Cedar Creek Solid Wood Folding Rocking Chair Lewys Fabric Arm Chair Magness Rocking Arm Chair For other uses, see Rocking Chair (disambiguation). A rocking chair or rocker is a type of chair with two curved bands (also known as rockers) attached to the bottom of the legs, connecting the legs on each side to each other. The rockers contact the floor at only two points, giving the occupant the ability to rock back and forth by shifting their weight or pushing lightly with their feet.[2] Rocking chairs are most commonly made of wood. Some rocking chairs can fold. The word rocking chair comes from the verb to rock.[3] The first known use of the term rocking chair was in 1766. A rocking chair designed by Swedish painter and furniture designer, Karin Bergöö Larsson Rocking chairs are often seen as synonymous with parenting, as the gentle rocking motion can soothe infants. Many adults find rocking chairs soothing because of the gentle motion. Gentle rocking motion has been shown to provide faster onset of sleep than remaining stationary, mimicking the process of a parent rocking a child to sleep.
Rocking chairs are also comfortable because, when a user sits in one without rocking, the chair automatically rocks backward until the sitter's center of gravity is met, thus granting an ergonomic benefit with the occupant kept at an un-stressed position and angle. Varieties of rockers include those mounted on a spring base (or platform) called "platform rockers" and those with swinging braces commonly known as gliders. A photo of man lounging in a rocking chair while reading Though American inventor Benjamin Franklin is sometimes credited with inventing the rocking chair, historians actually trace the rocking chair's origins to North America during the early 18th century, when Franklin was a child. Originally used in gardens, they were simply ordinary chairs with rockers attached. It was in 1725 that early rocking chairs first appeared in England. The production of wicker rocking chairs reached its peak in America during the middle of the 18th century. These wicker rockers, as they were popularly known, were famous for their craftsmanship and creative designs.
Michael Thonet, a German craftsman, created the first bentwood rocking chair in 1860.[8] This design is distinguished by its graceful shape and its light weight. These rocking chairs were influenced by Greek and Roman designs as well as Renaissance and colonial era artistry. During the 1920s, however, folding rocking chairs became more popular in the United States and in Europe. They were handy for outdoor activities and travel purposes. By the 1950s, rocking chairs built by Sam Maloof, an American craftsman, became famous for their durability and deluxe appearance. Maloof's rocking chairs are distinguished by their ski-shaped rockers. President John F. Kennedy made the P & P Chair Company's rocking chair famous. In 1955, Kennedy, who suffered with chronic back problems, was prescribed swimming and the use of a rocking chair by his physician. The President so enjoyed the rocker that, after he was inaugurated in 1961, he took the chair on Air Force One when he traveled around the country and the world.
He bought additional rockers for Camp David and for the Kennedy estates; and he gave them as gifts to friends, family, and heads of state. Kennedy's rocking chair from the White House is on permanent display at the John F. Kennedy Library and Museum. Per the manufacturing design, the Kennedy Rocking Chair is shaped, steam-bent, and assembled while the wood is still "green." Media related to Rocking chairs at Wikimedia CommonsSupport of the organic compounds in the nanoporous carbon should play a crucial role for the effective use of the capacity of organic compounds. Because of the low- or non-conductivity of AQ and TCHQ, their crystalline bulk could not be utilized for electrochemical redox reactions without a carbon support. However, as indicated above, the organic compounds held in nanoporous carbon contributed to the energy storage. X-Ray diffraction (XRD) and1H-NMR studies revealed that the most of the organic compounds were held on the surface of the nanoporous carbon with less-crystalline or nanocrystalline structures (see Supplementary Figs.
Because the proportion of the organic molecules contacting the carbon surface to the total of the loaded organic molecules increases by downsizing the supporting pores, the interaction between the sp2 carbon surfaces and the aromatic rings will become apparent and stabilize the absorbed organic compounds in the nanometer-scaled pores. The organic compounds held in carbon materials with less-crystalline or nanocrystalline structures showed high utilization rate (see Supplementary Figs. S8 and S9 online). It is highly anticipated that such adsorption states of the organic compounds on a carbon material with electrical conductivity contribute to the redox reactions with a high utilization rate.We also evaluated the dependence of the cycle lifetime on the kinds of carbon materials for a single electrode system (see Supplementary Fig. In the measurements, AQ impregnated in the carbon materials was employed in the working electrode, where the excess amount of carbon material was employed in the counter electrode.
For a carbon material with a larger averaged pore size (ϕ11 nm), the retention rate of capacitance for the working electrode after 1000 charge/discharge cycles at 0.56 A/g was 41%. For the nanoporous carbon material (averaged pore size: ϕ2.2 nm) employed in this study, the retention rate after 1000 cycles was 82%. From this comparison, we found that the support of organic compounds in the nanoporous carbon also contributed to the cycle lifetime enhancement of the redox capacitor.Durability becomes a critical issue when using organic compounds as the redox-active materials, because of their solubility. Generally, as the molecular weight decreases, the solubility of quinones in aqueous solution generally increases. For example, the solubilities of benzoquinone and AQ in water at 25°C are approximately 10 g/l and 1.4 mg/l, respectively. Moreover, hydroquinones, which forms by proton insertion reaction with quinones, are more soluble than quinones (the solubility of hydroquinone in water at 25°C are 80 g/l).
Therefore, the dissolution of organic compounds during charge/discharge degrades the cycle performance of the aqueous capacitor that uses such compounds. It was supposed that the support by carbon in the nanometer-scaled pores would be effective against dissolution. It is known that the nanoporous carbon employed in this study has a complicated branching pore structure24. Support inside this structure would prevent organic compounds from dissolving out of the carbon matrix, and enable their reversible redox reactions with long cycle lifetimes. Figure 4a shows the rechargeable energy density of the redox capacitor device as a function of cycle time. The coulombic efficiency was above 99% for almost all charge-discharge cycle. At a current density of 0.28 A/g, the energy density exhibited an initial growth until about the 100th cycle, and then gradually decreased. At present, the delay time that it takes for the redox capacitor to show its maximal energy density has not been fully controlled, and remains a challenge.
After 1000 cycles, the retention rate based on the maximum energy density was approximately 70%.Figure 4: (a) Rechargeable energy density of the redox capacitor (TCHQ-AQ) in 0.5 M H2SO4 aqueous solution at 0.28 A/g as a function of cycle time, and (b) the evolution profiles of the potential corresponding to the positive (TCHQ) and negative (AQ) electrodes at the 100th and 1000th cycles.Finally, we suggest a strategy for further enhancement of cycle lifetime. Figure 4b shows the evolution of the potential corresponding to the positive and negative electrodes. The final potential after the discharge process completed at the 1000th cycle, 0.38 V vs. Ag/AgCl, was much higher than that at the 100th cycle, 0.25 V vs. Ag/AgCl. This increase in the final potential (0.13 V) implies that the decrease in the rechargeable energy density after many cycles results from the degradation of the negative electrode, because the evolution of the potential for the negative electrode caused by its shortened plateau region interrupts the full-capacity charge/discharge of the positive electrode.
It was conjectured that the degradation of the negative electrode could be attributed to the dissolution of AQ into the aqueous electrolyte as anthrahydroquinone. Therefore, instead of AQ, we employed 1,5-dichloroanthraquinone (DCAQ) as the redox-active material in the negative electrode. The attachment of hydrophobic functional groups was effective in minimizing dissolution of the organic compounds into the aqueous solution. For example, the solubility of TCHQ, which has 4 hydrophobic chloro groups, in water at 25°C is quite low, 76 mg/l, compared with that of hydroquinone (80 g/l).Figure 5a shows the rechargeable energy density of the redox capacitor using the DCAQ and TCHQ couple as a function of cycle time at 0.26 A/g. Similar to the redox capacitor that used the AQ and TCHQ couple, the energy density reached its maximum around at the 100th cycle. On the other hand, compared with the case of AQ/TCHQ, the cycle performance was enhanced by the attachment of the hydrophobic chloro groups, and the degradation of the rechargeable energy density was not observable after 1000 cycles.
In addition, the cycle performance of the redox capacitor (TCHQ-DCAQ) at 2.6 A/g, the degradation of the rechargeable energy density was not observable after 10000 cycles (see Supplementary Fig. These results suggest that the attachment of hydrophobic functional groups was effective as a strategy for the further enhancement of cycle lifetime. Figure 5b shows a typical galvanostatic cycle and the evolution of the potential corresponding to the positive and negative electrodes in the redox capacitor. The potentials of the redox reactions with protons were −0.05 V (vs. Ag/AgCl) for DCAQ and 0.50 V (vs. Ag/AgCl) for TCHQ. Therefore, the potential plateaus around 0.55 V corresponded to the difference of the redox reaction potential between DCAQ and TCHQ, and it was confirmed that the energy storage of this capacitor relies on the redox reactions of DCAQ and TCHQ. Compared with the AQ and TCHQ couple, the decrease in the energy density resulted from the decrease in the potential difference.
However, in this case, the decrease in the final potential after the discharge process was not observed. This indicated that the suppressed solubility of DCAQ by the attachment of hydrophobic functional group contributed to avoid the degradation of the negative electrode and the interruption of the full-capacity charge/discharge of the positive electrode.Figure 5: (a) Rechargeable energy density of the redox capacitor (TCHQ-DCAQ) in 0.5 M H2SO4 aqueous solution at 0.26 A/g as a function of cycle time, and (b) the evolution profiles of the potential corresponding to the positive (TCHQ) and negative (DCAQ) electrodes at the 100th and 1000th cycles.In summary, we demonstrated an aqueous redox capacitor using a couple comprising organic compounds that enabled a proton rocking-chair-type energy storage. Fundamentally unlike conventional batteries and supercapacitors, the employed electrodes, which consisted only of light elements (hydrogen, carbon, oxygen, and chlorine), can be installed with low material and manufacturing costs.
By employing nanoporous carbon, a redox capacitor with a long cycle lifetime and a high energy density, derived from the high utilization rate of the redox reaction of the organic compounds, was achieved. Moreover, this capacitor can respond to rapid variability. These features are promising for large stationary applications in electrical energy storage systems for the energy grid.Furthermore, we proposed a strategy to further enhance cycle lifetime by controlling quinone/hydroquinone solubility. In addition to hydrophobicity, the required properties of the organic compounds in the capacitor were low molecular weights, ability to participate in fast redox reactions for high energy density, and high power capability. The coupling of different organic compounds having different redox potentials in the limiting operating voltage of an aqueous solution was also important. Further improvements via the choice of the best organic-based couple and the optimized loading of the organic compounds on carbon will accelerate the replacement of current electrical energy storage systems for grid use.