Bulk Characterisation

Scanning Probe microscopy techniques are extremely useful for analysing surfaces, but cannot lead to bulk information. They will be used each time surface properties are important, i.e. when surfaces are used for themselves (tribological applications, adhesion, etc.). However, in some cases, the study of transport phenomena (such as thermal or electrical conductivity) by modified AFM may lead to bulk characterisation such as the formation of a percolating nanotube network for instance. 

Turning to fcc(lll) surfaces, let us first compare the bulk properties of the alloys under consideration (Table 2). Stoichiometric PtFe, PtCo and PtNi form LIq phases in the bulk, characterised by an increase of the number of unlike nearest neighbours (8) with respect to an fee random alloy with 50% Pt (6 unlike NN). PtCu forms the peculiar LI, ordered phase, where the number... 

Quantitative structure-activity or structure-performance (property) relationships (QSAR and QSPR respectively) are of increasing interest in a wide diversity of technology areas. With some notable exceptions, most QSA(P)R studies associated with heterogeneous catalysis are restricted to zeolite-based catalysts. The reasoning is simple -the well defined 3-D structures, of molecular-sieve zeolites, are a reasonable representation of the catalyst "surface", hence bulk characterisation provides information on the catalyst. It is for a similar reason that the majority of modelling studies involves zeolites and zeotypes. 

Scanning transmission X-ray microscopy has been used most extensively for polymer research, e.g. for bulk characterisation of polymeric materials with chemical sensitivity at a spatial resolution of 50 nm [739], STXM has also been used for the analysis (morphology, size distributions, spatial distributions and quantitative chemical compositions) of copolymer polyol-reinforcing particles in polyurethane [740], Pitkethly [741] has reviewed the role of microscopy in the evaluation of fibre/matrix interfacial properties and micromechanical characteristics of fibre-reinforced plastic composites. 

Basic separator types can be characterised in two ways, firstly by main function (bulk or mist separation) and secondly by orientation (either vertical or horizontal). 

In 2004, Dieguez et al. reported the development of novel C2-symmetric dithioether ligands derived from the corresponding binaphthyl or biphenanthryl diols. Thus, various (i )-binaphthyl dithiols substituted by alkyl groups on the sulfur atom in order to increase the steric bulk were synthesised, and the corresponding mononuclear cationic Ir(I) -cyclooctadiene complexes were prepared and characterised (Scheme 8.20). NMR studies demonstrated that, in all cases, the coordination of the ligands proceeded with complete stereoselectivity at the... 

Alternative approaches consist in heat extraction by means of thermal analysis, thermal volatilisation and (laser) desorption techniques, or pyrolysis. In most cases mass spectrometric detection modes are used. Early MS work has focused on thermal desorption of the additives from the bulk polymer, followed by electron impact ionisation (El) [98,100], Cl [100,107] and field ionisation (FI) [100]. These methods are limited in that the polymer additives must be both stable and volatile at the higher temperatures, which is not always the case since many additives are thermally labile. More recently, soft ionisation methods have been applied to the analysis of additives from bulk polymeric material. These ionisation methods include FAB [100] and LD [97,108], which may provide qualitative information with minimal sample pretreatment. A comparison with FAB [97] has shown that LD Fourier transform ion cyclotron resonance (LD-FTTCR) is superior for polymer additive identification by giving less molecular ion fragmentation. While PyGC-MS is a much-used tool for the analysis of rubber compounds (both for the characterisation of the polymer and additives), as shown in Section 2.2, its usefulness for the in situ in-polymer additive analysis is equally acknowledged. 

Bulk property detectors function by measuring some bulk physical property of the mobile phase, e.g., thermal conductivity or refractive index. As a bulk property is being measured, the detector responses are very susceptible to changes in the mobile phase composition or temperature these devices cannot be used for gradient elution in LC. They are also very sensitive to the operating conditions of the chromatograph (pressure, flow-rate) [31]. Detectors such as TCD, while approaching universality in detection, suffer from limited sensitivity and inability to characterise eluate species. 

CPAA measures the characteristic decay radiation of the radionuclides produced by the incident charged particles. The technique has been widely applied in the determination of trace elements concentrations in bulk samples, but it also has possibilities for surface characterisation, provided the thickness of the layer to be characterised is less than the range of the charged particles employed. 

Presently the effective role of sulphur additive is not well explained because sometimes activation or deactivation phenomena are observed. Such a versatile behaviour is well-illustrated over noble metal-based catalysts particularly when they are dispersed on perovskite supports [111]. The catalytic performances of a prereduced Pt/LaCo03 in H2 at 450°C are illustrated in Figure 10.13a. After preactivation in H2 subsequent bulk and surface characterisation highlighted an extensive reduction of the perovskite... 

Major effort has therefore been applied to study of the helical channels by non-erystallographic methods in order to discriminate unambigously between the likely models. This has resulted in the gramicidin ion channel not only being the first clearly identified example but also the most characterised in structural terms. The bulk of... 

One system studied by the authors(3) used LG56 triol which had been characterised by molar-mass as well as end-group determinations. The data for the samples used are given in Table III, indicating a true number-average functionality (fn) of between 2.95 and 2.99. The triol was reacted with HDI in bulk (see Figure 1) and at various dilutions in benzene, and values of Nr and ac determined. To estimate functionality from ac, equations... 

In this paper, the bulk material was obtained by impregnation of the silica host with GFP solution and nanosised by sonication, preserving the features of both the biomolecule and the mesoporous structure. An exhaustive physical chemical characterisation of the nanosized materials was performed by structural (X-Ray Diffraction, Transmission Electron Microscopy), volumetric and optical (photoluminescence spectroscopy) techniques. 

The effect of D on kp was discussed by Stannett et al. (1979) in some detail, and they concluded that their results, shown as a plot of In kp+ versus 1 ID, agree with Laidler s equation, according to which In kp varies rectilinearly with 1 ID. Their Figure 3 shows results for EVE and IPVE which include their rate-constants for the bulk polymerisations which we now know should be characterised by a first-order rate-constant, and it includes results obtained at a very high concentration of monomer, where the significance of the formal kp+ is far from obvious. Therefore their conclusion cannot be accepted now, and it is clear that the relation between kp+ and D needs to be investigated with a Class A monomer, e.g., isobutene, and at low m. 

An example of a much faster catalyst, equally well characterised is depicted in Figure 16.11. This catalyst gives thousands of turnovers of cis-2-pentene in a few minutes at 25 °C. The electron withdrawing fluoroalkoxides make the metal centre nucleophilic and the steric bulk prevents dimer formation or other degradation reactions. 

Vanadium phosphorus oxides (VPO) are commercially used as catalysts for the s5mthesis of maleic anhydride from the partial oxidation of n-butane. The phase constitution and the morphology of the catalyst are found to be dependent on the preparation routes and the applied solvent [78]. Recently, a method to prepare VPO catalysts in aqueous solution at elevated temperature was reported [79]. In addition to the linear relationship between specific activity and surface area, a small group of catalysts exhibit enhanced activity, which could be due to the combination of a higher proportion of V phases in the bulk of vanadyl pyrophosphate (V0)2P207 catalyst [79, 80]. With high relevance to the catalytic properties, the microstructure characterisation of VPO therefore is of great importance. 

---