In situ XRD

Fig. 9. Schematic drawing of the apparatus for combined QEXAFS/XRD in situ experiments [adapted from Clausen et al. (53)].

Fig. 10. Apparatus for combined DEXAFS/XRD in situ experiments. [Adapted with permission from Nature, Ref. 53. Copyright 1991 Macmillan Magazines Limited.]...

The catalysts were characterized by BET surface area measurement, XRD, in-situ CO2 H2 chemisorption measurements, and Temperature Programmed Reduction (TPR). CO2 hydrogenation was carried out in a fixed bed flow reactor made of stainless steel. Prior to the activity studies, the catalysts were reduced in 99.99 % H2 flow at 723K for 12hrs. After this, the reaction gas (H2/CO2 = 3) was introduced into the reactor at 573K at 10 atm. The gas phase effluents were analyzed by on-line GC. 

Elsewhere we have summarised how XAFS or combined XAFS-XRD in situ studies have elucidated the nature of the catalytically active sites in several oxidic systems ... 

Many other examples have been described elsewhere and several new types of catalyst are currently under investigation using either XAFS alone or combined XAFS/XRD (in situ) procedures /... 

It has become possible to imderstand Si s lithiation/delithiation mechanisms due to the use of ex situ and in situ methods. X-ray diffraction (XRD) in situ, nuclear nagnetic resonance (NMR), microscopy techniques in... 

There are many techniques for the experimental observation in catalytic investigation, such as BET and chemisorptions, XRD in situ), EPR, SEM, VPR, TEM, TPD, TPR in situ), EMPA, TG, AES, GC, LEED, EELS, EXAFS in situ), XPS (ESCA), Mossbauer in situ), IR (FTIR) in situ), RAM and so on. Many of these techniques require extra-high vacuum conditions and can only investigate crystal faces of solids or model catalysts, which have a large difference with practical catalytic systems and catalysts. 

Fig. 8.11 XRD in situ reduction of 8 % Ni/aAl203 catalyst with time and different reduction temperatures...

XRD offers unparalleled accuracy in the measurement of atomic spacings and is the technique of choice for determining strain states in thin films. XRD is noncontact and nondestructive, which makes it ideal for in situ studies. The intensities measured with XRD can provide quantitative, accurate information on the atomic arrangements at interfaces (e.g., in multilayers). Materials composed of any element can be successfully studied with XRD, but XRD is most sensitive to high-Z elements, since the diffracted intensity from these is much lar r than from low-Z elements. As a consequence, the sensitivity of XRD depends on the material of interest. With lab-based equipment, surface sensitivities down to a thickness of -50 A are achievable, but synchrotron radiation (because of its higher intensity)... 

The second approach is to study real catalysts with in situ techniques such as infrared and Mossbauer spectroscopy, EXAFS and XRD, under reaction conditions, or, as is more often done, under a controlled environment after quenching of the reaction. The in situ techniques, however, are not sufficiently surface specific to yield the desired atom-by-atom characterization of the surface. At best they determine the composition of the particles. 

STM, SXRD, and X-ray reflectivity are excellent techniques for in situ studies of metal and alloy deposition. XRD is also useful for determining the crystal orientation of deposits. 

FIGURE 27.3 Spectroelectrochemical cell for in situ XRD on battery electrode materials. 

In situ XRD spectra were collected on beam line X18A at the National Synchrotron Light Source (NSLS) located at Brookhaven National Laboratory (BNL). The X-ray wavelength (X) was 1.195 A. The step size of the 29 scan was 0.02° in the regions with Bragg reflections and 0.05° in the regions without reflections. The XRD spectra were collected in the transmission mode (Liu et al., 2004). 

FIGURE 27.5 In situ XRD patterns of an Al203-coated LiCo02 cathode during the first charge from 3 to 5.2 V at the 12-h rate. The three panels from left to right show spectra in (003), the (101) to (105), and (107) to (113) regions, respectively. (From Liu et al, 2004, with permission from The Electrochemical Society.)... 

Experimentally, different structure- and surface-sensitive techniques such as in situ scanning tunnelling microscopy (STM), in situ X-ray diffraction (XRD), transition electron microscopy (TEM), and in situ infrared (IR) spectroscopy have been... 

The effects of tin/palladium ratio, temperatnre, pressnre, and recycling were studied and correlated with catalyst characterization. The catalysts were characterized by chemisorption titrations, in situ X-Ray Diffraction (XRD), and Electron Spectroscopy for Chemical Analysis (ESCA). Chemisorption studies with hydrogen sulfide show lack of adsorption at higher Sn/Pd ratios. Carbon monoxide chemisorption indicates an increase in adsorption with increasing palladium concentration. One form of palladium is transformed to a new phase at 140°C by measurement of in situ variable temperature XRD. ESCA studies of the catalysts show that the presence of tin concentration increases the surface palladium concentration. ESCA data also indicates that recycled catalysts show no palladium sulfide formation at the surface but palladium cyanide is present. 

The catalysts were characterized by chemisorption titrations, in situ XRD and ESCA. 

In situ XRD stndies of thermally and chemically induced transformations were monitored with a totally automated diffractometer-micrometer system (9). Samples were thermally ramped in 5°C increments from 30 to 160°C, maintained at 160°C for 0.5 hr, and then cooled in 5°C increments to 30°C under 500 torr hydrogen. 20 scans were obtained after each temperatnre increment. The individnal scans conld be stacked to show the temperature evolution of the stracture. 

We report the discovery of a new Pd-Sn catalyzed hydrogenolysis reaction to produce thiol product in high yields. The relationship between catalyst activity and surface characterization (chemisorption, ESCA, and in situ temperature-dependent XRD,) has aided om understanding of the reasons why these catalysts are sulfur resistant, extremely active, and activated at certain temperatures and pressures. The predominant mode of deactivation appears to be the formation of Pd-CN species rather than the formation of Pd-S species on the surface of the catalyst. 

XRD was used to investigate the spacings of silicate layers of montmorillonite (from 1.9 to 4nm) in PP/montmorillonite (MMT) nanocomposites prepared by in situ graft-intercalation in the presence of acrylamide [331]. Similarly, XRD and TEM were used to study the dispersibility of PP/MMT nanocomposites prepared by melt intercalation using organo-montmorillonite and conventional twin screw extrusion [332]. Various delaminated and intercalated polymer (PA6, PA 12, PS,... 

Platinum complexes [PtCl2(diphosphine)] and [PtCl(SnCl3)(diphosphine)] of the ferrocenyl diphosphine ligands (35a), (35b), and (36) have been synthesized. Complexes [PtCl2(35)] and [PtCl2(36)] have been structurally characterized by XRD. Both the preformed and the in situ catalysts have been used in the hydroformylation of styrene.112... 

The experimental tools for this research were chronopotetiometry (galvanostatic cycling),25 atomic force microscopy (AFM),26,27 scanning electron microscopy (SEM), and X-ray diffraction (XRD).21,25 It should be mentioned that the AFM imaging was conducted in-situ under potential control and in a special homemade glove box filled with highly pure argon atmosphere. This system has been already described in detail in the literature.28... 

In this paper we present results from independent studies on the stage 2 to stage 1 transition area that show some unexpected features (anomalies). The results are obtained by electrochemical impedance spectroscopy (EIS), entropy measurements (AS(x)) and in situ x-ray diffractometry (XRD). The aim is to understand the mechanism of stage transition dealing with the observed anomalies. 

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