阅读说明：本技术 一种基于钨酸镍/多壁碳纳米管复合材料的氨气传感器 (Ammonia gas sensor based on nickel tungstate/multi-walled carbon nanotube composite material ) 是由 苏元捷 杨敏 李丹 姚明亮 谢光忠 龚琪琛 潘虹 蒋亚东 于 2020-05-13 设计创作，主要内容包括：本发明涉及一种基于钨酸镍/多壁碳纳米管复合材料的氨气传感器,包括以陶瓷管为基底的旁热式传感器和位于所述陶瓷管表面的所述复合材料；所述复合材料包括以下组分：30-50mg三维花状钨酸镍、0.05-0.15ml质量分数为5.6％的多壁碳纳米管和0.05ml松油醇；所述三维花状钨酸镍包括以下组分：0.087g Ni(NO<Sub>3</Sub>)<Sub>2</Sub>·6H<Sub>2</Sub>O、0.098g NaWO<Sub>4</Sub>·2H<Sub>2</Sub>O、0.1mL-0.7ml水合肼和30mL去离子水。本发明的一种基于钨酸镍/多壁碳纳米管复合材料的氨气传感器,可以解决目前普通氨气传感器通常具有的应用范围小,氨气敏感材料的表面积较小,灵敏度差和选择性较差等问题。本发明提出的氨气气体传感器合成方法简单、形貌可控且实用性高。(The invention relates to an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material, which comprises an indirectly heated sensor taking a ceramic tube as a substrate and the composite material positioned on the surface of the ceramic tube; the composite material comprises the following components: 30-50mg of three-dimensional flower-shaped nickel tungstate, 0.05-0.15ml of multi-wall carbon nano-tube with the mass fraction of 5.6 percent and 0.05ml of terpineol; the three-dimensional flower-shaped nickel tungstate comprises the following components: 0.087g Ni (NO) 3 ) 2 ·6H 2 O、0.098g NaWO 4 ·2H 2 O, 0.1m L-0.7 ml hydrazine hydrate and 30m L deionized water, the ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material can solve the problems that the common ammonia gas sensor has a small application range, a small surface area of an ammonia gas sensitive material and poor sensitivityAnd poor selectivity. The ammonia gas sensor provided by the invention has the advantages of simple synthesis method, controllable appearance and high practicability.)

1. An ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material is characterized by comprising an indirectly heated sensor taking a ceramic tube as a substrate and the composite material positioned on the surface of the ceramic tube;

the composite material comprises the following components: 30-50mg of three-dimensional flower-shaped nickel tungstate, 0.05-0.15ml of multi-wall carbon nano-tube with the mass fraction of 5.6 percent and 0.05ml of terpineol;

the three-dimensional flower-shaped nickel tungstate comprises the following components: 0.087g Ni (NO)₃)₂·6H₂O、0.098g NaWO₄·2H₂O, 0.1m L-0.7 ml hydrazine hydrate and 30m L deionized water.

2. The ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material as claimed in claim 1, wherein the diameter of the three-dimensional flower-like nickel tungstate is 4-5 μm.

3. The ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material as claimed in claim 1, wherein the weight ratio of the three-dimensional flower-like nickel tungstate to the multi-walled carbon nanotubes is 10%.

4. The ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material, according to claim 1, wherein the three-dimensional flower-like nickel tungstate and the multi-walled carbon nanotubes are compounded by mechanical grinding.

5. A preparation method of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material is characterized by comprising the following steps:

preparing three-dimensional flower-like nickel tungstate: 0.087g of Ni (NO) was taken₃)₂·6H₂Dissolving O in deionized water (20 m L), stirring to obtain a first product, and collecting 0.098g NaWO₄·2H₂Dissolving O in 10m L deionized water, adding the first product after stirring uniformly, heating to 60 ℃, adding 0.1m L-0.7 ml of hydrazine hydrate after the temperature is stabilized, stirring to be uniform to form a second product, centrifuging the second product, washing, drying, calcining and cooling to room temperature to obtain three-dimensional flower-shaped nickel tungstate;

preparing the composite material: adding 0.05-0.15ml of multi-walled carbon nanotubes with the mass fraction of 5.6% into 30-50mg of three-dimensional flower-shaped nickel tungstate, mechanically grinding to form a third product, adding 0.05ml of terpineol into the third product, and blending into paste to obtain the composite material;

preparing the ammonia gas sensor: and coating the composite material on the surface of a ceramic tube substrate of the indirectly heated sensor to obtain the ammonia gas sensor.

6. The preparation method of the ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material as claimed in claim 1, wherein the time for adding the hydrazine hydrate is 15 s.

7. The preparation method of the ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material as claimed in claim 1, wherein the washing treatment comprises washing with deionized water and absolute ethyl alcohol alternately for 2-3 times.

8. The preparation method of the ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material as claimed in claim 1, wherein the drying temperature is 65 ℃ and the drying time is 12 h.

9. The preparation method of the ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material, which is characterized in that the calcination treatment comprises calcination at 800 ℃ for 2h in a muffle furnace; the temperature rise rate of the muffle furnace is 2 ℃/min.

10. Use of the ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material as described in any one of claims 1 to 4, wherein the ammonia gas sensor detects the ammonia gas concentration in industrial and agricultural production through the resistance change of the nickel tungstate/multi-walled carbon nanotube composite material.

Technical Field

The invention belongs to the technical field of sensors and nano materials, and particularly relates to an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material.

Background

With the rapid development of industrialization and urbanization, air pollution has attracted extensive attention in various fields all over the world. Ammonia is derived from automobile exhaust and fossil fuel combustion, and is a major source of photochemical smog, acid rain, and greenhouse effect. In addition, ammonia has corrosive and irritant effects on contacted skin tissues, has extremely high solubility, has irritant and corrosive effects on the upper respiratory tract of animals or human bodies, and is adsorbed on skin mucosa and eye conjunctiva, so that irritation and inflammation are generated. It can paralyze respiratory tract cilia and damage mucosal epithelial tissue, so that pathogenic microorganisms can easily invade, and the resistance of human body to diseases is weakened. Thus, gaseous NH is detected quickly and reliably₃The detection means is very important for guaranteeing the environment and the human health.

Cr that has been developed over the past decades₂O₃，Ni₃V₂O₈，TiO₂@WO₃And SnO based solid electrolyte gas sensors₂、In₂O₃、Fe₂O₃The oxide semiconductor type gas sensor of (1) is widely used for detecting NH₃. But a sensor based on a single metal oxide hasThe selectivity and the stability are poor, so that the improvement of the service performance of the sensor has important social and economic values. Although the noble metal is used as the gas sensitive electrode, the noble metal is favorable for testing the gas sensitive characteristic at high temperature, but the noble metal is high in price and has limitation on gas detection.

Disclosure of Invention

The invention aims to solve the technical problems in the prior art, provides an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material, and solves the problems that the conventional common ammonia gas sensor is small in application range, small in surface area of an ammonia gas sensitive material, poor in sensitivity and poor in selectivity.

In order to solve the technical problems, the embodiment of the invention provides an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material, which comprises an indirectly heated sensor taking a ceramic tube as a substrate and the composite material positioned on the surface of the ceramic tube;

the composite material comprises the following components: 30-50mg of three-dimensional flower-shaped nickel tungstate, 0.05-0.15ml of multi-wall carbon nano-tube with the mass fraction of 5.6 percent and 0.05ml of terpineol;

the three-dimensional flower-shaped nickel tungstate comprises the following components: 0.087g Ni (NO)₃)₂·6H₂O、0.098g NaWO₄·2H₂O, 0.1m L-0.7 ml hydrazine hydrate and 30m L deionized water.

On the basis of the technical scheme, the invention can be further improved as follows.

Furthermore, the diameter of the three-dimensional flower-shaped nickel tungstate is 4-5 μm.

Further, the weight ratio of the three-dimensional flower-shaped nickel tungstate to the multi-wall carbon nano tubes is 10%.

Further, compounding the three-dimensional flower-like nickel tungstate and the multi-wall carbon nano-tubes by mechanical grinding.

In order to solve the technical problems, the embodiment of the invention provides a preparation method of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material, which comprises the following steps:

preparation of three-dimensional flower-shaped tungstic acidNickel: 0.087g of Ni (NO) was taken₃)₂·6H₂Dissolving O in deionized water (20 m L), stirring to obtain a first product, and collecting 0.098g NaWO₄·2H₂Dissolving O in 10m L deionized water, adding the first product after stirring uniformly, heating to 60 ℃, adding 0.1m L-0.7 ml of hydrazine hydrate after the temperature is stabilized, stirring to be uniform to form a second product, centrifuging the second product, washing, drying, calcining and cooling to room temperature to obtain three-dimensional flower-shaped nickel tungstate;

preparing the composite material: adding 0.05-0.15ml of multi-walled carbon nanotubes with the mass fraction of 5.6% into 30-50mg of three-dimensional flower-shaped nickel tungstate, mechanically grinding to form a third product, adding 0.05ml of terpineol into the third product, and blending into paste to obtain the composite material;

preparing the ammonia gas sensor: and coating the composite material on the surface of a ceramic tube substrate of the indirectly heated sensor to obtain the ammonia gas sensor.

On the basis of the technical scheme, the invention can be further improved as follows.

Further, the time for adding hydrazine hydrate was 15 s.

Further, the washing treatment comprises washing for 2-3 times by using deionized water and absolute ethyl alcohol alternately.

Further, the temperature of the drying treatment is 65 ℃, and the time of the drying treatment is 12 hours.

Further, the calcination treatment comprises calcination in a muffle furnace at 800 ℃ for 2 h; the temperature rise rate of the muffle furnace is 2 ℃/min.

Further, the time for mechanical grinding is 2 h.

In order to solve the technical problems, the embodiment of the invention provides application of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material, wherein the ammonia gas sensor detects the ammonia gas concentration in industrial and agricultural production through the resistance change of the nickel tungstate/multi-walled carbon nanotube composite material.

Further, the working temperature of the ammonia gas sensor is 460 ℃.

The invention has the beneficial effects that:

1. in the ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material, NiWO₄The synthesis method is simple, the energy consumption is low, the yield is high, and the morphological growth of the hydrazine hydrate can be controlled by controlling the addition amount of the hydrazine hydrate; NiWO₄The compounding with MWCNTs is simple mechanical grinding, the carbon nano tube has small size and large specific surface area, and has excellent conductive performance of semiconductor metal. NiWO with single compounding ratio through carbon nanotube material₄The material has better NH₃Response, response time is shortened, recovery characteristics of the device are better, and gases with different components are easy to identify. Therefore, the specific surface area of the ammonia gas sensor material can be greatly increased by compounding the two materials, and gas adsorption sites are increased.

2. The ammonia gas sensor has the advantages of good response speed, excellent selectivity, excellent stability and high practicability, and can realize the rapid and reliable monitoring of the ammonia gas concentration in industrial and agricultural life production.

Drawings

FIG. 1 shows a three-dimensional flower-like NiWO of an embodiment of the present invention₄Synthetic flow chart and three-dimensional flower-shaped NiWO₄SEM picture of (1);

FIG. 2 is a Scanning Electron Microscope (SEM) image of a nickel tungstate/multi-walled carbon nanotube composite material according to an embodiment of the invention;

FIG. 3 is a schematic diagram of a sensing mechanism of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material according to an embodiment of the invention;

FIG. 4 shows a nickel tungstate/multi-walled carbon nanotube composite material, NiWO₄And MWCNTs for 20-80ppmNH, respectively₃Real-time resistance curve graph of;

FIG. 5 shows nitrogen (N) of a nickel tungstate/multi-walled carbon nanotube composite material according to an embodiment of the present invention₂) Adsorption-desorption isotherm graphs, wherein the inset is a line graph of pore diameter;

FIG. 6 is a graph showing the response/recovery time of a nickel tungstate/multi-walled carbon nanotube composite-based ammonia gas sensor to 50ppm NH3, wherein the inset shows the test results of the effect of relative humidity on the performance of the sensor;

FIG. 7 is a selectivity test chart of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material according to an embodiment of the invention;

FIG. 8 is a stability test chart of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material according to an embodiment of the invention;

Detailed Description

The principles and features of this invention are described below in conjunction with the following drawings, which are set forth by way of illustration only and are not intended to limit the scope of the invention.

The ammonia gas sensor based on the nickel tungstate/multi-walled carbon nanotube composite material comprises an indirectly heated sensor taking a ceramic tube as a substrate and the composite material positioned on the surface of the ceramic tube;

the composite material comprises the following components: 30-50mg three-dimensional flower-like nickel tungstate (NiWO)₄) 0.05-0.15ml of multi-walled carbon nanotubes (MWCNTs) with the mass fraction of 5.6% and 0.05ml of terpineol;

the three-dimensional flower-shaped nickel tungstate comprises the following components: 0.087g Ni (NO)₃)₂·6H₂O、0.098g NaWO₄·2H₂O, 0.1m L-0.7 ml hydrazine hydrate and 30m L deionized water.

Optionally, the diameter of the three-dimensional flower-shaped nickel tungstate is 4-5 μm.

Optionally, the weight ratio of the three-dimensional flower-like nickel tungstate to the multi-walled carbon nanotubes is 10%.

Optionally, the three-dimensional flower-like nickel tungstate and the multi-walled carbon nanotubes are composited by mechanical grinding.

In the above embodiment, the model of the ceramic tube-based indirectly-heated sensor may be MQ-4, MQ-137, QM-N5, etc. and may be used to detect NH₃The indirectly heated sensor of (1).

As shown in fig. 1, a second embodiment of the present invention provides a method for preparing an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material, which includes the following steps:

the method comprises the following steps: synthesis of three-dimensional flower-like NiWO by simple wet-chemical method₄

①, 0.087g of Ni (NO)₃)₂·6H₂O was dissolved in 20m L of deionized water and stirred on a magnetic stirrer until homogenous to form the first product (FIG. 1 a).

②, 0.098g of NaWO is taken₄·2H₂Dissolving O in 10m L deionized water, stirring, slowly adding into the first product with a dropper for 15s, heating to 60 deg.C, and slowly adding 0.1m L-0.7 ml hydrazine hydrate after the temperature is stabilized.

③, after the solution is homogenized, maintaining the temperature at 60 ℃, and magnetically stirring for 2h to form a second product.

④, stirring, centrifuging, washing with deionized water and anhydrous ethanol for 2-3 times, and drying at 65 deg.C for 12 hr (FIG. 1 b).

⑤, heating the muffle furnace to 800 ℃ at a heating rate of 2 ℃/min, then calcining the mixture at 800 ℃ for 2h, and cooling the calcined mixture to room temperature (figure 1c) to obtain NiWO₄Sample (fig. 1 d). NiWO is seen from SEM image₄The micro-topography was three-dimensional flower-like (FIGS. 1e-1 g).

Step two: preparation of Ammonia gas sensor

A. Cleaning a grinding vessel: after the cleaning and brushing, the fabric is washed alternately by absolute ethyl alcohol and deionized water and dried in an oven at 60 ℃.

B. Mechanical grinding NiWO₄And MWCNTs, and then coating the MWCNTs on the surface of a ceramic tube substrate of the indirectly heated sensor.

The step B specifically comprises the following steps:

①, weighing 30-50mg NiWO₄And (3) dropwise adding 0.05-0.15ml of MWCNTs with the mass fraction of 5.6% into a grinding vessel, and mechanically grinding for 2h to form a third product.

②, 0.05ml of terpineol was added dropwise to the powdery third product to prepare a paste, and a composite material was obtained.

③, coating the composite material on the surface of the ceramic tube of the indirectly heated sensor.

The above-mentioned fruitNickel tungstate/multiwalled carbon nanotube composite material (NiWO) as described in example₄MWCNTs) is shown in FIG. 2, and from FIG. 2, it can be seen that NiWO synthesized with different hydrazine hydrate addition amounts₄With different micro-morphologies. In the absence of hydrazine hydrate addition, NiWO₄Disordered particle packing (fig. 2a), when the hydrazine hydrate addition was 0.1ml, the grain size of the sample was seen to increase (fig. 2 b). NiWO when the amount of hydrazine hydrate increased to 0.2ml (FIG. 2c) and 0.3ml (FIG. 2d)₄The particles are tightly combined to form a remarkable flower-like structure. When the addition amount of hydrazine hydrate is 0.4ml, the daisy-shaped NiWO is obtained₄(FIG. 2e), FIG. 2f shows NiWO when hydrazine hydrate is added in an amount of 0.5ml₄The microscopic shape of (a) is transformed from daisy-like to rosette-like. When the hydrazine hydrate addition amount was 0.6 and 0.7ml, the crystallization of the sample was improved, the flower-like structure surface was sufficiently decorated by the nanorod structure, with uniform size and unique morphology (fig. 2g and 2 h). It can be seen that NiWO, in the absence of hydrazine hydrate₄The appearance of the nano-particles is disordered particle accumulation, the micro-particles are tightly combined with each other along with the increase of the using amount of hydrazine hydrate to form an obvious flower-shaped structure, the surface of the flower is fully decorated by huge nano-rods, and the flower-shaped structure has uniform size and unique shape, can obviously improve the specific surface area of a sample and is beneficial to NH₃Adsorption and dissociation.

In the above embodiments, the grinding vessel is preferably an agate mortar.

The working principle of the invention is as follows: in the nickel tungstate/multi-wall carbon nano tube composite material of the invention, NiWO₄The interface with MWCNTs forms a large number of heterostructures, NiWO₄The majority is an electron and the MWCNTs majority is a hole, therefore, NiWO₄Electrons on the conduction band will migrate to the MWCNTs and establish an electric field within the interface. Since NiWO₄The resistance is much higher than that of MWCNTs, so that the resistance change caused by gas adsorption is mainly in NiWO₄. When exposed to reducing NH₃When being molecular, NH₃Transfer of electrons in the molecule to NiWO₄In (1), making n-type NiWO₄The electron concentration increases (as shown in fig. 3) and the resistance decreases. NiWO compounded by MWCNTs₄Has the advantages ofThe sensor has better response due to larger specific surface area, more adsorption sites. The electron concentration in the built-in electric field increases, the faster the electron transport speed, and the response/recovery time of the sensor is shortened. From the analysis of the first principle, the nickel tungstate/multi-wall carbon nano tube composite material is contacted with NH₃When nickel atoms promote NH₃The dissociation of (2) enhances the ammonia-sensitive reaction and thus has a higher selectivity ratio.

The ammonia gas sensor prepared by the embodiment is stabilized in an air atmosphere, a voltage electrode of the sensor is connected with a voltage-stabilizing direct-current power supply, and a resistance electrode of the sensor is connected with a data collector Keithley 2700. Applying voltage to the sensor by a voltage stabilizing direct current power supply to change the temperature of the ceramic tube, introducing ammonia gas, and monitoring the resistance change of the sensor by a data collector Keithley2700, so as to obtain a real-time resistance change curve of the nickel tungstate/multi-walled carbon nanotube composite material in an ammonia gas environment of 20-80ppm, as shown in a curve 1 in figure 4, and a curve 2 and a curve 3 in figure 4 respectively represent 20-80ppm NH₃Environmental NiWO₄And the real-time resistance change curve of MWCNTs, and as can be seen from FIG. 4, the nickel tungstate/multi-walled carbon nanotube composite material of the embodiment of the invention is more pure NiWO₄And a pure MWCNTs response is high.

FIG. 5 shows nitrogen (N) of nickel tungstate/multi-walled carbon nanotube composite material prepared by the invention₂) Adsorption-desorption isotherm graphs, with the inset being a line graph of pore diameter. As can be seen from FIG. 5, the good adsorption performance of the ammonia gas sensor prepared by the invention is attributed to the mesoporous structure generated in the calcination process, wherein NiWO is synthesized₄H produced in the process of (1)₂WO₄The decomposition produces a gas, thereby creating a porous structure. According to the nitrogen adsorption-desorption result, the specific surface area of the nitrogen sensor is calculated by using the formula S-4.354 Vm (4.354 is the monolayer occupied area of each ml of nitrogen molecules, Vm-1/(slope + intercept), and the slope and intercept are the slope and intercept of a desorption curve), and the calculation result shows that the specific surface area of the nitrogen sensor prepared by the invention is 49.14m²·g^-1The pore diameter is mainly distributed around 20-60 nm. The larger specific surface area of the nitrogen sensor enhances the adsorption and desorption of gas molecules, and is favorable for gas detectionAnd (6) measuring.

FIG. 6 shows 50ppm NH of a nickel tungstate/multi-walled carbon nanotube composite-based ammonia gas sensor pair prepared by the method₃The response time/recovery time of the ammonia gas sensor is 57s and the recovery time is 177s according to the response time/recovery time calculation formula of the sensor; the inset shows the test result of the effect of the relative humidity on the performance of the sensor, and the relative humidity of the curves in the graph is 22.5%, 32.8%, 57.6%, 75.3% and 97.3% from bottom to top in sequence.

FIG. 7 is a graph showing selectivity test of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material according to an embodiment of the invention; as can be seen from FIG. 7, the ammonia gas sensor of the present invention is paired with NH₃Has the highest response and good selectivity.

FIG. 8 is a stability test chart of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material according to an embodiment of the invention; as can be seen from fig. 8, the sensor of the present invention has good stability.

The third embodiment of the invention provides application of an ammonia gas sensor based on a nickel tungstate/multi-walled carbon nanotube composite material, wherein the ammonia gas sensor detects the ammonia gas concentration in industrial and agricultural production through the resistance change of the nickel tungstate/multi-walled carbon nanotube composite material.

In the description of the present invention, it is to be understood that the terms "central," "longitudinal," "lateral," "length," "width," "thickness," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," "clockwise," "counterclockwise," "axial," "radial," "circumferential," and the like are used in the orientations and positional relationships indicated in the drawings for convenience in describing the invention and to simplify the description, and are not intended to indicate or imply that the referenced devices or elements must have a particular orientation, be constructed and operated in a particular orientation, and are therefore not to be considered limiting of the invention.

Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.

In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.

In the present invention, unless otherwise expressly stated or limited, the first feature "on" or "under" the second feature may be directly contacting the first and second features or indirectly contacting the first and second features through an intermediate. Also, a first feature "on," "over," and "above" a second feature may be directly or diagonally above the second feature, or may simply indicate that the first feature is at a higher level than the second feature. A first feature being "under," "below," and "beneath" a second feature may be directly under or obliquely under the first feature, or may simply mean that the first feature is at a lesser elevation than the second feature.

In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.