阅读说明：本技术 一种铜掺杂聚多巴胺纳米颗粒的制备方法及其应用 (Preparation method and application of copper-doped polydopamine nanoparticles ) 是由 何永勇 陈广炎 金宝 李玉龙 雒建斌 于 2020-11-29 设计创作，主要内容包括：本发明属于材料技术领域,尤其涉及一种铜掺杂聚多巴胺纳米颗粒的制备方法及其应用。本制备方法包括：将盐酸多巴胺粉末加入硫酸铜的水/乙醇混合溶液,得到含有多巴胺和硫酸铜的混合液；向混合液中加入少量过氧化氢,在室温下搅拌,进行多巴胺的氧化聚合反应,得到聚多巴胺混合液；将混合液加热升温,并滴加次磷酸钠溶液搅拌,与铜离子进行还原反应,得到铜掺杂的聚多巴胺混合液；对混合液进行离心、清洗、干燥,得到铜掺杂聚多巴胺纳米颗粒。本方法简单高效,且得到的纳米颗粒可作为润滑添加剂,展现出优异的分散性和润滑效果,可直接添加到润滑液中发挥减摩抗磨的作用,具有极大的应用前景。(The invention belongs to the technical field of materials, and particularly relates to a preparation method and application of copper-doped polydopamine nanoparticles. The preparation method comprises the following steps: adding dopamine hydrochloride powder into a copper sulfate water/ethanol mixed solution to obtain a mixed solution containing dopamine and copper sulfate; adding a small amount of hydrogen peroxide into the mixed solution, stirring at room temperature, and carrying out oxidative polymerization reaction on dopamine to obtain polydopamine mixed solution; heating the mixed solution, dropwise adding a sodium hypophosphite solution, stirring, and carrying out reduction reaction with copper ions to obtain a copper-doped polydopamine mixed solution; and centrifuging, cleaning and drying the mixed solution to obtain the copper-doped polydopamine nanoparticles. The method is simple and efficient, and the obtained nanoparticles can be used as a lubricating additive, show excellent dispersibility and lubricating effect, can be directly added into lubricating liquid to play a role in friction reduction and wear resistance, and have great application prospects.)

1. A preparation method of copper-doped polydopamine nanoparticles is characterized by comprising the following steps:

(1) adding dopamine hydrochloride powder into a water/ethanol mixed solution of copper sulfate, wherein the adding proportion is as follows: obtaining a mixed solution containing dopamine and copper sulfate, wherein the volume ratio of ethanol to water in water/ethanol is 1 (2-3), and the ratio of copper sulfate to water/ethanol in the copper sulfate water/ethanol mixed solution is as follows: 3.5-15 mg/ml, wherein the mass ratio of the dopamine hydrochloride to the copper sulfate in the mixed solution of the dopamine and the copper sulfate is 1 (4-8);

(2) dropwise adding hydrogen peroxide into the mixed solution obtained in the step (1) at room temperature, stirring, wherein the volume ratio of the hydrogen peroxide to the mixed solution is 0.03-0.06, and the stirring time is 2-3 hours, and carrying out oxidative polymerization on dopamine to obtain a polydopamine mixed solution;

(3) heating the polydopamine mixed solution obtained in the step (2) to 60-80 ℃, stirring for 0.5-1 hour, dropwise adding a sodium hypophosphite solution to ensure that the mass ratio of sodium hypophosphite to copper sulfate in the step (1) is 1 (2-4), stirring for 0.5-1 hour, and carrying out reduction reaction on the sodium hypophosphite and copper ions to obtain a copper-doped polydopamine mixed solution;

(4) and (4) carrying out centrifugal separation, cleaning and drying on the copper-doped polydopamine mixed solution obtained in the step (3) to obtain the copper-doped polydopamine nano-particles.

2. The method for preparing copper-doped polydopamine nanoparticles as claimed in claim 1, wherein in the step (5), the centrifugation speed is 10000-12000rpm, and the centrifugation time is 10-30 minutes.

3. The method for preparing copper-doped polydopamine nanoparticles according to claim 1, wherein in the step (5), the drying temperature is 40-70 ℃ and the drying time is 20-28 hours.

4. The application of the copper-doped polydopamine nanoparticles prepared by the preparation method according to claim 1, which is characterized in that the copper-doped polydopamine nanoparticles are added into a lubricating fluid as an additive of the lubricating fluid, wherein the additive accounts for the following weight percentages in the lubricating fluid: 0.1 to 1 wt%.

5. The use of copper-doped polydopamine nanoparticles as claimed in claim 4, wherein the lubricating fluid is a lubricating oil commonly used in industry, including PAO6 base oil, polyethylene glycol base oil, gear oil or aviation hydraulic oil.

Technical Field

The invention belongs to the technical field of materials, and particularly relates to a preparation method and application of copper-doped polydopamine nanoparticles.

Background

Mussels adhere to a variety of substrates because of the strong chemical activity of 3, 4-Dihydroxyphenylalanine (DOPA) contained in byssus proteins. Dopamine is a derivative of DOPA, which forms polydopamine films on various materials, especially with strong binding to metals or metal oxides, by oxidative autopolymerization in alkaline solutions. Therefore, inspired by marine mussels, polydopamine has attracted attention because of its property of forming strong chemical bonds with many functional surfaces, and has been widely used in various fields such as modification of substrates and synthesis of composite materials. In addition, the lubricating properties of polydopamine also make it open potential in tribological applications. As a lubricating additive, the polydopamine nanoparticles can form a firm adsorption film in the contact area of the metal friction pair, so that the direct contact of the friction pair is avoided. It has been shown that compounding polydopamine with other nanomaterials is an effective way to enhance their performance. Such as copper/polydopamine/graphene oxide lubricant additives, silver/polydopamine lubricant additives, and the like, exhibit excellent tribological properties. Therefore, the preparation of the nano-composite material of polydopamine and metal and the application of the nano-composite material as a lubricating additive have great potential.

However, oxidative polymerization of dopamine requires more than 24 hours in alkaline Tris-HCl buffer solution or ammonia or NaOH solution, but most of the metal ions cannot be present in such alkaline solution (pH 8.5). Therefore, the synthesis of current polydopamine/metal composites must employ a two-step process: first, polydopamine is prepared in an alkaline solution, and then the composition with metal is performed in another solution, which makes the current synthesis process of polydopamine nanocomposite very cumbersome (more than 24 hours). Therefore, based on the advantages of the polydopamine composite material, it is desirable to develop a simple and efficient preparation method to synthesize the polydopamine and metal particle composite material and expand the application of the polydopamine and metal particle composite material as a lubricating additive.

Disclosure of Invention

Aiming at the problems in the prior art, the preparation method of the polydopamine nanoparticles is improved, so that the polydopamine nanoparticles are simple in preparation process and high in efficiency, and are used as lubricating additives.

The preparation method of the copper-doped polydopamine nanoparticles comprises the following steps:

(1) adding dopamine hydrochloride powder into a water/ethanol mixed solution of copper sulfate, wherein the adding proportion is as follows: obtaining a mixed solution containing dopamine and copper sulfate, wherein the volume ratio of ethanol to water in water/ethanol is (1) - (2-3), and the ratio of the mass of copper sulfate to the volume of the water/ethanol solution in the water/ethanol mixed solution of copper sulfate is as follows: 3.5-15 mg/ml, wherein the mass ratio of the dopamine hydrochloride to the copper sulfate in the mixed solution of the dopamine and the copper sulfate is 1 (4-8);

(2) dropwise adding hydrogen peroxide into the mixed solution obtained in the step (1) at room temperature, stirring, wherein the volume ratio of the hydrogen peroxide to the mixed solution is 0.03-0.06, and the stirring time is 2-3 hours, and carrying out oxidative polymerization on dopamine to obtain a polydopamine mixed solution;

(3) heating the polydopamine mixed solution obtained in the step (2) to 60-80 ℃, stirring for 0.5-1 hour, dropwise adding a sodium hypophosphite solution to ensure that the mass ratio of sodium hypophosphite to copper sulfate in the step (1) is 1 (2-4), stirring for 0.5-1 hour, and carrying out reduction reaction on the sodium hypophosphite and copper ions to obtain a copper-doped polydopamine mixed solution;

(4) and (4) carrying out centrifugal separation, cleaning and drying on the copper-doped polydopamine mixed solution obtained in the step (3) to obtain the copper-doped polydopamine nano-particles.

In the step (5) of the preparation method of the copper-doped polydopamine nanoparticle, the centrifugation rotation speed is 10000-12000rpm, and the centrifugation time is 10-30 minutes.

In the step (5) of the preparation method of the copper-doped polydopamine nanoparticles, the drying temperature is 40-70 ℃, and the drying time is 20-28 hours.

The application of the copper-doped polydopamine nanoparticles prepared by the preparation method is that the copper-doped polydopamine nanoparticles are used as a lubricating liquid additive and added into the lubricating liquid, and the additive accounts for the lubricating liquid in percentage by weight: 0.1 to 1 wt%. The lubricating liquid is industrial common lubricating oil, and comprises PAO6 base oil, polyethylene glycol base oil, gear oil or aviation hydraulic oil.

The preparation method and the application of the copper-doped polydopamine nano-particles have the advantages that:

the preparation method of the copper-doped polydopamine nanoparticles adopts a one-pot in-situ synthesis method, utilizes copper ions capable of catalyzing dopamine oxidation as precursors for synthesizing the copper nanoparticles, and can uniformly dope the copper nanoparticles in the polydopamine nanoparticles after the copper nanoparticles are reduced by sodium hypophosphite. The process is simple and efficient, saves a large number of steps compared with a two-step method, and greatly reduces the preparation time. In addition, the preparation method of the invention can ensure that the prepared copper-doped polydopamine lubricating additive has excellent dispersion characteristics and can be directly added into lubricating oil to play an excellent lubricating effect. Therefore, by adopting the preparation method of the copper-doped polydopamine nano-particles, the technical problems and practical problems of complex preparation of the polydopamine/metal composite material and the like can be effectively solved. In the invention, copper ions and hydrogen peroxide can catalyze the polymerization of dopamine, and the copper ions can be directly reduced into copper nanoparticles and polydopamine to form composite nanoparticles. The copper-doped polydopamine nanoparticles can form a synergistic protective film on the metal surface in the friction process as a lubricating additive, so that continuous and stable lubricating performance is provided. The preparation method is simple and efficient, can be directly added into lubricating liquid as an additive to play a role in friction reduction and wear resistance, is convenient to use, and has a great application prospect.

Drawings

Fig. 1 is an SEM photograph of copper-doped polydopamine nanoparticles according to example 1 of the present invention.

Fig. 2 is a TEM photograph of copper-doped polydopamine nanoparticles according to one embodiment 1 of the present invention.

Fig. 3 is copper-doped polydopamine nanoparticles as a lubricant additive according to one embodiment 1 of the present invention, which are dispersible in lubricating oil.

Fig. 4 is an SEM photograph of copper-doped polydopamine nanoparticles according to example 2 of the present invention.

Fig. 5 is an SEM photograph of copper-doped polydopamine nanoparticles according to example 3 of the present invention.

Detailed Description

The invention provides a preparation method of copper-doped polydopamine nanoparticles, which comprises the following steps:

(1) adding dopamine hydrochloride powder into a water/ethanol mixed solution of copper sulfate, wherein the adding proportion is as follows: obtaining a mixed solution containing dopamine and copper sulfate, wherein the volume ratio of ethanol to water in water/ethanol is (1) - (2-3), and the volume ratio of copper sulfate to water/ethanol in the copper sulfate water/ethanol mixed solution is as follows: 3.5-15 mg/ml, wherein the mass ratio of the dopamine hydrochloride to the copper sulfate in the mixed solution of the dopamine and the copper sulfate is 1 (4-8);

(2) dropwise adding hydrogen peroxide into the mixed solution obtained in the step (1) at room temperature, stirring, wherein the volume ratio of the hydrogen peroxide to the mixed solution is 0.03-0.06, and the stirring time is 2-3 hours, and carrying out oxidative polymerization on dopamine to obtain a polydopamine mixed solution;

(3) heating the polydopamine mixed solution obtained in the step (2) to 60-80 ℃, stirring for 0.5-1 hour, dropwise adding a sodium hypophosphite solution to ensure that the mass ratio of sodium hypophosphite to copper sulfate in the step (1) is 1 (2-4), stirring for 0.5-1 hour, and carrying out reduction reaction on the sodium hypophosphite and copper ions to obtain a copper-doped polydopamine mixed solution;

(4) and (4) carrying out centrifugal separation, cleaning and drying on the copper-doped polydopamine mixed solution obtained in the step (3) to obtain the copper-doped polydopamine nano-particles.

In the step (5) of the preparation method of the copper-doped polydopamine nanoparticle, the centrifugation rotation speed is 10000-12000rpm, and the centrifugation time is 10-30 minutes.

In the step (5) of the preparation method of the copper-doped polydopamine nanoparticles, the drying temperature is 40-70 ℃, and the drying time is 20-28 hours.

The application of the copper-doped polydopamine nanoparticles prepared by the preparation method is that the copper-doped polydopamine nanoparticles are used as a lubricating liquid additive and added into the lubricating liquid, and the additive accounts for the lubricating liquid in percentage by weight: 0.1 to 1 wt%. The lubricating liquid is industrial common lubricating oil, and comprises PAO6 base oil, polyethylene glycol base oil, gear oil or aviation hydraulic oil.

The lubricating fluid is a lubricating oil commonly used in industry, and includes, but is not limited to, PAO6 base oil, polyethylene glycol base oil, gear oil, aviation hydraulic oil, and the like. Thus, the use of copper doped polydopamine nanoparticles as lubricant additives may be provided. The lubricating oil added with the copper-doped polydopamine nanoparticles can be widely applied to the fields of mechanical engineering and aerospace, such as automobile engine lubrication, and lubrication of parts such as gear boxes and airplane actuators.

According to a specific embodiment of the present invention, the preparation method of copper-doped polydopamine nanoparticles comprises the following steps:

(1) weighing ethanol and pure water in a certain volume ratio by using a measuring cylinder, and stirring by using a glass rod to fully mix the ethanol and the pure water, wherein the volume ratio of the ethanol to the water is 1 (2-3), and preferably 1: 2.5. Weighing copper sulfate powder and dopamine hydrochloride powder in sequence by using a balance, sequentially adding the copper sulfate powder and the dopamine hydrochloride powder into the mixed solution, and stirring by using a glass rod to fully dissolve the copper sulfate powder, wherein the mass ratio of the dopamine hydrochloride to the copper sulfate is 1: (4-8), preferably 1: 6. Thus, a blue mixed solution containing dopamine and copper sulfate was obtained.

(2) 0.05-0.1 ml of 30% hydrogen peroxide aqueous solution, preferably 0.08ml, is sucked by a pipette and added dropwise to the mixed solution in the step (1). And then putting a rotor into the beaker filled with the mixed solution, covering the rotor with a preservative film, and carrying out magnetic stirring at room temperature for 2-3 hours, preferably 2.5 hours. Therefore, dopamine is subjected to oxidative polymerization reaction under the catalytic action, and the solution is gradually changed from blue to black to obtain a polydopamine mixed solution.

(3) A certain amount of sodium hypophosphite powder is weighed, added into pure water and stirred by a glass rod to be fully dissolved, and the mass ratio of the sodium hypophosphite to the copper sulfate in the step (1) is 1 (2-4), preferably 1: 2.75. And (3) simultaneously heating the mixed solution in the step (2) in water bath at the temperature of 60-80 ℃, preferably 70 ℃. When the solution is heated to the specified temperature, the prepared sodium hypophosphite solution is added dropwise, and magnetic stirring is continued for 0.5 to 1 hour, preferably 0.5 hour. Therefore, the copper ions can fully perform reduction reaction to obtain the polydopamine mixed solution doped with copper.

(4) And (3) centrifuging the mixed solution of the copper-doped polydopamine in the step (3) by using a high-speed desktop centrifuge, wherein the centrifugation speed is 10000-12000rpm, the centrifugation time is 10-30 minutes, and preferably 10000rpm is used for 20 minutes to obtain copper-doped polydopamine nanoparticle precipitate, and discarding the upper-layer waste liquid. Washing the lower layer precipitate with ethanol, centrifuging again, removing the supernatant, and washing repeatedly for 3 times. Finally dispersing the lower layer precipitate with ethanol, and drying in an electric heating constant temperature blast drying oven at 40-70 deg.C, preferably 60 deg.C. And after the ethanol is completely volatilized, obtaining the copper-doped polydopamine nano-particles.

The invention tests the obtained copper-doped polydopamine nanoparticles as a lubricating additive, and the specific process is as follows:

and (4) weighing a certain mass of copper-doped polydopamine nanoparticles obtained in the step (4), adding the copper-doped polydopamine nanoparticles into lubricating oil, and then carrying out magnetic stirring for 1 hour and ultrasonic dispersion for 1 hour. Therefore, the lubricating liquid containing the copper-doped polydopamine nanoparticles is obtained, and the content is 0.1-1 wt%, preferably 0.4 wt%. A ball-disk reciprocating friction test is carried out by using an SRV4 high-temperature friction wear testing machine, wherein an upper sample is a GCr15 steel ball with the diameter of 10mm, and a lower sample is a GCr15 steel disk.

The test result shows that: the copper-doped polydopamine nanoparticles obtained by the invention are used as a lubricating additive, have good dispersibility and lubricating effect, can be directly added into lubricating liquid to play a role in friction reduction and wear resistance, and have great application prospects.

To further illustrate the present invention, the preparation method and application of the copper-doped polydopamine nanoparticles disclosed in the present invention are described in detail with reference to the following examples, but the scope of the present invention includes, but is not limited to, the following examples.

Example 1

(1) 40ml of ethanol and 100ml of pure water were weighed in a measuring cylinder and stirred with a glass rod to be mixed well. 1.68g of copper sulfate powder and 0.28g of dopamine hydrochloride powder are weighed in sequence by a balance, added into the mixed solution in sequence and stirred by a glass rod to be fully dissolved.

(2) 0.08ml of 30% aqueous hydrogen peroxide solution was sucked up by a pipette and added dropwise to the mixture in step (1). Then, a rotor is placed in a beaker filled with the mixed solution, a preservative film is covered on the beaker, and magnetic stirring is carried out at room temperature for 2.5 hours.

(3) 4.63g of sodium hypophosphite powder was weighed out by a balance, added to 10ml of pure water, and stirred with a glass rod to be sufficiently dissolved. And (3) simultaneously heating the mixed solution in the step (2) in water bath, heating to 70 ℃, then dropwise adding the prepared sodium hypophosphite solution, and continuing to magnetically stir for 0.5 hour.

(4) And (4) centrifuging the mixed solution in the step (3) by using a high-speed desk centrifuge, wherein the centrifugal speed is 10000rpm, the centrifugation time is 20 minutes, so as to obtain copper-doped polydopamine nanoparticle precipitate, and discarding the upper-layer waste liquid. Washing the lower layer precipitate with ethanol, centrifuging again, removing the supernatant, and washing repeatedly for 3 times. Finally, dispersing the lower-layer precipitate by using ethanol, and drying the precipitate in an electric heating constant-temperature air-blast drying oven at the temperature of 60 ℃. And after the ethanol is completely volatilized, obtaining the copper-doped polydopamine nano-particles.

(5) The resulting copper-doped polydopamine nanoparticles were added as a lubricant additive to polyethylene glycol base oil at an additive content of 0.4 wt% and subsequently used for friction testing.

The obtained copper-doped polydopamine nanoparticles are subjected to SEM analysis, and the result is shown in figure 1. Fig. 1 is an SEM photograph of copper-doped polydopamine nanoparticles according to example 1 of the present invention. As can be seen from FIG. 1, the copper-doped polydopamine nanoparticles prepared in example 1 of the present invention are spherical particles with a particle size of 100-300 nm.

The obtained copper-doped polydopamine nanoparticles are subjected to TEM analysis, and the result is shown in FIG. 2. Fig. 2 is a TEM photograph of copper-doped polydopamine nanoparticles according to example 1 of the present invention. As can be seen from fig. 2, the polydopamine prepared in example 1 of the present invention has copper nanoparticles uniformly incorporated therein.

The effect of the obtained copper-doped polydopamine nanoparticles as the lubricating additive is tested, the lubricating oil containing different additives is kept still for one week, the dispersion stability of the lubricating oil is compared, and the result is shown in fig. 3. Fig. 3 is copper-doped polydopamine nanoparticles as a lubricant additive according to example 1 of the present invention, their dispersancy in lubricating oils. As can be seen from fig. 3, the copper-doped polydopamine nanoparticles as a lubricant additive have excellent dispersion stability in the lubricant and do not settle down after standing for one week.

Example 2

(1) 40ml of ethanol and 100ml of pure water were weighed in a measuring cylinder and stirred with a glass rod to be mixed well. 1.12g of copper sulfate powder and 0.28g of dopamine hydrochloride powder were weighed out in sequence by a balance, added to the mixed solution in sequence, and stirred with a glass rod to be dissolved sufficiently.

(2) 0.1ml of 30% aqueous hydrogen peroxide solution was aspirated by a pipette and added dropwise to the mixture in step (1). Then, a rotor is placed in a beaker filled with the mixed solution, a preservative film is covered on the beaker, and magnetic stirring is carried out at room temperature for 2.5 hours.

(3) 3.09g of sodium hypophosphite powder was weighed out by a balance, added to 10ml of pure water, and stirred with a glass rod to be sufficiently dissolved. And (3) simultaneously heating the mixed solution in the step (2) in water bath, heating to 70 ℃, then dropwise adding the prepared sodium hypophosphite solution, and continuing to magnetically stir for 0.5 hour.

(4) And (4) centrifuging the mixed solution in the step (3) by using a high-speed desk centrifuge, wherein the centrifugal speed is 10000rpm, the centrifugation time is 20 minutes, so as to obtain copper-doped polydopamine nanoparticle precipitate, and discarding the upper-layer waste liquid. Washing the lower layer precipitate with ethanol, centrifuging again, removing the supernatant, and washing repeatedly for 3 times. Finally, ethanol is used for dispersing the lower-layer precipitate, and the precipitate is placed in an electric heating constant-temperature air-blast drying oven for drying, wherein the temperature is 70 ℃. And after the ethanol is completely volatilized, obtaining the copper-doped polydopamine nano-particles.

(5) The resulting copper doped polydopamine nanoparticles were added as a lubricant additive to PAO6 base oil at an additive level of 0.4 wt% and subsequently used for the friction test.

Fig. 4 is an SEM photograph of the copper-doped polydopamine nanoparticles of example 2.

Example 3

(1) 35ml of ethanol and 95ml of pure water were weighed out with a measuring cylinder and stirred with a glass rod to be mixed well. 2.24g of copper sulfate powder and 0.28g of dopamine hydrochloride powder are weighed in sequence by a balance, added into the mixed solution in sequence and stirred by a glass rod to be fully dissolved.

(2) 0.08ml of 30% aqueous hydrogen peroxide solution was sucked up by a pipette and added dropwise to the mixture in step (1). Then, a rotor is placed in a beaker filled with the mixed solution, a preservative film is covered on the beaker, and magnetic stirring is carried out at room temperature for 2 hours.

(3) 6.17g of sodium hypophosphite powder was weighed out by a balance, added to 10ml of pure water, and stirred with a glass rod to be sufficiently dissolved. And (3) simultaneously heating the mixed solution in the step (2) in water bath, heating to 70 ℃, then dropwise adding the prepared sodium hypophosphite solution, and continuing to magnetically stir for 0.5 hour.

(4) And (4) centrifuging the mixed solution in the step (3) by using a high-speed desk centrifuge, wherein the centrifugal speed is 10000rpm, the centrifugation time is 25 minutes, so as to obtain copper-doped polydopamine nanoparticle precipitate, and discarding the upper-layer waste liquid. Washing the lower layer precipitate with ethanol, centrifuging again, removing the supernatant, and washing repeatedly for 3 times. Finally, dispersing the lower-layer precipitate by using ethanol, and drying the precipitate in an electric heating constant-temperature air-blast drying oven at the temperature of 50 ℃. And after the ethanol is completely volatilized, obtaining the copper-doped polydopamine nano-particles.

(5) The obtained copper-doped polydopamine nanoparticles were added as a lubricant additive to No. 15 aviation hydraulic oil, with an additive content of 0.7 wt%, and subsequently used for a friction test.

Fig. 5 is an SEM photograph of copper-doped polydopamine nanoparticles according to example 3.

From the above examples, it can be seen that the copper-doped polydopamine nanoparticles of the present invention can form a stable and firm chemisorption film on the metal surface during the friction process, and the chemisorption film can be used as a lubricant additive, such that the copper-doped polydopamine nanoparticles have good dispersibility and lubrication effects.

The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art can make modifications and improvements on the disclosed techniques without departing from the spirit of the invention, and such modifications and improvements are intended to be within the scope of the invention.