Microstructure uniformity

However, PM forgings with near-theoretical density (99 per cent plus) when combined with microstructure uniformity and low interstitial... 

The desired results after sintering and annealing are 100% conversion to the ) " phase for maximum sodium ion conductivity maximum mass density to eliminate porosity, particularly large pores, in the microstructure uniform, fine grain size below 10 pm, to maximize strength and minimize sources or singularities for fracture and no loss of NaaO to control composition and eventually the sodium ion conductivity. 

Figures 6 and 7 show microstructures of the samples sintered at a heating rate of 200 and 700°C/ min, respectively. In general, sintered samples with higher relative densities exhibit greater mechanical properties. However, there is also an influence of microstructural uniformity on mechanical properties. Figure 6 (a) to (d) shows various SEM micrographs of fracture surfaces of the samples. The microstructure seems to be like a green compact for the 1300 C sample because the sintering temperature was too low for sintering. In the case of...

Fig. 5. Micrographs of the microstructure of fully hardened and tempered tool steels produced by the powder metallurgy technique, showing uniform distribution and fine carbide particles in the matrix, (a) M-42 (see Table 6) and (b) cobalt-free AlSl T-15 having a higher concentration of fine carbide...

Types of damage can be classified as uniform or localized metal removal, corrosion cracking or detrimental effects to the environment from the corrosion products. Local attack can take the form of shallow pits, pitting, selective dissolution of small microstructure regions of the material or cracking. Detrimental effects are certainly not the case with buried pipelines, but have to be considered for environments in vessels and containers. It is usual, where different results of reactions lead... 

Different microstructural regions in a material which has an almost uniform composition can also lead to the formation of corrosion cells (e.g., in the vicinity of welds). Basically, corrosion cells can be successfully overcome by cathodic protection. However, in practice, care has to be taken to avoid electrical shielding by large current-consuming cathode surfaces by keeping the area as small as possible. In general, with mixed installations of different metals, it must be remembered that the protection potentials and the protection range depend on the materials (Section 2.4). This can restrict the use of cathodic protection or make special potential control necessary. 

Finally, it should be noted that in both cases the effect of crystal defects and microstructural features must, in general, be to tend to make the corrosion less uniform and more localised. 

By the use of microstructured mixers, pigment and other particulate syntheses can be improved. In this way, finer particles with more uniform size distribution were yielded for the commercial azo pigment Yellow 12 (see Fig. 2) [11]. The particles formed in the microstructured mixer have better optical properties such as the glossiness or transparency at similar tinctorial power. Since the micro-mixer made pigments have more intense colour, lower contents of the costly raw material in the commercial dye products can now be employed which increases the profitability of the pigment manufacture. 

Thin sections cut with a diamond knife microtome can be of great advantage in locating regions of catalyst where important chemical or structural changes take place during reaction. Comparison of equivalent areas of fresh and deactivated catalyst can be a difficult problem if the catalyst support does not have a uniform microstructure as in carbon supports produced from plant materials. Even when specimen selection and preparation are adequate, it may be difficult to know upon which image features to place the electron beam to solve the problem at hand. 

Compared with laboratory fixed-bed reactors or conventional extruded monoliths, such a microstructured monolith is smaller in characteristic dimensions, lower in pressure loss by optimized fluid guiding and constructed from the catalytic material solely [3]. The latter aspect also leads to enhanced heat distribution within the micro channels, giving more uniform temperature profiles. 

In terms of measuring emulsion microstructure, ultrasonics is complementary to NMRI in that it is sensitive to droplet flocculation [54], which is the aggregation of droplets into clusters, or floes, without the occurrence of droplet fusion, or coalescence, as described earlier. Flocculation is an emulsion destabilization mechanism because it disrupts the uniform dispersion of discrete droplets. Furthermore, flocculation promotes creaming in the emulsion, as large clusters of droplets separate rapidly from the continuous phase, and also promotes coalescence, because droplets inside the clusters are in close contact for long periods of time. Ideally, a full characterization of an emulsion would include NMRI measurements of droplet size distributions, which only depend on the interior dimensions of the droplets and therefore are independent of flocculation, and also ultrasonic spectroscopy, which can characterize flocculation properties. 

Galindo, H.M., Carvajal, Y., Njagi, E., Ristau, R.A. and Suib, S.L. (2010) Fadleone-step template-free synthesis of uniform hollow microstructures of cryptomelane-type manganese oxideK-OMS-2. Langmuir, 26, 13677-13683. 

There are three important points about Equation (3.47). Firstly the viscosity is the low shear limiting value, rj(0), indicating that we may expect some thinning as the deformation rate is increased. The reason is that a uniform distribution was used (ensured by significant Brownian motion, i.e. Pe < 1) and this microstructure will change at high rates of deformation. Secondly there is a difference between the result for shear and that for extension. Thirdly the equation is only accurate up to cp < 0.1 as terms of order 3 become increasingly important. If we write the equation in the form often used for polymer solutions we have for Equation (3.47 a) ... 

The microstructure of a catalyst layer is mainly determined by its composition and the fabrication method. Many attempts have been made to optimize pore size, pore distribution, and pore structure for better mass transport. Liu and Wang [141] found that a CL structure with a higher porosity near the GDL was beneficial for O2 transport and water removal. A CL with a stepwise porosity distribution, a higher porosity near the GDL, and a lower porosity near the membrane could perform better than one with a uniform porosity distribution. This pore structure led to better O2 distribution in the GL and extended the reaction zone toward the GDL side. The position of macropores also played an important role in proton conduction and oxygen transport within the CL, due to favorable proton and oxygen concentration conduction profiles. 

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