Metal electrode for aluminum electrolysis, coating composition thereof, and preparation method therefor

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of International Application No. PCT/CN2024/086412, filed on Apr. 7, 2024, which claims priority to Chinese Patent Application No. 202310376813.X, filed on Apr. 7, 2023. The disclosures of the above-referenced applications are hereby incorporated by reference in their entirety.

BACKGROUND

Inert anode aluminum electrolysis technology does not consume carbon anodes and does not emit CO₂. During an electrolysis process, what is emitted is O₂, and an anode is no need to be changed, and thus a labor intensity of workers is greatly reduced, a working environment of workers is improved, and a lot of carbon resources is saved, thereby being environmentally friendly, and conforming to a concept of green development. Green aluminum electrolysis technology with an inert anode as a core is an important strategic support for an upgrading of aluminum industry.

At present, what is selected as materials for the inert anode is mainly concentrated in three aspects: metal alloy anodes, oxide ceramic anodes, and cermet anodes. It is researched and pointed out in an article “Inert Anodes for Aluminium Electrolysis: an Update ( )” that metal inert anodes have excellent conductivity and mechanical properties, and thus are suitable for processing and preparing complex-shaped spare parts, are easy to be connected to metal guide rods, and have raw materials that are easy to obtain and low processing and preparation costs. As a result, the metal inert anodes have become one of the most promising materials for the inert anodes and have received much attention from research institutions and enterprises. However, alloy anodes have a fatal flaw, that is, poor resistance to high-temperature molten salt corrosion. During an electrolysis process of the metal anodes, a dense oxide layer will form on a surface of an anode. Otherwise, the metal anodes will be directly corroded by an electrolyte. When the anode is polarized and not passivated, this corrosion will intensify and lead to direct stripping of an anode metal, resulting in a catastrophic result of abnormal interruption of electrolysis.

A metal on a working surface of the metal anode is highly prone to an oxidation reaction with a newly generated oxygen in an electrolysis reaction. An oxide and alloy substrate are dissolved into the electrolyte to diffuse to a cathode, liquid aluminum, and then are reduced into the liquid aluminum. Not only a service life of the metal anodes is shortened, but also problems such as high pollution to a newly generated aluminum are caused. Therefore, a research on the alloy anodes mainly focuses on how to reduce an alloy corrosion rate and extend a service life of the anode. To this end, researches on the alloy anodes is mainly carried out through the following two approaches. First approach is to optimize a material system and microstructure of the alloy anode, add alloy elements, and improve a corrosion resistance of an alloy in a high-temperature molten salt system of cryolite. Second approach is to in advance form a dense, corrosion-resistant oxide film or coating on a surface of the alloy anode through surface modification techniques such as pre-oxidation, surface spraying, and chemical deposition, so as to avoid direct contact between a metal substrate and the electrolyte, thereby protecting the alloy substrate.

SUMMARY

The disclosure relates to the technical field of aluminum electrolysis, and in particular to a metal electrode for aluminum electrolysis, a coating composition of the metal electrode, and a method for preparing the metal electrode.

The disclosure provides a metal electrode for aluminum electrolysis, and a coating composition of the metal electrode, and a method for preparing the metal electrode, so as to improve a problem of short service life of a metal anode.

According to a first aspect of the disclosure, a coating composition of a metal electrode for aluminum electrolysis is provided. Compositions of the coating composition, by mass fraction, include: NiFe₂O₄: 65%-75% and a metal component: 25%-35%. Chemical constituents of the metal component include: Ni, Fe, and Y.

According to a second aspect of the disclosure, a metal electrode for aluminum electrolysis is provided. The metal electrode includes a substrate and a coating attached to the substrate. A composition of the coating includes the coating composition described in the first aspect.

According to a third aspect of the disclosure, a method for preparing a metal electrode for aluminum electrolysis is provided, including: obtaining a NiFe₂O₄ powder; obtaining a metal component powder; mixing the NiFe₂O₄ powder and the metal component powder to obtain a coating composition; and coating the coating composition to a surface of a substrate to obtain a metal electrode for aluminum electrolysis.

BRIEF DESCRIPTION OF DRAWINGS

The accompanying drawings, which are incorporated in and constitute a portion of this specification, illustrate embodiments consistent with the disclosure and, together with the description, serve to explain the principles of the disclosure.

In order to more clearly illustrate the embodiments of the disclosure or the technical solutions in some implementations, the drawings required for use in the embodiments or the description of some implementations will be briefly introduced below. Obviously, for those skilled in the art, other accompanying drawings can be obtained based on these accompanying drawings without paying any creative labor.

FIG. 1 is a surface morphology of an uncoated metal anode according to some embodiments of the disclosure;

FIG. 2 is a surface morphology of a coated metal anode according to some embodiments of the disclosure;

FIG. 3 is a cross-sectional SEM image of a coating of a metal electrode according to some embodiments of the disclosure;

FIG. 4 is a SEM image of a metal electrode after an electrolysis according to some embodiments of the disclosure; and

FIG. 5 is a flowchart of a method according to some embodiments of the disclosure.

In the accompanying drawings, corresponding relationships between reference signs and component names are as follows: 1, oxide layer; 2, substrate; 3, interpenetration zone between surface layer and substrate; 4, coating.

DETAILED DESCRIPTION

In order to make the purposes, technical solutions, and advantages of the embodiments of the disclosure clearer, the technical solutions in the embodiments of the disclosure will be clearly and completely described below in conjunction with the accompanying drawings in the embodiments of the disclosure. Obviously, the described embodiments are only a portion of embodiments of the disclosure, not all the embodiments. Based on the embodiments in the disclosure, all other embodiments obtained by ordinary technicians in the field without making any creative work shall fall within the scope of protection of the disclosure.

Unless otherwise specified, various raw materials, reagents, instruments and apparatuses used in the disclosure can be purchased from the market or prepared by existing methods.

A coating composition of a metal electrode for aluminum electrolysis is provided according to an embodiment of the disclosure. Compositions of the coating composition, by mass fraction, include: NiFe₂O₄: 65%-75% and a metal component: 25%-35%. Chemical constituents of the metal component include: Ni, Fe, and Y.

In some embodiments, the chemical constituents of the metal component, by mass fraction, includes: Ni: 55%-65%, Fe: 35%-45%, and Y: 0.5%-1.5%.

In an aluminum electrolysis system, an anode is a metal electrode; a cathode is an liquid aluminum; and an electrolyte is an alumina solution. During a process of aluminum electrolysis, aluminum ions in the electrolyte gain electrons at the cathode to form the liquid aluminum and produce an oxygen. The oxygen undergoes an oxidation reaction with the metal electrode to form an oxide. The oxide is dissolved in the electrolyte and undergoes a reduction reaction with the liquid aluminum at the cathode to generate impurity products, thereby polluting a newly generated aluminum. A coating made of the present coating composition is to prevent a metal substrate from directly contacting a high-temperature molten salt, to protect a substrate of a metal anode. A service environment of an electrolytic anode requires that a coating must have good electrical conductivity, thermal stability, oxidation resistance and corrosion resistance. NiFe₂O₄ ceramic phase has good electrical conductivity, thermal stability, strong corrosion resistance and high-temperature oxidation resistance to the electrolyte. Therefore, a component of the coating selects NiFe₂O₄ as a basic raw material for preparing the coating. A content of the NiFe₂O₄ ceramic phase is controlled to range from 65%-75%, with a remainder being a metal phase, and thus it can not only play a due protective role, but also further improve a conductivity of the coating. If a mass fraction of the NiFe₂O₄ ceramic phase is too large, not only a thermal shock resistance of the coating will be deteriorated, but also a conductivity of the coating will be decreased, thereby increasing a reactive power consumption. If the mass fraction of the NiFe₂O₄ ceramic phase is too small, a protective performance will be insufficient, thereby affecting a service life of an inert electrode.

An introduction of the metal component can not only improve a thermal shock resistance of the NiFe₂O₄ ceramic phase, but also mainly improve the conductivity of the coating. The coating reacts with an oxygen newly generated by an electrolysis of alumina in an electrolytic environment to produce a nickel and iron oxides which reduce a corrosion diffusion rate of the coating, thereby further improving the protective performance of the coating. The mass fraction of the metal component is controlled to range from 25%-35%. If the mass fraction of the metal component is too high, a corrosion rate will be increased and a protection period of the coating will be shortened. If the mass fraction of the metal component is too low, an improvement of a conductivity will be limited. In an electrolytic environment, a nickel and iron can form new oxides, on a surface of the coating, with the oxygen newly generated by the electrolysis of alumina, to play a protective role and reduce the corrosion diffusion rate of the coating. The NiFe₂O₄ and metal components are controlled to be within a specific range of mass fraction, in this way, it has an effect of self-forming an oxygen-containing atmosphere microenvironment in an environment of high-temperature electrolysis. Oxides of nickel and iron can be partially generated as NiFe₂O₄ ceramic phases, further improving a corrosion resistance of the coating. An added rare earth element Y is mainly enriched in phase boundaries and grain boundaries. A large amount of large atomic rare earths on interfaces of boundaries hinders an outward diffusion of metal elements such as Fe and Ni, and also blocks an inward diffusion of atoms such as oxygen and fluorine in an electrolytic environment, thereby effectively inhibiting a corrosion diffusion rate of metal elements and increasing a service life of the coating. In addition, due to a strong affinity between rare earth elements and oxygen and a unique “pinning effect” of the rare earth elements, an oxidation resistance of an alloy and a bonding strength between a film layer and a substrate can be improved, thereby generating an oxidation-resistant film layer that is more resistant to an electrolyte melt corrosion. A content of rare earth Y of this coating is controlled in a range of 0.5%-1.5%. If the content of rare earth Y is too low, an effect is not obvious, while if the content of rare earth Y is too high, a preparation cost will be increased, which is not conducive to industrial-scale application.

In some embodiments, the coating composition is in a granular form; a volume particle size of the coating composition may range from 55 μm-70 μm.

The volume particle size of the coating composition is controlled to range from 55 μm-70 μm. Within this range of particle size, the coating composition has a good spraying quality, a good powder fluidity, and is easy to disperse, and thus a spraying temperature is appropriate. If the particle size is too large, the spraying temperature is increased, a bonding force between a spray layer and a substrate is deteriorated, and a surface finish is decreased. If the particle size is too small, the coating composition has a poor powder fluidity and is easy to agglomerate, and thus the coating composition is easy to clog a nozzle during a spraying process.

FIG. 2 is a surface morphology of a coated metal anode according to some embodiments of the disclosure. FIG. 3 is a cross-sectional SEM image of a coating of a metal electrode according to some embodiments of the disclosure. As shown in FIG. 2 and FIG. 3, a metal electrode for aluminum electrolysis is also provided according to an embodiment of the disclosure. The metal electrode includes a substrate and a coating attached to the substrate. A composition of the coating includes the coating composition provided above.

In some embodiments, a thickness of the coating ranges from 250 μm-350 μm. The substrate is a NiFe metal anode.

The thickness of the coating is controlled to range from 250 μm-350 μm to ensure that a protection period of the metal inert anode is prolonged as much as possible without adversely affecting a bonding strength between the coating and the substrate. If the thickness is too large, the bonding strength between the coating and the substrate will be reduced, and in severe cases, cracks or even falling off will occur. If the thickness is too small, a protective effect will be reduced and a service life of an inert metal anode will be shortened.

An anti-oxidation and corrosion-resistant layer that is plasma sprayed on a surface of an existing corrosion-resistant NiFe-based metal anode (FIG. 1 is a surface morphology of an uncoated metal anode according to some embodiments of the disclosure, as shown in FIG. 1) can not only effectively reduce a direct erosion of a high-temperature electrolytic molten salt on a metal anode substrate, but also can anew generate a protective film layer by the substrate and the coating while an outside surface of a protective coating is dissolved, thereby achieving a dynamic relative balance between a corrosion oxidation and a dissolution of the metal anode, maintaining a relatively stable thickness of a film layer during a service life thereof, and greatly delaying a consumption of the metal anode, such that a service life of the metal anode can be increased from several to dozens of hours at present, to 35-45 weeks. A metal impurity content of an electrolytic primary aluminum can also be stably below 0.7% for a long time. Therefore, problems of short electrolysis time and shorter stabilization time of low content of metal impurities in the electrolytic primary aluminum in some implementations can be overcomed. FIG. 4 is a SEM image of a metal electrode after electrolysis according to some embodiments of the disclosure. Moreover, in a process of using the metal anode of the disclosure, as an electrolysis process is improved, the service life of the inert anode will be further extended, thereby realizing an universal application of the inert anode in industrial electrolysis production.

FIG. 5 is a flowchart of a method according to some embodiments of the disclosure. A method for preparing a metal electrode for aluminum electrolysis is further provided according to an embodiment of the disclosure. As shown in FIG. 5, the method includes steps S1 to S4.

In Step S1, a NiFe₂O₄ powder is obtained.

In some embodiments, the NiFe₂O₄ powder is obtained by mixing NiO and Fe₂O₃, and then calcining the mixture.

In some embodiments, NiO and Fe₂O₃ is a molar ratio of 1:1 are uniformly stirred by a kneader, and then calcined at 900° C.-1050° C. in an air atmosphere to form a NiFe₂O₄ ceramic powder.

In Step S2, a metal component powder is obtained.

In some embodiments, the metal component powder is obtained by smelting Ni, Fe, and Fe—Y intermediate alloy, and then granulating.

In some embodiments, Ni, Fe, and Fe—Y intermediate alloy are vacuum smelted to prepare a Ni—Fe—Y ternary master alloy, and metal powder with a particle size of 44 μm-60 μm is obtained through a vacuum atomization method.

In Step S3, the NiFe₂O₄ powder and the metal component powder are mixed to obtain a coating composition;

In some embodiments, the NiFe₂O₄ powder and the metal component powder are mixed to obtain the coating composition by dispersing the NiFe₂O₄ powder and the metal component powder in a solvent, and then performing a spray granulation.

In some embodiments, a calcined NiFe₂O₄ ceramic powder and a metal powder are mixed in proportion, stirred thoroughly using a stirring mill with a deionized water added in, granulated through a spray granulator, and then sieved to obtain a mixed powder with a particle size of 55 μm-70 μm, that is, the coating composition is obtained. Process parameters of the spray granulation include: a processing capacity ranging from 45 kg/h-55 kg/h, an atomization pressure ranging from 3 MPa-5 MPa, and a discharge temperature ranging from 85° C.-95° C.

In Step S4, the coating composition is coated to a surface of a substrate to obtain a metal electrode for aluminum electrolysis.

In some embodiments, a way of a spraying is adopted for coating.

In some embodiments, the mixed powder is evenly sprayed, with a thickness ranging from 250 μm-350 μm, onto the surface of a NiFe metal anode using a plasma spraying process. Process parameters of the plasma spraying process include: a powder-feeding gas flow rate ranging from 0.5 m³/h-0.6 m³/h, a spray gun moving speed ranging from 900 mm/min-1000 mm/min, and a spraying distance ranging from 80 mm-100 mm.

The disclosure is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the disclosure but are not used to limit the scope of the disclosure. The experimental methods without specific conditions indicated in the following examples are usually measured in accordance with standards in China. If there is no corresponding standards in China, the experimental methods without specific conditions in the following examples are proceeded according to the general international standards, conventional conditions, or the conditions recommended by the manufacturer.

Example 1

A method for preparing a metal electrode for aluminum electrolysis includes the followings.

NiO and Fe₂O₃ in a molar ratio of 1:1 are uniformly stirred by a kneader, and then pre-sintered at 900° C.-1050° C. in an air atmosphere into a NiFe₂O₄ ceramic powder. Ni, Fe, and Fe—Y intermediate alloy are vacuum smelted to prepare a Ni—Fe—Y ternary master alloy, and a metal powder with a particle size of 44 μm-60 μm is obtained through a vacuum atomization method. The NiFe₂O₄ powder and metal powder are mixed in a mass ratio of 75%:25%, stirred thoroughly using a stirring mill with a deionized water added therein, granulated through a spray granulator, and then sieved to obtain a mixed powder with a particle size ranging from 55 μm-70 μm, that is, a coating composition is obtained. The mixed powder is uniformly sprayed, with a spraying thickness of 250 μm, onto a surface of a Ni—Fe-based metal anode with a size of 180*150*30 mm using a plasma spraying process, to be used as a stand-by electrolytic anode.

Example 2

A method for preparing a metal electrode for aluminum electrolysis includes the followings:

NiO and Fe₂O₃ in a molar ratio of 1:1 are uniformly stirred by a kneader, and then pre-sintered at 900° C.-1050° C. in an air atmosphere into a NiFe₂O₄ ceramic powder. Ni, Fe, and Fe—Y intermediate alloy are vacuum smelted to prepare a Ni—Fe—Y ternary master alloy, and a metal powder with a particle size ranging from 44 μm-60 μm is obtained through a vacuum atomization method. The NiFe₂O₄ powder and metal powder are mixed in a mass ratio of 72%:28%, stirred thoroughly using a stirring mill with a deionized water added therein, granulated through a spray granulator, and then sieved to obtain a mixed powder with a particle size ranging from 55 μm-70 μm, that is, a coating composition is obtained. The mixed powder is uniformly sprayed, with a spraying thickness of 280 μm, onto a surface of a Ni—Fe-based metal anode with a size of 180*150*30 mm using a plasma spraying process, to be used as a stand-by electrolytic anode.

Example 3

A method for preparing a metal electrode for aluminum electrolysis includes the followings:

NiO and Fe₂O₃ in a molar ratio of 1:1 are uniformly stirred by a kneader, and then pre-sintered at 900° C.-1050° C. in an air atmosphere into a NiFe₂O₄ ceramic powder. Ni, Fe, and Fe—Y intermediate alloy are vacuum smelted to prepare a Ni—Fe—Y ternary master alloy, and a metal powder with a particle size ranging from 44 μm-60 μm is obtained through a vacuum atomization method. The NiFe₂O₄ powder and metal powder are mixed in a mass ratio of 70%:30%, stirred thoroughly using a stirring mill with a deionized water added therein, granulated through a spray granulator, and then sieved to obtain a mixed powder with a particle size ranging from 55 μm-70 μm, that is, a coating composition is obtained. The mixed powder is uniformly sprayed, with a spraying thickness of 300 μm, onto a surface of a Ni—Fe-based metal anode with a size of 180*150*30 mm using a plasma spraying process, to be used as a stand-by electrolytic anode.

Example 4

A method for preparing a metal electrode for aluminum electrolysis includes the followings:

NiO and Fe₂O₃ in a molar ratio of 1:1 are uniformly stirred by a kneader, and then pre-sintered at 900° C.-1050° C. in an air atmosphere into a NiFe₂O₄ ceramic powder. Ni, Fe, and Fe—Y intermediate alloy are vacuum smelted to prepare a Ni—Fe—Y ternary master alloy, and a metal powder with a particle size ranging from 44 μm-60 μm is obtained through a vacuum atomization method. The NiFe₂O₄ powder and metal powder are mixed in a mass ratio of 68%:32%, stirred thoroughly using a stirring mill with a deionized water added therein, granulated through a spray granulator, and then sieved to obtain a mixed powder with a particle size ranging from 55 μm-70 μm, that is, a coating composition is obtained. The mixed powder is uniformly sprayed, with a spraying thickness of 330 μm, onto a surface of a Ni—Fe-based metal anode with a size of 180*150*30 mm using a plasma spraying process, to be used as a stand-by electrolytic anode.

Example 5

A method for preparing a metal electrode for aluminum electrolysis includes the followings:

NiO and Fe₂O₃ in a molar ratio of 1:1 are uniformly stirred by a kneader, and then pre-sintered at 900° C.-1050° C. in an air atmosphere into a NiFe₂O₄ ceramic powder. Ni, Fe, and Fe—Y intermediate alloy are vacuum smelted to prepare a Ni—Fe—Y ternary master alloy, and a metal powder with a particle size ranging from 44 μm-60 μm is obtained through a vacuum atomization method. The NiFe₂O₄ powder and metal powder are mixed in a mass ratio of 65%:35%, stirred thoroughly using a stirring mill with a deionized water added therein, granulated through a spray granulator, and then sieved to obtain a mixed powder with a particle size ranging from 55 μm-70 μm, that is, a coating composition is obtained. The mixed powder is uniformly sprayed, with a spraying thickness of 350 μm, onto a surface of a Ni—Fe-based metal anode with a size of 180*150*30 mm using a plasma spraying process, to be used as a stand-by electrolytic anode.

Comparative Example 1

A nickel-iron-based metal with a size of 180*150*30 mm is used as an electrolysis anode.

Comparative Example 2

A method for preparing a metal electrode for aluminum electrolysis includes the followings.

A nickel-iron-based metal anode with a size of 180*150*30 mm is placed in a heat treatment furnace for a pre-oxidation treatment at 1000° C. for heat preservation of 10 h. After a protective layer with a thickness of about 100 μm is formed on a surface of the nickel-iron-based metal anode, the nickel-iron-based metal anode is used as an electrolytic anode.

The metal electrodes provided in Example 1 to Example 5 and Comparative Example 1 to Comparative Example 2 are used as anodes and respectively assembled to form electrolysis devices for performance testing. A specific process is as follows: a hot isostatically pressed TiB₂ is used as a cathode; the cathode and anode adopted a vertical structure; an electrolysis current density is 0.5 A/cm²; an electrolysis test adopts a KF—NaF—AlF₃3 electrolyte system; a KF content is about 20 wt %; a molecular ratio is 1.4-1.5 (a sum of molar numbers of a sodium fluoride and a potassium fluoride divided by a number of moles of an aluminum fluoride ([NaF]+[KF])/[AlF₃]); an alumina content ranges from 4.2 wt %-5.2 wt %; and a temperature is 820° C. Test results are shown in the following table.

It can be seen from the above table that the service life of the metal electrode prepared by the method according to the embodiments of the disclosure is increased from several to dozens of hours at present to 35-45 weeks. The metal impurity content of the electrolytic primary aluminum can also be stably lower than 0.7% for a long time.

The coating composition according to some embodiments of the disclosure, that can be applied to a surface of existing corrosion-resistant NiFe-based metal anodes, can not only effectively reduce a direct erosion of a high-temperature electrolytic molten salt on a metal anode substrate, but also can anew generate a protective film layer by the substrate and the coating while an outside surface of a protective coating is dissolved, thereby achieving a dynamic relative balance between a corrosion oxidation and a dissolution of the metal anode, maintaining a relatively stable thickness of a film layer during a service life thereof, and greatly delaying a consumption of the metal anode, such that a service life of the metal anode can be increased from several to dozens of hours at present, to 35-45 weeks. A metal impurity content of the electrolytic primary aluminum can also be stably below 0.7% for a long time, overcoming problems of short electrolysis time and shorter stabilization time of low content of metal impurities in the electrolytic aluminum in some implementations.

Various embodiments of the disclosure may exist in the form of a range; it should be understood that the description in the form of a range is only for convenience and simplicity and should not be understood as a hard limit to the scope of the disclosure; therefore, the described range should be considered to have specifically disclosed all possible subranges as well as the single values within such a range. For example, a description of a range from 1 to 6 should be considered to have specifically disclosed subranges, such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, and from 3 to 6, and a single number within the stated range, such as 1, 2, 3, 4, 5, and 6, which applies regardless of the range. Additionally, whenever a numerical range is indicated herein, it is intended to include any cited number (fractional or whole) within the indicated range.

In the disclosure, unless otherwise specified, directional words such as “upper” and “lower” used to refer specifically to the directions of drawings in the accompanying drawings. Additionally, in the description of the disclosure, the terms “including”, “comprising” and the like mean “including but not limited to”. In the disclosure, relational terms such as “first” and “second” are merely used to distinguish one entity or operation from another and do not necessarily require or imply any such actual relationship or sequence among these entities or operations. In this article, “and/or” describes the association relationship of associated objects, indicating that three relationships may exist. For example, A and/or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. In the disclosure, “at least one” refers to one or more, and “plurality” refers to two or more. “At least one”, “at least one of the following” or similar expressions thereof refers to any combination of these items, including single items or any combination of plural items. For example, “at least one of a, b, or c”, or “at least one of a, b, and c” can mean: a, b, c, a-b (that is, a and b), a-c, b-c, or a-b-c, where a, b, and c can each be single or multiple.

The above descriptions are only embodiments of the disclosure enabling those skilled in the art to understand or implement the disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principle defined in the invention may be practiced in other embodiments without departing from the spirit or scope of the disclosure. Therefore, the disclosure is not to be limited to the embodiments shown in the disclosure but is to be accorded the widest scope consistent with the principles and novel features claimed in the disclosure.