Average Micro Research Articles

Preparation of High Silicon Steel by Multi-Arc Ion Coating and Diffusion

High silicon steel has been prepared by physical vapor deposition, i. e. multi-arc ion coating and diffusion. Subsequent annealing in vacuum at 1180 and 1200 °C result in penetration of silicon into the substrate. X-ray diffraction (XRD) reveals that the surface layers of all samples remain α-Fe bcc structure after high temperature-diffusion treatment. Once Fe3Si is formed in the surface layer, a further heat treatment will make the composition of the sample homogenizations. The silicon concentration distribution along the cross-section is 4.6 wt%∼5.1 wt% after annealing at 1200 °C for 1 h which was tested by field emission scanning election microscopy (FE-SEM) equipped with energy dispersive spectroscope (EDS), and was further confirmed by micro Vickers-hardness, where the average cross-section micro Vickers-hardness is 2800 MPa.

Experimental Study on Laser Melting of Cemented Carbide Coatings by High Velocity Oxy-Fuel Spraying

Ni60AA and DZ-WC-12Co cemented carbide layer was prepared on 45 steel by high-speed flame spraying, then remelted by 5KW continuous wave CO2 laser. The micro-structure was analyzed by Olympus GX51 .micro hardness and the micro hardness was measured by HXY-1000TAY micro hardness meter. The wear resistant of coating was tested by MM-W1B vertical universal testing machine. The results showed that laser melting significantly eliminate the carbide layer unmelted carbide particles, holes and cracks and other defects, the micro-structure is finer and more uniform. After laser re-melted, the average micro hardness of hard alloy layer is up to 647HV, which is five times of the matrix. Under the experimental conditions, the friction coefficient of hard alloy layer drops from 0.1373 to 0.0948 by 31%.The wear-resistance of cemented carbide layer is improved by laser melting.

A novel multiple soaking temperature (MST) method to prepare polylactic acid foams with bi-modal open-pore structure and their potential in tissue engineering applications

Bi-modal pore structures were obtained by stepwise depressurization in batch foaming method. In this study, a novel method was developed to produce polylactic acid (PLA) foam with bi-modal pore structure by using multiple soaking temperature (MST) method based on one-step pressure release. The effects of soaking time and temperatures on the formation of bi-modal pore structure were investigated in detail. The formation of macro pores was attributed to the synergistic effect of the supercritical carbon dioxide (SC-CO2) aggregation and the depressurization process. Moreover, bi-modal open-pore structures could be obtained at certain processing conditions. The PLA foams achieved porosity and open pore content as high as 87.9% and 82.4%, with average macro and micro pore size of 150μm and 8μm, respectively. The biocompatibility of the PLA open-pore foams was verified by 3T3 fibroblast cell culture.

Dry Sliding and Abrasive Wear Behavior of Nanostructure Zr–W–N Coating

Zirconium tungsten nitride (Zr–W–N) coating has been deposited on 304 SS substrates by pulse DC magnetron sputtering. The average micro hardness and roughness of Zr–W–N coating were obtained as ~1,963 HV and ~13 nm respectively. The dry sliding and abrasive wear tests of coated samples were performed in open atmosphere at various loads (15–45 N) with constant speed (0.1 m/s) up to maximum life of a coating. The coefficient of friction (COF) and cumulative weight loss were measured as a function of distance travelled by the coating. The change (minimum to maximum) in COF of the coated samples at various loads was obtained as ~0.15–0.68 and ~0.20–0.27 for dry sliding wear and abrasive wear tests respectively. The cumulative weight loss of the coated samples at various loads was calculated as 1 × 10−6–6 × 10−6 g/m for dry sliding wear and 6 × 10−6–26 × 10−6 g/m for abrasive wear test. Finally, coatings were compared on COF and cumulative weight loss as a function of sliding distance with SS substrate at 15 N load with 0.1 m/s speed.

Training English Language Pre-service Teachers Using a Team Based Learning Approach

Team Based Learning which focuses on enhancing positive group dynamics is a relatively popular instructional approach in several disciplines such as Health Sciences and Business but has yet to gain popularity in Education. This paper examines the use of Team Based Learning in teacher training as well as the receptiveness towards the approach as indicated by a group of Teaching English as a Second Language teacher trainee. The trainees were asked to write diaries regarding their experiences working in a team during a course for a semester which were then collected in three cycles throughout the semester. Entries were analysed in terms of whether there were positive, negative or neutral reference to working in teams. All members of a team were also required to participate in individual micro teaching sessions for which they were evaluated. Findings indicate that Team Based Learning has a potential role in teacher training as positive entries outnumbered negative entries. Additionally, teams with high average micro teaching scores also had more positive diary entries.

Fabrication of Al/AlN nano-composite layers by friction stir processing of 6061 Al-T6 substrate

Friction stir processing was employed for the production of Al/AlN nano-composite layers on a 6061 Al-T6 substrate. Nano-sized AlN powder was inserted in a groove in the middle length of the substrate. Defect-free layers were achieved using tool rotation and substrate advancing speeds in the range of 900–1400 rpm and 63–310 mm/s, respectively. Subsequent passes were conducted to break-up AlN clusters that formed in a non-uniform fashion after initial pass. The grain size of aluminum matrix was found to decrease by the introduction of AlN powder. A nano-composite layer with near uniform dispersion of nano-sized AlN reinforcements with a ~9.6% volume fraction was achieved in a matrix of fine dynamically restorated Al grains with a mean size of ~2.5 µm after three subsequent passes. This layer showed an average micro hardness value of ~164 HV (much greater than ~103 HV of the underlying substrate). In addition, the nano-composite layer exhibited superior dry sliding wear performance against hardened steel compared to that of 6061-T6 substrate. Increasing tool rotation and substrate advancing speeds were found to decrease the AlN content of the processed layer possibly due to increasing in powder scattering by the pin tool. This was associated with a decrease and increase in hardness values and wear-loss data, respectively. Copyright © 2014 John Wiley & Sons, Ltd.

Formulation of the Total Western Diet 2, a whole food‐based rodent diet that emulates average American micro‐ and macronutrient intakes for colorectal cancer and gut microflora studies (816.6)

Previously, we used NHANES data to formulate the TWD, a rodent diet that emulates average American intake levels for macro and micronutrients using nutrient density. We have demonstrated that the TWD increases basal CRC by ~2‐fold compared to the standard AIN93‐G diet in two different models. However, the TWD is comprised of purified ingredients and does not recapitulate the complex food matrix consumed by Americans. Using the latest version of the USDA Food Intakes Converted to Retail Commodities Database, we modified the TWD by using the most commonly consumed whole foods as ingredients. The TWD2 has the same micro and macronutrient content as the previous TWD but contains 25 ingredients including: sweeteners (sucrose and high fructose corn syrup), flours (wheat, potato, corn, rice and oat), meats (beef, poultry, pork, eggs and fish), dairy (lactose, whey and casein) and fruits/vegetables (oranges, apples, bananas, grapes, strawberries, soy, snap beans, peanuts and cashews). Whole foods were cooked (meats), freeze‐dried and homogenized. Only low fat foods were used and the dietary fat profile was adjusted to the American average by adding a diverse blend of oils. Ingredients were then blended, pelleted and baked to dryness. The TWD2 will narrow the gap between human nutrition and rodent models as the food matrix, secondary compounds and cooking byproducts have been shown to influence CRC and gut microflora.Grant Funding Source: Utah Agricultural Experiment Station

Microstructure and Mechanical Property Analysis of the Metal Part by SLM

The objective of the research was that analyzed the microstructure and mechanical properties of metal part built by SLM in this paper. The tensile samples were made by SLM, the rupture gotten with tensile experiment was scan by SEM, and the rupture property was analyzed. The results of experiment showed: the parts formed by optimized parameters have a density above 96%, a tensile strength of 635MPa, an extension of 55.679% and an average micro hardness of HV307 for stainless steel powder. It is interesting to find that the phase of the built parts is also austenite by XRD, which is the same as that of the starting material.

Abrasion Resistance of Al-Ni-Mm-Fe Amorphous and Nanocrystalline Composite Coating on the Surface of AZ91 Magnesium Alloy

Abstract An Al-Ni-Mm-Fe amorphous and nanocrystalline composite coating was prepared onto the surface of AZ91 magnesium alloy by high velocity arc spraying process. And the microstructure of the coating was analyzed by scanning electron microscope (TEM) and X-ray diffraction (XRD). The analysis results indicated that the coating consists of amorphous, nanocrystalline and crystalline phases. It has a dense structure with a low porosity of about 2.0%. Its average micro Vickers hardness value is about 330 HV 0.1 , which is five times than that of AZ91 magnesium alloy (62 HV 0.1 ) and four times than that of pure Al coating (71 HV 0.1 ). The abrasion tests showed that the Al-Ni-Mm-Fe coating exhibits a good abrasion resistance.

Joining of Mild Steel Plates Using Microwave Energy

This paper describes joining of bulk MS (mild steel) plates using a domestic microwave oven at a frequency of 2.45 GHz and a power of 900 W. Microwave Hybrid Heating (MHH) is used for joining of MS plate by placing an interlayer of Ni powder of average thickness of about 0.3 mm between two interfacing surfaces. Characterization of the joints has been carried out using X ray diffraction (XRD), SEM (Scanning Electron Microscope), and Vickers micro indentation. The back scattered electron (BSE) image shows complete melting of powder particle yielding diffusion bonding between interfacing powder particles and MS plates The average micro hardness of the joints observed to be 420 ± 30 Hv which is significantly higher than the substrate hardness of 230 ± 10 Hv. The results obtained after performing tensile test show that the joints have an average strength of 250 MPa with a percentage elongation of 6 percent

Study of Electroluminescence in Pr Doped ZnS

Electroluminescence study of Pr doped ZnS phosphor has been reported in this work. The phosphor is prepared by heat treatment technique. It is observed that the intensity of emission varies with the applied voltage and excitation frequency according to the universal laws. Pr is found to enhance the EL intensity of ZnS phosphor. The average grain size and micro strain (μ) of Pr-doped ZnS is found to be 37.25 μm and 0.46, respectively.

Optimization of burnishing parameters and determination of select surface characteristics in engineering materials

The present study is aimed at filling the gaps in scientific understanding of the burnishing process, and also to aid and arrive at technological solutions for the surface modifications based on Burnishing of some of the commonly employed engineering materials. The effects of various burnishing parameters on the surface characteristics, surface microstructure, micro hardness are evaluated, reported and discussed in the case of EN Series steels (EN 8, EN 24 and EN 31), Aluminum alloy (AA6061) and Alpha-beta brass. The burnishing parameters considered for studies principally are burnishing speed, burnishing force, burnishing feed and number of passes. Taguchi technique is employed in the present investigation to identify the most influencing parameters on surface roughness. Effort is also made to identify the optimal burnishing parameters and the factors for scientific basis of such optimization. Finally, a brief attempt is made to construct the Burnishing maps with respect to strength level (in this case, average micro hardness of unburnished material).

Fabrication of Al<sub>2</sub>O<sub>3</sub> Based Ceramic Matrix Composite by Conventional Sintering and Sol-Gel Process

Alumina (Al2O3) matrix composites reinforced with 10%, 20% and 40% of 10µm size aluminum particles were fabricated by two processes, namely cold pressing and sintering process and Sol-Gel process. Al2O3, Al, 5% volume fraction of cobalt was mixed together, compacted and then sintered at 400-500oC for 30 minutes to fabricate the CMC. In the Sol-Gel fabrication route the Al2O3, Al, Co were blended with water and aged for 2-3 days to remove all the moisture and to enable oxidation of Al reinforcement. The mixture was cold pressed and sintered at 400-500oC to produce the CMC. The composition analysis of the CMC carried out by EDAX clearly showed that Al2O3 particles were formed by oxidation of Al reinforced in the matrix, effectively forming Al2O3/Al2O3 particulate reinforced ceramic matrix composite. The nature of the bonding at the interface was characterized using Scanning Electron Microscopy (SEM). The amount of porosity was determined using image analyzer based on ASTM B 276 standard. The average micro hardness of the samples was measured. The optimum volume fraction of aluminum for better interface bonding and reduced porosity was determined using the results obtained.

Study on test instrument and filtration theory of the carbonized micron wood fiber DPF

In this paper, a method of utilizing the carbonized micron wood fiber (CMWF) as the filter material is presented and a corresponding numerical simulation method is applied. Furthermore, a kind of detachable diesel particulate filters (DPF) is developed, a diesel engine bench test is conducted and the influence elements upon Δ p/ H are researched. Theory and test show that the smaller the average micro pore diameter is, the larger the focal length of parabola is, which means that the numerical simulation method can be consistent with the test very well. Meanwhile, a lot of tests prove that the DPF filters with bigger pore diameter and longer length should take priority over the others, together with the increase of the filter length, the PM arresting efficiency will be improved and Δ p/ H also climbs up rapidly and a kind of modified CMWF DPF, of which the micro pore diameter reduces gradually from entry to exit end, possesses high filtration efficiency and low pressure drop and be suited to filter the exhaust gases of diesel.

PELAPISAN PERMUKAAN DALAM NOSEL ROKET RKX100 DENGAN Cr2C3-NiCr HVOF: OPTIMASI KEKUATAN LEKAT MELALUI VARIASI KEKASARAN PERMUKAAN

Nozzle of RKX100 rocket contributes 30 percent to the total weight of the structure, so that allowing further research on weight reduction. An alternative for this is by substitution of massive graphite, which is currently used as thermal protector in the nozzle, with thin layer of HVOF (High Velocity Oxy-Fuel) thermal spray layer. A series of study on the characteristics of various type of HVOF coating material have been being conducted. This paper presented the investigation on the HVOF Cr2C3-NiCr thermal spray coating, in particular, the optimization of bonding strength by varying surface roughness of substrates. Characterization included bonding strength test, micro hardness measurement and micro structural observation with optical microscope and scanning electron micriscope (SEM). The results showed that grit blasting pressure increass the surface roughness from 4,54 um to 5.72 um at the pressure of 6 bar. Average micro hardness of the coating was 631 VHN 300. Coating applied to the surface with rougness of 5.42 um possessed the highest bonding strength, 44 MPa. Microstructural observation by using optical microscope and scanning electron microscope (SEM) confirmed dense lamellae structure with variable composition. High coating adherence was found to be due to mechanical interlocking.

Experimental Study on the Nickel-Based Metal Parts Manutactured by Laser Cladding

This paper presents an experimental research on the metal parts manufactured by laser cladding. The present studies showed two processes were conducted ,including coaxial powder-feed cladding and pre-placed powder cladding. The effect of processing parameters were studied and optimum set of parameters for the superior surface quality was established by employing the orthog -onal design. The manufactured parts were subjected to metallographic examination and micro -hardness measurement. Results showed that the microstructure of coaxial cladding parts was better than that of pre-placed powder cladding parts. The micro-hardness of the manufactured specimen along and vertical the scanning direction were measured using a HVS-1000 micro-hardness tester with a 200g applied load. Analysis of the physical properties provided further evidence of differences in micro-hardness produced by different process conditions, and the average micro -hardness value of pre-placed power cladding layer was lower than that of the coaxial powder-feed cladding layer.

Micro power generation of PMN‐PZT triple morph cantilever for electric harvesting devices

AbstractPiezoelectric cantilever was manufactured using the PMN‐PZT thick film for electric harvesting device. In order to find the better properties, the piezoelectric cantilever was manufactured by two forms (bi‐morph and triple‐morph). The generation characteristics were investigated according to the variations of frequency, load resistance and mass weight. The piezoelectric cantilever output voltage increased according to the increase of load resistance and the output power quality was also investigated by changing the load resistance, mass weight and frequency. The bi‐morph piezoelectric cantilever output power which resulted from the conditions of 33 kΩ, 0.25 g, 197 Hz was 230 μW at 2.75VRMS. And then, Average micro power from triple‐morph piezoelectric cantilever was 432 μW, 6.57 VRMS at 154 Hz. This paper presented the possibility of electric harvesting devices with using PMN‐PZT triple‐morph cantilever for remote control and sensor node. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Micro Power Generation of PMN-PZT Triple Morph Cantilever for Electric Harvesting Devices

Piezoelectric cantilever was manufactured using the PMN-PZT thick film for electric harvesting device. In order to find the better properties, the piezoelectric cantilever was manufactured by two forms (bi-morph and triple-morph). The generation characteristics were investigated according to the variations of frequency, load resistance and mass weight. The piezoelectric cantilever output voltage increased according to the increase of load resistance and the output power quality was also investigated by changing the load resistance, mass weight and frequency. The bi-morph piezoelectric cantilever output power which resulted from the conditions of 33 kΩ, 0.25 g, 197 Hz was 230 μW at 2.75VRMS. And then, Average micro power from triple-morph piezoelectric cantilever was 432 μW, 6.57 VRMS at 154 Hz. This paper presented the possibility of electric harvesting devices with using PMN-PZT triple-morph cantilever for remote control and sensor node. (© 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Co 3O 4 nanoparticles by chemical combustion: Effect of fuel to oxidizer ratio on structure, microstructure and EPR

In this work we describe and discuss the synthesis, (micro)structure (XRD, SEM) and EPR of Co 3O 4 (normal spinel structure with a = 0.808 nm) nanoparticles synthesized by urea-based combustion method using cobalt nitrate precursor. Fuel-to-oxidizer ratio ( Ψ ) is used as a control parameter to investigate how lattice parameter, particle size and EPR susceptibility vary with Ψ = 0.25 – 2 in steps of 0.25. The average crystalline size of Co 3O 4 was estimated from the X-ray diffraction peaks of powders using Scherrer’s formula and Williamson–Hall equation. The average crystalline size varies from 7(±0.1) nm to 18(±0.28) nm. The surface areas were measured using BET method and size of the particles thus deduced agree with XRD based values. The FT–IR confirms formation of Co 3O 4. We also calculated average micro strain of the Co 3O 4 nanoparticles with varying Ψ . The SEM micrographs give evidence for increased porosity upon increasing Ψ . EPR spectra has yielded the paramagnetic susceptibility of the Co 3O 4 nanoparticles. Band gap of Co 3O 4 nanoparticles was determined by UV-visible absorption edge.

Generic Absorbing Transition in Coevolution Dynamics

We study a coevolution voter model on a complex network. A mean-field approximation reveals an absorbing transition from an active to a frozen phase at a critical value [see text for formula] that only depends on the average degree micro of the network. In finite-size systems, the active and frozen phases correspond to a connected and a fragmented network, respectively. The transition can be seen as the sudden change in the trajectory of an equivalent random walk at the critical point, resulting in an approach to the final frozen state whose time scale diverges as tau approximately |p(c) - p|(-)} near p(c).