Nanostructured thermoelectric materials receiving great attention for its high thermoelectric performance. In this research, nanostructured n-type Bi2Te2.7Se0.3 alloys have prepared using high energy ball milling and followed by spark plasma sintering. Also, we have varied ball milling time to investigate milling time parameter on the thermoelectric properties of n-type Bi2Te2.7Se0.3 powder. The powders were discrete at 10 min milling and later particles tend to agglomerate at higher milling time due to cold welding. The bulk fracture surface display multi-scale grains where small grains intersperse in between large grains. The maximum Seebeck coefficient value was obtained at 20-min milling time due to their lower carrier density. The κ values were decreased with increasing milling time due to the decreasing trend observed in their κL values. The highest ZT of 0.7 at 350 K was observed for 30-min milling time which was ascribed to its lower thermal conductivity. The Vickers hardness values also greatly improved due to their fine microstructure.

In this study, an oxide reduction process and a reduction-sintering process were employed to synthesize a thermoelectric alloy from three thermoelectric composite oxide powders, and the thermoelectric properties were investigated as a function of the milling duration. Fine grain sizes were analyzed by via X-ray diffraction and scanning electron microscopy, to investigate the influence of the milling duration on the synthesized samples. It was found that microstructural changes, the Seebeck coefficient, and the electrical resistivity of the compounds were highly dependent on the sample milling duration. Additionally, the carrier concentration considerably increased in the samples milled for 6 h; this was attributed to the formation of antisite defects introduced by the accumulated thermal energy. Moreover, the highest value of ZT (=1.05) was achieved at 373K by the 6-h milled samples. The temperature at which the ZT value maximized varied according to the milling duration, which implies that the milling duration of the three thermoelectric composite oxide powders should be carefully optimized for their effective application.

In this paper, an experimental surface roughness analysis in milling of tungsten carbide using a monolithic torus cubic boron nitride (CBN) tool is presented. The tungsten carbide was received using direct laser deposition technology (DLD). The depth of cut (ap), feed per tooth (fz) and tool wear (VBc) influence on surface roughness parameters (Ra, Rz) were investigated. The cutting forces and accelerations of vibrations were measured in order to estimate their quantitative influence on Ra and Rz parameters. The surface roughness analysis, from the point of view of milling dynamics was carried out. The dominative factor in the research was not feed per tooth fz (according to a theoretical model) but dynamical phenomena and feed per revolution f connected with them.

In this paper, an analysis of various factors affecting machined surface texture is presented. The investigation was focused on ball end mill inclination against the work piece (defined by surface inclination angle a. Surface roughness was investigated in a 3D array, and measurements were conducted parallel to the feed motion direction. The analysis of machined surface irregularities as a function of frequency (wavelength A), on the basis of the Power Density Spectrum - PDS was also carried out. This kind of analysis is aimed at valuation of primary factors influencing surface roughness generation as well as its randomness. Subsequently, a surface roughness model including cutter displacements was developed. It was found that plain cutting with ball end mill (surface inclination angle a= 0°) is unfavorable from the point of view of surface roughness, because in cutter’s axis the cutting speed vc ~ 0 m/min. This means that a cutting process does not occur, whereas on the machined surface some characteristics marks can be found. These marks do not appear in case of a* 0°, because the cutting speed vc * 0 on the fill I length of the active cutting edge and as a result, the machined surface texture is more homogenous. Surface roughness parameters determined on the basis of the model including cutter displacements are closer to experimental data for cases with inclination angles a* 0°, in comparison with those determined for plain cutting (a= 0°). It is probably caused by higher contribution in surface irregularities generation of plastic and elastic deformations cumulated near the cutter’s free end than kinematic and geometric parameters, as well as cutter displacements.

In the present paper, elemental Fe, Cr and Ni powders were used to fabricate nano-structured duplex and ferritic stainless steel powders by using high energy planetary ball milling. We have studied the effect of milling atmosphere like wet (toluene) and dry (argon) milling of elemental Fe-18Cr-13Ni (duplex) and Fe-17Cr-1Ni (ferritic) powders for 10 h in a dual drive planetary mill. Stearic acid of 1wt. % was added during milling to avoid agglomeration. The dry and wet milled duplex and ferritic stainless steel powders were characterized by XRD, SEM and particle size analysis techniques. We have found that both the milling atmospheres have great influence in controlling the final particle morphology, size and phase evolution during milling. It was reported that dry milling is more effective in reducing particle size than the wet milling. The Nelson-Riley method of extrapolation was used to calculate the precise lattice parameter and Williamson-Hall method was used to calculate the crystallite size and lattice strain of both the stainless steel milled in argon atmosphere. Dry milled duplex and ferritic stainless steel were then consolidated by conventional sintering method at 1100, 1200 and 1300°C temperatures under argon atmosphere for 1 hour.

In this paper, we have studied the evolution of morphology and brazing behavior of Ag-28Cu alloy filler processed by high energy ball milling. The milling of the powder mixture was carried out for 40 h. The structural and morphological analyses were performed by the X-ray diffraction and scanning electron microscopy. The melting temperature of the braze filler was determined by differential thermal analysis. The filler wetting properties were assessed from the spread area ratio measurements on various Ti substrates. The results indicate that the ball milling can effectively depress the filler melting point and enhance the brazeability. The milled powder mixture showed Ag(Cu) solid solution with a crystallite size of 174-68 nm after 40 h. It was shown that the high energy ball milling can be a potential method to develop low temperature brazing fillers for advanced microjoining applications.

In this study, we have developed Sn-Ag alloy by a simple high energy ball milling technique. We have ball-milled the eutectic mixture of Sn and Ag powders for a period of 45 h. The milled powder for 45 h was characterized for particle size and morphology. Microstructural investigations were carried out by scanning electron microscopy and X-ray diffraction studies. The melting behavior of 45 h milled powder was studied by differential scanning calorimetry. The resultant crystallite size of the Sn(Ag) solid solution was found to be 85 nm. The melting point of the powder was 213.6oC after 45 h of milling showing depression of ≈6oC in melting point as compared to the existing Sn-3.5Ag alloys. It was also reported that the wettability of the Sn-3.5Ag powder was significantly improved with an increase in milling time up to 45 h due to the nanocrystalline structure of the milled powder.

Owing to the excellent properties, graphene nanoplatelets (GNPs) show great reinforcing ability to improve the mechanical and tribological properties of Al nanocomposites for many automotive applications. In this work, the GNPs dispersion and reinforcing effect in Al nanocomposite was tested. Solvent dispersion via tip sonication and facile low energy ball milling (tumbling milling) using two milling speeds 200 and 300 rpm were employed to develop GNPs/Al powders. Sintering response of the GNPs/Al sintered samples was gauged at two temperatures (550oC and 620oC). The effects of GNPs content, milling rotation speed and sintering temperature on the density, hardness and wear properties of the nanocomposite were examined. The results indicate that relative density % decreases with increasing GNPs content due to possible reagglomeration. The highest hardness of 35.6% and wear rate of 76.68% is achieved in 0.3 wt.% GNPs/Al nanocomposite processed at 300 rpm and 620oC as compared to pure Al due to uniform dispersion, higher diffusion rate at a higher temperature and effective lubrication effect.

The work presented here, concentrates on experimental surface roughness analysis in the milling of hardened steel using a monolithic torus mill. Machined surface roughness with respect to milling process dynamics has been investigated. The surface roughness model including cutter displacements has been developed. Cutting forces and cutter displacements (vibrations) were measured in order to estimate their quantitative influence on Ra and Rz parameters. The cutter displacements were measured online using a scanning 3D laser vibrometer. The influence of cutting speed vc on surface roughness parameters (Ra, Rz) was also studied. The research revealed that real surface roughness parameters are significantly higher than those calculated on the basis of a kinematic-geometric basic model, and their values are strongly dependent on dynamic cutter displacements.

During the machining processes, heat gets generated as a result of plastic deformation of metal and friction along the tool–chip and tool–work piece interface. In materials having high thermal conductivity, like aluminium alloys, large amount of this heat is absorbed by the work piece. This results in the rise in the temperature of the work piece, which may lead to dimensional inaccuracies, surface damage and deformation. So, it is needed to control rise in the temperature of the work piece. This paper focuses on the measurement, analysis and prediction of work piece temperature rise during the dry end milling operation of Al 6063. The control factors used for experimentation were number of flutes, spindle speed, depth of cut and feed rate. The Taguchi method was employed for the planning of experimentation and L18 orthogonal array was selected. The temperature rise of the work piece was measured with the help of K-type thermocouple embedded in the work piece. Signal to noise (S/N) ratio analysis was carried out using the lower-the-better quality characteristics. Depth of cut was identified as the most significant factor affecting the work piece temperature rise, followed by spindle speed. Analysis of variance (ANOVA) was employed to find out the significant parameters affecting the work piece temperature rise. ANOVA results were found to be in line with the S/N ratio analysis. Regression analysis was used for developing empirical equation of temperature rise. The temperature rise of the work piece was calculated using the regression equation and was found to be in good agreement with the measured values. Finally, confirmation tests were carried out to verify the results obtained. From the confirmation test it was found that the Taguchi method is an effective method to determine optimised parameters for minimization of work piece temperature.

The paper concerns development of original method of optimal control at energy performance index and its application to dynamic processes surveillance of some mechatronic systems. The latter concerns chatter vibration surveillance during highspeed slender milling of rigid details, as well as motion control of two-wheeled mobile platform. Results of on-line computer simulations and real performance on the target objects reflect a great efficiency of the processes surveillance.

The objective of the study was to assess the potential use of optical measuring instruments to determine the minimum chip thickness in face milling. Images of scanned surfaces were analyzed using mother wavelets. Filtration of optical signals helped identify the characteristic zones observed on the workpiece surface at the beginning of the cutting process. The measurement data were analyzed statistically. The results were then used to estimate how accurate each measuring system was to determine the minimum uncut chip thickness. Also, experimental verification was carried out for each mother wavelet to assess their suitability for analyzing surface images.

Studies of background donor concentration (BDC) in HgCdTe samples grown with different types of technology were performed with the use of ion milling as a means of eliminating the compensating acceptors. In bulk crystals, films grown with liquid phase epitaxy and films fabricated with molecular beam epitaxy (MBE) on Si substrates, BDC of the order of ~10¹⁴ cm^-3 was revealed. Films grown with metal−organic chemical vapour deposition and with MBE on GaAs substrates showed BDC of the order of ~10¹⁵ cm^-3. A possibility of assessing the BDC in acceptor (arsenic)−doped HgCdTe was demon− strated. In general, the studies showed the effectiveness of ion milling as a method of reducing electrical compensation in n−type MCT and as an excellent tool for assisting evaluation of BDC.

The aim of these studies was to obtain single phase cubic modification of Li7La3Zr2O12 by mechanical milling and annealing of La(OH)3, Li2CO3 and ZrO2 powder mixture. Fritsch P5 planetary ball mill, Rigaku MiniFlex II X-ray diffractometer, Setaram TG-DSC 1500 analyser and FEI Titan 80-300 transmission electron microscope were used for sample preparation and investigations. The applied milling and annealing parameters allowed to obtain the significant contribution of c-Li7La3Zr2O12 in the sample structure, reaching 90%. Thermal measurements revealed more complex reactions requiring further studies.