Patent Number: 050362054
Section: summary

The present invention concerns the field of transmissive electron microscopy, particularly under a controlled atmosphere, of samples, especially graphite insertion compounds and has as an object a device for the transfer and insitu reactions under a controlled atmosphere of samples intended for such study. This apparatus may also be used, either internally even of the microscope chamber, or in the gate of this latter, for conducting chemical reactions between the sample or samples mounted on the grid or grids and gases of controlled temperature, pressure, composition and nature, which is particularly useful for performing a kinematic study of these reactions. Insertion compounds of graphite have been the subject of intense study for a number of years, notably because, on the one hand, of their electrical conductivity parallel to the graphite layers, which is very high at ambient temperature and for certain compounds close to that of cooper, together with a strong anisotropy which may be as high as 10.sup.6, and on the other hand, of the superconductive character of certain compounds which can attain the temperature of liquid helium and, finally, of the great variety of species which may be inserted between the graphite layers, namely from alkaline metals to halogens including metallic alloys, alkaline hydrides, the alkaline-earth metals, certain lanthanides, acids, halides or oxyhalides of transition metals, etc... The class of insertion compounds of graphite comprises at present 300 to 400 different phases taking account of the stage phenomenon. Thus, a compound is said to be stage 1, 2, 3... according as two successive inserted layers are separated by 1, 2, 3... layers of graphite. In certain cases, the stage may attain the value of 12 or 13. The great variety of reagents confers to the insertion compounds various properties amply justifying the intense study that has been devoted thereto. The insertion compounds frequently have phase transitions which are revealed by variations of electrical resistivity or thermal dilation. In a great number of compounds, there exists in addition an incommensurability between the host lattice and inserted lattice and the reflections obtained are sometimes of very weak intensity when examined with x-rays. It is therefore especially interesting to be able to study these compounds by any possible methods of investigation, and more particularly by transmissive electron microscopy. Such methods of investigation are nevertheless difficult to practice, because the insertion compounds are for the most part very fragile in air, such that there arise problems in transferring the samples to the chamber of an electron microscope. Specifically, emphasis has been placed on insertion compounds of graphite for which a transfer under a controlled atmosphere proves to be indispensable. The known sample holders may certainly be used for any types of materials whose geometric characteristics, especially thickness, are compatible with the observation by transmission in an electron microscope. In addition, they allow positioning of the samples, even those not fragile in air, such that they are caused to penetrate into the reaction chamber of the sample holder after a first examination with the electron microscope, to cause them thereafter to react and to analyze them without having to use other equipment and, above all, without them being returned into contact with the air. Thus, there does not exist at present sample holders adaptable to any type of side-inlet electron microcope, which permits both a transfer of samples under a controlled atmosphere and in-situ reactions. This latter concept is very important, because it permits performing chemical reactions when the sample holder is at the very interior of the microscope chamber and the grid holder rod is in the so-called transport position. There thus arises the problem of introducing a microscope grid, first prepared in a sterile chamber under controlled atmosphere, into the examining chamber of an electron microscope, without it coming into contact with the air. To this end, a rod enclosing the sample holders, which may be of variable diameter and provided with a projection serving to maneuver its opening through the vacuum pumps, then through the door to the gate of the microscope, must penetrate into the said gate to a length of about 20 cm. Protection of the sample by an exterior sleeve and kinematic studies could be effected by equipment mounted on a clamp for connection with the gate of the microscope, leading to a modification of this latter. Such modification, aside from being inconvenient, requires a lengthening of the sample holders which is incompatible with the size of most sterile chamber gates. It would also be possible to construct a sterile chamber mounted directly on the outlet of the gate of the microscope provided this latter is suitably modified. Such an embodiment is nevertheless rather complicated. On the other hand, a transfer device is known of which the forward part is provided with an exterior gasket which is received at the interior of the microscope chamber. This device nevertheless has a number of disadvantages, namely, on the one hand, a risk of deterioration of the gasket when sliding the movable portion of the sample holder between the guide rails of the object holder, on the other hand, a lack of control of the precise positioning of the object interiorly of the chamber because the guiding of the movement in this latter is effected through the intermediary of an elastic gasket and, finally, the provision of a single grid housing on the stage, which leads to relatively long operations of loading the grid for each sample. The present invention has as an object to overcome these disadvantages. Specifically, it has as an object a device for the transfer and in-situ reactions under a controlled atmosphere of samples for transmissive electrode microscopy, essentially constituted by a cylindrical rod of slight diameter comprising, near one end, two grid holders and slidably mounted in a cover of greater diameter provided with a sealed chamber for housing the grid holders in transport position, by a traction bar integrated with the end of the rod of slight diameter opposite the grid holders, guided in the cover of greater diameter and provided at its other end with a manipulating button, the grid holders being advantageously provided in a flat of the end of the rod and the cover being advantageously formed in two parts and having a front part of lesser diameter intended to penetrate into the gate of the microscope and provided with a longitudinal opening corresponding at least to the section of the grid holders of the rod in analysis position of this latter, characterized in that it is provided in addition with a means for guiding and locking in transport and analysis positions the rod provided with the grid holders, the said rod being advantageously integrated by screwing with the corresponding end of the traction bar which is guided in the cover, of which the opening of the front part of lesser diameter is extended over a portion of the length of this front part, on both sides, by longitudinal grooves, the said front part being connected to the rest of the cover by screwing of a shouldered portion, a gasket effecting the sealing at the level of the screwed assembly.