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1.
We report a novel biomimetic gel that undergoes autonomous swelling–deswelling oscillations without on–off switching of external stimuli, similar to heartbeat. The mechanical oscillation of gel was produced via oscillating chemical reaction, called the Belousov–Zhabotinsky (BZ) reaction. We have prepared an ionic gel consisting of the cross-linked poly(N-isopropylacrylamide) chain to which ruthenium tris(2,2′-bipyridine), a catalyst for the BZ reaction, was covalently bonded. The BZ reaction occurring within the gel matrix generates periodic redox changes of the catalyst moiety. This chemical oscillation is converted into the mechanical oscillation of the polymer network. As a result, the gel exhibits a periodical swelling–deswelling change. The self-oscillating behaviors of the gel were investigated in detail. When the gel size is smaller than the chemical wavelength, the redox change occurs homogeneously in the gel. In this case, the volume change is isotropic and the mechanical oscillation synchronizes with chemical oscillation without a phase difference. The period and amplitude can be controlled by changing the outer substrate concentrations. In the case of rectangular shape, chemical wave propagates along the length of the gel. The wavelength and velocity depend on the reaction rate of autocatalytic process as well as the diffusivity of the activator. The dynamic behavior that locally shrunken (or swollen) parts propagate was observed, similar to the peristaltic motion of worms. By using lithography technique, a ciliary motion actuator made of the gel has been demonstrated. These self-oscillating gels may be useful in a number of important applications to intelligent biomaterials such as pulse generator or chemical pacemaker, auto-mobile actuators or micropumps with peristaltic motion, device for signal transmission, etc.  相似文献   

2.
The propagation control of chemical waves via a pentagonal patterned structure in a self‐oscillating polymer brush composed of N‐isopropylacrylamide and a metal catalyst for the Belousov–Zhabotinsky (BZ) reaction is reported. The patterned self‐oscillating polymer brush is prepared by combining surface‐initiated atom transfer radical polymerization and maskless photolithography. Surface modification is confirmed by X‐ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, 3D measuring laser microscopy, and fluorescence microscopy. The polymer brush patterns are fabricated with gaps between the pentagonal regions, and investigations on the effect of the gap distance on the BZ reaction reveal that at the appropriate distance, chemical waves propagate across the array from the plane to the corner between the patterns. Unidirectional control is achieved not only in the 1D array, but also in a 2D curved array. This patterned self‐oscillating polymer brush is a novel and advantageous approach for creating an autonomous dynamic soft interface.  相似文献   

3.
Information on chemical speciation is much needed in mechanistic and kinetic studies on catalyst formation processes in pharmaceutical research. Speciation analysis was applied to the identification and quantification of various rhodium species involved in a ligand exchange process leading to formation of catalyst dirhodium(II) tetrakis[methyl 2-oxopyrrolidin-5(S)-carboxylate]. Inductively coupled plasma mass spectrometry (ICPMS) was used as an element-specific detector following species separation by reversed-phase high-performance liquid chromatography (RP-HPLC), and electrospray ionization mass spectrometry (ESI-MS) was used for species identification and confirmation. A novel interface between the HPLC and ICPMS, which consisted of an eluent splitter, a desolvation unit, and the ICPMS built-in peristaltic pump, enabled the use of RP-HPLC with gradient elution and up to 100% organic components in the LC eluent without organic loading in the plasma. A variety of reaction intermediates were identified and quantified along the pathway to formation of the desired product, including isomeric di-, tri-, and tetrasubstituted species previously believed to be absent. This has provided new insights into the mechanism and kinetics of the reaction. The combination of HPLC-ICPMS and HPLC-ESI-MS has proven to be a valuable tool for the investigation of species evolution in catalyst formation process.  相似文献   

4.
应用FLUENT软件对二维的亥姆霍兹喷嘴自振射流进行了模拟,并以此为基础研究了上喷嘴出口凸出部深入振荡腔对亥姆霍兹喷嘴自激振荡特性的影响。结果表明,上喷嘴的出口凸出部长度和喷嘴壁厚度都对自激振荡特性产生显著的影响。长度为0~0.15D_1时,自振射流的脉动幅值可以提高20%~80%,提升幅度在射流速度较低时更大;凸出部长度为0.15~0.25D_1时,射流振幅的提升逐渐降低;长度0.25~0.3D_1时,射流振幅比普通喷嘴更低,稳定性下降;长度超过0.3D_1时自振射流会完全消失。凸出部分喷嘴壁厚度在0δ0.1D_1范围内对射流性能几乎没有影响,但随着厚度δ的不断增大,性能会减弱,δ0.15D_1时无法形成自振射流。总之,上喷嘴出口凸出可改善射流振荡性能,但长度和厚度需在一定范围内,否则无法产生自振射流。  相似文献   

5.
Heterogeneous catalysts have been pivotal to the development of the modern chemical industry and are essential for catalysing many industrial reactions. However, reaction rates are different for every individual catalyst particle and depend upon each particle's morphology and size, crystal structure and composition. Measuring the rates of reaction on single nanocrystals will enable the role of catalyst structure to be quantified. Here, using surface plasmon spectroscopy, we have directly observed the kinetics of atomic deposition onto a single gold nanocrystal and also monitored electron injection and extraction during a redox reaction involving the oxidation of ascorbic acid on a gold nanocrystal surface. These results constitute the first direct measurement of the rates of redox catalysis on single nanocrystals.  相似文献   

6.
Catalytic nanomotors are nano-to-micrometer-sized actuators that carry an on-board catalyst and convert local chemical fuel in solution into mechanical work. The location of this catalyst as well as the geometry of the structure dictate the swimming behaviors exhibited. The nanomotors can occur naturally in organic molecules, combine natural and artificial parts to form hybrid nanomotors or be purely artificial. Fabrication techniques consist of template directed electroplating, lithography, physical vapor deposition, and other advanced growth methods. Various physical and chemical propulsion mechanisms have been proposed to explain the motion behaviors including diffusiophoresis, bubble propulsion, interfacial tension gradients, and self-electropho-resis. The control and manipulation based upon external fields, catalytic alloys, and motion control through thermal modulation are discussed as well. Catalytic nanomotors represent an exciting technological challenge with the end goal being practical functional nanomachines that can perform a variety of tasks at the nanoscale.  相似文献   

7.
End-of-pipe solutions as a regulatory approach have been practised in industry with a view that the technology is perfect and only the effluent should be treated. Although total waste cannot be eliminated, there are several approaches that can be easily adopted by industry to reduce waste and also to improve economics. In the case of industrial phase transfer catalysed processes, the catalyst is not recovered but treated as a waste since the quantities are very small and do not contribute much to the expensive product. Although totally waste-free chemical processes are not realizable in practice, the concept of eco-efficiency is useful for optimizing chemical processes with the aim of minimizing risk, resource depletion, and waste-generation. In this context it is necessary to make the popular phase transfer catalysis (PTC) more acceptable to industry by unusual strategies. So combining several steps in a single-pot reaction and using the same catalyst and solvent without separation or with partial replenishment of the reactants for all the steps fits elegantly into the concept of waste minimization. The use of liquid–liquid–liquid, solid–liquid–liquid PTC, including a change in nature of the phase, reactant, and product state, can be advantageously made in a cascaded reaction. Cascade engineered PTC (CEPTC) will offer the additional benefit of enhancing the selectivity of the desired product through manipulation of various parameters such as the number of phases, catalyst loading, type of catalyst, stoichiometric ratio of the starting materials and temperature. In agrochemicals and pharmaceuticals this approach can be employed where multi-step synthesis coupled with several separation stages add to the cost of the product. This paper discusses the novel concept of CEPTC, which is illustrated with the production of an agrochemical fenvalerate. Here the same catalyst is used without separation and the nature of phases is changed to achieve a reduction of waste. The concept is discussed with experimental data and has a lot of promise.  相似文献   

8.
Chemical networks and molecular switches dominate the area of research geared toward macroscopic motion of materials. A counter‐intuitive approach to create self‐sustained oscillation by light irradiation of ordinary photostabilizers in splay‐aligned liquid‐crystalline networks made from commercial mesogens is developed. Photostabilizers or any molecules that are able to quickly dissipate the absorbed light through heat, by vibrational and/or rotational modes, can reach self‐oscillating macroscopic motion where self‐shadowing plays a critical role. The mechanical self‐oscillation is linked to temperature oscillations and the asymmetric response over the film thickness. Only a localized responsive zone, acting as hinge, activates the oscillation of a beam‐shaped device. The outcome of this research is extended from UV to near‐IR actuation, making bulk applications to convert sunlight into mechanical work within reach.  相似文献   

9.
The present paper builds upon the results of two recent theoretical studies on the influence of friction by normal and sideways oscillations. The findings are in part rewritten to a more compact and dimensionless form so as to present the results for both oscillation modes side by side in a consistent manner. Thereby, it is shown that for the considered system the macroscopic coefficient of friction is only a function of a dimensionless sliding velocity and a dimensionless oscillation amplitude. Furthermore, the energy efficiency is characterized for both modes for the first time by comparing the total energy needed for a sliding motion which includes the superimposed oscillations with the energy needed for the same sliding motion without the additional oscillations. It is shown that this ratio is also only a function of the two dimensionless system parameters. We consider a simple one-spring model in a displacement-controlled setting. Any system-dynamical feedback is neglected. The lower end of the spring either slides, sticks or jumps on a rigid plane. In the case of normal oscillations, the macroscopic coefficient of friction can be reduced only when the contact point undergoes a stick-slip motion (“stiff control of friction”) whereas with sideways oscillations the macroscopic coefficient of friction can be reduced also when the contact point is continuously sliding (“soft control of friction”). It is found that the motion with superimposed sideways oscillations requires more energy for any combination of system parameters, than the corresponding motion without the oscillations. For the case of normal oscillations however, there are combinations of system parameters for which the motion with the superimposed oscillations requires less, the same, or more energy than for the reference case without the oscillations.  相似文献   

10.
车辆蛇形运动状态下重载铁路轮轨系统振动特性   总被引:2,自引:0,他引:2  
王开云  刘鹏飞 《工程力学》2012,29(1):235-239
该文针对重载铁路货车车辆,从大系统角度,研究了蛇形失稳时的轮轨动态相互作用特征,仿真计算了当货车车辆以高于其非线性临界速度运行时的轮轨系统振动姿态。理论分析结果表明,轮对蛇形运动时,轮轨接触点在车轮踏面与轮缘根部交替变化,导致轮轴横向力变化非常剧烈,最大值接近正常值的10 倍。在轮轨横向力的作用下,轮对以11.25Hz 频率在轨道中心线左右横向运动,幅度达到了15mm,且摇头角位移较大,轮对蛇形运动波长为3.4m;钢轨横向振动也非常明显,将进一步加剧轮对横向运动。另外,轮轨横向相互作用力及钢轨横向振动位移的主频与轮对蛇形频率一致。  相似文献   

11.
The study reports mechanical performance of the recycled glass fibres produced from a water-based solvolysis technology, known as the hydrolysis process. The chemical reaction was carried out using sub-critical water to dissolve polyester resin and recover the glass fibres from composites. The effect of temperatures, times, catalyst and water amount on mechanical properties of the recovered glass fibres were investigated. Scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and time-of flight secondary ion mass spectroscopy (ToF-SIMS) analyses were also employed to examine the fibre surface associated with the polyester resin eliminated level after the hydrolysis reaction. The results revealed that by carefully adjusting the hydrolysis parameters the tensile strength and failure strain of the recycled fibres decrease by approximately 40-70% in comparison with virgin fibres while Young’s moduli remain similar. The relationship between the hydrolysis conditions, recovered fibres and mechanical performance was discussed in this study.  相似文献   

12.
首先将桐油与甲醇经过酯交换反应得到桐酸甲酯,再将其与过氧化氢和乙酸反应制备环氧桐酸甲酯;然后以三芳基硫金翁盐为催化剂,在UV光条件下催化环氧桐酸甲酯与二乙醇胺开环,制备桐油基多元醇;最后以桐油基多元醇、异佛尔酮二异氰酸酯、甲基丙烯酸羟乙酯等为原料,以二月桂酸二丁基锡为催化剂,经过两步法反应制备了桐油基超支化聚氨酯丙烯酸酯。结果表明,在UV光条件下,三芳基硫金翁盐可以催化环氧桐酸甲酯开环制备桐油基多元醇,其羟基值为599.54 mg KOH/g,相对分子质量为544;以桐油基多元醇为核得到的聚氨酯丙烯酸酯具有良好的光固化活性,以及良好的热稳定性能和力学性能,并且成膜的表面光滑、平整,其玻璃化转变温度为37.2℃,拉伸强度为8.58 MPa,断裂伸长率为23.31%,表面张力为41.36 mJ/m 2。  相似文献   

13.
To date, it has been a great challenge to design high‐performance flexible energy storage devices for sufficient loading of redox species in the electrode assemblies, with well‐maintained mechanical robustness and enhanced electron/ionic transport during charge/discharge cycles. An electrochemical activation strategy is demonstrated for the facile regeneration of carbon nanotube (CNT) film prepared via floating catalyst chemical vapor deposition strategy into a flexible, robust, and highly conductive hydrogel‐like film, which is promising as electrode matrix for efficient loading of redox species and the fabrication of high‐performance flexible pseudosupercapacitors. The strong and conductive CNT films can be effectively expanded and activated by electrochemical anodic oxygen evolution reaction, presenting greatly enhanced internal space and surface wettability with well‐maintained strength, flexibility, and conductivity. The as‐formed hydrogel‐like film is quite favorable for electrochemical deposition of manganese dioxide (MnO2) with loading mass up to 93 wt% and electrode capacitance kept around 300 F g?1 (areal capacitance of 1.2 F cm?2). This hybrid film was further used to assemble a flexible symmetric pseudosupercapacitor without using any other current collectors and conductive additives. The assembled flexible supercapacitors exhibited good rate performance, with the areal capacitance of more than 300 mF cm?2, much superior to other reported MnO2 based flexible thin‐film supercapacitors.  相似文献   

14.
The problem is examined of motion of a single spherical bubble with mass transfer in a swirling liquid flow. It is assumed that the bubble rotates without tangential slip while the dissolution process occurs without chemical reaction and heat release. A numerical solution is performed of the system of motion and dissolution equations by the method of prediction and correction. The floating velocity and the change in bubble mass as it moves toward the vortex axis are computed.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 59, No. 1, pp. 48–51, July, 1990.  相似文献   

15.
The effect of Poiseuille flow on peristaltic transport of a particle-fluid mixture has been investigated in a two-dimensional mathematical model for the case where the walls of the channel execute sinusoidal motion of small amplitude. The driving mechanism of the muscle is represented by assuming the channel walls to be elastic or viscoelastic. The fluid-particle interaction problem is investigated by considering equations of motion for both the fluid and particle phases with the deformable boundaries. The wall characteristics appear in their equations of motion, which are solved to represent boundary conditions of the fluid motion. Solutions for free pumping case and interaction with Poiseuille flow are obtained for small values of Poiseuille flow parameter in closed form as well as by a series method. The effect of the particulate phase is observed throughout the analysis both qualitatively and quantitatively.  相似文献   

16.
Fatty acid-based polyurethane films were prepared for use as potential wound dressing material. The polymerization reaction was carried out with or without catalyst. Polymer films were prepared by casting-evaporation technique with or without crosslink-catalyst. The film prepared from uncatalyzed reaction product with crosslink-catalyst gave slightly higher crosslink density. The mechanical tests showed that, the increase in the tensile strength and decrease in the elongation at break is due to the increase in the degree of crosslinking. All films were flexible, and resisted to acid solution. The films prepared without crosslink-catalyst were more hydrophilic, absorbed more water. The highest permeability values were generally obtained for the films prepared without crosslink catalyst. Both the direct contact method and the MMT test were applied for determination of cytotoxicity of polymer films and the polyurethane film prepared from uncatalyzed reaction product without crosslink-catalyst showed better biocompatibility property, closest to the commercial product, Opsite.  相似文献   

17.
Tungsten oxide can change its colour reversibly upon electron injection. It can be produced by sputtering, evaporation, chemical vapour deposition or other processes. In addition to its high colouration efficiency and fast reaction kinetics, the redox potential of the electron injection is low enough to allow various switchable systems, such as electrochromic, gasochromic, photoelectrochromic or photochromic glazing. In this paper, electrochromic devices with a redox electrolyte are introduced. This is related to the photoelectrochromic device, which is an electrochromic device with redox electrolyte and an additional dye-sensitised layer of TiO2, which generates the energy for the colouration of the device by sunlight. The photochromic device is in principal a photoelectrochromic device, where the catalytic layer for the reaction of the redox electrolyte is in direct contact with the electrochromic layer. In gasochromic devices, tungsten oxide reacts with diluted hydrogen and oxygen gases. This paper aims to give an overview of these different approaches.  相似文献   

18.
19.
The detailed study of bifunctional phosphinic acid resins has recently been introduced. It has been shown that they operate through the dual mechanism of ion exchange and metal-ion reduction. A key component in the synthesis is the Friedel-Crafts catalyst used for the reaction between PCl3 and polystyrene. We now find that the order of catalyst activity is AlCl3 > FeCl3 > ZnCl2 > SnCl4. Ferric chloride catalysis also operates by an additional redox mechanism which yields a phosphonic acid resin. The extent of loading onto phosphinic and sulfonic acid resins by zinc ions at equilibrium was studied as a function of the anion present both with and without the presence of an excess of sodium ions. Both sets of resins exchange at a comparable rate upon the introduction of macroporosity into the polystyrene support. The influence of the redox process as an additional variable in the phosphinic resin kinetics was studied with silver and mercury(II) nitrate solutions. All of the primary acid sites are oxidized after a 9-hour contact time with Ag(I) ions and a 2-hour contact time with Hg(II) ions. The mercury loading curves and the different behavior of silver, which shows more ion exchange than redox at short times while leaving a residual ion concentration on the resin irrespective of whether all of the primary acid sites have been oxidized or not, can be explained by the termolecular nature of the Ag(I) redox reaction in contrast to the bimolecular nature of the Hg(II) reaction. Studies with other ions show that the minimum metal-ion reduction potential below which no redox occurs with the phosphinic resins is probably between 0.0 and 0.3 V.  相似文献   

20.
钇稳定氧化锆薄膜的制备及其微细加工   总被引:3,自引:0,他引:3  
以甲醇为溶剂,硝酸氧锆、硝酸钇为前驱物,采用溶胶-凝胶方法,通过引入化学修饰剂乙酰丙酮(AcAcH),使乙酰丙酮和锆离子形成螯合物,得到了具有紫外光感光性的溶胶及其凝胶薄膜,提出了YSZ薄膜的微细图形加工新方法.UV-Vis.分光光度计的紫外光谱测试结果表明:乙酰丙酮与锆离子形成的螯合物在室温、可见光、大气环境下,可以存在于凝胶薄膜中,并具有较好的热稳定性和光化学稳定性,其紫外光谱的特征吸收峰大约在310nm附近;325nm紫外激光光源照射凝胶薄膜,能破坏、分解凝胶薄膜中的这种螯合物结构,使凝胶薄膜的物理化学性质发生变化,实验发现,经过紫外激光照射的凝胶薄膜在适当的有机溶剂(如甲醇等)中的溶解度和溶解速度显著降低,利用这一特性,采用325nm紫外激光通过掩膜照射凝胶薄膜,并在适当的有机溶剂中溶洗掉未受照射的区域,经过800℃,20min热处理,得到了具有微细图形的YSZ薄膜,XRD测试表明该薄膜相结构为立方相.  相似文献   

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