FIELD OF THE INVENTION

The present invention is in the field of a nanoreactor com prising a membrane condenser, wherein the nanoreactor comprises an input, an output, a sample area, wherein the sample area is transparent for electrons and conducts heat, a method of con densing gases using said nanoreactor in a microscope, such as an electron microscope.

BACKGROUND OF THE INVENTION

Wet corrosion of alloys or metals is considered to be an electrochemical process that involves oxidation of metal and re duction of other species in contact of an electrolyte and with corresponding charge transfer which usually occurs through metal or alloy. These phenomena occur as uniform or local damages at an interface of metal/electrolyte or within the structure of a metal. Corrosion resistance of a metal or alloy is considered to be highly dependent on its microstructure and composition.

Traditionally electron microscopy (EM) has been widely uti lized to analyse sites affected by corrosion as well as their surroundings in order to obtain fundamental knowledge on corro sion processes, such as in analysing of corrosion products and influence of structure and composition of alloys or metals on these processes. However these analytical techniques are limited because corrosion reactions occur at an interface between a metal surface and electrolyte. Other chemical and physical pro cesses at the liquid/solid interface may be studied in a similar manner as the above corrosion. Also placing the samples under observation in an EM vacuum may cause artefacts, such as a dehy drated surface. The use of MEMS devices in transmission electron microscopy (TEM) for experiments as the ones indicated above is booming. In particular for local heating with very low power consumption (and thus negligible specimen drift), these devices have become the new standard for in-situ heating TEM in just few years. In the next few years, MEMS-based nanoreactors (NRs) will conquer the market for operando TEM experiments involving sample interaction with static/dynamic gas or liquid systems. A nanore actor allows in principle the interaction of a liquid electro lyte and a metal, but to image in-situ such an interaction, re quires that the area of interest can be seen in the electron mi croscope without much additional image distortion due to the electrolyte and/or the reaction products that are present along the path of the electron beam. This is very hard to achieve with the state-of-the-art liquid nanoreactors. The same problem oc curs for any other studies of a reaction between a liquid and a solid state, whereby one is interested in the nanometer scale changes in the solid.

Some background art can be found in Creemer et al . , J. Micro electromechanical Systems, IEEE Service Center, Vol . 19, No. 2, April 1 2010, wherein a nanoreactor is recited with a fluid in put and output .

The present invention therefore relates to a nanoreactor for use in (combination with) microscopy, and a microscope compris ing said nanoreactor, which solve one or more of the above prob lems and drawbacks of the prior art, providing reliable results, without jeopardizing functionality and advantages.

SUMMARY OF THE INVENTION

The present invention relates to a nanoreactor. Inventors have developed MEMS based nanoreactors (NRs) (such as in

PCT/NL2015/050758, W02017/003286, EP 13 710 624, and

NL2014/050825) to create events of fluids, such as liquids and gas mixtures, with solid materials, such as metals, which can be investigated directly inside electron microscope columns. For reactions of gasses with solid materials reasonably good resolu tions can be achieved. In contrast, dynamics in liquid-solid in teractions allow only relatively poor resolution because the height of the liquid not well controlled and often far too large to obtain a good resolution. So far there is no MEMS device de veloped for TEM application that allows for local condensing of gases and solidification of fluids. A MEMS device in which the complete tip is cooled down i.e. global condensing is available for TEM studies, whereas applying additional heating allows for a reliable desired temperature on a membrane. However, it is not yet possible to locally condense a gas, such as water vapour, or in general, an aerosol, on a sample area while the surrounding MEMS device and holder are at relatively higher temperature. The capability to locally cool down a part of the membrane in a nanoreactor provides a unique opportunity for researchers to carry out high resolution in-situ TEM studies on a specimen with a locally condensed (water) vapour on the sample to form a very thin liquid water film for wet corrosion, typically in a well- controlled manner. For instance, this technique can be applied to elucidate the mechanisms of pit initiation, passive layer and protective scale breakdown and prediction of onset or growth of stress corrosion cracks, which requires atomic-scale knowledge of corrosion and failure processes, such as based on detailed TEM studies .

In the present nanoreactor for instance partial removal of reaction products (like corrosion products) may be done by con trolled evaporation of water in such a way retraction of the liquid front is done such that the retraction starts at the area or areas that one investigates with e.g. a TEM and the final evaporation occurs at the point where one wants to collect the corrosion products. This is achieved by creating, during warming up of the cold area, a thermal gradient. An alternative is to use differences (for instance in width) in the hydrophilic areas such as their width as shown in Figure 13b.

Likewise in the present nanoreactor a temperature gradient can be created, such as of DT=10K. Over this temperature gradi ent the behaviour of a sample can be studied.

The present NR comprises a body 6,11 (see e.g. fig. If), and within a space of the body at least two thin reactor membranes 1 opposite of one and another. The two thin membranes allow one to enclose a gas and/or liquid in between the membranes and still maintain a very good vacuum condition such as in an electron mi croscope column. The reactor further comprises a fluid input 7, a fluid output 8, at least one sample area 9, wherein the sample area is a very thin membrane that is well transparent for elec trons and conducts heat, wherein the sample area is located on at least one membrane, wherein the membrane comprises at least one MEMS condenser 2 comprising a controller, and at least one electric or thermal contact 4,5; the fluid may relate to a liq uid, a gas, a gas mixture, and combinations thereof. The sample area may be considered as an area on the active membrane. It is considered that in order to make an electrical/thermal flow typ ically at least 2 contacts are provided. It is typically the sample area 3 where the condensation is performed. For wet cor rosion it is found to be essential to have a layer of water on the surface of the sample. This can be realised by creating a cold spot on a membrane in the NR where the specimen is located. This design with a local cold spot allows the operator to use water vapour purged into the NR to locally condensate on the specimen area and form a thin liquid water layer as electrolyte film. Furthermore by fine-tuning the surface chemistry, for in stance using hydrophobic and hydrophilic stripes, by providing a volume of gas, and heat flux rate, one can control the thickness of a condensed water layer. The condensation should occur only on a cooled area because if it takes place elsewhere it might result in clogging and subsequent pressure pulses, which could rupture the membrane. At present, there is no local cooling method that has been utilized for in situ TEM studies. The pre sent nanoreactor enables different types of experiments for which it is important that the sample temperature is lower than the ambient temperature. Apart from the condensation of water for corrosion studies, this setup can be used to condensate other solvents or gasses for instance for TEM studies of liquid sensors like ZnO/porous Si sensors for liquid ethanol or acetone sensors for medical applications . Also the property of sensors and liquid/gas solvents can be studied using this technique in atomic scale using electron beams.

In a second aspect the present invention relates to a method of operating a nanoreactor according to the invention, compris ing inserting the nanoreactor in a microscope, such as an TEM, SEM, FIB, and optical microscope, and forming a liquid layer of 1-1000 nm on the MEMS condenser nanoreactor. The liquid conden sation may form small droplets on the active condensing area of the MEMS condenser nanoreactor and on the sample located in this area .

In a third aspect the present invention relates to a method of operating a nanoreactor according to the invention, compris ing lowering a membrane (1) temperature, and forming a condensa tion product, such as a liquid or a solid, such as water or ice.

In a fourth aspect the present invention relates to a micro scope comprising a nanoreactor according to the invention.

Thereby the present invention provides a solution to one or more of the above mentioned problems and drawbacks.

Advantages of the present description are detailed throughout the description.

DETAILED DESCRIPTION OF THE INVENTION

The present invention relates in a first aspect to a nanore actor according to claim 1. In an exemplary embodiment of the present nanoreactor the condenser may comprise an n-type layer, a p-type layer, such that these layers form an N/P- junction, and an electrical con tact to the junction. The n- and p-type semiconductors may be placed thermally in parallel to each other and electrically in series. The n-type and p-type layers may comprise thermoelectric materials. Examples are nano-structured materials in form of novel super-lattices. Therewith a thermoelectric condenser is provided with sufficient condensing capacity to form a water layer or even an ice layer (e.g. from water vapor or wet gas mixtures), typically in a specific and active condensing area on the membrane .

In an exemplary embodiment of the present nanoreactor the condenser is placed in the middle of a relatively large mem brane, whereby the membrane is several times larger than the ac tive condensing area such that the condensing area is not sub stantially heated by the chip body (e.g., Si) through the outer part of the membrane. The outer part of the membrane has prefer ably a low thermal conductivity.

In an exemplary embodiment of the present nanoreactor the condenser may have a cooling capacity of 0.2xl0 ^~3 -l W, preferably 1*10 ³ -7*10 ^~1 W. Typically a voltage of 0.1-1 V is applied, such as 200-700 mV, and/or a current of 10 ³ -1 A, preferably 3*10 ³ - 1*10 ^~3 A. In an exemplary embodiment of the present nanoreactor an n-type layer may comprise Bi2Te3, such as Bi2Tea-xSe _x , BiSb, PbTe, or polycrystalline Si/PolySi, and a p-type layer may com prise Sb2Tes, such as SbsTea/Bi2Tes, Sb, or polycrystalline

SiGe/polySiGe . These materials are found to be particularly suited for cooling, providing a good coldness flux, and provid ing very low temperatures, such as around 200 K in case the cooling elements are stacked.

In an exemplary embodiment of the present nanoreactor the at least one condenser each individually may have a planar geometry selected from rectangular, square, trigonal, multigonal, and combinations thereof. In an example 4 trigonal condensers may form a butterfly geometry, providing excellent condensing. It is preferred to use 2-6 similar or the same condensers in view of controllability on heat flux.

In an exemplary embodiment of the present nanoreactor 2-1024 condensers may be present, preferably 3-64 condensers, such as 4-16 condensers.

In an exemplary embodiment of the present nanoreactor at least one condensing area (sample area) of the membrane occupies 1-25% of the total membrane area, preferably 2-20%, more prefer ably 3-15%, such as 5-7.5%, wherein the sample may occupy the complete sample area, preferably 1-30% of this area. The remain der of the membrane may be provided with a thicker layer and/or supports preferably of a poor thermal conductivity, especially at the edges thereof, whereas the sample area is typically rela tively thin and has preferably a good thermal conductivity.

In an exemplary embodiment of the present nanoreactor the sample area, each individually, may have a thickness of 20-50 nm .

In an exemplary embodiment of the present nanoreactor the sample area, each individually, may have a width of 10-150 pm, such as 20-50 pm.

In an exemplary embodiment of the present nanoreactor the sample area, each individually, may have a length of 1-50 p , such as 2-10 pm.

In an exemplary embodiment the present nanoreactor may com prise at least one thin and electron transparent window

9,34,36,38 for electron microscopy on the membrane, such as with a thickness of 10-20 nm.

In an exemplary embodiment of the present nanoreactor spacers are provided in between membranes.

In an exemplary embodiment the present nanoreactor may com prise at least one further membrane 33,35,37, which further mem brane is parallel to the at least one membrane, such as two- three further membranes. In total then three to six membranes would be present. A top membrane could be bulging, such as up wards, a bottom membrane could be bulging, such as downwards, whereas a middle membrane stays in horizontal position and no focus needs to be reset as a consequence.

In an exemplary embodiment of the present nanoreactor the nanoreactor may comprise at least one nanoreactor rim, typically three to five nanoreactor rims, such as for fixation of the sam ple. The nanoreactor rims may be slightly thicker than the mem brane, such as 200-1000 nm, e.g. 300-500 nm. The nanoreactor rims may be provided on one side of the membrane, or on both sides (bottom and top) . In an exemplary embodiment of the present nanoreactor the controller each individually may be operated at a current of 1- 1000 mA. In an exemplary embodiment of the present nanoreactor the condenser may have a heat flux of 0.2-10000 W/cm ² , such as 500-10000 mW/cm ² . So an exceptionally good control of temperature and temperature change is achieved as well as creation of liquid (water) layers. Also, by increasing to higher heat fluxes, such as 0.2-500 W/cm ² , the temperature in the active condensing area can be reduced more. For instance to 200 K or lower. An option is to apply a series of these condensers or coolers stacked on each other to increase the heat flux and thereby to establish a lower temperature on the membrane area, wherein the top one acts as a condenser. This design may be in planar and in vertical form .

In an exemplary embodiment of the present nanoreactor at least one of the input and the output may comprise tubes for transporting a fluid to and from the nanoreactor, respectively, such as a gas mixture or a liquid.

In an exemplary embodiment of the present nanoreactor the in put and the output may comprise of a "closing system", such as a valve, such that the amount of gas that can condense on the cold area can be controlled and therewith also the amount of conden sation on the cold area.

In an exemplary embodiment of the present nanoreactor the body may comprise a top part 11, a bottom part 6, and a seal 10. In addition, or as alternative to a seal a glue line and unequal width of the top (smaller) and bottom (larger) are provided to allow easy gluing at the side of the top and simultaneously at an edge of the bottom.

In an exemplary embodiment of the present nanoreactor the seal may have a thickness of 0.1-200 pm, i.e. slightly larger than or as large as a thickness of the fluid chamber of the nanoreactor. The seal may have a similar form as the nanoreactor boundary, e.g. substantially square or rectangular, substan tially multigonal, oval, and sometimes also circular.

In an exemplary embodiment of the present nanoreactor at least one membrane 1 each individually may have at least one of a thickness of 100-600 nm, a length of 40-1000 pm, and a width of 40-1000 pm. It is noted that the samples are typically much thinner, as it is mentioned above. In an exemplary embodiment of the present nanoreactor at least one of the nanoreactor, the input, and the output, or a part thereof, may be coated internally thereof, such as with a corrosion resistant material, such as SiC, with a hydrophobic coating, with a hydrophilic coating, and combinations thereof. Such a coating may be applied on parts of the present reactor, or may be applied elsewhere, such as by using an FIB and appro priate chemicals or precursors. Very precisely deposited (with 10 nm precision) coatings can be applied as such.

In an example a hydrophilic coating is adjacent at opposite or all side to a hydrophobic coating. It has been found that the edge of a formed aqueous layer is limited thereby, and edges of the aqueous layer have contact angles of 40-50°. A good control of aqueous layer thickness is provided thereby. In an alterna tive, or in addition, layer thickness control is also provided by limiting an amount of liquid being present, such as by limit ing a volume thereof.

A similar approach may be used for the sample (see e.g. figs. 9 and further) . The sample may comprise on or more coating, and/or one or more coated areas .

In an exemplary embodiment of the present nanoreactor the re actor may have a volume of less than 10 ^s pm ³ .

In an exemplary embodiment of the present nanoreactor the membranes may be located at a distance dl of 0.1-5 pm for a re actor for a liquid, and at a distance d2 of 0.1-100 pm for a re actor for a gas. The liquid typically has a height of 1-10% of the above distance d2, leaving free space between the liquid and an upper membrane. In an exemplary embodiment of the present nanoreactor may further comprise at least one heater.

In an exemplary embodiment of the present nanoreactor may further comprise at least one aligner D, preferably at least one aligner for x,y aligning, and at least one aligner for rota tional aligning. When assembling the reactor aligning may be cumbersome, both in view of dimensions of reactor elements, mak ing these difficult to handle, in view of overlapping features; therefore aligner may be provided allowing aligning with a pre cision of better than 2 pm, typically in the order of 500-1000 nm. Often such an aligner is not necessary as using relatively simple techniques, such as an optical microscope, already pro vides sufficient aligning of better than 2 pm. In an exemplary embodiment of the present nanoreactor may further comprise a biasing system on the active condensing area on the membrane to be able to apply/measure potential/current of a sample. This biasing line or lines can, for instance, be made of platinum or any conductive material that should be inert to the applied electrolyte. These lines can be coated with non-con- ductive materials and then get opened on desirable areas which sample is attached to them. The presence of an electrolyte layer (e.g. water) combined with this biasing system and reference electrodes (e.g., Pt, Au) provide proper conditions to perform electrochemistry as well.

In an exemplary embodiment of the present method, a temper ature gradient may be applied to the sample or sample area. With the present nanoreactor such advanced experimental circumstance can be created.

In an exemplary embodiment of the present method a limited gas volume may be provided. Such is an advantage, as physi cal/chemical behavior can be precisely controlled and studied.

In an exemplary embodiment of the present method a thermo couple can be placed onto the active cooling area on the mem brane to read out the real-time temperature of the sample.

In an exemplary embodiment of the present method a sample may be coated, such as with at least one of a hydrophilic coat ing, and a hydrophobic coating, preferably 2-3 non-overlapping hydrophilic coatings, and 2-3 non-overlapping hydrophobic coat ings. Therewith condensation products can be provided precisely at intended areas. The coatings are typically provided adjacent to one and another, and not overlapping. In between coatings ar eas may be left open, such that a sample surface is pristine.

In an exemplary embodiment of the present method a sample may be provided with at least one reaction product collector. Such can be achieved by creating the above hydrophobic and hy drophilic areas. Upon removal, e.g. evaporation, of the liquid, a small volume of liquid remains up to total removal of the liq uid, which small volume can comprise reaction products, which reaction products remain on a surface of the sample after full evaporation .

In an exemplary embodiment of the present method a liquid layer may be formed with a thickness of 1-25% of the membrane distance, preferably 2-15%, such as 3-10%. It is an advantage of the present system that e.g. a thickness of the liquid layer may be controlled very precisely, by using the present nanoreactor with the condenser, such that only a portion of an available height is used.

The one or more of the above examples and embodiments may be combined, falling within the scope of the invention.

EXAMPLES

Inventors disclose a new approach to perform liquid cell electron microscopy using a local condensing method in MEMS based NRs . This design provides conditions to force water vapour which is purged into the NRs to locally condensate on the speci men area and form a thin liquid water layer to act as electro lyte film.

In an example a 25 ml.min ¹ oxygen/water vapor mixture at room temperature passes over a MEMS device with a local conden ser results in fast and controllable water layer formation on the cooled part of the membrane area, such as a water layer of 5-300 nm. For this particular device, applying 300mV, results in temperature drop around 10°C of the condensing area on the mem brane which is sufficient to form a liquid water layer from a humid gas mixture. This liquid water layer with the ions forms an electrolyte that allows for corrosion of a sample placed on the condensing area. Removing this condensed water is found to halt the corrosion, showing that an electrolyte is required.

High resolution TEM imaging and analytical EM studies can be carried out in two manners: 1) the TEM is done with the water layer present, in which case it is essential to have a control over the thickness of the water layer and 2) the water layer can be removed by turning off the cooling system followed by in creasing the temperature of the cooled area to the ambient tem perature. When the liquid is removed, TEM studies can be done, without the presence of the liquid layer. In case TEM is done through the liquid, the height of the liquid can be tuned by controlling the heat flux, flow rate, and closing the inlet and outlet of the nanoreactor such that only a small gas volume is present to condense on the cooled area, and/or one patterns the surface of the sample lamellae with for instance hydrophobic stripes, whereby the height of the condensate is governed by the width of the hydrophilic stripes. Inventors designed a reactor to utilize a MEMS based conden ser to perform some quasi in-situ corrosion studies to elaborate the ability of this approach for further in-situ corrosion stud ies in TEM (Fig. 2-4) . Tests were done with this reactor, whereby an electron transparent steel sample, called in general lamella, (made from cold rolled DP1000 steel) was made by cut ting out the lamella from the bulk steel sample using dual-beam focused ion beam/scanning electron microscope (FIB/SEM) after which the lamella was placed on MEMS devices with thermoelectric cooler (TEC) modules to cool down only an active condensing area on the membrane area. The gas supply system to provide a mixture of corrosive gas and water vapour for these simplified studies is illustrated in Fig. 3.

Example 1; wet H2S corrosion cracking (H2S gas and acidic solution with chlorine)

The cold rolled samples with a thickness of 0.2mm, without any post treatment from DP1000 steel were used to prepare TEM lamellae. Samples were cut and thinned down to -100 pm followed by standard metallographic sample preparation methods (mechani cal grinding with final polishing by 35pm to 1pm diamond

pastes) . These disks are evaluated in advance in a home-made setup to study their susceptibility to the wet H2S corrosion cracking before preparing FIB samples. These samples are ob served to be highly sensitive to the wet H2S cracking failures and consequently stress corrosion cracking (SSC) and hydrogen- induced cracking (HIC) can be observed in less than one hour ex posure time to the corrosive saturated H2S solution (based on standard evaluation tests; ANSI/NACE MR0175/ISO15156) . About 100ml of this corrosive solution (5.0 %Wt . NaCl and 0.5 %Wt .

acetic acid, the pH is measured to be about 2.5) was transferred to a 3-neck flask. Nitrogen gas was used to remove oxygen from the solution and tubing. For quasi in-situ studies, H2S gas (with flow rate of -2.0 ml. min ¹ ) was purged into this corrosive solu tion, which is saturated with H2S gas. Thereafter, this mixture of H2S gas and water vapor was conducted to the NR using a peri staltic pump with a flow rate of 1.0 ml. min ¹ (Figs. 2&3) .

The membrane on the present TEC device that was used had -lpm Si _xNy , wherein holes were made with a FIB/SEM in the membrane (Fig. 4a) . Then with the lamella loaded, the TEC device is moved to a NR (fig. 4b) before passing the mixture of H2S gas and water vapor over the membrane. A DC current is applied to TEC device to cool down the membrane around 10 °C below the ambient tempera ture for water condensation. When the cooling is on with a 10°C drop in temperature in the sample area, passing a mixture of EhS gas and water vapor resulted in a very significant corrosion re actions on samples even as soon as after a few minutes of expo sure (Figs. 4b-d) . Energy-dispersive X-ray spectroscopy (EDS) analysis and TEM images for some corroded steel lamellae (made of cold rolled DP1000 steel) are presented in Figs. 4-5.

Example 2; wet H2S corrosion studies (H2S gas and deionized water)

Similar to the example 1, TEM lamellae were made of DP1000 cold rolled steel and placed onto the TEC devices but instead of corrosive solution (5.0 %Wt . NaCl and 0.5 %Wt . acetic acid), DI water is used in this tests. TEC device was cooled down 10°C relative to the room temperature (RT) and the mixture of H2S gas and DI water vapour passed through the membrane. EM images and analysis on two steel lamellae are presented in Figs. 6&8 before and after turning the TEC device on in the NR.

For comparison, the steel lamellae were exposed to the mix ture of H2S gas and water vapor mixture in these tests before turning on the cooling system on the membrane while the corro sive gas mixture is passed through the NR. TEM studies resulted in no significant/observable changes (such as due to corrosion reactions) on these samples, even after exposing them to the wet H2S gas for about 20min (see Figs. 6a-b, 7b and 8a) .

Further investigation and analytical EM studies were carried out to characterize corrosion products for these samples. Re sults of electron energy loss spectroscopy (EELS) and selected area electron diffraction (SAED) studies before and after expos ing the sample to the wet H ₂ S gas while the membrane was cooled down 10°C relative to the RT are shown in Fig. 8. SAED patterns for a corroded sample (inset in fig. 8b) shows the formation of Mackinwite tetragonal FeS (AMCSD 0014518) which plays a key role in wet H2S cracking failure for carbon steels. EELS studies on low loss energy region and Fe L2, 3-edges for this sample before and after corrosion are shown in fig. 8c&d. The plasmon peak is shifted 2. OeV by formation of iron sulphide products on the sur face of sample. The sulphur K-edge which is displayed on Fig. 8e shows the presence of sulphur products on the surface of the corroded sample as well.

The invention is further detailed by the accompanying fig ures, which are exemplary and explanatory of nature and are not limiting the scope of the invention. To the person skilled in the art it may be clear that many variants, being obvious or not, may be conceivable falling within the scope of protection, defined by the present claims.

Optimisation of the sample preparation, to be used in the claimed NR with its ability to locally provide condensation on the sample, is not only related to making the sample thin enough to obtain electron transparency, but it is also preferably pre pared in such a manner that the changes, like for instance the movement of a corrosion front, is occurring at a specific loca tion/locations. In this experimental strategy the searched in formation is to be collected in a most efficient manner, which requires careful preparation of the shape of the sample as well as the applications of coatings on the selected surface areas of the sample. In this strategy the start of the corrosion as well as its propagation can be steered such that the TEM experiments have the highest information content.

FIGURES

The invention although described in detailed explanatory con text may be best understood in conjunction with the accompanying figures .

Figs, la-f show details of the present nanoreactor.

Figs. 2a-b show schematics of a sample holder.

Fig. 3 shows a gas supply system.

Figs. 4a d, and 5-7, 8a-d-9a-e, 10-13a-b and 14a-b-15a-b show experimental details.

DETAILED DESCRIPTION OF THE FIGURES

List of elements:

1 Membrane

2 cooling elements

3 Active condensing area

4 Electrical contacts (+)

5 Electrical contacts (-)

6 Body of bottom chip

6a Body of the top chip

7 Gas inlet

8 Gas outlet 9 Electron transparent windows

10 O-ring

11 Body of top chip

13 Bottom membrane

13a Thick part of bottom membrane

13b Thin part of bottom membrane

14 Top membrane

14a Thick part of top membrane

14b Thin part of the top membrane

15 Platinum deposited by FIB to fix the specimen to the membrane

16 Specimen

16a pristine surface of specimen

16b thin part of the specimen

16c pristine surface of the edge of specimen

17 Gas

18 Liquid droplet

19 (hydrophobic) coating

19a Narrowing coating

20 Collector of corrosion products

21 Corrosion products

22 Glue

23 Nanoreactor Rim

24 Propagating corrosion front

25 Electron beam direction

33 thick part middle membrane

34 thin part middle membrane and specimen area

35 thick part top membrane

36 thin part top membrane

37 thick part bottom membrane

38 thin part bottom membrane

39 Si part of MEMS device

40 Spacer

41 Thin top membrane (note no thick part is present)

42 Thin bottom membrane (note no thick part is present)

A-A cross-section

D aligner

Figure la-g. Exemplary details of the present reactor. Fig. la shows a top view. Fig. lb shows a cross sectional view A-A of a bottom part 6. Fig. lc shows an enlargement of the central part of Fig lb showing the membrane 1 and condenser part 2 and condensing area 3. Figs. Id and le show an enlarged condensing area, including membrane 1, cooling elements 2, active condens ing area 3, and electron transparent windows 9. Figure If shows assembly of a nanoreactor with top part 11, O-ring 10, and bot tom part 6. Fig. lg shows a top chip body 11, a (mono/multi layer) vertical condensing device 2, an O-ring 10 for sealing the nanoreactor, membranes 1, and gas inlet/outlet 7/8.

Figure 2a-b. Schematic of specimen holder (as a closed NR) with ability to purge gas into it and apply the bias on TEC de vice .

Figure 3. Gas supply system to purge a mixture of corrosive gas (e.g. oxygen or hydrogen sulfide) and water vapor through the NR. H2S gas was used to do wet H2S cracking on carbon steel samples. Oxygen can be used for other type of corrosion studies.

Figure 4a-d. SEM images taken from a TEC (a) before loading TEM lamellae on holes which are made by ion beam (b-d) with TEM lamellae on holes after exposing to a mixture of H2S gas and wa ter vapor while the membrane was cooled down 10°C relative to the room temperature for 1 min. Black spots, which are made of S and Fe, are observed on the surface of lamellae after test (corro sion products on steel lamella) .

Figure 5. STEM image (left) shows a damaged steel lamella (cold rolled DP1000 steel) . The chemical composition analysis indicates that iron sulphide (right, top and bottom respec tively) (as corrosion products) is made on the surface of steel lamella (after exposing to the H2S gas/water vapor mixture for about lmin) . The membrane area was cooled down ~10°C relative to the ambient temperature. Inset in (a) shows the X-ray elemental line scan extracted from the area on the dotted line on STEM im age .

Figure 6. STEM images captured from a cold rolled DP1000 steel lamella before (a&b) and after (c&d) exposing to the wet H2S gas while sample is kept 10°C below room temperature. The ex posure time is about lOmin. EDS analysis on the corroded samples results in presence of iron and sulfide which is an indication of the formation of iron sulfides as corrosion products.

Figure 7. STEM image recorded from a corroded sample under wet H2S gas flow for ~10 min and 10°C cooler than ambient temper ature. EDS analysis indicates an extensive formation of iron sulfide products. SEM image of this sample before corroding the thin lamella sample with wet H2S gas is illustrated in "d" . Due to magnetic properties of this sample, Pt welds were used to bond the lamella to the membrane for TEM analysis.

Figure 8. TEM images recorded from cold rolled DP100 steel lamella before (a) and after (b) corroding with wet H2S gas by locally cooling the sample area 10°C below room temperature for about 10 min. SAED pattern (inset on "b") and EELS spectra ("c- e") from low loss energy, Fe L2,3 edges and S K-edge are shown on specified regions of images "8a" and "8b".

Fig. 9 shows an experimental set-up, in which small droplets 18 are present on the sample 16 located on the thin part of the lower membrane 13b if the condensation is activated, whereas in between the two membranes the majority is gas 17. Since the gas scatters about 10 ³ times less, the effect of this gas is rela tively small and one can allow a relatively large distance be tween the membranes 13,14, which relaxes strongly the need for a very precise control over the distance between the membranes, which would be needed is case of a nanoreactor fully filled with a liquid.

Fig. 10 shows an experimental set-up in which hydrophobic coating strips 19 are deposited on the surface of the sample 16. The effect of the strips is that the liquid droplets 18 are con fined. The smaller the width of the naked sample surface the less high the droplet will be, thus allowing control over the height of the liquid.

Fig 11. Experimental set-up with hydrophobic stripes 19 to control the height of the liquid layer on the surface and col lectors 20 that have an affinity to trap the corrosion products 21.

Fig. 12 shows an experimental gluing set-up. Because the top chip 11 is less wide than the bottom chip 6 a glue line 22 can be easily applied for instance with a single wire and the glue can be so viscous that the glue does not penetrate deep between the two chips. A spacer 40 controls the distance between the two chips .

Fig. 13a shows an experimental set-up in which hydrophobic stripes 19 and a corrosion product collector 20 are present. The corrosion can occur on the pristine surfaces 16a of the sample 16. Collection of the corrosion products 21 on the collector re quires that a liquid film is formed over the whole surface and that by controlled evaporation the liquid film such that the liquid film retracts ending on the corrosion product collector. In figure 14b the hydrophobic stripes are progressively narrower on one side to allow larger droplets on that side to steer the evaporation front towards the corrosion product collector 20.

Figures 14 show a typical shape of a sample lamella with a rim 23 to provide strength. If the rim has a pristine surface and the rest of the sample is coated as in Figure 14b, hydrogen can only absorb on the rim and can subsequently migrate to the thin area 16b of the lamella such that hydrogen induced cracking can be investigated. In Fig. 14a hydrophobic stripes are pre sent. In Figure 14c a large part of the lamella is coated with an amorphous material 19 that is not or poorly penetrable for corrosive components. Only the edge 16c of the lamella is pris tine such that corrosion can only start on the edge 16c and can proceed inwards in a direction that is largely perpendicular to the electron beam 25. This provides the best imaging condition for TEM analysis of the moving corrosion front 24.

Figure 15a shows a layout of the present nanoreactor with three membranes 33,35,37, each membrane having a thin part

34,36,38 respectively. Further cooling elements 2 and a gas vol ume 17 is shown. Figure 15b shows a layout with three membranes in which the top 41 and bottom 42 ones are relatively small and consist only of a thin membrane, which is in size comparable to the thin area (specimen area) 34 of the middle membrane. The latter contains also a thicker part 38 and contains also some holes to allow an equal pressure on both sides of the middle membrane .