Lu et al. Reply:The authors of the preceding Comment [1] argue that the patterns we measured on highly oriented pyrolytic graphite (HOPG) by electric field microscopy (EFM) [2] were a result of surface contamination (e.g., water film) and cannot be attributed to the potential fluctuations of graphite. We disagree with their arguments.The method we used is indeed suitable to measure absolute contact potential differences (CPD), and the voltage dependence shown in Fig. 1 in Ref.[2] is necessary for the calibration. The curves shown in that figure are normalized at the minimum; that is why they coincide. Even if they were not normalized, the difference in CP between the two chosen areas in that figure is about 0.1 V, which in the scale of Fig. 1(a) is within the order of the symbol width [2]. We measured relative values of potentials with the same calibration in a surface region atomically flat as observed by atomic force microscopy. In a homogeneous metal there are no CP fluctuations, neither in a HOPG sample of 0.8 mosaicity measured under similar conditions [2] as the 0.4 -HOPG, a fact that speaks against contamination. Independently done measurements using Kelvin force microscopy in HOPG as well as in Pd-Au structures provide the same CPD as the EFM parabola shift, supporting our interpretation.The authors [1] do not seem to be aware of a key point to understand the EFM experiments. Graphite is not a metal; it conducts in-plane but is practically insulating normal to the planes [3]. Therefore, ideal graphite screens poorly [4] and has a positive dielectric constant [5], an insulator property. Therefore, the applied electric field penetrates 100 nm, and the potential information is not only from the surface but from far inside the bulk. Imagine a condenser consisting of an air gap and 100 nm graphite. In EFM, we are measuring the fluctuation in the energy of this condenser. In this case, it is clear that the role played by an impurity dielectric layer of 1 nm thickness is irrelevant. In particular, one should understand the point of the screening of the electric field. The fluctuation patterns observed are a consequence of regions with different graphite structures or defect densities, which also may link graphite planes changing the density of states at Fermi level.Although the regions with different potentials appear rounded, they are not circles but nearly polygons. Electron backscatter diffraction (EBSD) provides an independent confirmation of the observed patterns on a similar HOPG sample; see Fig. 1. The EBSD patterns look similar to the EFM ones [2] and are related to different dislocation or crystallographic defect density and orientation, which originate the CPD.There have been recent angle-resolved photoemission spectroscopy experiments [6] on clean surfaces of graphite samples in UHV, etc., where regions with a different density of states at the Fermi level were clearly observed. These results provide an indication for the existence of fluctuations of the potential on the sample surface, in agreement w...

We present measurements of the electric potential fluctuations on the surface of highly oriented pyrolytic graphite using electrostatic force and atomic force microscopy.Micrometric domain-like potential distributions are observed even when the sample is grounded. Such potential distributions are unexpected given the good metallic conductivity of graphite because the surface should be an equipotential. Our results indicate the coexistence of regions with metallic and insulating behaviors showing large potential fluctuations of the order of 0.25V. We discuss the implications of these measurements in the disorder structure of graphite. PACS: 81.05. Uw, 84.37.+q,

When discussing the resistance of an atomic-or nanometre-size contact we should consider both its ballistic and its diffusive contributions. But there is a contribution of the leads to the resistance of the contact as well. In this context, the geometry and the roughness of the surfaces limiting the system will contribute to the resistance, and these contributions should be added to the ideal ballistic resistance of the nanocontact. We have calculated, for metallic materials, the serial resistance of the leads arising from the roughness, and our calculations show that the ohmic resistance is as important as the ballistic resistance of the constriction. The classical resistance is a lower limit to the quantum resistance of the leads. Many examples of earlier experiments show that the mean free path of the transport electrons is of the order of the size of the contacts or the leads. This is not compatible with the idea of ballistic transport. This result may put in serious difficulties the current, existing interpretation of experimental data in metals where only small serial resistances compared with the ballistic component of the total resistance have been taken into account. The two-dimensional electron gas (2DEG) is also discussed and the serial corrections appear to be smaller than for metals. Experiments with these last systems are proposed that may reveal new interesting aspects in the physics of ballistic and diffusive transport.

Effects of parameters including temperature, time and coal ratio on the reduction behaviour of preheated iron-bearing converter sludge pellets in a simulated rotary kiln are studied through orthogonal tests. ANOVA analyses show that reduction time and temperature have remarkable influence on the metallisation degree, occupying 55.02 and 30.08% of the total contribution, while temperature is the most significant factor affecting the compressive strength, with 90.98% contribution. The metallisation degree increases with the increasing time from 1.5 to 2.5 h, and first increases and then decreases with the increasing temperature from 1000 to 1100°C. The compressive strength increases with the increasing temperature. Under the optimal condition of temperature 1050°C, time 2.5 h, coal ratio 1.3, the metallisation degree is 72.92%, and the compressive strength is 1310 N/p, which satisfies the requirement of iron burden for blast furnace.

Direct reduced iron (DRI) shaft furnace flow field has important influence to the DRI production process, and the ventilation is a key factor for the velocity and pressure distribution of the gas flow in the furnace. At present works, the direct reducing gas velocity distribution and pressure distribution of DRI shaft furnace were studied with different ventilation. By the analysis of numerical simulation, the result was found that the direct reducing gas velocity increase with height in the shaft furnace reduction section. The velocity of the direct reducing gas augment with the increase of ventilation. The direct reducing gas pressure add with increasing height in the shaft furnace reduction section. With ventilation increasing, the pressure of the shaft furnace ventral part increase, and the pressure gradient increase in the direction of height in the DRI shaft furnace.