High Temperature Furnace Under 18/20 T Strong Field And Its Applications

Magnet technology has made great progress in recent years.The record of the high limit of static magnetic field was broken constantly.The combination of a magnetic field and high temperature have been proved valuable for studying phenomena such as crystal growth,grain boundary development,and phase transitions.Applications of magnetic field in research of superconducting,phase transformation in alloys and hydrothermal synthesis have been reported frequently since 1980s.Important results from these reports can be concluded to following aspects.(1)Magnetic annealing method can texture some polycrystalline grains,and therefore better performance,such as greater critical superconducting current,enhanced electrochemical activity,can be achieved.(2)Magnetic annealing can also change the distribution of grain size of some nanosheets.A bimodal curve grain size distribution was induced by magnetic-annealing method.(3)Magnetic grains in alloys can be oriented to form need-like structure in strong magnetic field at proper high temperature.(4)In solution synthesis,magnetic field can change assembly behavior of some ferromagnetic metal oxide product.Anisotropy in macroscopic morphology was enhanced by the applied magnetic field,and therefore aggregates like chains,clusters,arborescent branches.Almost all reported magnetic filed-induced texture effects become more apparent when the field is enlarged.This is because the texture effect has a positive correlation with magnetic anisotropy energy,which is proportional to the square of the field.Greater magnetic field and more kinds of samples are growing research trend.Magnetic-annealing of weak-magnetic samples like carbon nanotubes has been reported.It can be predicted that more effects,which can only occur in very high magnetic field,will arise in next few decades.As superconducting magnet is the most widely used way to obtain strong magnetic field,it is important to enlarge the field limit of magnetic-annealing in this kind of magnet.Without an exception,the superconducting magnets used in reported applications all have a room temperature bore.Compared to room temperature bore superconducting magnets,cold bore magnets has lower fabrication cost and they are easier to reach greater field limit.However,the author has not found any high temperature applications in cold bore magnet reported.This paper presents a new kind of furnace,which can solve the problem how high temperature up to 940 ? acquired in restricted liquid helium room.In the furnace chamber,a liquid nitrogen jacket plays a core role in isolation the radiation heat transfer from high temperature area.Benefit from this,it allows the consumption rate of liquid hellum not to be influenced by the rising temperature of the furnace.In applications of the new furnace,samples were treated in conditions of 15 T and 900 ? respectively.The 15 T magnetic field is greater than the highest reported magnetic field with a high temperature application in room bore superconducting magnet.On the other side,running superconducting magnets needs liquid helium,so the magnetic field room inside the magnets is precious.In all published reports,the author can not find a structure can make full use of the whole uniform magnetic field space.The furnace in this paper changes the phenomenon.We specially designed a structure which can heat a 0.5 meter long room nearly uniformly.This structure can be built in a restricted 23 mm cylinder room.Tested by experiments,the structure is compatible with strong magnetic field.Calculations indicate the heating structure has weaker induced magnetic field,which may affect the samples,caused by heating wires.After the furnace being tested successfully,it was used in several applications.Two of them are presented in this paper.One application is a 200 ? solution synthesis of cobalt oxide nanoparticles in 15 T static magnetic field.The other is a 900 ? heat treatment of cobalt thin film in 6.8 T static magnetic field.Chapter 1 will present the high-temperature furnace designed for 18/20 T 52 mm cold bore magnet.Relevant instrument article was published on Cryogenics,2018.89.Another way to enlarge field limit is to build a furnace system in water-cooling magnet,which can have larger field limit than superconducting magnet at present.We are developing a furnace in a 32 mm bore water-cooled magnet.The limit will be enlarged to 27 T/45 T after the furnace system is built.To measure the samples treated in the mentioned furnace in the magnet,the author built a magnetic force microscopy equipment which can work at low temperature and strong magnetic field.This equipment also fits to the 18/20 T magnet,it can observe the surface morphology and magnetic domain of the sample surface.The microscopy is capable to search large area.Chapter 6 will present this part.Relevant instrument article was published on Chinese Journal of Low Temperature Physics,2017.4.Hydrothermal synthesis in magnetic field develops gradually in recent years.Reports has already show that even weak magnetic field induced by an electromagnet can cause great difference in shape and assemble behavior of the ferromagnetic oxide product.As the bore diameter is too small to accommodate a autoclave furnace,we choose another cold bore magnet to establish the furnace.The magnet has a magnetic field limit of 7 T and 89 mm bore diameter.The furnace structure in Chapter 1 realizes its value in designing and manufacturing a autoclave furnace in the 7 T magnet.Several reactions were carried out after the autoclave furnace was built.Assemble behavior of nickle oxide product was affected by the applied magnetic field.This autoclave furnace and its applications will be presented in Chapter 2.Not only in physics and chemistry research,but also in biology,especially in cell science,application of strong magnetic field raises lots of concerns since 1990s.Magnetro-biology has made great progress in following area:(1)The measurement of magnetism of some biological materials was reported.Measurement method of magnetic anisotropy was developed.It is also reported that a-helix,DNA,and circle protein relatively have stronger magnetic anisotropy.(2)The static mechanical effects of magnetic field were reported.Suspension of cells or frog in gradient magnetic field was observed.(3)Magnetic field also has dynamic effect on biological processes including cell metabolism,proliferation and ion transport,etc.Qualitative mechanic was proposed infrequently.Most biological materials are diamagnetic.That means both static mechanical and dynamic effects are related to the square of magnetic field intensity.The limit of magnetic field applied in biology research become higher and higher since 1990s.It is valuable to build equipment suiting for water-cooled magnets.So,we designed and developed an equipment designed for cell experiments in 27 T water-cooled magnet.This equipment can control temperature for small living things and cells.It also has a gas control system and it can increase humidity through the system.Using this equipment,we and Xin Zhang's laboratory carried out some experiments.Xin Zhang is from high magnetic field laboratory of the Chinese academy of science.These experiments studied the influence of 27 T static magnetic field to orientation and morphology of mitotic spindles in human cells.Results were published on Elife,2017.6.Another application of this equipment is to explore the influence of 27 T magnetic field to the grow period of Caenorhabditis elegans.Other biologic samples,such as plant seeds,drosophila,DNA,were also exposed to 27 T strong static magnetic field.More work is needed to get certain conclusions.The collaborator is An Xu,from institute of technical biology.The equipment and its applications is in Chapter 3.To explore whether the strong static magnetic field will change the grow rate of tumor,we established a mice experimental device which is used in 50 mm bore water-cooled magnet.Two 24.5 T magnetic field treatments were applied to the same 8 mice.Some influence were observed.But more efforts need to make to get an certain conclusion.This equipment for mice experiment in 50 mm bore water-cooled magnet is described in Chapter 3.