Study On The Method Of Stabilizing The Pressure In Sample Cell And Design Of New Type Water-cooling DAC

Currently,scientific researchers interpret the tseismic data through the understanding of the physical and chemical properties of material inside the earth by simulatingthe interior high temperature high pressure(HTHP)environment of the earth.This is an important way to know the deep stucture of the earth.At the same time,this is also an effective methodto studied substance transformation and novel properties under high temperature and high pressure.For example,melt curve,in situ X-ray study,the equation of state and the phase diagram,etc.Although the domestic experimental technology and methods have a certain foundation,the experiments are still faced with various challenges and the technical issues.For example,the advanced international level has been walking in front of usin instrument-precision,temperature-pressure indicators and experiment-method,etc..And we has obvious gap with them,because of which the domestic experimental data International researchers are difficult to accept from the researchers in our country.The diamond anvil cell(DAC)is the only apparatus to generate high hydrostatic pressure exceeding 600 GPa at present.Combining with various heating methods,ithas been enabled derict investigations of materials under extreme pressure-temperature conditions.There are two main heating methods in DAC:laser heating and resistance heating.The laser heating method has been widely adopted in experiments with temperature above 1200 K.Major technical progress hasbeen made in the areas of heating capability and stability,temperature control,and temperaturemeasurement.While resistive heating has been successful in achieving steady and stable high temperature experiments conditions below 1300 K.Nowadays either of the two is extensively uesed for generating high temperature-pressure conditions on DAC.However,a serious problem in the high temperature high pressure experiments on normal DAC that temperature inevitablely induces the instability of pressure in the sample chamber facese us waiting for a solution currently.This is the question which is unable to avoid and a technical problem.The researchershavealready found this issu and have been trying to solve it for all the time.It is noticeable that the rising temperature of the whole DAC can countribut to thepressure loss in the sample chamber in high temperature-high pressure experiments.However no paper has been reported about the extent to the effect and how to handle the problem.In the paper I have improved the normal DAC and invented a new type of DAC called the internal-cooled DAC which can reduce the effect of pressure loss with the circlating water system embeded inside.It can realize keeping the sample pressure constant even under high pressure and high temperature.A technology problom has been successfully solved.In the paper,a series of experiments to test the working state of the normal DAC and the internal-cooled DAC has been conducted at the temperature up to 470 K and pressure up to 32 GPa.What we do is trying to sovel the uncontrollable pressure loss problem exiting in localizing heating of a sample.(1)Through the study of the normal DAC,we get the results that:the sample pressure loss resulting from the rised temperature of the DAC bodyas high as 22.0%in high pressure range,which is already much slighter than that in the low pressure range.This temperature-induced sample pressure loss can be declined or disapeared as long as the temperature of the DAC body is kept at room-temperature.Enough attention should be given to the temperature increasing of the DAC body.The formula to calculate presssure we select in our experiment with the error of 14.9%.As the temperature of DAC body arrive at 365.15 K,the sample pressure has dropped 12.9 %.And 371.15 K corresponds to 16.1 %,above which temperature special attention must be paid to the heated DAC body.(2)Our new designed DAC with internal water-cooling-system will be showed and a series of comparisons with the common diamond anvil cells has been conducted at the temperature up to 450 K and pressure up to 30 Gpa.We simulated the working status of normal DAC by the internal-cooled DAC without water.The experimental results show that:the internal cooled machine can keep the sample pressure constant so that it can be more suitable for high temperature and high pressure experiments.(3)We also collect the high pressure-high temperature Raman spectra of Ba Mo O4 powder on two kinds DAC to test our experimental conclusions.And we got a perfect consistent in the Raman shifts of Ba Mo O4 with our conclusion.This work will drastically increase the reliability of the result of the high pressure-high temperature experiments and improve the accuracy of experimental results.