308 results about "Pseudocapacitance" patented technology

An electrical component includes an inkjet-printed graphene electrode. Graphene oxide flakes are deposited on a substrate in a graphene oxide ink using an inkjet printer. The deposited graphene oxide is thermally reduced to graphene. The electrical properties of the electrode are comparable to those of electrodes made using activated carbon, carbon nanotubes or graphene made by other methods. The electrical properties of the graphene electrodes may be tailored by adding nanoparticles of other materials to the ink to serve as conductivity enhancers, spacers, or to confer pseudocapacitance. Inkjet-printing can be used to make graphene electrodes of a desired thickness in preselected patterns. Inkjet printing can be used to make highly-transparent graphene electrodes. Inkjet-printed graphene electrodes may be used to fabricate double-layer capacitors that store energy by nanoscale charge separation at the electrode-electrolyte interface (i.e., “supercapacitors”).

The invention provides a graphene composite electrode which comprises a current collector and electrode active materials arranged on the surface of the current collector, wherein the electrode active materials comprise graphene and manganese dioxide. The graphene is in a stratified structure and is arranged on the surface of the current collector, and the manganese dioxide is arranged on the surface of the graphene in the stratified structure. Mass percentage content of the graphene in the electrode active materials is 80%-90%. In addition, the invention further relates to a preparation method and an application of the graphene composite electrode. Oxidized graphene and the manganese dioxide are deposited on the current collector step by step, adhesion agents are not needed, and therefore equivalent series resistance of the whole electrode is reduced effectively, capacity and pseudocapacitance of an electric double-layer of the graphene and the manganese dioxide are developed simultaneously, and stability and conductivity of the electrode are well improved by addition of the graphene. In addition, through the method of electro-deposition, the electrode materials are directly deposited on an electrode plate, a complex coating process is saved, the process is simple, and time is short.

The invention relates to a manganese dioxide asymmetric super capacitor and a manufacturing method of the super capacitor; the manganese dioxide asymmetric super capacitor is characterized in that a positive pole of the super capacitor is made of flower-like manganese dioxide or nano manganese dioxide / active carbon composite material with higher pseudocapacitance, and a negative pole of the super capacitor is made of porous carbon with large specific surface area; a water solution system containing univalent or divalent cation is adopted as electrolyte of the super capacitor; and the asymmetric super capacitor formed by encapsulation has the characteristics of being higher in energy density, low in cost, safe and free from pollution.

The invention relates to a flexible symmetrical pseudocapacitance super capacitor and a preparation method thereof. The flexible symmetrical pseudocapacitance super capacitor comprises a positive electrode, a negative electrode and electrolyte, wherein the electrolyte is arranged between the positive electrode and the negative electrode; the flexible symmetrical pseudocapacitance super capacitor is characterized in that with a nano nickel particle / multiwalled carbon nanotube / conductive carbon cloth electrode employing conductive carbon cloth as a current collector and a nano nickel particle / multiwalled carbon nanotube as an active material as the positive electrode and the negative electrode, the flexible symmetrical pseudocapacitance super capacitor is formed by growing the nano nickel particle on a multiwalled carbon nanotube / conductive carbon cloth base; and the nano nickel particle and the multiwalled carbon nanotube are combined in situ. The nano nickel particle / multiwalled carbon nanotube / conductive carbon cloth electrode has the advantages of high global electronic mobility and excellent rate capability; the pseudocapacitance super capacitor assembled by the nano nickel particle / multiwalled carbon nanotube / conductive carbon cloth electrode has a symmetrical structure, and is capable of charging and discharging in positive and negative directions without distinguishing of the polarity; compared with a traditional carbon-based super capacitor, relatively high specific capacity of pseudocapacitance can be provided; and the flexible symmetrical pseudocapacitance super capacitor has excellent mechanical flexibility.

Disclosed is an ultracapacitor having electrodes containing mineral microtubules, an electrolyte between the electrodes, and a separator in the electrolyte to provide electrical insulation between the electrodes, while allowing ion flow within the electrolyte. The electrodes may be formed from a paste containing microtubules, a conductive polymer containing mineral microtubules, or an aerogel containing the mineral microtubles. The mineral microtubules may be filed with carbon, a pseudocapacitance material, or a magnetoresistive material. The mineral microtubules may also be coated with a photoconductive material.

An ultracapacitor comprising a first electrode containing mineral microtubules, a second electrode containing mineral microtubules, an electrolyte disposed between the first electrode and the second electrode, and a separator disposed in the electrolyte to provide electrical insulation between the first electrode and the second electrode, while allowing ion flow within the electrolyte. The electrodes may be formed from a paste containing mineral microtubules, or may consist essentially of a conductive polymer containing mineral microtubules, or an aerogel containing the mineral microtubules. The mineral microtubules may be filled with carbon, a pseudocapacitance material, or a magnetoresistive material. The mineral microtubules may also be coated with a photoconductive material.

The invention discloses a manganese dioxide electrochemical supercapacitor, comprising the following steps: the pseudocapacitance of the manganese dioxide and a double electrode layer capacitance mechanism of large specific surface area carbon material are combined into a maintaining power, the positive electrode adopts manganese dioxide material with high capacity, the negative electrode adopts high large specific surface area carbon material, an aqueous solution system or a non-aqueous solution system containing bivalent cations, thus forming the asymmetric electrochemical capacitor. As different materials are adopted in different electrochemical windows of the same electrolyte, individual voltage of the asymmetric electrochemical capacitor can be up to 2V or more, and as the bivalent cations are adopted as the cations of the electrolyte, the specific capacity of the positive electrode and the negative electrode are improved; therefore, the supercapacitor is characterized of high energy density and high power density, etc.

The invention relates to a method for preparing a lacunaris carbon / nanometer oxide composite material used in an ultra capacitor electrode. The prepared material is capable of evenly dispersing a nanometer oxide into a lacunaris carbon substrate. When the ultra capacitor electrode is prepared by the material, with a combination of a double-electric-layer capacitor and a metal oxide pseudocapacitance, the electrode can has a higher unit capacitor and a carbon framework can provide a favorable conductive passage for nanometer metal oxide particles dipersed in the carbon framework to reduce an equivalent internal resistance of the capacitor, thereby the capacitor has a high power and power density.

Provided is an internal hybrid electrochemical cell comprising: (A) a pseudocapacitance cathode comprising a cathode active material that contains a conductive carbon material and a porphyrin compound, wherein the porphyrin compound is bonded to or supported by the carbon material to form a redox pair for pseudocapacitance, wherein the carbon material is selected from activated carbon, activated carbon black, expanded graphite flakes, exfoliated graphite worms, carbon nanotube, carbon nanofiber, carbon fiber, a combination thereof; (B) a battery-like anode comprising lithium metal, lithium metal alloy, or a prelithiated anode active material (e.g. prelithiated Si, SiO, Sn, SnO2, etc.), and (C) a lithium-containing electrolyte in physical contact with the anode and the cathode; wherein the cathode active material has a specific surface area no less than 100 m2 / g which is in direct physical contact with the electrolyte.

The invention discloses lead carbon battery cathode diachylon. The lead carbon battery cathode diachylon is prepared from raw materials of 100 parts of lead powder, 4-100 parts of sulfuric acid, 0.1-8 parts of bonding agents, 0.1-2 parts of barium sulfate, 0.01-2 parts of hydrogen evolution inhibitors, 50-100 parts of graphene oxide, 0.05-1 part of acetylene black, 1-4 parts of humic acid, 5-15 parts of red lead, 12-21 parts of water and 0.1-0.2 part of short fibers. The invention also discloses a preparation method of the cathode diachylon as well as a lead carbon battery cathode comprising the diachylon as well as a preparation method of the lead carbon battery cathode and a lead carbon battery. According to the invention, graphene oxide is added into the cathode diachylon; graphene oxide contains a plurality of oxygen-containing functional groups, and a plurality of faradaic pseudocapacitance can be generated in sulfuric acid, so that the using quantity of lead powder in the cathode material can be reduced; meanwhile, electricity of the lead cathode can be shared under the condition of high-current charge and discharge; sulfation of a storage battery is relieved greatly; the service life of a storage battery is prolonged.

The invention discloses a carbon-based ternary composite electrode material for a super capacitor and a preparation method for the carbon-based ternary composite electrode material. The preparation method for the carbon-based ternary composite electrode material comprises the following steps of: firstly, performing ultrasonic dispersion on reactivated active carbon and a nanometer metallic oxide to prepare an active carbon / nanometer metallic oxide composite material; controlling the molar ratio of the active carbon / nanometer metallic oxide composite material to aniline monomer to be (3:1)-(10:1) through an in-situ polymerization method, and performing stirring reaction for 5-25h to obtain the carbon-based ternary composite electrode material for the super capacitor. According to the material, electric double-layer capacitance is provided for the super capacitor by effectively utilizing high-specific surface area active carbon. By combining with Faraday pseudocapacitance provided by conductive polyaniline, and meanwhile, by utilizing the high mechanical strength and a nanometer synergistic effect of the nanometer metallic oxide, the initial specific capacitance of the material in an organic electrolyte can reach 178F / g, and if the material is circulated for 2000 times, the specific capacitance can still be kept to be 148F / g.

The invention discloses a manufacturing method for a redox activity electrolyte based nitrogen-doped graphene supercapacitor, and specifically discloses manufacturing methods for a pseudocapacitance active water system electrolyte, nitrogen-doped porous graphene and a pseudocapacitance active electrolyte system supercapacitor. The capacitive performance of the supercapacitor is greatly improved mainly through the dual-capacitive contribution of electrode materials and the electrolyte. The specific capacity of the supercapacitor is improved by about three times through the pseudocapacitance contribution of the redox activity ingredients in the electrolyte, so that the great improvement potential exists in supercapacitor specific capacity and the energy density.

Provided is an internal hybrid electrochemical cell comprising: (a) a pseudocapacitance-like cathode comprising a cathode active material that contains both graphene sheets and a porphyrin compound, including porphyrin or a porphyrin complex, wherein the porphyrin compound is bonded to or supported by primary surfaces of graphene sheets to form a redox pair for pseudocapacitance; (b) a battery-like anode comprising an anode active material selected from sodium metal, a sodium metal alloy, a sodium intercalation compound, a sodium-containing compound, or a combination thereof, and (c) a sodium-containing electrolyte in physical contact with the anode and the cathode; wherein the cathode active material has a specific surface area no less than 100 m2 / g which is in direct physical contact with the electrolyte.

Provided is an internal hybrid electrochemical cell comprising: (A) a pseudocapacitance cathode comprising a cathode active material that contains both graphene sheets and a porphyrin complex, wherein said porphyrin complex is bonded to or supported by primary surfaces of said graphene sheets to form a redox pair for pseudocapacitance; (B) a battery-like anode comprising lithium metal, lithium metal alloy, or a prelithiated anode active material (e.g. prelithiated Si, SiO, Sn, SnO2, etc.), and (C) a lithium-containing electrolyte in physical contact with the anode and the cathode; wherein the cathode active material has a specific surface area no less than 100 m2 / g which is in direct physical contact with the electrolyte.

Provided is an internal hybrid electrochemical cell comprising: (A) a pseudocapacitance cathode comprising both graphene sheets and a 2D inorganic material, in a form of nanodiscs, nanoplatelets, or nanosheets that are bonded to or supported by primary surfaces (not the edges) of the graphene sheets and the 2D inorganic material and graphene sheets form a redox pair for pseudocapacitance; (B) a battery-like anode comprising a prelithiated anode active material (e.g. prelithiated Si, SiO, Sn, SnO2, etc.), and (C) a lithium-containing electrolyte in physical contact with the anode and the cathode; wherein the cathode active material has a specific surface area no less than 100 m2 / g which is in direct physical contact with the electrolyte.

The invention relates to a full-pseudocapacitance super capacitor. The full-pseudocapacitance super capacitor is composed of a positive electrode, a negative electrode, a diaphragm and electrolyte, wherein the diaphragm and the electrolyte are located between the positive electrode and the negative electrode. The full-pseudocapacitance super capacitor is characterized in that cobaltosic oxide (Co3O4) is attached to and grows on a multi-walled carbon nanotube / conductive carbon cloth substrate to form the positive electrode, ferric oxide (Fe2O3) is attached to and grows on a multi-walled carbon nanotube / conductive carbon cloth substrate to form the negative electrode, the diameter of multi-walled carbon nanotubes in the multi-walled carbon nanotube / conductive carbon cloth substrates ranges from 30 nanometers to 40 nanometers, and the multi-walled carbon nanotubes in the multi-walled carbon nanotube / conductive carbon cloth substrates are cross-linked and distributed in conductive carbon cloth space evenly and densely to show a three-dimensional net shape. Compared with a traditional carbon-based super capacitor, the full-pseudocapacitance super capacitor has higher pseudocapacitance specific capacity and good rate capability.

The invention discloses a two-dimensional layered nitrogen-doped Ti<3>C<2> ''paper'' nanocomposite and a preparation method therefor, and a method for preparing a composite electrode by employing the nanocomposite. The Ti<3>C<2> nanomaterial is used as a substrate; the two-dimensional layered nitrogen-doped Ti<3>C<2> ''paper'' nano composite electrode material is prepared by steps of urea chemical stripping, thermal treatment and nitrogen doping; and the composite electrode material is applied to an electrochemical capacitor. Compared with other reported preparation methods, the method provided by the invention can control the layered stripping and the nitrogen element doping of a laminated sheet in a convenient, rapid, environment-friendly and safe manner; the Ti<3>C<2> is stripped by urea, so that the number of layers of the Ti<3>C<2> nanosheets can be reduced and the spacing between the layers can be enlarged; therefore, the specific surface area is enlarged; the Ti<3>C<2> nanosheets are further layered through nitrogen doping, so that the conductivity of the material is improved, and the utilization rate of the pseudocapacitance active site is increased; and finally, the specific capacity, the rate capability and other electrochemical performances of the Ti<3>C<2> composite electrode are enhanced.

The invention discloses self-supporting CNT (Carbon Nano-Tube) film-faradaic pseudocapacitance composite material and a preparation method thereof. A CNT film participates in reaction by being used as a self-supporting continuous base body, the wall of a single CNT or the surface of a CNT bundle in a network structure of the CNT film is compounded with material with good faradaic pseudocapacitance performance, and the faradaic pseudocapacitance material comprises MnO2, Ni(OH)2 and PANI. According to the preparation method disclosed by the invention, the process is simple, and the defects of tedious technology and the like of a traditional electrode coating preparation method are overcome; and a prepared composite thin film has the advantages of large mechanical strength and good electrical conductivity, has excellent ductility and flexibility, is flexible electrode material and has a great application prospect in fields of a super capacitor and the like.

The invention relates to a preparation method for different carbon fibers / a cobalt hydroxide electrode and a solid-liquid composite electrode system. By means of pretreatment and modification of different carbon fibers, the carbon fibers serve as a substrate, composite of metal oxide or hydroxide and the carbon fibers are realized by the electrochemical deposition, and a solid electrode is obtained and has high specific capacitance in the alkaline aqueous solution. Redox substances are added into the alkaline aqueous solution, a composite electrode system that the solid electrode and liquid-phase electrolyte supply the pseudocapacitance jointly is obtained. The composite electrode system has ultra-high specific capacitance, is applied in supercapacitors, and has the advantages of ultra-high energy density, high power density and long service life. The specific capacitance of the composite electrode system can be adjusted by changing the concentration and volume of the redox substances, and the energy density and power density of the supercapacitors can be further changed to meet different using requirements.

The invention relates to a super-capacitor electrode material and a preparation method thereof. A conventional commercial super-capacitor product still has lower energy density, but the greatest defect of low energy density of the super-capacitor is hopeful to be overcome and the energy density of a carbon nano tube / nickelous hydroxide / graphene composite material can be greatly improved if a carbon nano tube / nickelous hydroxide / graphene composite material with reasonable structure and composition can be manufactured due to the fact that nickelous hydroxide has a large pseudocapacitance value and good reversibility, graphene has a large specific surface area and excellent electrical conductivity, the nickelous hydroxide and the graphene are stacked in a layered manner and can generate an synergistic effect, and a small quantity of conductive carbon nano tubes are doped. The super-capacitor electrode material is a carbon nano tube / nickelous hydroxide / graphene composite prepared with a microwave method. According to the super-capacitor electrode material, micromolecular non-toxic and harmless ethylene glycol is adopted as a reaction medium, microwave heating is adopted to promote fast completion of a reaction, the reaction is finished in one pot, and the prepared composite has a large specific capacity and a large energy density.

An electrical component includes an inkjet-printed graphene electrode. Graphene oxide flakes are deposited on a substrate in a graphene oxide ink using an inkjet printer. The deposited graphene oxide is thermally reduced to graphene. The electrical properties of the electrode are comparable to those of electrodes made using activated carbon, carbon nanotubes or graphene made by other methods. The electrical properties of the graphene electrodes may be tailored by adding nanoparticles of other materials to the ink to serve as conductivity enhancers, spacers, or to confer pseudocapacitance. Inkjet-printing can be used to make graphene electrodes of a desired thickness in preselected patterns. Inkjet printing can be used to make highly-transparent graphene electrodes. Inkjet-printed graphene electrodes may be used to fabricate double-layer capacitors that store energy by nanoscale charge separation at the electrode-electrolyte interface (i.e., “supercapacitors”).

The invention discloses a preparation method and application of a novel chloride ion removal material Ti3C2Tx / Ag. The method includes: etching a block Ti3AlC2 to obtain laminar Ti3C2Tx-MXene; ultrasonically stripping the Ti3C2Tx-MXene solution, and taking a supernatant to obtain a few-lamella Ti3C2Tx-MXene solution; dissolving a certain amount of AgNO3 in deionized water, and adding a certain amount of hydrochloric acid under an ultrasonic condition to obtain an AgCl colloidal solution; adding the obtained AgCl colloid into the few-lamella Ti3C2Tx-MXene solution, and performing oscillation fora certain time under the conditions of constant temperature and constant rotating speed; and carrying out vacuum filtration and separation on the reacted mixed solution, performing washing with deionized water for several times, and conducting natural drying at room temperature to obtain the Ti3C2Tx / Ag film. An in-situ self-reduction technology is utilized, AgCl colloid is used as an oxidizing agent, Ti3C2Tx-MXene is used as a reducing agent, the loading capacity and the particle size of Ag are regulated and controlled by controlling the reaction time, and the synthesis method is simple and practicable; based on the battery effect (conversion reaction) of Ag nanoparticles and the pseudocapacitance behavior (ion intercalation) of Ti3C2Tx, the prepared and synthesized Ti3C2Tx / Ag film showsexcellent chloride ion removal capability and good desalination performance.

The invention discloses a sodium ion battery cathode material based on an MXene and pseudocapacitance transition metal oxide nano composite structure, and a synthetic method, and belongs to the technical field of new materials. The sodium ion battery cathode material consists of a carbon coated MXene two-dimensional nano sheet uniformly loaded with pseudocapacitance transition metal oxide nano particles on the surface, and has a two-dimensional nano structure. The synthetic method comprises the steps of dissolving MXene, a carbon source precursor and metal salt in water, adding absolute ethylalcohol and ammonia water to prepare a suspension, performing stirring, reaction, separation and washing to obtain a mixture, and performing calcination treatment in a high-temperature furnace under inert gas shield to obtain the carbon coated MXene two-dimensional nano sheet cathode material uniformly loaded with the pseudocapacitance transition metal oxide nano particles on the surface. The structure and the component of the cathode material are adjustable. The synthetic method is simple in technology, low in energy consumption, easy to control, green and environment-friendly, has the universality, and can be used for large-scale industrial popularization and application; and the obtained cathode material represents high specific capacity, excellent cycling stability and excellent rate capability in a sodium ion battery.

The invention discloses a preparation method of an in-situ self-assembling N-doped super-hydrophilic carbon aerogel supercapacitor electrode material. The preparation method comprises the steps of introducing an N-containing conducting polymer and a borate radical framework in a gel three-dimensional net structure, and preparing a super-hydrophilic high-capacitance N-doped carbon aerogel supercapacitor electrode material which is of a porous structure after high-temperature activating, wherein N plays dual functions of increasing pseudocapacitance of the material and increasing the electronic transmission capacity, and borate radical ions are not only used as a cross-linking agent for maintaining a gel framework, but also have the effect of a self-assembling template so as to promote the generation of macroporous gaps. According to the preparation method of the in-situ self-assembling N-doped super-hydrophilic carbon aerogel supercapacitor electrode material, disclosed by the invention, excellent super-hydrophility can be shown without treatment of ultraviolet irradiation, or additional surface chemical modification and the like; solvent exchange needs not to be adopted, a freeze drying technology is used, the cost is low, the preparation method is simple and easy, the special three-dimensional net structure in gel is maintained, and environment friendliness is realized.

The invention discloses a preparation method of a novel cobaltous dihydroxycarbonate-nitrogen-doped graphene combined electrode material. The preparation method is characterized in that on the basis of simple one-step hydro-thermal reaction, cobaltous dihydroxycarbonate nano wires are uniformly distributed at a two-dimensional nitrogen-doped graphene skeleton uniformly in a product. According to the invention, the graphene with high specific surface area, high conductivity, and high flexibility is combined with the faradaic-pseudocapacitance cobaltous dihydroxycarbonate nanometer material, so that defects of low capacitance of the dual-electrode-layer material and poor conductivity of the faradaic pseudocapacitance can be overcome. Especially, the shape of the combined electrode material can be regulated by the reactant concentration, thereby realizing performance optimization. The specific capacitance of the combined material under the electric current density of 1.0Ag<-1> can reach 1690Fg<-1>; and the capacitance retention rate can reach 94.2% after the ten thousand of times of charging and discharging circulation. The preparation method has advantages of simple operation, low cost, and easy control.

The invention discloses a fabrication method of a PEDOT:PSS-coated nano MnO<2> particle-based graphene nano wall electrode. The method comprises the following steps: (1) preparing a graphene nano wall; (2) carrying out modification on the surface of the graphene nano wall; (3) depositing a PEDOT:PSS / MnO<2> thin film on the graphene nano wall; and (4) carrying out heat treatment on a PEDOT:PSS / MnO<2> thin film-loaded graphene wall / substrate in a nitrogen environment at 100-400 DEG C. According to the super capacitor electrode prepared by the method disclosed by the invention, the conductivity of the graphene wall is enhanced through a PEDOT:PSS conductive polymer; corrosion to MnO<2> caused by an electrolyte is reduced by the super capacitor electrode as a protection layer; the electrode with electric double layers and pseudocapacitance characteristic is achieved through the graphene nano wall and PEDOT:PSS-coated MnO<2> nano-particles; compared with a traditional graphene wall, the specific capacitance is improved by more than 10 times; and the graphene nano wall electrode is simple in technological process and low in cost, and can be produced on a large scale.

The invention belongs to the field of flexible wearable energy storage equipment, and relates to a preparation method of a high-capacity linear supercapacitor electrode based on MXene / PANI. After thata MXene dispersion liquid is mixed with a hydrochloric acid solution of aniline in proportion, self-assembly is carried out at a low temperature to generate an MXene / PANI composite material, a smallamount of deionized water is added into the MXene / PANI composite material, ground into slurry, and coated on a glass plate to prepare a composite film, freeze drying is carried out, an adhesive tape is used to implement stripping, and a motor carries out twisting to prepare the film into a linear electrode. According to the linear supercapacitor, the MXene material and the PANI material can show extra pseudocapacitance in the acid electrolyte, and compared with an electrode structure which is too tight in wet spinning, the electrode has richer pores after mechanical twisting, and a higher active surface area is brought. In addition, the problems of high brittleness and poor mechanical properties after MXene film formation are solved.

The invention relates to a two-dimensional transition metal carbide / titanium dioxide / graphene composite material, preparation and application thereof. The prepared composite material is composed of graphene, oxide, and two-dimensional transition metal carbide. According to the two-dimensional transition metal carbide / titanium dioxide / graphene composite material of the sandwich structure constructed by the invention, due to the intercalated structure, self-stacking of sheets of graphene and two-dimensional transition metal carbide can be prevented, and capacitive active positions are increased. The small amount of oxide titanium dioxide produced by a thermal reduction process can provide the embedded pseudocapacitance activity, and the large-sized graphene sheet layer can also enhance the electrical conductivity between the two-dimensional transition metal carbide sheets, further improving the electrochemical performance of the composite material and the performance of a lithium ion capacitor.

The present invention generally relates to the use of electrical charge storage devices in the rotors of induction machines. Optimal induction machine rotor electrical field requirements increase with rotational velocity and inversely to frequency. Pseudocapacitance and other inverse frequency capacitance adjustment methods are employed to provide for that need and thereby improve induction machine rotor performance parameters. Optimization of electrical reactance is the foundation for improvements in power transfer, torque, efficiency, stability, thermodynamics, vibration, thermodynamics and bearing life in rotational induction machines. LC rotor methods and designs are outlined herein to achieve these objectives.