Development of the multi-anvil deformation apparatus and rheology of the upper mantle

我们开发了利用现有预算购买的汽车自动制造高压实验用硬陶瓷零件的工程。这家汽车厂最初设计的目的不是生产硬陶瓷，而是生产金属。因此，我们开发了特殊的技术来制造高精度的硬陶瓷，而不会损坏机器。研制了多砧装置的高压产生技术。我们分别用碳化钨和烧结金刚石砧成功地产生了34和63 GPa。我们尝试在一个立方砧装置上进行变形实验，在一个砧上打一个孔，用微活塞使样品通过孔变形。首先，由于带孔的铁砧强度很低，我们优化了铁砧的形状，使其能够承受4 GPa的压力。在试验中，我们采用A12O3棒作为假样本，并试图通过减去微活塞接触样本前后的载荷来估计假样本上的偏应力。然而，即使我们尝试了多种样品环境，我们也无法观察到微活塞所受载荷的任何明显变化。我们得到了地幔矿物流变学的实验结果如下：1) Mg_2SiO_4 wadsleite的体积模量和剪切模量的温度导数分别为-0.0175(3)和-0.0159(1)GPa/K。2) Mg_2SiO_4环woodite的体积模量和剪切模量的温度导数分别为-0.0193(9)和-0.0148(3)GPa/K。3) MgSiO_3钙钛矿的体积模量和剪切模量的温度导数分别为-0.029(2)和-0.024(1)GPa/K。4)地幔过渡带下部Mg_2SiO_4环伍德岩的热膨胀系数为2.6×10^<-5>/K。5)地幔过渡带下部Mg_2SiO_4环伍德岩的热膨胀系数为3.2×10^<-5>/K。

We developed the engineering to automatically manufacture hard-ceramics parts for high-pressure experiments using automill that was purchased by the present budget. The automill was originally designed to manufacture not hard-ceramics but metal. Therefore, we developed special techniques to manufacture hard-ceramics with high precision and without damaging the machine.We developed technique of high-pressure generation for a multi-anvil apparatus. Using tungsten carbide and sintered diamond anvils, respectively, we successfully generated 34 and 63 GPa.We tried to conduct deformation experiments in a cubic-anvil apparatus in which a hole was made in one anvil and micropiston was applied to deform the sample through the hole. First, because an anvil with a hole has very low strength, we optimize the anvil shape to survive at 4 GPa. In a trial experiment, we adoped A12O3 rod as a dummy sample, and tried to estimate the deviatoric stress on the dummy sample by subtracting the load applied to the micropiston before and after touching the sample. However, we were not able to observe any clear change of applied load to the micropiston, even though we tried many kinds of sample environments.We obtained the following experimental results on rheology of the mantle minerals. 1) The temperature derivatives of bulk and shear moduli of Mg_2SiO_4 wadsleyite are -0.0175(3) and -0.0159(1) GPa/K, respectively. 2) The temperature derivatives of bulk and shear moduli of Mg_2SiO_4 ringwoodite are -0.0193(9) and -0.0148(3) GPa/K, respectively. 3) The temperature derivatives of bulk and shear moduli of MgSiO_3 perovskite are -0.029(2) and -0.024(1) GPa/K, respectively. 4) Thermal expansion coefficient Mg_2SiO_4 ringwoodite in the lower part of the mantle transition zone is 2.6×10^<-5>/K. 5) Thermal expansion coefficient Mg_2SiO_4 ringwoodite in the lower part of the mantle transition zone is 3.2×10^<-5>/K.