Bulk property

The properties of ions in solution depend, of course, on the solvent in which they are dissolved. Many properties of ions in water are described in Chapters 2 and 4, including thermodynamic, transport, and some other properties. The thermodynamic properties are mainly for 25°C and include the standard partial molar heat capacities and entropies (Table 2.8) and standard molar volumes, electrostriction volumes, expansibilities, and compressibilities (Table 2.9), the standard molar enthalpies and Gibbs energies of formation (Table 2.8) and of hydration (Table 4.1), the standard molar entropies of hydration (Table 4.1), and the molar surface tension inaements (Table 2.11). The transport properties of aqueous ions include the limiting molar conductivities and diffusion coefficients (Table 2.10) as well as the B-coefficients obtained from viscosities and NMR data (Table 2.10). Some other properties of 

Thermodynamic properties of ions in nonaqueous solvents are described in terms of the transfer from water as the source solvent to nonaqueous solvents as the targets of this transfer. These properties include the standard molar Gibbs energies of transfer (Table 4.2), enthalpies of transfer (Table 4.3), entropies of transfer (Table 4.4) and heat capacities of transfer (Table 4.5) as well as the standard partial molar volumes (Table 4.6) and the solvation numbers of the ions in non-aqueous solvents (Table 4.10). The transfer properties together with the properties of the aqueous ions yield the corresponding properties of ions in the nonaqueous solvents. 

Another quantity of interest is the ionic viscosity -coefficient. Equation 2.29, that in aqueous solutions describes the effect of the ion on the structure of the solvent water. Some values of in nonaqueous solvents have been compiled by Jenkins and Marcus [9] and are reproduced in Table 5.7. It should be noted that practically in all the solvents (except light and heavy water), all the Brj values are positive and the ions appear to enhance the structure of the solvent. However, the splitting of the 

Ion MeOH EtOH PrOH EG Me CO PC PA NMP DMP TMU HMPT MeCN DMSO MeNOj PhNOj Py 

There are some data available for the (static) dielectric decranents of salts in non-aqueous solvents in the compilations by Barthel et al. [33,152], Values of the relative limiting decrements, that is, -5le (c =0), in nonaqueous solvents are shown in Table 5.8, where the corresponding values for aqueous salts are also shown for comparison. Note that the linearity of the = f(c) curves breaks down at considerably lower concentrations than in water in solvents of relatively low permittivity, in which ion pairing is expected. This may explain the discrepancies in the values obtained in methanol between the entries in Refs. [152] and [33], 

The electronic or electrical properties of carbons are a most immediate consequence of their structure. The nanostructure anisotropy, and its degree of replication at the macrostructure level, is responsible for the entire range available here, from good conductors to effective insulators [72]. 

Thermal properties most often follow the electronic properties quite closely. For example, thermoelectric power (TEP) studies have revealed the unique semiconductor properties of carbons. In a pioneering and largely neglected study [73,74], Walker and Tietjen had already documented the recently rediscovered [75-79] TEP changes in both flat and curved sp carbons [80]. These can lead to both p- and n-type semiconducting behavior of carbons and thus make possible the fabrication of inter- and intramolecular logic gates, the basic units of 

Optical properties [84,85] of interest for catalytic applications are particularly those that reveal contributions of the inter-band transitions of k-electrons  

Until very recently, interest in the magnetic properties [98-101] has been focused on diamagnetic and paramagnetic susceptibility issues in conjunction with the electronic properties of carbons [102,103], In fact, in the early development of electron spin resonance as an analytical technique, carbon materials played a very prominent role [104-110], Interestingly, the pioneering investigations of carbon catalyst supports by Walker, Vannice, and co-workers [111-115] also included a magnetic susceptibility study [116,117], in which the effective electron mass of the delocalized electrons and the Fermi level were estimated  

Among the mechanical properties of greatest practical impact on catalysis applications is the attrition and crushing resistance of powdered or granular activated carbons, the most commonly used catalytic carbon materials, versus that of activated carbon fibers (ACFs) or of other, less-surface-active carbons (e.g.. 

In this section, we describe the applications of the density functional pseudopotential scheme to the bulk properties of solids. Since this is a very active area, only specific prototypical calculations are featured to illustrate major subareas. The results on semiconductors were calculated using the plane wave method whereas results on transition metals and insulators were obtained either using the mixed basis approach or the LCAO approach. 

This leads to a major enhancement in the precision of a calculation. 

The mechanical consequences of defect populations are less frequently considered than optical or electronic aspects, but they are of importance in many ways, especially when thin films or nanoparticles are considered. 

The conductometric titration shown in Fig. 6 (adapted from Ref. [135]) exhibits the expected conductivity increase for LiBF4 and LiS03CF3 solutions in PC / 5-crown-5 mixtures at 25 °C, i.e., for salts which are known to be strongly associated despite the relatively high permittivity of the solvent. 

It is worth mentioning that single-ion conductivities of lithium ions and anions at infinite dilution, and transference numbers of ligand-solvated lithium ions estimated therefrom, increase due to the replacement of more than one (generally four) solvent molecules. Table 6 demonstrates this beneficial feature. 

In continuance of our quest for the source of the surprising and unexpected catalytic activity shown by gold, we must now consider its physical 

Its optoelectronic properties are also unpredictable by extrapolation from its antecedents in Group 11. Its electrical resistivity is greater than that of silver (see Table 2.1), and its colour more closely resembles that of copper its optical absorption in the visible region of the spectrum is due to the relativistic lowering of the gap between the 5d band and the Fermi level, without which it would be white like silver and have the same propensity to tarnish and corrode.27 Polycrystalline gold surfaces have been characterised by Auger electron spectroscopy (AES). 

Gold is extremely malleable 1 g can be beaten into a foil of area 1 m2, the thickness of which is less than 250 atomic diameters. The same amount can also be drawn into 165 m of wire that is 20p,m in diameter.25 These characteristics, together with many others, were discussed in detail in a lengthy but fascinating paper by Michael Faraday in 1857.47 

Gold forms alloys and intermetallic compounds with many other elements48 (Section 2.6). It has no apparent ability to dissolve or occlude simple gases, although there is indirect evidence that hydrogen atoms can diffuse through it if formed on its surface by dissociation of molecules.49 

If the cut is made at a slight angle to the plane, the resulting surface comprises a series of flat terraces separated by steps of monatomic height.51,52 These stepped surfaces have been widely investigated, because of their supposed closer resemblance to the small metal particles found in 

The order parameter associated with the SmC - SmA transition can be written as = 

Here t =(T-T )/T ) is the reduced temperature with being the transition temperature. The coefficients a and c are usually positive constants. For a continuous SmA-SmC transition b 0 and for a first order one b 0. The special case, b = 0, is the mean-field tricritical point. Huang and Viner [55] proposed a dimensionless parameter tQ=b l(ac) to describe the crossover temperature between the mean-field tricritical region (111 1q) the ordinary mean- 

The width of the critical region may be estimated from the following Ginzburg criterion [67]  

Due to the unusually large value of the mean-field heat capacity jump (AC 10 erg/ cm K), the critical region of the SmA-SmC 

In light of the abnormal behavior of ultrasound velocity and attenuation near the SmA-SmC transition [70, 71], Benguigui and Martinoty [72] advanced a theory to explain the experimental data. They concluded that the Ginzburg crossover parameter Gq) determined by the static properties, (e.g. heat capacity) could be much smaller than that obtained from the measurement of the elastic constant. However, a quantitative comparison between the theoretical prediction and the experimental data is still lacking. 

---

To define the thennodynamic state of a system one must specify fhe values of a minimum number of variables, enough to reproduce the system with all its macroscopic properties. If special forces (surface effecls, external fields—electric, magnetic, gravitational, etc) are absent, or if the bulk properties are insensitive to these forces, e.g. the weak terrestrial magnetic field, it ordinarily suffices—for a one-component system—to specify fliree variables, e.g. fhe femperature T, the pressure p and the number of moles n, or an equivalent set. For example, if the volume of a surface layer is negligible in comparison with the total volume, surface effects usually contribute negligibly to bulk thennodynamic properties. 

Much of the work done on metal clusters has been focused on the transition from cluster properties to bulk properties as the clusters become larger, e.g. the transition from quantum chemistry to band theory [127]. 

Luengo G ef a/1997 Thin film rheology and tribology of oonfined polymer melts oontrasts with bulk properties Macromolecules 30 2482-94... 

Computer simulations act as a bridge between microscopic length and time scales and tlie macroscopic world of the laboratory (see figure B3.3.1. We provide a guess at the interactions between molecules, and obtain exact predictions of bulk properties. The predictions are exact in the sense that they can be made as accurate as we like, subject to the limitations imposed by our computer budget. At the same time, the hidden detail behind bulk measurements can be revealed. Examples are the link between the diffiision coefficient and... 

Clusters are intennediates bridging the properties of the atoms and the bulk. They can be viewed as novel molecules, but different from ordinary molecules, in that they can have various compositions and multiple shapes. Bare clusters are usually quite reactive and unstable against aggregation and have to be studied in vacuum or inert matrices. Interest in clusters comes from a wide range of fields. Clusters are used as models to investigate surface and bulk properties [2]. Since most catalysts are dispersed metal particles [3], isolated clusters provide ideal systems to understand catalytic mechanisms. The versatility of their shapes and compositions make clusters novel molecular systems to extend our concept of chemical bonding, stmcture and dynamics. Stable clusters or passivated clusters can be used as building blocks for new materials or new electronic devices [4] and this aspect has now led to a whole new direction of research into nanoparticles and quantum dots (see chapter C2.17). As the size of electronic devices approaches ever smaller dimensions [5], the new chemical and physical properties of clusters will be relevant to the future of the electronics industry. 

Colloidal particles can be seen as large, model atoms . In what follows we assume that particles with a typical radius <3 = lOO nm are studied, about lO times as large as atoms. Usually, the solvent is considered to be a homogeneous medium, characterized by bulk properties such as the density p and dielectric constant t. A full statistical mechanical description of the system would involve all colloid and solvent degrees of freedom, which tend to be intractable. Instead, the potential of mean force, V, is used, in which the interactions between colloidal particles are averaged over... 

AS )) the function to be minimized is exp (-AS p/R)/ [36]. A quantitative expression for AS can be found by noting that the A monomers in an unstrained loop (N > 4) have essentially two possible confonnations, pointing either inwards or outwards. For loops smaller than a critical size the inward ones are in an apolar environment, since the enclosed water no longer has bulk properties, and the outward ones are in polar bulk water hence the electrostatic charges on... 

On one hand, there are the dielectric properties, which are especially important for polai solvents like water. Bulk properties can, on the other hand, only be modeled by using a supermolecule approach with explicitly defined solvent molecules. 

The explicit definition of water molecules seems to be the best way to represent the bulk properties of the solvent correctly. If only a thin layer of explicitly defined solvent molecules is used (due to hmited computational resources), difficulties may rise to reproduce the bulk behavior of water, especially near the border with the vacuum. Even with the definition of a full solvent environment the results depend on the model used for this purpose. In the relative simple case of TIP3P and SPC, which are widely and successfully used, the atoms of the water molecule have fixed charges and fixed relative orientation. Even without internal motions and the charge polarization ability, TIP3P reproduces the bulk properties of water quite well. For a further discussion of other available solvent models, readers are referred to Chapter VII, Section 1.3.2 of the Handbook. Unfortunately, the more sophisticated the water models are (to reproduce the physical properties and thermodynamics of this outstanding solvent correctly), the more impractical they are for being used within molecular dynamics simulations. 

The correct treatment of boundaries and boundary effects is crucial to simulation methods because it enables macroscopic properties to be calculated from simulations using relatively small numbers of particles. The importance of boundary effects can be illustrated by considering the following simple example. Suppose we have a cube of volume 1 litre which is filled with water at room temperature. The cube contains approximately 3.3 X 10 molecules. Interactions with the walls can extend up to 10 molecular diameters into the fluid. The diameter of the water molecule is approximately 2.8 A and so the number of water molecules that are interacting with the boundary is about 2 x 10. So only about one in 1.5 million water molecules is influenced by interactions with the walls of the container. The number of particles in a Monte Carlo or molecular dynamics simulation is far fewer than 10 -10 and is frequently less than 1000. In a system of 1000 water molecules most, if not all of them, would be within the influence of the walls of the boundary. Clecirly, a simulation of 1000 water molecules in a vessel would not be an appropriate way to derive bulk properties. The alternative is to dispense with the container altogether. Now, approximately three-quarters of the molecules would be at the surface of the sample rather than being in the bulk. Such a situation would be relevcUit to studies of liquid drops, but not to studies of bulk phenomena. 

Meares, P., Polymers Structure and Bulk Properties, D. Van Nostrand, London, 1965. 

Table 2. Cured Bulk Properties of Common 2-Cyanoacrylic Esters...

The bulk properties of regenerated cellulose are the properties of Cellulose II which is created from Cellulose I by alkaline expansion of the crystal stmcture (97,101) (see Cellulose). The key textile fiber properties for the most important current varieties of regenerated cellulose are shown in Table 2. Fiber densities vary between 1.53 and 1.50. 

The effects of release additives on bulk properties must also be carefully considered, particularly with integral additives to plastics. Eor example, partial solubiHty usually confers some plastici2ing effect. This may improve impact strength but could reduce the heat distortion temperature. Some release additives such as metallic soaps have secondary antioxidant and heat-stabiH2er benefits. Such effects are exploited in multipurpose formulations. 

The usehilness of surfactants stems from the effects that they exert on the surface, interfacial, and bulk properties of their solutions and the materials their solutions come in contact with. 

The data available are generally for the Athabasca materials, although workers at the University of Utah (Salt Lake City) have carried out an intensive program to determine the processibiUty of Utah bitumen and considerable data have become available. Bulk properties of samples from several locations (Table 3) (9) show that there is a wide range of properties. Substantial differences exist between the tar sands in Canada and those in the United States a difference often cited is that the former is water-wet and the latter, oil-wet (10). 

In principle, the nonmining recovery of bitumen from tar sand deposits is an enhanced oil recovery technique and requires the injection of a fluid into the formation through an injection weU. This leads to the in situ displacement of the bitumen from the reservoir and bitumen production at the surface through an egress (production) weU. There are, however, several serious constraints that are particularly important and relate to the bulk properties of the tar sand and the bitumen. In fact, both recovery by fluid injection and the serious constraints on it must be considered in toto in the context of bitumen recovery by nonmining techniques (see PETROLEUM, ENHANCED OIL RECOVERY). 

By far the most used detector is the thermal conductivity detector (TCD). Detectors like the TCD are called bulk-property detectors, in that the response is to a property of the overall material flowing through the detector, in this case the thermal conductivity of the stream, which includes the carrier gas (mobile phase) and any material that may be traveling with it. The principle behind a TCD is that a hot body loses heat at a rate that depends on the... 

Another classification of detector is the bulk-property detector, one that measures a change in some overall property of the system of mobile phase plus sample. The most commonly used bulk-property detector is the refractive-index (RI) detector. The RI detector, the closest thing to a universal detector in lc, monitors the difference between the refractive index of the effluent from the column and pure solvent. These detectors are not very good for detection of materials at low concentrations. Moreover, they are sensitive to fluctuations in temperature. 

The upper-bound hne connects discontinuous points, but polymers exist near the bound for separations of interest. Whether these will be available as membranes is a different matter. A useful membrane requires a polymer which can be fabricated into a device having an active layer around 50 nm thick. At this thickness, membrane properties may vary significantly from bulk properties, although not by a factor of 2. 

The electrical-resistance measurement has nothing to do with the electrochemistry of the corrosion reaction. It merely measures a bulk property that is dependent upon the specimens cross-section area. Commercial instruments are available (Fig. 28-5). 

But probably the most serious barrier has been the paralysis that overtakes the inexperienced mind when it is faced with an explosion. This prevents many from recognizing an explosion as the orderly process it is. Like any orderly process, an explosive shock can be investigated, its effects recorded, understood, and used. The rapidity and violence of an explosion do not vitiate Newton s laws, nor those of thermodynamics, chemistry, or quantum mechanics. They do, however, force matter into new states quite different from those we customarily deal with. These provide stringent tests for some of our favorite assumptions about matter s bulk properties. 

Many considerations enter the choice of material for a bearing. It must have bulk properties which meet the need to support loads and transmit heat fluxes. It must be processable that is, capable of being shaped, finished and joined. It must meet certain economic criteria limits on cost, availability and suchlike. If it can do all these things it must further have - or be given - necessary surface properties to minimise wear, and, when necessary, resist corrosion. 

Fibrous proteins can serve as structural materials for the same reason that other polymers do they are long-chain molecules. By cross-linking, interleaving and intertwining the proper combination of individual long-chain molecules, bulk properties are obtained that can serve many different functions. Fibrous proteins are usually divided in three different groups dependent on the secondary structure of the individual molecules coiled-coil a helices present in keratin and myosin, the triple helix in collagen, and P sheets in amyloid fibers and silks. 

All three techniques probe 500 A to 1 pm or so in depth for opaque materials, depending on the penetration depth of the incident light. For transparent materials, essentially bulk properties are measured by PL and Modulation Spectroscopy. All three techniques can be performed in ambient atmosphere, since visible light is used both as incident probe and signal. 

---