Research On The Preparation And Physical Properties Of Nano-Cu/ZnO Coated Wood-based Composites

In recent years,wood improvement technology with high efficiency,environmental protection and versatility has been increasingly favored.Inorganic nanomaterials have many peculiar properties in mechanics,theriology,optics,electricity,magnetism and chemistry.The preparation of multifunctional wood-based inorganic nanocomposites by compounding various inorcanic nanomaterials with wood has important research value and practical significance for improving wood functional properties,expanding wood application fields and increasing added value.However,traditional chemical methods can cause degradation of wood components,volume shrinkage and other impurities,which have great damage to the naturalness of wood.There are also a series of problems such as complicated preparation process,environmental pollution,unsafe,and human health.Aiming at the problems of the traditional chemical methods mentioned above,this paper takes 31-year-old Pinus sylvestris L.van mongholica Litv.wood veneers as the base material,uses sealing agent and ultrasonic wave to treat wood veneer,and uses magnetron sputtering to grow copper film and ZnO film on the surface of wood veneer to realize the preparation of nano-Cu/ZnO coated wood-based composites.The structure,mechanical properties,electrical conductivity,wettability,aging resistance,surface morphology and surface elements of nano-Cu/ZnO coated wood-based composites are characterized by nanoindentation,square resistance tester,contact angle tester,spectrophotometer,X-ray diffraction(XRD),scanning electron microscopy(SEM)and X-ray energy dispersive spectroscopy(EDS).The effects of different sputtering time on the metallization structure and physical properties of wood veneers are investigated.The effects of magnetron sputtering substrate temperature and ultrasonic treatment on the physical properties of copper-plated wood veneers are studied.Wood veneers are treated by different methods,and "sealing agent" nanoZnO/wood composite material and"environmentally friendly" are prepared by magnetron sputtering.The physical properties of wood-based nanoZnO composites are studied by changing sputtering time and substrate temperature.The main conclusions are as follows:(1)Magnetron sputtering is used to realize the metallization of wood veneers.With the increase of sputter coating time,there are still characteristic diffraction peaks of wood cellulose,but the intensity of difiraction peaks is obviously weakened.At the same time,characteristic diffraction peaks of Cu(111),Cu(200)and Cu(220)of metallic copper appear near 20 equal to 43.3°,50.4° and 74.1°,and the intensity of characteristic diffraction peaks gradually increases with the coating time.The elastic modulus and hardness of wood veneer are increased rapidly by growing copper film on the surface of wood veneer.The elastic modulus and hardness of samples coat for 15min increased by 24.1 times and 17.3 times.At the initial stage of sputter copper plating,no continuous film is formed,and the surface of the metallized wood veneer is inferior in electrical conductivity.As the sputter coating time increases,the electrical conductivity of the metallized wood veneer increases.The wettability of wood veneers surface also change from hydrophilicity to hydrophobicity.Sputtering copper atoms gradually nucleate and grow up on the surface of wood veneers,and the growth of copper film goes through three typical stages,from island to network to continuous film formation.(2)The substrate temperature has a great influence on the physical properties of the magnetron sputter-plated copper veneer.At the substrate temperature of 200?,the crystallinity,mechanical properties(modulus of elasticity and hardness)and hydrophobicity of metallized wood veneers are better.In addition,the square resistance of the 200°C sputtering sample is about 4.6 times that of the normal temperature sample,and the conductivity is obviously decreased.The grain size of the copper film is mainly small particles,which are composed by nanoparticles.The grown copper film is uniform,compact,smooth,small roughness,no cracks,and the quality is also superior.(3)Ultrasound treatment can aggravate the porous structure of wood surface and make the surface and internal pore passages clean and smooth,while magnetron sputtering can metallize wood veneers and obtain wood veneers with excellent electrical conductivity.However,the transverse grain resistance of metallized wood veneer is much larger than that of the parallel grain resistance,and the transverse grain resistance is 2-3 times that of the parallel grain resistance.The sample with a sputtering time of 15min(200?)has a water contact angle of 149.9°,which is almost hydrophobic.(4)Nano ZnO/wood composites with "sealing agent" are prepared by magnetron sputtering.Near 2? equal to 17.0°,22.5°,35.0°,there are still diffraction peaks on the crystalline surface of wood cellulose(101,002 and 040),but the intensity of the diffraction peaks and the crystallinity of cellulose are reduced.For the sample with sputtering time of 40 min,the characteristic diffraction peaks of ZnO(100)and ZnO(101)appear,but the intensity of the diffraction peak is weak.The indentation load-displacement curve of the sputter coating for 40min(200?)has a large shape change,and the elastic modulus and hardness increase by 6.6 and 0.23 times respectively.Magnetron sputtering is used to grow ZnO film on the surface of wood veneer,which can improve the wettability of wood.The water contact angle of the sample sputter coated for 40 min(200?)is 140.2°,and the wettability of the wood surface change from hydrophilic to hydrophobic.(5)Without chemical reactions or any chemical organic solutions used to treat the wood veneer,the ZnO film grows on the surface of the wood veneer directly by magnetron sputtering to realize the preparation of "environmentally friendly" wood-based nanoZnO composites.For the samples with the sputtering time of 75min,the characteristic diffraction peaks of ZnO(100),ZnO(002)and ZnO(101)appear on the XRD pattern.The water contact angles of wood-based nanoZnO composites are all over 1300,which have good hydrophobic properties.The 168h ultraviolet(UV)accelerated aging test proves that the wood-based nano ZnO composites has good resistance to UV light erosion.Among them,the total color change(?E*)of the sample with 75min(200?)sputter coating is 3.98,not much,only 23%of the original wood.In a word,nano-Cu/ZnO coated wood base composite materials are successfully prepared by magnetron sputtering method,which realize multi-functional wood improvement,and provide new ideas and feasible methods for the preparation of conductive wood,hydrophobic wood,super-hardness wood and magnetic wood.