Search results

The beneficial effect on the fracture resistance of fine-grained mortar specimens compared to plain cement pastes was quantified.
Portland cement type CEM I 42.5 R was used as a binder and standard quartz sand with the maximum grain size of 2 mm as aggregate.
In parallel, acoustic emission tests showed the maximum number of AE counts in the same positions (at crack initiation and maximum load).
The higher number of acoustic emission events indicates also the higher numbers of micro-cracks in the mortar specimens (B).
The higher number of small cracks in mortar specimens B leads to the higher energy release which in turn causes higher fracture resistance.

The study reveals that the graphite cathode with smaller, cross-linked grains generates higher current at shorter current risetime compared to the cathode with larger grains.
Fig. 1(a) reveals that the average grain size of graphite 1# is less than 5 μm in diameter.
Comparatively, the raw carbon powder accumulates into much larger grains for graphite 2# and the grain edges are evident (Fig. 1(b)).
It depends on the number of the emitting centers and the distribution of them [8].
For graphite 1#, fine grain size results in great electric field enhancement.

In the ARB processed sheet, the grains are elongated along roll direction (RD) and the thickness of the elongated grains gradually decreased with increasing the number of ARB cycles.
Sample Annealed 2 Cycles 4 Cycles 7 Cycles 10 Cycles 13 Cycles dt[µm] 35 5.1 2.1 1.2 0.61 0.49 dl[µm] 33 16.3 7.1 3.5 1.7 1.4 In the sheet ARB processed by 2 cycles, a number of dislocations generated in the original grains and it made subgrain structures.
The fraction of the UFG regions increased with increasing the number of ARB cycles, i.e. strain.
(3) The reduction of the grains thickness and length was carried out with increasing the number of ARB cycles.
(4) In the ARB processed sheet,the rate of grains thickness decreasing was more than the rate of grains length decreasing and the grains were elongated along RD.

Grain size, morphology and spatial distribution.
It is clear from Figs 4(a) and (b) that the number of Cube grains in the CR_A and IA_1 materials is not very high.
As is well established, depending on the size of the particles with which the recrystallizing grains interact, the number of potential nuclei may be increased by PSN or recrystallization may be inhibited by Zener drag [9].
That is, while the overall number of successful nuclei was significantly lower in the IA_1 treated material than in the case of the IA_2 treatment (compare Figs 4(b) and (c)), there was apparently a sufficient number of PSN-grains with sizes that exceed dcrit so that a more extensive development of the Cube texture was prevented (during the IA_1 treatment).
In fact, the number of Cube grains in the IA_2 material is higher than in the IA_1 case but the corresponding area fraction (16.8%) in the latter is not that different from that of the former (15.9%).

Northern Shaanxi is one of the pilot zones for implementating of Grain for Green Project.
Meanwhile, the carbon (C) stock benefits of Grain for Green Project were analyzed through the different land cover types and slope gradients.
The results in this study indicated that the Grain for Green project resulted in good C stock benefits.
Introduction Northern Shaanxi, a typical epitome with all features of the Loess Plateau, is one of the first pilot regions of implementation Grain for Green project in China.
The estimate formula is represented as: (2) Where i is the number of monitored years (1-8); Slope explain that trend changes of the NPP in this pixel from years 1 to 8.

Impedance/modulus analyses indicate that a third resistance-capacitance (RC) response is present in the sample, in addition to the grain and grain-boundary RC elements above 573K.
Variation of bulk ac conductivity as a function of temperature shows that Ba(Ti0.8Sn0.2)O3 follows the classical Arrhenius relation.The results show that the activation energy of grains and grain boundaries are 0.61 and ~1.08 eV, respectively.
The impedance spectra (IS) are widely used to study microstructure such as grain, grain-boundary, and interface in materials for their different electric responds in frequency domain.
The number of Z'' peaks increases with temperature, which means more components are detected at higher temperature.
At 773 K, three different contributions are observed, which should corresponding to grain, grain boundaries and layer effects[11] respectively as frequency decreasing.

The hybrid material model developed by the strain gradient theory in which the dislocation cell structure, cell densities (interior and wall) engaged to define the polycrystalline aggregate and calculated the dislocations in a grain (grain interior and grain wall).
In the thick sheet, it easy to analyze the effect of a large number of grains in the thickness direction but for the thin sheet, no mechanism has been developed yet.
The grains located at the free surface of material have less hardening effect than the inner grains, so the strengthening effect in surface layer can be neglected [22].
Grain size effect of thickness/average grain size on mechanical behaviour, fracture mechanism and constitutive model for phosphor bronze foil.
"Size effect on the tensile strength of fine-grained copper."

The C2-2 material contains a much higher number density of precipitated particles than that in C2-3 material.
It is well established that dispersoids affect recovery and recrystallization behavior through the pinning they exert on migrating sub-grain and grain-boundaries, i.e. the Zener drag effect.
The different softening behaviors are also reflected in quite different final grain structures as illustrated in Fig. 3, where the most coarse grained material is obtained for C2-0 where the grain size in the rolling direction (RD) and normal direction (ND) is measured to be 132µm and 33µm, respectively (Fig. 3a), while C2-3 gives a fine grained equi-axed grain structure (RD-ND: 27µm-18µm; Fig. 3d).
This will limit nucleation through pinning of the sub-grain structure and slow down recrystallization kinetics (few and slowly growing grains) and thus explain the very slow kinetics and resulting coarse grain structure in this case.
The present work and the examples presented have clearly shown that the softening behavior during back annealing of cold rolled Al-Mn(-Fe-Si) alloys is the result of a critical balance between the processing conditions and microchemistry and its associated changes during processing, in terms of size and number of constituents, solute level of alloying elements and in particular the presence of high number of small dispersoids, whether pre-existing or precipitated concurrent with the recovery and recrystallization reaction which will exert a considerable Zener drag and strongly retard the kinetics and give a coarse and uneven grain structure.

Particles of the powder have an irregular shape with a large number of protrusions and irregularities on the surface.
The material has a non-uniform coarse-grained structure.
The average grain size is of the order of 100-200 μm (Fig. 2a).
The average grain size is 5-20 μm.
The presence of such sections is due to the facilitated passage of the indenter through the near-surface layer with an increased number of cracks.

When a large number of high-power electrical appliances work together in the same system, the current of the electrical system will exceed its rated current.
White color represents the air poles in the melted marks and other colors represent different grain orientations relevantly; black color represents grain boundary. 3.2 Grain misorientation in melted marks of copper wire The grain misorientation (grain boundary angle) of the PMMs and OMMs are obtained (Fig. 2).
The horizontal ordinate delegates those grain boundary angles >15° and the vertical ordinate is on behalf of the relative frequency of each grain boundary angle correspondingly.
The ratios of high-angle grain boundaries to total grain boundaries in melted marks are calculated.
PMMs of copper wires were filled with columnar crystals in which there was a large number of air pores scattered, whereas the OMMs of copper wires were occupied by numerous dendrite crystals in which air pores were hardly detected.