Direct Precipitation Method of Nano-CuO

Different reaction conditions were studied through orthogonal experiment and single factor experiment. Using Cu(NO3)2 as the reactant, water-alcohol solution (H2O:CH2CH3OH was 3:1) as solvent at 20 and reaction for 45min could get nano-CuO with good dispersion and uniform size. Different kinds of characterization method were used to characterize the resultant. The average diameter of nano-CuO was 20.38nm after calculated using some relevant formula, the surface area was about 21.988 m2/g, the pore diameter was about 3.079 nm and the pore volume was 1.349 10-1 cc/g . So the method is a feasible, low cost way to industry..


Introduction
With small structure units, high specific surface area and unique mechanical, optical, magnetic properties, nanocrystalline materials have become a focus of common attention in the 21st century [1][2][3][4].Among nano materials, nano-CuO has played an important role in catalytic technology, bio-medicine technique, fine chemical industry and other fields and it is likely to have a good future [5,6].However, bulk particle is easy to form during the preparation and application losing characteristics of nano materials [7,8], so the preparation process is very essential.Commonly, solid state reaction method, hydrothermal method, alcohol-thermal method, precipitation method are the methods used in industry and laboratory, recently other methods [9][10][11][12] are found such as micro-emulsion method and laser heating gas-evaporation method.Compared with other methods, direct precipitation method has the advantages of simple preparation and low cost, so it can be widely used in industrial production [11].
In the work, different kinds of reactants, temperature, reaction time and ratio of water's volume (V water ) and alcohols' volume (V R-OH ) were studied through orthogonal experiment and single factor experiment, then the nano-CuO generated was characterized using X-ray diffraction (XRD), fourier transform infrared (FTIR), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and particle surface area measurements to find the best preparation condition.What's more, the diameter, surface area, pore diameter and the pore volume of the CuO generated under best condition were measured and calculated.solution was added under magnetic stirring condition for a period of time.

Filtration, washing, dying and roasting
Put mixture into centrifuge tubes and centrifuged for a period of time, then washed the precipitate using ethanol twice and put it into vacuum drying oven for 3h at 50 to get Cu 2 (OH) 2 CO 3 precursor.Heated Cu 2 (OH) 2 CO 3 to 400 for 2h with heating rate 2 •min -1 .

Characterization
X-ray diffraction (XRD), fourier transform infrared (FTIR), thermogravimetric analysis (TG), scanning electron microscopy (SEM) and particle surface area measurements were used to analyse chemical composition, structure and properties of the nano-CuO generated.

Factors influence the experimental process
The volume of CH 3 CH 2 OH was studied in single factor experiment and then the orthogonal test method was adopted to explore the influences of 4 factors on the products in order to study the factors that influenced nano-CuO.Influence of single factor was given in table 1and orthogonal factors were given in table 2.

SEM analysis of Nano-CuO
Tested nano-CuO above using Hitachi S-4700 under operation voltage of 30 kV.From figure 4, the nano-CuO generated under condition 16 was better than that under condition 1.

FTIR analysis of nano-CuO
Tested the nano-CuO prepared under condition 16 using FTIR using TENSOR 27.

TG and DTG of nano-CuO
Tested nano-CuO above using Seiko TG/DTA 6300 with temperature varying from 30 to 480 and the heating rate was 5 /min.Figure 6 gave TG and DTG of Cu 2 (OH) 2 CO 3 under condition 16.
From figure 9   (1) Where D C is the size of crystal (nm), K is the Xeror constant (to cube particles K=0.94, to spherical particles K=0.89), λ is the wavelength of X-ray (using CuKa radiation, O =1.5406A≈0.154nm),β is full width at half maximum, θ is the diffraction angle of the peak.Particle size of CuO and Cu 2 (OH) 2 CO 3 under condition 1 and 16 were given in table 3.

Particle surface area measurements
CuO generated under condition 16 was analysed using NOVA 4200 to get its surface area, average pore diameter and total pore volume.The nitrogen adsorption-desorption curve of nano-CuO under condition 16 was given in figure 11.

Figure 11. Nitrogen adsorption-desorption curve of nano-CuO under condition 16
After dealing with some procedures, the pore diameter was got, which was about 3.079 nm using BJH method.The surface area is 21.988 m 2 /g using multipoint BET method and the pore volume was 1.349u10 -1 cc/g using BJH method. 1 Direct precipitation method of nano-CuO using Cu(NO 3 ) 2 and Na 2 CO 3 is feasible way to industry that is low cost and easy to achieve. 2 After orthogonal test, single factor experiment and characterization, best process conditions are got: reactant is Cu(NO 3 ) 2 , temperature is 20 , precipitant's (Na 2 CO 3 ) concentration is 0.1mol/L, H 2 O-CH 3 CH 2 OH ratio is 3:1, reaction time is 45min, roasting time is 2h and temperature is 400 .

Conclusions
3 Nano-CuO generated using best condition above is spherical, uniform and with good dispersivity, the average diameter of nano-CuO is 20.38 nm, the surface area is about 21.988 m/g ,the pore diameter was about 3.079 nm and the pore volume was 1.349u10 -1 cc/g .

Figure 1
was SEM micrographs of nano-CuO under different conditions with one factor changing.(a, b were the micrographs under condition I; c, d were the micrographs under condition II; e, f were the micrographs under condition III; g, h were the micrographs under condition IV).

Figure 5
gave the results of final resultant and the precursor.From figure5, peaks around 536cm −1 for strong bands of the Cu-O stretching vibrations and 582 cm −1 for strong bands of the lattice vibration were observed, and peaks of the O-C-O stretching vibrations were found at 1379cm −1 and 1481cm −1 .Peaks at 839cm −1 and 754cm −1 for the O-H stretching vibrations were observed as well, and in addition, peak of Cu-OH around 487 cm −1 was noticed.This observation provides evidence that the final resultant and the precursor were CuO and Cu 2 (OH) 2 CO 3 respectively.

Figure 4 .DOI
Figure 4. SEM micrographs of nano-CuO with different magnifications under condition 1 and 16

Figure 9 .Figure 10 .
Figure 9. XRD spectrum of precursor under condition 4 5H 2 O, C 2 H 5 OH produced by Beijing chemical plants; CuCl 2 2H 2 O, Cu(NO 3 ) 2 3H 2 O, Na 2 CO 3 produced by Beijing Yili Fine Chemical Co; C 4 H 6 CuO 4 H 2 O by Sinopharm Chemical Reagent Beijing Co.All of the chemicals and reagents used were analytical grade and were used without further purification.

Table 3 .
Particle size of CuO and Cu 2 (OH) 2 CO 3 under condition 1 and 16 From table 3, materials' diameter became smaller after calcinations and the size of CuO generated using Cu(NO 3 ) 2 changes more significantly than that of other materials after calcinations.