CN110228811B - Low-dimensional rare earth boride nano material and solid phase preparation method thereof - Google Patents
Low-dimensional rare earth boride nano material and solid phase preparation method thereof Download PDFInfo
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Abstract
The invention discloses a low-dimensional rare earth boride nano material and a solid phase preparation method thereof, wherein the preparation method comprises the following steps: s1, catalyst film synthesis: depositing a catalyst onto a substrate; s2, solid phase source thermal evaporation and deposition: under the protection of carrier gas, the boron source, anhydrous rare earth halide and the substrate are placed at the growth temperature of 700-1200 ℃ and the growth pressure of 0.1-100 kPa, and are evaporated and grown for 0.5-4 h, so that the low-dimensional rare earth boride nano material is obtained on the substrate. Different catalysts can be used for realizing the controllable preparation of the large-area, high-density and single-crystal rare earth boride nano-structure on various substrates.
Description
Technical Field
The invention relates to a preparation method of a nano material, in particular to a low-dimensional rare earth boride nano material and a solid phase preparation method thereof.
Background
In the prior art, three methods are used for preparing the low-dimensional rare earth boride nano material.
Using chemical vapor deposition with BCl 3 Gas is used as a boron source to synthesize PrB 6 Nanowire and PrB 6 Nanotube (The synthesis of PrB) 6 nanowires and nanotubes by the self-catalyzed method, center. Required BCl 3 Gases are dangerous chemicals that are harmful to the body when inhaled, taken orally or absorbed through the skin, and can cause chemical burns. This inevitably involves a risk in terms of safety and environmental pollution of people, and increases the cost of raw materials.
By using a hydrothermal synthesis method, respectively using Sm and H 3 BO 3 Mg and I 2 The SmB is obtained by a solid mixture through a plurality of reaction and treatment steps 6 Nanowires (Low temperature Synthesis and electronic transport of biological insulator SmB) 6 nanowires.). However, the product obtained by the method has low density and more process flows, which not only increases the preparation period, but also makes the regulation and control of the morphology and crystallinity of the product more difficult. And the cost of the used Sm is too high, and meanwhile, the Mg powder has very active property and certain potential safety hazard.
LaB etching by using ultraviolet lithography, electron beam deposition combined with electrochemical etching or plasma etching 6 Method for obtaining LaB by using single crystal substrate 6 Single crystal nanocone arrays (Field emission characteristics of single crystal LaB) 6 field entities organized by electrochemical interaction method). This method uses LaB on the one hand 6 The single crystal is used as a substrate, so that the cost of raw materials is high; on the other hand, the electrochemical etching has specific requirements and selectivity for a substrate, the plasma etching rate is slow, and the production equipment of the ultraviolet lithography system, the electron beam evaporation system and the plasma etching system is expensive and is not suitable for large-scale popularization and use, so that the use process has no small limitation.
Therefore, the current preparation process of the low-dimensional rare earth boride nano material greatly restricts the further development of the low-dimensional rare earth boride nano material in the field of micro-nano electronic devices.
Disclosure of Invention
In order to overcome the defects of the prior art, the invention provides the low-dimensional rare earth boride nano material and the solid phase preparation method thereof. The method can prepare the large-area high-density monocrystal nano material and effectively regulate and control the growth morphology of the nano material.
The invention also aims to provide a low-dimensional rare earth boride nano material.
In order to solve the technical problems, the invention adopts the technical scheme that:
a low-dimensional rare earth boride nano material and a solid phase preparation method thereof comprise the following steps:
s1, catalyst film synthesis: depositing a catalyst onto a substrate;
s2, solid phase source thermal evaporation and deposition: under the protection of carrier gas, the boron source, anhydrous rare earth halide and the substrate are placed at the growth temperature of 700-1200 ℃ and the growth pressure of 0.1-100 kPa for evaporation and growth for 0.5-4 h, and the low-dimensional rare earth boride nano material is obtained on the substrate.
The reaction principle is as follows: at high temperature, the boron source evaporates to form a boron-containing vapor; or redox to B 2 O 2 Gas, subsequently boron-containing steam or B 2 O 2 The gas is carried over the substrate by a carrier gas; mixing with anhydrous rare earth halide gas molecules evaporated at high temperature, and reacting to generate rare earth boride molecules. In the heating process of the step S2, the catalyst on the substrate is melted into catalyst liquid drops, the generated rare earth boride molecules are continuously dissolved into the catalyst liquid drops, and when the solubility of the rare earth boride in the catalyst liquid drops reaches a supersaturated state, the rare earth boride is precipitated along the optimal energy direction to form a low-dimensional rare earth boride nano structure. The obtained low-dimensional rare earth boride nano material is a pure substance with a large-area, high-density and single crystal rare earth boride nano structure.
Using boron powder, boron oxide powder and SmCl 3 Synthesis of SmB 6 Nanowire is taken as an example, and B in gas state at the initial stage of reaction 2 O 3 、SmCl 3 SmB generated by catalytic reaction 6 Dissolving into catalyst liquid drop, precipitating B and Sm atoms along low energy surface after supersaturation to form SmB 6 And (3) granules. The catalyst liquid drop has low acting force with the substrate and can be used forSmB grown on the bottom 6 And (4) jacking up the particles. While SmB is continuously generated along with the reaction 6 Molecules are continuously dissolved into the catalyst and are continuously separated out, and finally a one-dimensional nanowire structure is formed. As the growth temperature and growth gas pressure are increased, more catalyst particles will be activated, resulting in an increasing density of nanowires. And, increasing the growth temperature and growth pressure also increases the growth rate of the nanowires, resulting in longer nanowires at lower temperatures or pressures for the same growth time.
Further, the substrate is a silicon wafer, FTO glass, a carbon fiber substrate, a graphite paper substrate, a metal substrate or a high-melting-point organic substrate.
Wherein, silicon chip and FTO glass are substrate materials commonly used in the microelectronic industry, and carbon fiber, graphite paper, metal and high melting point organic substrates are flexible or rigid substrate materials with excellent performance.
The low-dimensional rare earth boride nano material is LaB 6 、SmB 6 、CeB 6 、YbB 6 、GdB 6 Or EuB 6 One or more of them.
The catalyst is a magnetic nano material or a noble metal nano material.
Further, the catalyst is in the form of particles or films.
Still further, the catalyst is in particulate form.
Further, in step S1, the substrate deposited with the catalyst is subjected to heat preservation treatment for 0.5 to 1 hour at a heat preservation temperature of 500 to 700 ℃.
The invention herein provides a process for the preparation of a particulate catalyst: the catalyst is deposited on the substrate by magnetron sputtering, ion beam sputtering or thermal evaporation. And (3) carrying out heat preservation treatment on the substrate deposited with the catalyst for 0.5-1 h at the heat preservation temperature of 500-700 ℃. At the temperature of 500-700 deg.c or during the temperature raising to required growth temperature, the catalyst is dissolved into catalyst liquid drop of 0.1-1 micron thickness.
The substrate is insulated to enable the catalyst to be fully melted into metal droplets, and the continuous film is cracked into the nano-particle film.
Further, the magnetic nano-particles are one or more of Fe, co or Ni, and the noble metal nano-particles are one or more of Au, ag, pd or Pt.
Generally, the nanobelt is prepared when the growth air pressure is 0.1kPa to 2kPa, the nanowire or the nanocone is prepared when the growth air pressure is 10kPa to 100kPa, and the mixture of the nanobelt and the nanowire or the nanocone is prepared when the air pressure is 2k to 10 kPa.
Further, the anhydrous rare earth halide is LaF 3 、LaCl 3 、LaBr 3 、LaI 3 、SmF 3 、SmCl 3 、SmBr 3 、SmI 3 、CeF 3 、CeCl 3 、CeBr 3 、CeI 3 、YbF 3 、YbCl 3 、YbBr 3 、YbI 3 、GdF 3 、GdCl 3 、GdBr 3 、GdI 3 、EuF 3 、EuCl 3 、EuBr 3 Or EuI 3 One or more of them.
Further, the growth time is 1-1.5 h.
By controlling the growth time, the length-diameter ratio and the growth density of the low-dimensional rare earth boride nano material can be effectively regulated and controlled.
Further, the distances between the boron source and the substrate and between the anhydrous rare earth halide and the substrate are respectively 1-6 cm.
Conventionally, the distance between the boron source or the anhydrous rare earth halide and the substrate refers to the distance from the center of the vapor after evaporation to the center of the substrate.
In general, when the distance between the boron source or the anhydrous rare earth halide and the substrate is 4-6 cm, preparing to obtain a nanobelt or a nanocone; when the distance between the mixture and the substrate is 1-3 cm, preparing to obtain the nanowire; and when the distance between the final mixture and the substrate is 3-4 cm, preparing to obtain a mixed morphology with the simultaneous existence of the nanobelts and the nanowires or the nanocones.
Further, the carrier gas is inert gas or H 2 One or more of them.
Further, the carrier gas is an inert gas and H 2 The mixed gas of (1), H in the mixed gas 2 The volume fraction of (A) is 1-10%. H at high temperature 2 The treatment effect of the catalyst film is to crack the continuous film into a nano-particle film, so that the catalyst film can be better treated to form uniform catalyst particles. At the same time, hydrogen facilitates the reduction of boron oxide.
Further, the growth temperature was 1100 ℃.
The nano-belt film with large area, high density and uniform distribution can be obtained at the temperature, and the surface of the nano-material is very smooth.
Further, the mass ratio of the boron source to the anhydrous rare earth halide powder is 2-4.
Further, the boron source is boron and boron oxide.
Further, the mass ratio of boron to boron oxide to anhydrous rare earth halide is 2. The density of the low-dimensional rare earth boride nano material on the whole substrate is very high, and the surface of the low-dimensional rare earth boride nano material is very smooth.
The invention also provides a low-dimensional rare earth boride nano material prepared by the preparation method.
The shape of the low-dimensional rare earth boride nano material is one or more of a nanobelt, a nanowire or a nanocone.
Compared with the prior art, the invention has the beneficial effects that:
the solid phase source thermal evaporation deposition technology of the low-dimensional rare earth boride nanostructure can realize the controllable preparation of a large-area, high-density and single crystal rare earth boride nanostructure;
by adjusting the distance between the boron source and the anhydrous rare earth halide powder and the substrate, the growth pressure and the growth temperature, different catalysts can be used on various flexible and rigid substrates, the appearance of the product can be regulated, and the operation is simple;
the used chemical vapor deposition equipment for growing the nano material and sputtering or thermal evaporation equipment for preparing the catalyst have low cost, can quickly realize the preparation of the nano material by utilizing one-step chemical reaction, and is suitable for large-scale popularization and use;
the raw materials adopted by the scheme are a boron source and anhydrous rare earth halide, are not flammable and explosive compounds, are solid-phase, and meanwhile, the rare earth halide is weak in chemical activity, safer and more environment-friendly, and meanwhile, due to weak chemical activity, excessive addition of reactants is not needed, and the cost can be saved.
The method only needs two steps, firstly synthesizing the catalyst film, secondly evaporating the solid phase source heat and depositing on the catalyst film, has few process flows, and has very high growth density and single appearance.
The method can grow the low-dimensional rare earth boride nano material within 0.5-4 h, and the growth rate is high.
Drawings
FIG. 1 shows LaB prepared on carbon fiber cloth 6 Scanning electron micrographs of the nanowire film at low and high magnification;
FIG. 2 shows a typical LaB 6 Low resolution and high resolution transmission electron microscopy images of nanowires;
FIG. 3 is SmB prepared on a graphite paper substrate 6 Scanning electron micrographs of nanoribbons at low and high magnification;
FIG. 4 shows a typical SmB 6 Transmission electron microscopy images of low and high resolution nanoribbons;
FIG. 5 shows CeB prepared on a silicon substrate 6 Scanning electron micrographs of the nanowire film at low and high magnification;
FIG. 6 is a typical CeB 6 Low resolution and high resolution transmission electron microscopy images of nanowires;
FIG. 7 shows YbB prepared on a silicon substrate 6 Nanobelt low and high scanning electron micrographs;
FIG. 8 is a typical YbB 6 Transmission electron microscopy images of low and high resolution nanoribbons;
FIG. 9 shows LaB growth times of the present invention 6 Scanning electron microscopy images of nanowires;
FIG. 10 shows SmB prepared at different growth pressures in the present invention 6 Typical morphology of the nano material and corresponding X-ray diffraction spectrum and Raman spectrum;
FIG. 11 shows LaB under different evaporation source and substrate distances in the present invention 6 Scanning electron microscope picture of the nanometer material and corresponding X-ray diffraction spectrum and Raman spectrum;
FIG. 12 shows LaB prepared from the raw materials of the present invention at different mass ratios 6 Typical morphology of the nanomaterial;
FIG. 13 shows SmB prepared at different growth temperatures according to the present invention 6 Scanning electron microscopy of nanoribbons.
FIG. 14 shows the synthesis of PrB by chemical deposition in comparative example 1 of the present invention 6 Scanning electron micrographs of the nanowires at low and high magnification;
Detailed Description
The present invention will be further described with reference to the following embodiments.
In the following examples, the holding temperature was 700 ℃ and the holding time was 1 hour.
Example 1
In this example, laB was synthesized on a carbon fiber cloth substrate by using a solid phase preparation technique 6 A thin film of nanowires. The preparation process is as follows.
By adopting a magnetron sputtering technology, firstly, a layer of Ni film with the thickness of about 10nm is grown on a C fiber cloth substrate as a catalyst in an Ar gas environment. The C fiber cloth substrate carrying the Ni film is put in Ar gas and H 2 (H 2 Ar =30sccm, 300sccm and the same below), heating to 700 ℃, and carrying out heat preservation treatment for 1h. Then, powder B (99.99%), powder B were mixed 2 O 3 Powder (99.99%) and anhydrous LaCl 3 Powder (99%) was mixed at a mass ratio of 2 2 O 3 In the reaction boat, B powder and B are mixed 2 O 3 Powder and anhydrous LaCl 3 The mixture of powders was placed 1cm from the substrate. Finally, the powder and the substrate are placed in Ar gas and H 2 Rapidly heating to 700 deg.C in carrier gas atmosphere, maintaining the growth pressure at 10kPa for 0.5h, and placing into C fiberGrowing a LaB with a single appearance on a fiber cloth substrate 6 A thin film of nanowires.
FIG. 1a shows LaB prepared on carbon fiber cloth 6 The macroscopic scanning electron microscope of the nanowire film is shown in FIG. 1b, which is LaB prepared on carbon fiber cloth 6 High power scanning electron microscope image of the nanowire film. LaB grown at 1000 ℃ as shown in FIGS. 1a and 1b 6 The length of the nano-wires is 10-30 μm, the average diameter is about 50nm, meanwhile, as shown in fig. 1b and fig. 14a, the growth density of the nano-wires on the whole carbon fiber cloth is very high, and the shapes and sizes of the materials in fig. 14b are different, as can be seen from fig. 1a, laB 6 The nanowire film has a single appearance.
As shown in FIG. 2, FIG. 2a is a typical LaB 6 Low resolution transmission electron microscopy and SAED spectra (inset) of nanowires, FIG. 2b for a typical LaB 6 High resolution transmission electron microscopy of the nanowires and international standard X-ray powder diffraction data (JCPDS) No. 73-1669 cards can prove that the prepared LaB 6 The nanowire is a single crystal cubic structure with a growth direction of [111 ]]。
Example 2
SmB is synthesized on graphite paper substrate by utilizing solid-phase preparation technology 6 Nanobelt film
By adopting an ion sputtering technology, firstly, a layer of Fe film with the thickness of about 15nm is grown on a graphite paper substrate as a catalyst in an Ar gas environment. Placing the graphite paper cloth substrate loaded with the Fe film in Ar gas and H 2 Heating to 700 ℃ under the protection of (1), and carrying out heat preservation treatment for 1h. Then, powder B (99.99%), powder B were mixed 2 O 3 Powder (99.99%) and anhydrous SmCl 3 The powder (99%) was mixed in a mass ratio of 1 2 O 3 In the reaction boat, B powder and B are mixed 2 O 3 Powder and anhydrous SmCl 3 The mixture of powders was placed 4cm from the substrate. Finally in Ar gas and H 2 Rapidly heating to 700 ℃ in the atmosphere of carrier gas, keeping the growth pressure at 0.1kPa, and growing the SmB with single morphology on the graphite paper substrate after keeping the temperature for 4 hours 6 A nanoribbon film.
SmB prepared by the solid phase reaction method 6 The surface topography of the nanobelt sample is shown in fig. 3. FIG. 3a shows SmB prepared on a graphite paper substrate 6 Nanoribbon low-power scanning electron microscopy image, FIG. 3b is SmB prepared on graphite paper substrate 6 High power scanning electron microscope image of the nano-belt, from which we can observe the SmB grown at 1000 deg.C 6 The length of the nano-belt is distributed between 50 and 100 mu m, the thickness is distributed between 20 and 100nm, and the width is distributed between 5 and 15 mu m. Meanwhile, the whole graphite paper substrate is uniformly distributed with the nano-belt structure with smooth surface.
As shown in FIG. 4, FIG. 4a shows a typical SmB 6 Low resolution transmission electron microscopy of nanoribbons, FIG. 4b for a typical SmB 6 The SmB prepared can be proved by high-resolution transmission electron microscopy images and SAED spectrums (insets) of the nanobelts and cards with the number 73-1669 of international standard X-ray powder diffraction data (JCPDS) 6 The nanoribbon is a single-crystal cubic structure with a growth direction of [110 ]]。
Example 3
Synthesis of CeB on Si substrate by solid phase preparation technique 6 Nanowire thin films
By adopting a thermal evaporation technology, firstly, an Au thin film with the thickness of about 10nm is grown on a Si substrate as a catalyst in an Ar gas environment. The Si substrate carrying the Au thin film is subjected to Ar gas and H 2 Heating to 700 ℃ under the protection of (2), and carrying out heat preservation treatment for 1h. Then, powder B (99.99%), powder B were mixed 2 O 3 Powder (99.99%) and anhydrous CeCl 3 The powder (99%) was mixed in a mass ratio of 1 2 O 3 In the reaction boat, the powder B and the powder B are mixed 2 O 3 Powder and anhydrous CeCl 3 The mixture of powders was placed 3cm from the substrate. Finally in Ar gas and H 2 Rapidly heating to 1200 ℃ in the atmosphere of carrier gas, keeping the growth pressure at 100kPa, and growing the CeB with single appearance and smooth surface on the Si substrate after 2.5h of heat preservation 6 A thin film of nanowires.
CeB prepared by the solid phase reaction method 6 The surface topography of the nanowire sample is shown in fig. 5. FIG. 5a is a CeB fabricated on a Si substrate 6 Scanning electron microscope image of nanowire film5b is CeB prepared on Si substrate 6 Scanning electron microscope image of nanowire film with high magnification, from which we can observe CeB grown at 1100 deg.C 6 The length of the nanowire samples is distributed between 30 and 50 mu m, and the average diameter is about 50nm. Meanwhile, the whole graphite paper substrate is uniformly distributed with the nano-belt structure with smooth surface.
As shown in FIG. 6, FIG. 6a is a typical CeB 6 The low resolution transmission electron microscopy and SAED spectra (inset) of the nanowires, FIG. 6b is a high resolution transmission electron microscopy and International Standard X-ray powder diffraction data (JCPDS) No. 73-1669 card, demonstrating that the prepared CeB 6 The nanowire sample is a single crystal cubic structure with a growth direction of [110 ]]。
Example 4
Synthesis of YbB on Si substrate by solid-phase preparation technology 6 Nanobelt film
By adopting a magnetron sputtering technology, firstly, a layer of Ni film with the thickness of about 10nm is grown on a Si substrate as a catalyst in the Ar gas environment. The Si substrate with the Ni film is put in Ar gas and H 2 Heating to 700 ℃ under the protection of (2), and carrying out heat preservation treatment for 1h. Then, powder B (99.99%), powder B were mixed 2 O 3 Powder (99.99%) and anhydrous YbCl 3 The powder (99%) was mixed in a mass ratio of 1 2 O 3 In the reaction boat, the powder B and the powder B are mixed 2 O 3 Powder and anhydrous YbCl 3 The mixture of powders was placed 6cm from the substrate. Finally in Ar gas and H 2 Rapidly heating to 1200 ℃ in the atmosphere of carrier gas, keeping the growth pressure at 2kPa for 1h, and growing the single-morphology YbB on the graphite paper substrate 6 A nanoribbon film.
YbB prepared by the solid-phase reaction method 6 The surface topography of the nanoribbon sample is shown in fig. 7. FIG. 7a shows YbB prepared on a Si substrate 6 A low power scanning electron micrograph of the nanobelt, FIG. 7b is YbB prepared on a Si substrate 6 A nanobelt high-power scanning electron micrograph; from the figure we can observe the YbB grown at 1100 deg.C 6 The average length of the nano-belt is about 80 mu m, and the thickness distribution is between 30 and 100nmThe width is distributed in 5-10 μm, and the surface is smooth. Meanwhile, in fig. 7a, compared with fig. 14a, the nanostructure structures with high density are uniformly distributed on the whole Si substrate in fig. 7 a.
As shown in FIG. 8, FIG. 8a is a typical YbB 6 Low resolution TEM and SAED spectra of the nanoribbons (inset), FIG. 8b for typical YbB 6 The high-resolution transmission electron microscope picture of the nanobelt and the cards of No. 73-1669 of the International Standard X-ray powder diffraction data (JCPDS) can prove that the prepared YbB 6 The nanoribbon is a single-crystal cubic structure with a growth direction of [110 ]]。
Example 5
LaB preparation from Si substrates at different growth times using the similar solid phase preparation technique of example 1 6 And (3) nano materials.
Preparing LaB by changing the growth time under the experimental conditions that the growth air pressure is 55kPa, the growth temperature is 1100 ℃ and the distance between the mixture and the substrate is not changed 6 A nanowire.
As shown in fig. 9:
(1) When the growth time is 0.5h, laB with shorter length can be prepared on a Si substrate 6 The nanowires have basically consistent shapes and higher densities on the whole Si substrate, and the lengths of the nanowires are basically distributed in the range of 7-12 mu m, as shown in FIGS. 9a, 9b and 9 c.
(2) When the growth time is 1h, laB with larger length can be prepared on a Si substrate 6 The nanowires are uniform in shape and high in density on the surface of the Si substrate, and the lengths of the nanowires are basically distributed in the range of 12-18 mu m, as shown in FIGS. 9d, 9e and 9 f.
(3) When the growth time is prolonged to 1.5h, laB with large length can be prepared on a Si substrate 6 The nanowires are uniform in appearance on the surface of the Si substrate, the density of the nanowires is very high, and the average length of the nanowires reaches 40 micrometers, as shown in FIGS. 9g, 9h and 9 i.
By controlling the growth time, the growth time of the LaB can be controlled 6 The length-diameter ratio and the growth density of the nanowire are effectively regulated, and the optimal growth time is 1-1.5 h.
Example 6
SmB was prepared on Si substrates at different growth atmospheres using a similar solid phase preparation technique as in example 1 6 And (3) nano materials.
B powder (99.99%) contains B 2 O 3 Powder (99.99%) anhydrous SmB 6 Powder (99%) =2 6 Growth morphology of the nanostructures.
FIG. 10 SmB prepared under different growth pressures in the present invention 6 Typical morphology of nanomaterials and corresponding X-ray diffraction (XRD) and Raman (Raman) spectra, as shown in fig. 10:
(1) The distance between the mixture and the substrate is 2cm at the growth pressure of 55kPa, and the SmB with large area and high density can be prepared on the Si substrate 6 A nanowire. Meanwhile, the morphology of the nanowires is substantially uniform across the entire Si substrate, the surface is very smooth, and the diameter of the nanowires from bottom to top (about 50 nm) is substantially constant, as shown in fig. 10a, 10 b.
(2) When the growth air pressure is 1kPa, the distance between the mixture and the substrate is 5cm, and SmB with high density and single appearance can be prepared on a Si substrate 6 The nanobelts, moreover, are very smooth on the surface of the Si substrate, have a high density, and have substantially the same width (about 8 μm) from bottom to top, as shown in fig. 10c, 10 d.
As shown in FIGS. 10e and 10f, the X-ray diffraction spectrum and the Raman spectrum indicate that the nanobelt and nanowire structures prepared by changing the growth gas pressure are still SmB 6 A single crystal cubic structure of (a). By controlling the growth gas pressure, smB can be realized 6 And (3) effectively regulating and controlling the growth morphology of the nano material.
Example 7
LaB preparation at different evaporation source and substrate distances using the similar solid phase preparation technique of example 1 6 A nano-material.
B powder (99.99%) contains B 2 O 3 Powder (99.99%) anhydrous LaB 6 Powder (99%) =2Controlling LaB by changing the distance between the mixture and the substrate under the experimental conditions of 1100 ℃ and constant growth pressure of 60kPa 6 Growth morphology of the nanostructures. As shown in fig. 11:
after mixing B powder (99.99%), B 2 O 3 Powder (99.99%) and anhydrous LaCl 3 (99%) when the mixture is placed at a distance of 5cm from the substrate, large-area and high-density LaB can be prepared on the Si substrate 6 A nanocone film. Meanwhile, the morphology of the nanocones is substantially uniform across the entire Si substrate, with the average diameter at the bottom end of about 500nm and the average diameter at the top end of about 50nm, and the surface is very smooth, as shown in fig. 11a, 11b, 11 c.
When the powder B (99.99 percent) and the powder B are mixed 2 O 3 Powder (99.99%) and anhydrous LaCl 3 (99%) when the mixture is placed at a distance of 2cm from the substrate, laB with high density and single appearance can be prepared on the Si substrate 6 A thin film of nanowires. Furthermore, the nanowires are very smooth on the surface of the Si substrate, have a high density, and have a substantially constant diameter from bottom to top, about 50nm, as shown in FIGS. 11d, 11e, and 11 f.
The X-ray diffraction spectrum and the Raman spectrum show that the nano-cone and nano-wire structure prepared by changing the distance between the substrate and the powder is still LaB 6 The single crystal cubic structure of (2). By the distance between the substrate and the powder, it is possible to achieve for LaB 6 The effective regulation and control of the growth morphology of the nano material are shown in FIGS. 11g and 11 h.
Example 8
LaB was prepared using a similar solid phase preparation technique as in example 1, at different ratios of starting materials 6 And (3) nano materials.
Under the experimental conditions of 1h of growth time, 1100 ℃ of reaction temperature, 60kPa of growth pressure and 4cm of distance between the mixture and the substrate, the mass ratio of the raw materials is changed to grow LaB 6 A nanocone film. As shown in fig. 12:
(1) When the powder B (99.99 percent) contains B 2 O 3 Powder (99.99%) anhydrous LaCl 3 Powder (99%) =2 6 Nanowire and method of manufacturing the sameA film. At the same time, the density of nanowires is high across the entire Si substrate, with nanowires having an average length of about 15 μm, an average diameter of about 50nm, and a very smooth surface, as shown in fig. 12a, 12b, 12 c.
(2) When the B powder (99.99 percent) is anhydrous LaCl 3 Powder (99%) =2, a lower density LaB can be prepared on Si substrate 6 The nanowires are thin film, and the distribution of the nanowires on the Si sheet is not uniform. Meanwhile, the nanowires have an average length of about 15 μm and an average diameter of about 50nm, but their surfaces are very rough, as shown in FIGS. 12d, 12e, and 12 f.
(3) When B is present 2 O 3 Powder (99.99%) anhydrous LaCl 3 Powder (99%) =2, a lower density LaB can be prepared on Si substrate 6 Thin film of nanowires, and very uneven distribution of nanowires on the Si-plate. Meanwhile, the nanowires have an average length of about 15 μm and an average diameter of about 50nm, but the surface thereof is very rough and exhibits significant wrinkle-type undulations, as shown in fig. 12g, 12h, and 12 i.
By controlling the proportion of the raw materials, the LaB can be treated 6 The growth density, growth morphology and crystallinity of the nanowire are effectively controlled. The optimal raw material mass ratio is B powder to B powder 2 O 3 Powder of anhydrous LaCl 3 Powder = 2.
Example 9
SmB was prepared at different growth temperatures using a similar solid phase preparation technique as in example 1 6 A nanoribbon.
B powder (99.99%) contains B 2 O 3 Powder (99.99%) anhydrous SmCl 3 Powder (99%) =2, growth time 1h, growth pressure 300Pa, and distance between mixture and substrate 6cm under constant experimental conditions varying growth temperature to prepare SmB 6 Nanocones, as shown in fig. 13:
(1) SmB can be prepared on a Si substrate at the growth temperature of 1000 DEG C 6 A nanoribbon film. But the nanoribbon film is or is doped with a portion of the nanowires throughout the Si substrate. While the average length of the nanoribbons is about 20 μm and the average width is aboutIs 1 μm and the edges of the nanobelts have a saw-tooth like morphology as shown in FIGS. 13a, 13b, 13 c.
(2) When the growth temperature is increased to 1100 ℃, smB with large area, high density and uniform distribution can be prepared on a Si substrate 6 A nanoribbon film. Meanwhile, the average length of the nanoribbon is about 60 μm and the average width is about 3 μm, and the surface of the nanoribbon is very smooth as shown in fig. 13d, 13e, 13 f.
By controlling the growth temperature, smB can be achieved 6 And (3) effectively regulating and controlling the growth surface of the nanowire. The optimum growth temperature is 1100 ℃.
Comparative example 1
First, the silicon wafer was cut into 1 × 1cm pieces 2 And a small piece with a thickness of 1 mm was used as a substrate. Next, metal Pr powder (purity 99.99%) was coated on the Si substrate, and then put into a quartz tube to react, and the temperature was raised to 1080 ℃. In a carrier gas (30% H) 2 And 70% Ar) flow of 80sccm, stabilized BCl 3 Gas flow, 5 minutes later, the quartz tube was cooled to room temperature. The product, distilled water, was then washed several times with dilute hydrochloric acid to eliminate impurities. Finally, after drying in vacuum at 80 ℃ for 4 hours, a layer of grey product was found to be deposited on the Si substrate to obtain PrB 6 A nanowire. As shown in fig. 14a and 14b, prB 6 The diameter of the nano-wire is 10-100 nm, and the length is 2-10 μm.
Comparative example 1 use of BCl 3 Gas is used as a boron source to synthesize PrB 6 A nanowire. Required BCl 3 Gases are dangerous chemicals which inevitably present a safety hazard to people and environmental pollution and increase the cost of raw materials.
In conclusion, the raw materials adopted by the scheme are the boron source and the anhydrous rare earth halide which are both solid phases, and meanwhile, the rare earth halide has weak chemical activity, is safer and more environment-friendly, and meanwhile, because the chemical activity is weak, excessive addition of reactants is not needed, and the cost can be saved. The method only needs two steps, firstly synthesizing the catalyst film, secondly evaporating the solid phase source heat and depositing on the catalyst film, has few process flows, and has very high growth density and single appearance. The method can grow the low-dimensional rare earth boride nano material within 0.5-4 h, and the growth rate is high. Thereby preparing the large-area, high-density and single-crystal low-dimensional rare earth boride nano material.
It should be understood that the above-described embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. This need not be, nor should it be exhaustive of all embodiments. Any modification, equivalent replacement, and improvement made within the spirit and principle of the present invention should be included in the protection scope of the claims of the present invention.
Claims (8)
1. A solid phase preparation method of a low-dimensional rare earth boride nano material is characterized by comprising the following steps:
s1, catalyst film synthesis: depositing a catalyst onto a substrate;
s2, solid phase source thermal evaporation and deposition: under the protection of carrier gas, placing a boron source, anhydrous rare earth halide and a substrate at the growth temperature of 700 to 1200 ℃ and the growth pressure of 60kPa, evaporating and growing for 0.5 to 4 hours to obtain a low-dimensional rare earth boride nano material on the substrate;
the distances between the boron source and the anhydrous rare earth halide and the substrate are respectively 5 cm;
the low-dimensional rare earth boride nano material is a nanocone.
2. The solid phase preparation method of the low dimensional rare earth boride nanomaterial of claim 1, wherein the anhydrous rare earth halide is: laF 3 、LaCl 3 、LaBr 3 、LaI 3 、SmF 3 、SmCl 3 、SmBr 3 、SmI 3 、CeF 3 、CeCl 3 、CeBr 3 、CeI 3 、YbF 3 、YbCl 3 、YbBr 3 、YbI 3 、GdF 3 、GdCl 3 、GdBr 3 、GdI 3 、EuF 3 、EuCl 3 、EuBr 3 Or EuI 3 One or more of them.
3. The solid phase preparation method of the low dimensional rare earth boride nanomaterial according to claim 1, wherein in step S1, the substrate deposited with the catalyst is subjected to heat preservation treatment at a temperature of 500 to 700 ℃ for 0.5 to 1 hour.
4. The solid phase preparation method of the low-dimensional rare earth boride nanomaterial according to claim 1, wherein the growth time is 1 to 1.5 hours.
5. The solid phase preparation method of low dimensional rare earth boride nano-material of claim 1, wherein the carrier gas is inert gas, H 2 One or more of them.
6. The solid phase preparation method of low dimensional rare earth boride nanomaterial of claim 1 wherein the growth temperature is 1100 ℃.
7. The solid phase preparation method of the low-dimensional rare earth boride nano material according to claim 1, wherein the mass ratio of the boron source to the anhydrous rare earth halide powder is 1 to 4; the boron source is boron and boron oxide.
8. The solid phase preparation method of the low dimensional rare earth boride nanomaterial of claim 7, wherein the mass ratio of boron, boron oxide and anhydrous rare earth halide is 2.
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