[0001 ]

Technical Field

[0002]

Background Art

Generally, nanoscience and nanotechnology involve in the manipulation of materials and creation of structures and systems at a scale of nanometers dimension. Thereafter, nanomaterials have attracted much attention because of their surface effect (large surface-to-volume ratio) and quantum confinement effect (size-dependent properties). These factors affect their physical and chemical properties which are different from those of their molecular and bulk counterparts. Nanoparticles with zero-dimensional nanostructures are generally classified according to their composition: metal oxides, noble metals, transition metals, magnetic metals, and semiconductor nanomaterials or quantum dots. Like all nanostructures, magnetic metals nanoparticles are dependent on their size and shape. Nowadays, magnetic oxides nanoparticles have attracted considerable interest for their wide application ranging from fundamental research to industrial applications. Several nanotechnology preparation methods for fabrication of magnetic ferrites and ortho ferrites nanocrystals have been reported, including sol-gel method, co-precipitation, reverse micelles and hydrothermal method. Because of these, various precipitation agents and additional physical treatments have been used to produce spinel ferrite nanocrystals for specific size and shape, for example, metal hydroxides in the co-precipitation method, surfactants and ammonia in the reverse micelles and micro-emulsion methods, organic matrices in the sol-gel method and high temperature and pressure in the hydrothermal method. Most of these methods have achieved nanocrystals of required size and shape but they are impractical for large-scale applications because it requires expensive and complicated procedures, high reaction temperatures, long reaction times and produces toxic by-products that may harm the environment. The used microwave-thermal treatment method in this research is the modified thermal treatment method. The advantages offered by the thermal treatment method included low-cost, simplicity and low reaction temperatures. Moreover, the method is environment friendly because it produces no by-product effluents within a periodic of 48 hours (from preparation until calcination). The most significant change in microwave-thermal treatment method to compare with thermal treatment method is the reduction of time from 24 hours to 5 minute by microwave irradiation (instead of oven) used in the drying process. Therefore, this significant reduction in the drying time decreased the total time of fabrication of the ferrite and rare-earth orthoferrites nanocrystals from 48 to 24 hours (from preparation until fabrication).

[0003] Summary of Invention

The present invention relates to a process for producing magnetic ferrite and orthoferrites nanocrystals by using microwave-thermal treatment method. The ferrite and orthoferrites nanocrystals are synthesized from metal nitrate precursors including iron nitrate and another metal nitrate or rare earth elements nitrates in diluted polyvinyl pyrrolidone solution and thereafter the solution is undergone thermal drying and crystallization, grinding into powder, and calcination at 500-700oC. The detailed of the process is as follows: firstly polyvinyl pyrrolidone is diluted in deionized water by heating and stirring to form a PVR solution; secondly, metal nitrate precursors including iron nitrate and another metal nitrate or rare earth elements nitrates (such as cerium nitrate) are added into PVR solution at 80 oC for 2 h and stirred until becomes transparent solution; thirdly, the nitrate precursors/PVP solution is placed on a Petri dish and heated by microwave irradiation (power 1000 W) for 5 min until water was eliminated; fourthly, solid crystals that are formed are crushed and ground in a mortar to form powder, and finally the powder are placed in a furnace and calcined at 500-700oC for 3 h for eliminating organic compounds and to favor the crystallization.

The present invention will be fully understood from the detailed description given herein below and the accompanying preferred drawings which are given by way of illustration only, and thus are not limitative of the present invention, wherein:

Figure 1 shows XRD patterns of (a) the precursor and the CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (b) 500, (c) 600 and (d) 700 *C

Figure 2 shows The FT-IR spectra of precursor and CeFeO3 nanocrystals synthesized by Microwave- Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C in the wave-number ranging between 500 and 4000 cm-1.

Figure 3 shows the FESEM images of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (a) 500, (b) 600, (c) 700 *C and (d) EDXA spectrum of CeFeO3 nanocrystals calcined at 700 *C.

Figure 4 shows Hysteresis loops of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C.

Figure 5 shows Tauc plot of band gap energy CeFeO3 nanocrystals synthesized by Microwave- Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C.

Figure 6 shows the dye degradation of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method was performed under visible light at different temperatures.

Table 1: Average particle sizes (nm), optical and magnetic properties CeFeO3 nanocrystals were determined by XRD, FESEM, UV-visible and VSM techniques.

[0004]

Technical Problem [0005]

Solution to Problem

[0006]

Advantageous Effects of Invention

[0007]

Brief Description of Drawings

The present invention will be fully understood from the detailed description given herein below and the accompanying preferred drawings which are given by way of illustration only, and thus are not limitative of the present invention, wherein:

Figure 1 shows XRD patterns of (a) the precursor and the CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (b) 500, (c) 600 and (d) 700 *C

Figure 2 shows The FT-IR spectra of precursor and CeFeO3 nanocrystals synthesized by Microwave- Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C in the wave-number ranging between 500 and 4000 cm-1.

Figure 3 shows the FESEM images of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (a) 500, (b) 600, (c) 700 *C and (d) EDXA spectrum of CeFeO3 nanocrystals calcined at 700 *C.

Figure 4 shows Hysteresis loops of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C.

Figure 5 shows Tauc plot of band gap energy CeFeO3 nanocrystals synthesized by Microwave- Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C.

Figure 6 shows the dye degradation of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method was performed under visible light at different temperatures.

Table 1: Average particle sizes (nm), optical and magnetic properties CeFeO3 nanocrystals were determined by XRD, FESEM, UV-visible and VSM techniques.

[0008]

Flg.1

[0009] [Fig.1]

[0010] [Fig.2] [0011] [Fig.3]

[0012] [Fig.4]

[0013] [Fig.5] [0014] [Fig.6]

[0015] [tablel]

Description of Embodiments

The present invention relates to fabrication of nano-ferrites and nano-orthoferrites by microwavethermal treatment method. In fact, microwave-thermal treatment method is modified thermal treatment method. It is worth nothing that thermal treatment method (with application No. PI 2011005744 and date of filing: 25.11.2011) was invented by Mahmoud (Goodarz) Naseri and Elias Saion in Universiti Putra Malaysia. Since the present invention relates to fabrication of nano-ferrites and nano-orthoferrites by microwave-thermal treatment method, therefore, we separate applications and properties ferrites and orthoferrites nanostructures in two section.

A: The spinel ferrites and hexagonal ferrites nanocrystals with general formula MFe2O4 (M = Co, Ni, Zn, or other metals) and MO · 6Fe2O3 where M represents a divalent ions such as Ba 2+, Sr2+, or Pb2+, have received significant attention respectively in recent years The ferrite nanocrystals comprising of metal nitrate precursors including ion nitrate, polyvinyl pyrrolidone, and deionized water (the final product includes this composition). The polyvinyl pyrrolidone is used as a capping agent. The polymeric matrix is not limited to only polyvinyl pyrrolidone but any matrix selected in a group of water soluble polymer such as polyvinyl alcohol. The nanomaterials retain many of their morphological structure, magnetic and catalytic properties of ferrite (how is the nanomaterials related to ferrite) that are useful for core for transformers and inductors, electromagnetic filtering, and catalysts. Ferrite cores are used in electronic inductors, transformers and electromagnets where high electrical resistance of the ferrite leads to very low current losses. It should be understood, however, that the disclosed preferred embodiments are merely exemplary of the invention, which may be embodied in various forms. Therefore, the details disclosed herein are not to be interpreted as limiting, but merely as the basis for the claims and for teaching one skilled in the art of the invention.

B: Nanosized perovskite-type oxides of the type REFeO3 (where RE is a rare earth elements e.g., Ce, La, Ga, Nd, Dy, Lu, Tb, Er) are regarded as one of the most attractive and interesting ternary oxides with perovskite structure. In the REFeO3 perovskite orthorhombic structure with octahedral coordination, the unit cell consists of four formula units of REFeO3, where Fe3+ is surrounded by six oxygen ions. The applications of perovskite nanomaterials has attracted the attention of many researchers in different scientific and applicative fields. These materials are promising in fields such as heterogeneous catalysis, solid oxide fuel cells, gas separating techniques and gas sensing. Binary and ternary metal oxides are generally used as gas sensitive materials in resistive gas sensors. Ternary oxides have some advantages such as good thermal and chemical stability, and sensitive to various gases. Therefore, many studies have been dedicated to the synthesis and application of ternary metal oxides for gas sensors.

The ferrite and orthoferrites nanocrystals are synthesized from metal nitrate precursors including iron nitrate and another metal nitrate or rare earth elements nitrates in diluted polyvinyl pyrrolidone solution and thereafter the solution is undergone thermal drying and crystallization, grinding into powder, and calcination at 500-700oC. The detailed of the process is as follows: firstly polyvinyl pyrrolidone is diluted in deionized water by heating and stirring to form a PVP solution; secondly, metal nitrate precursors including iron nitrate and another metal nitrate or rare earth elements nitrates (such as cerium nitrate) are added into PVP solution at 80 oC for 2 h and stirred until becomes transparent solution; thirdly, the nitrate precursors/PVP solution is placed on a Petri dish and heated by microwave irradiation (power 1000 W) for 5 min until water was eliminated; fourthly, solid crystals that are formed are crushed and ground in a mortar to form powder, and finally the powder are placed in a furnace and calcined at 500-700oC for 3 h for eliminating organic compounds and to favor the crystallization. A preferred example (cerium orthoferrites (CeFeO3) nanocrystals) of the above mentioned process is given below: PVP (Polyvinyl pyrrolidone), deionized water and metal nitrates (Iron nitrate and Cerium nitrate) were the raw materials used. PVP (MW = 31000 g/mol) in 100 ml deionized water was used as the capping agent. The metal nitrates with equal molar ratios were added to the PVP solution while the temperature of solution was kept at 80 oC for 2 h. The mixed solution was poured into a glass beaker and was exposed to microwave irradiation (power 1000 W) for 5 min until water was eliminated. The remaining solid precursor was ground to form a fine powder. The final products were placed in a furnace and calcined at 500-700oC for 3 h for eliminating organic compounds and crystallize the rare-earth orthoferrites of CeFeO3 nanocrystals.

The XRD patterns of (a) the precursor and the CeFeO3 nanocrystals synthesized by Microwave- Thermal Treatment Method calcined at (b) 500, (c) 600 and (d) 700 *C as shown in Figure 1. The FT- IR spectra of precursor and CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C in the wave-number ranging between 500 and 4000 cm-1 as shown in Figure 2. The FESEM images of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (a) 500, (b) 600, (c) 700 *C and (d) EDXA spectrum of CeFeO3 nanocrystals calcined at 700 *C as shown in Figure 3. Hysteresis loops of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C as shown in Figure 4. Tauc plot of band gap energy CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method calcined at (a) 500, (b) 600 and (c) 700 *C as shown in Figure 5. The dye degradation of CeFeO3 nanocrystals synthesized by Microwave-Thermal Treatment Method was performed under visible light at different temperatures as shown in Figure 6. Table 1: Average particle sizes (nm), optical and magnetic properties CeFeO3 nanocrystals were determined by XRD, FESEM, UV-visible and VSM techniques.

The present invention has the advantages of less expensive and complicated procedures, low reaction temperatures and very short reaction times. The advantages offered by the previous inventor (thermal treatment method) included low-cost, simplicity and low reaction temperatures. Moreover, this modified method is environment friendly because it produces no by-product effluents within a periodic of 48 hours (from preparation until fabrication). The most significant change in microwave-thermal treatment method to compare with thermal treatment method is the reduction of time from 24 hours to 5 minute by microwave instrument (instead of oven) used in the drying process. Therefore, this significant reduction in the drying time decreased the total time of fabrication of the ferrite and rare-earth orthoferrites nanocrystals from 48 to 24 hours (from preparation until fabrication).

[0016]

Examples

[0017]

Industrial Applicability

[0018]

Reference Signs List

[0019] Reference to Deposited Biological Material [0020]

Sequence Listing Free Text [0021]

Citation List

[0022]

Patent Literature

[0023] PTL1 :

Non Patent Literature

[0024] NPL1 :

Table1