free-flowing microcapsules were obtained. The chemical properties of core and shell materials were characterized by Attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) and proton nuclear magnetic resonance spectroscopy (1H-NMR). Differential scanning calorimetry (DSC) analysis showed a glass transition around −15 °C due to the alkyd, and a melting temperature at around 200 °C due to the shell. Thermogravimetric analysis (TGA) results showed that the core and shell thermally degraded within the temperature range of 200–600 °C. Field emission scanning electron microscope (FESEM) examination of the ruptured microcapsule showed smooth inner and rough outer surfaces of the shell. Flexural strength and microhardness (Vickers) of the cured epoxy compound were not affected with the incorporation of 1%–3% of the microcapsules. The viability of the healing reactions was demonstrated by blending small amounts of alkyd with epoxy and hardener at different ratios. The blends could readily cure to non-sticky hard solids at room temperature and the reactions could be verified by ATR-FTIR.

Preparation of high thermal stability polysulfone microcapsules containing lubricant oil and its tribological properties of epoxy composites

Polysulfone (PSF) microcapsules containing lubricant oil have been successfully prepared using solvent evaporation method. The results show that lubricant oil was successfully encapsulated and the encapsulation capacity of about 56.0 wt.% was achieved. The uniform microcapsules have nearly spherical shape and quite smooth outer surface. The mean diameter is approximately 156 and 169 μm by using different dispersant solutions. The wall material is porous in structure with wall thickness of about 20 μm. The initial decomposition temperature of PSF is 480 °C. It is higher than traditional poly(urea-formaldehyde) (PUF) and poly(melamine-formaldehyde) (PMF) wall materials with 245 °C and 260 °C initial decomposition temperature, respectively. High thermal stability of PSF microcapsules can be considered as additives in high temperature resistant polymer materials. The frictional coefficient and wear rate of epoxy composites decreased significantly by incorporating microcapsules containing lubricant oil into epoxy. When the concentration of microcapsules was 25 wt.%, the frictional coefficient and specific wear rate were reduced by 2.3 and 18.3 times, respectively, as compared to the neat epoxy.

Surface‐Energy‐Driven Growth of ZnO Hexagonal Microtube Optical Resonators

A distinct “split and recoalescence” growth mechanism of tubular ZnO micro/nanostructures is observed for the first time. On the basis of experimental growth studies and first‐principles calculations, it is proposed that H2/H2O vapor, added to the traditional carbothermal reduction process, changes the intrinsic surface energy of ZnO crystal, which affects the ZnO crystal growth mode and subsequently controls the geometry of ZnO micro/nanotubes. It is shown that these tubular ZnO micro/nanostructures exhibit regular hexagonal cross sections and smooth outer and inner surfaces. Optical studies of ZnO micro/nanotubes reveal characteristic coherent intensity modulations of their emission spectra which reflect the excitation of either whispering gallery modes or wave‐guided modes. The specific type of mode can be selected by controlling the microtube geometry, specifically by its wall thickness to diameter ratio, as demonstrated both experimentally by photoluminescence spectroscopy, and theoretically by finite‐element‐method simulations.