In this study, we explored an experimental method to control the grain size during the crystallization of NiTi amorphous thin ﬁlms. A simple mathematical treatment of the Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory generated a simple expression for the grain size, which depends only on temperature and time of crystallization. Real-time in situTEM methods were adopted to eﬀectively capture such information. By capturing the values of nucleation and growth at diﬀerent temperatures, we are able to solve the equation derived from the JMAK theory. This generated a powerful microstructure map, which can provide annealing conditions (time and temperature) for a desired grain size. Our preliminary data also conﬁrms that the samples produced with diﬀerent grain size follow the
AuNRs with different ARs were investigated by in-situTEM heating. The results illustrated a structural change of AuNRs with increasing temperature, as shown in figure 3. The aspect ratio clearly started changing, albeit with only a small decrease, at relatively low temperatures ca. 100ºC. More significant changes were observed at higher temperatures, with the rod length decreasing and the rod width increasing. The rate of change of AR, the slope of the graph in figure 3(b), was large for temperatures up to 300ºC and then reduced and became relatively constant at higher temperatures. For temperatures ˃600ºC, particles became increasingly spherical for all rods monitored. There were some variation in results with some rods exhibiting a significant change in AR at high temperatures, e.g. < 700ºC for rods 1, 2 and 3.
The development of advanced computational methods used for predicting performance lifetimes of materials exposed to harsh radiation environments are highly dependent on fundamental understanding of solid-radiation interactions that occur within metal components. In this work, we present successive and concurrent in situTEM dual-beam self-ion irradiation of 2.8 MeV Au 4+ and implantation of 10 keV He 1+ , utilizing a new facility at Sandia National Laboratories. These experiments, using a model material system, provide direct real-time insight into initial interactions of displacement damage and ﬁ ssion products that simulate damage from neutron exposure. In successive irradiation, extensive dislocation loop and stacking fault tetrahedra damage was formed and could be associated with individual ion strikes, but no evidence of cavity formation was observed. In contrast, concurrent irradiation to the same dose resulted in the onset of cavity formation at the site of a heavy-ion strike. This direct real-time observation provides insight into the complex interplay between the helium and vacancy dynamics.
To conﬁrm whether or not the SV actually occurs in bcc solid-solution, the following experiments were performed by using HVEM: (1) the melt-spun specimen was irradiated at room temperature for the introduction of defects in the bcc solid-solution, and (2) the specimen with the irradiation defects was in situ annealed from room temperature to 873 K according to a stepwise temperature-increase program (a temperature vs. time diagram is shown in Fig. 5). The change in microstructure of bcc solid-solution phase was investigated in situ using HVEM. Above mentioned in situ experiment has advantages compared with that using conventional TEM; (1) the enhancement of thermal diffusion via introduced defects may stimulate SV at the temperature lower than 873 K. An amorphous phase is not a thermal equilibrium phase, and changes to crystalline phases at the crystallization temperature. The lower the onset temperature of SV is, the longer the lifetime of an amorphous phase is. The enhance- ment of atomic diffusion at temperatures lower than 873 K may be effective for detecting SV by in situTEM if SV is realistic. (2) Blatter et al. pointed out that SV ability of the Ti 60 Cr 40 alloy was strongly related with the sample
The objective of this study is to determine the validity of in situ transmission electron microscopy (TEM) micro-compression of pillars in as received and ion- irradiated Fe-9%Cr oxide dispersion strengthened (ODS) alloy. The growing role of charged particle irradiation in the evaluation of nuclear reactor candidate materials requires the development of novel methods to assess mechanical properties in near- surface irradiation damage layers just a few micrometers thick. In situTEM mechanical testing is one such promising method, yet size effects must be understood to validate the technique. In this work, a micro-compression pillar fabrication method is developed. Yield strengths measured directly from TEM in situ compression tests are within expected values, and are consistent with predictions based on the irradiated
A thin film of ordered α’-FeRh alloy (~ 55 nm thick) was grown epitaxially on a clean (001) MgO substrate (~ 500 µm thick) by conventional DC magnetron sputter co-deposition, as described in . The sample was fixed onto a glass slide (FeRh film face-down) using Kemdent® wax and cut into ~ 1.5 mm square sections using a circular diamond saw. The glass slide was then placed on a hot plate to melt the wax and release the square sections, which were cleaned with acetone to remove any waxy residue. A dried square section was then fixed, again with FeRh film face-down, onto a Pyrex® specimen stub using ethyl cyanoacrylate (Loctite® ‘super glue’) and cured at 80°C for 2 hours. It was then mounted onto a tripod polisher and thinned to ∼ 5 µm with a Struers® Labopol wheel polisher and diamond paper, using progressively finer grades (30 – 1µm grit). An Omniprobe® Cu grid was then overlaid onto the sample and fixed using an epoxy adhesive (Araldite®) and cured at 80◦C for 12 h. The stub / sample / Cu-grid combination was then immersed fully in acetone for 2 hours to dissolve the ‘super glue’ and release the remaining thinned sample / Cu-grid combination. The sample was then inserted in a FEI Dual Beam FIB Nova 200 for transfer to a DENSsolutions® MEMS-based heating chip (mounted on the custom SEM stub with 45° faces), as well as final thinning of the FeRh planar sample for the purpose of in situTEM investigation. The FIB instrument comprises a 30 kV electron (e - ) column for SEM and a 30 kV sidewinder ion column (Ga + ), mounted at 52° to the e - column. The system is equipped with an in situ micro-manipulator and a gas injector for the in situ deposition of Pt. Magnetic imaging was performed using a JEOL ARM-200cF TEM in Lorentz mode and Fresnel fringes in over- or under-focus provides contrast from in-plane DWs.
the decomposition temperature of this carbon layer, metal particles suddenly evaporate or sublimate. The introduction of oxygen gas is indispensable for eliminating of organic molecules or polymer layers on the particle surfaces at lower temperatures. Carbon layers on the surface have already been reported to prevent the structural changes of ﬁne particles and nanoparticles of metals whose melting temperatures are lower than that of nickel, such as gold, silver, and copper. 13,14) However, the urchin type nickel ﬁne particles with the nanoneedles prepared in this study were synthesized in the absence of organic stabilizing molecules, and thus, no carbon layer was formed on the particle surfaces at high temper- atures. Therefore, the structural changes of these nickel ﬁ ne particles at high temperatures can be observed by in situTEM without the introduction of oxygen gas. Unlike noble metals such as gold or platinum, nanoparticles of the early transition metals can be readily oxidized with the introduc- tion of oxygen gas at high temperatures. The structural changes are affected by the formation of metal oxides. Our urchin structured nickel ﬁne particles were good candidates for observing the structural changes of anisotropic metallic nickel with a high aspect ratio in the metallic state.
(4) and at 1023K (5). However no bubble greater than 10 nm (spatial resolution limit) was observed for an irradiation temperature lower than 343K in similar glass (6). Concerning the actinide-doped glasses, two works can be cited. Inagaki et al. have observed by SEM some pores of around 0.2 µm diameter in a Cm- doped glass of type R7T7 at a helium content of around 0.3 at.% (7). On the contrary, no pores or bubbles greater than 10 nm were observed in a SON68 curium-doped glass after the same level of alpha decay (and thus helium content (8)). The conclusions of helium implantation experiments in glasses are also contradictory. Three studies mention the possibility of bubble formation without annealing for helium concentrations of around 2 at.% (9). On the other hand, for higher helium content (3-4 at.%) another study did not reveal any bubbles (10), either by TEM or by SAXS. Finally, very recently Bes et al. have performed the first in-situTEM helium implantation in SON68 glass and observed the nucleation of nanometer-sized bubbles at 143K at a local helium concentration of around 0.1 at.% (11). This disparity of results in the literature could be linked to several factors such as the synergetic effect of temperature, radiation damage and helium content. Moreover due to the high helium diffusivity (D = 10.2 ± 1.8 x 10 -18 m 2 .s -1 at room temperature (11)) it is vitally important to be very careful during each step of the experimental process (storage conditions, implantation and irradiation temperature ...). Thus in-situ experiments appear to be the best way to determine the nucleation and growth mechanisms of helium bubbles. In the present work, we have studied the effect of implantation fluence on bubble evolution using in-situTEM investigations.
pressure in the main gas line was regulated by a Back Pressure Controller (BPC, Bronkhorst) ‘TEM holder’, and the exhaust of the system was pumped by a dia- phragm pump. To direct a portion of the gas mixture to the in situ holder, a T-piece was placed before the BPC, connected to the inlet of the holder. The capillaries directly connected to the in situTEM holder were made of PEEK (poly ether ether ketone, a non-conducting material) to ensure electrical insulation of the holder when inserted into the TEM CompuStage. Vibration isolation was implemented by clamping the PEEK capillaries in-between two heavy metal slabs, reducing the mechanical noise introduced by the pumps running continuously. The exhaust capillary of the in situTEM holder was directly connected to a tur- bomolecular pump. This setup established a pressure diﬀerence between the inlet and the exhaust of the holder, resulting in gas ow through the narrow nano- reactor channel. The pressure inside the nanoreactor channel was dened as half
Figure 3b shows the result of an experiment in which a single-crystal Cu foil (with a <100> surface normal) has been implanted with 12 keV He at at room temperature. The bubble lattice can be clearly seen and closely resembles those reported by Johnson and Mazey for He implanted into bulk copper at 30 keV . The in-situ experiments also confirm that the bubbles first nucleate in a disordered arrangement which changes to an ordered one under continued irradiation. This process can be seen in Figure 3c) where a degree of ordering can be seen to develop on progressing to higher fluences (panel (i) to panel (iii)). The ordering can be seen as an alignment of bubbles approximately parallel to the black line in panel (iii). In this image sequence, the two bubbles indicated by the arrows can be seen to move closer to alignment with five bubbles below them in the image that have become aligned by the fluence in panel (iii). The analysis of many such image sequences is currently underway in our laboratories and will be compared with images generated from software such as that developed by Evans [13,14] to model the effects of 1-D and 2-D interstitial diffusion on bubble ordering. By direct comparison of the experimental and theoretical dynamics of bubble lattice formation we thus hope to
current through the coils. The 1st magnet is to generate the magnetic ﬁeld applied to the sample. Electron beam used for TEM observations are deﬂected by this ﬁeld. The 2nd magnet below the sample is to correct this deﬂection. The TEM image can be prevented from fatal deformation and move- ment by using this double-layer electromagnet. While no other details are given in Fig. 1(a) for the sake of simplicity, four electric terminals made of Pt are arranged in the chinks of the 1st magnet. Four-probe measurements of resistance are possible by using these terminals. Figures 1(b) and 1(c) are photographs of the TEM holder that was observed from the back. This is a side entry holder designed for a JEOL JEM- 200CX electron microscope. The sample cover is open in Fig. 1(b), and the 1st magnet can be seen. The sample on the substrate is placed by facing it against the magnet and ﬁxed by closing the sample cover. When the sample cover is closed (Fig. 1(c)), the contact pads of the sample are automatically made contact with the electrodes. The 2nd magnet is placed on the sample cover.
Understanding the fundamental processes taking place at the electrode-electrolyte interface in batteries will play a key role in the development of next generation energy storage technologies. One of the most fundamental aspects of the electrode-electrolyte interface is the electrical double layer (EDL). Given the recent development of high spatial resolution in - situ electrochemical fluid cells for scanning transmission electron microscopy (STEM), there now exists the possibility that we can directly observe the formation and dynamics of the EDL. In this paper we predict electrolyte structure within the EDL using classical models and atomistic Molecular Dynamics (MD) simulations. Classical models are found to greatly differ from MD in predicted concentration profiles. It is thus suggested that MD must be used in order to accurately predict STEM images of the electrode-electrolyte interface. Using MD and image simulation together for a high contrast electrolyte (the high atomic number CsCl electrolyte), it is determined that, for a smooth interface, concentration profiles within the EDL should be visible experimentally. When normal experimental parameters such as rough interfaces and low-Z electrolytes (like those used in Li-ion batteries) are considered, observation of the EDL appears to be more difficult.
102:& Motivation&for&in#situ#investigations&into&tribology&at&the&nanoscale& In addition to all the complexities of tribological contacts that were discussed in Sect. 1-1, the contacting interface is – by definition – buried between two bodies, which further complicates observation and investigation. As will be discussed in Chapters 2 and 3, this problem is often solved by performing a contact or sliding test using one apparatus (a pin-on-disk tribometer or an AFM, for example) then removing one or both surfaces from the apparatus and taking them to an external microscope or spectroscope for analysis, typically exposing them to air or some alternate environment in the process. Investigations using this ex situ investigation approach have yielded very useful information, but are fundamentally limited by not knowing which phenomena were caused by sliding, and which others occurred during the removal, transfer, and insertion into the subsequent characterization tool. Additionally, once removed from the
TEM dark ﬁeld did not favour two phases coexisting, and a BCC superlattice with twice the lattice parameter of the fundamental FCC lattice was suggested . The fourth structure of Nd-rich phases is a HCP structure with the lattice parameters a ¼ 0:383 nm and c ¼ 0:600 nm , which was proposed arising from the decomposi- tion of matrix phase (Nd 2 Fe l4 B) due to the
At the present time, a majority of in-situTEM video capture is performed with charge-coupled device (CCD) cameras. High-performance commercially available CCD cameras have readout rates in the range of a few tens of MB/s , which under appropriate binning conditions can provide video acquisition rates ( ∼ 30 ms acquisition rate) . Important progress has been made recently by the introduction of the direct detection camera (DDC), which utilizes CMOS technology, and thus provides an order of magnitude increase of the readout rate— it has been demonstrated that these cameras can be operated in the ms range . Importantly, DDCs pro- vide a new approach by directly recording the incoming electrons without the use of a scintillator. By avoid- ing the electron-to-light conversion, the DDC achieves unprecedented sensitivity. While improving temporal res- olution, the DDC also enables electron dose reduction, another key challenge for in-situTEM imaging. The lim- itation in implementing this technology (or any other hardware-based acquisition system), however, is that as the frame rates increase, reading out the images becomes a challenge—the issue then becomes a data transfer prob- lem rather than an electron detection problem.
In order to observe the microstructural change during heating in direct, we performed the in-situTEM observation. Figure 3 shows representative images showing of micro- structural change of as deposited a-Si/Al bilayer during in-situ heating TEM observation. The temperature is reached up to 533 K. A time interval from Figure 3(a) to (f) is approximately 15 s, respectively. In these ﬁgures, the black contrast can be observed in the vicinity of the interface between Al and a-Si and grows in the a-Si layer. In addition, we conﬁrmed that the further heating enhances the growth of the black contrast to the lateral direction in the initial a-Si layer.
The in-situTEM annealing of disordered zones created by 100 keV Au + ion irradiation shows that these zones are sensitive to electron beam irradiation and anneal under electron energies not sufficient to elastically displace lattice atoms, i.e. subthreshold energies for both constituent atoms In and P.
these films to Pt tips decreases from Pt-rich to Si-rich films. To ensure precise stoichiometric control, it is neces- sary to understand the synthesis mechanism at the atomic scale and the influence of initial precursor concentration in the ensuing chemical transformation. In situTEM experi- ments have opened up new frontiers for gaining such un- derstanding. 19 ‒ 23 Here, we use in situTEM to introduce two
The reduction of metal complexes inside SWCNTs is an interesting reaction because ultrathin metal nanowires, which are difﬁcult to synthesize in a normal bulk-scale reactor, can be formed via self-assembly. In particular, reduction reactions of metal halides are suitable targets for in situTEM observation since metal halides are highly sensitive to electron beam (e-beam) irradiation 8) and heat treatment; 9) metal halides are easily reduced to metal under high-dose e- beam irradiation or elevated temperature. TEM observations