Increasing Powder Concentration Research Articles

Enhancement of tribological performance of lubricants using polydimethylsiloxane powder additives.

This study explored the potential enhancement of lubrication performance by incorporating polydimethylsiloxane (PDMS) powder as a lubricant additive. The PDMS powder was successfully synthesized via mechanical and thermal processes, exhibiting a particle size distribution with an average diameter of 39 μm. XRD and FTIR analyses confirmed the amorphous structure and chemical composition of the PDMS-based silicone rubber powder. XPS analysis provided evidence of increased crosslinking in the crosslinked PDMS powders, with shifts in binding energies and changes in elemental ratios, supporting enhanced Si-O-Si network formation. The addition of the powder to the Poly alpha Olefin (PAO)-based lubricating oil induced notable changes in the physicochemical properties, including viscosity and contact angle. Friction tests revealed that the introduction of silicone rubber powder did not compromise the friction behavior of the lubricating oil owing to the soft and deformable nature of the powder particles, which minimized direct metal-to-metal contact. A significant observation was the decreasing trend in the wear rate with increasing powder concentration, which reached a minimum at 2 wt%. This phenomenon is attributed to a synergistic combination of particle deformation, stress absorption/dispersion effects, and lubricating film formation. Optical microscopy analysis provided visual evidence supporting the low wear rate, with specimens containing 1 wt% and 2 wt% concentrations exhibiting narrow wear widths and reduced wear particle adhesion. Further augmentation of the wear resistance and durability is anticipated through the addition of silicone rubber curing agents, which are expected to bolster the mechanical strength and load-bearing capacity of PDMS powder particles while enhancing the stability of the lubricating film.

Deposition of tantalum carbide on Ti6Al4V alloy by electric discharge treatment

Titanium alloys attract wide attention of researchers due to the unique combination of low density, high strength, corrosion resistance, biocompatibility, etc. Therefore, the study of new methods for processing titanium and the creation of protective coatings seems relevant. Metal-ceramic coatings were obtained by electrospark treatment of a titanium alloy Ti6Al4V in a mixture of titanium granules with tantalum carbide powder. Three mixtures of granules were prepared with a TaC content of 2.4; 4.6 and 6.7 vol.%. Coatings were deposited by rectangular pulses with an energy of 0.33 J and a frequency of 1 kHz for 8 minutes in an argon stream. The increase of the volume fraction of tantalum carbide powder in the mixture of granules from 2.4 to 6.7 vol.% does not lead to a significant increase in cathode gain. The average coating thickness ranged from 29 to 36 microns. Using scanning microscopy and energy dispersive analysis methods, it was found that the coating structure is represented by a metal Ti – Ta – C matrix with large ceramic grains. According to x-ray phase analysis, it was found that tantalum carbide TaC prevails in the coating composition. It content increases with increasing powder concentration in the mixture of granules. In addition to it, there are phases of titanium carbide and tantalum subcarbibide TaC0.6, which are the products of TaC decarburization during its interaction with the titanium melt. With an increase of the tantalum carbide concentration in the mixture of granules, the hardness of TaC/Ti coatings increased from 6.1 to 8.9 GPa, which is 2–3 times higher than that of the Ti6Al4V alloy. Coefficient of friction of coatings was in the range of 0.5–0.9. Dry sliding wear tests showed that TaC/Ti coatings had a wear rate ranging from 0.1·10–5 mm3/Nm to 1.7·10–5 mm3/Nm. Thus, the use of these coatings makes it possible to increase the wear resistance of the Ti6Al4V alloy up to 128 times.

Effect of Zinc Oxide Nanoparticles on Staphylococcus AureusIsolated From CowsʼMastitic Milk

The current spreading of nanomaterial applications supports the search for further possible functions of theses diminutive particles. The antibacterial potentiality of zinc oxide (ZnO) nanoparticles (NPs) againstS. aureus causing mastitis was evaluated using qualitative and quantitative assays. These tests were performed in nutrient broth and nutrient agar following standard methods. In addition, the effect of different concentrations of ZnO nanoparticles on the growth of S. aureus was measured.MIC was determined using six different concentrations of ZnO nanoparticles including 16, 8, 4, 2, 1 and 0.5 mg/ml. The MIC value S. aureus was 0.5 mg/ml. The results showed that ZnO nanoparticles have antibacterial inhibition zone of 29 mm at the concentration of 10 mg/ml against S. aureus., and the antibacterial activity of ZnO nanoparticles increased with increasing powder concentration in vitro.

Novel Biomimatic Synthesis of ZnO Nanorods Using Egg White (Albumen) and Their Antibacterial Studies.

Zinc oxide (ZnO) is well-recognized as a biocompatible multifunctional material with outstanding properties as well as low toxicity and biodegradability. In this work, a simple and versatile technique was developed to prepare highly crystalline ZnO nanorods by introducing egg white to a bio-inspired approach. X-ray diffraction (XRD) and selected area electron diffraction (SAED) pattern results indicated that the ZnO nanorods have single phase nature with the wurtzite structure. Field emission scanning electron microscopy (FESEM) and Transmission electron microscopy (TEM) results showed the nanometer dimension of the nanorods. Raman, FTIR, and TGA/DTA analyses revealed the formation of wurtzite ZnO. The antibacterial properties of ZnO nanorods were investigated using both Gram-positive and Gram-negative microorganisms. These studies demonstrate that ZnO nanorods have a wide range of antibacterial activities toward various microorganisms that are commonly found in environmental settings. Survival ratio of bacteria decreased with increasing powder concentration, i.e., increase in antibacterial activity. The antibacterial activity of the ZnO nanorods toward Pseudomonas aeruginosa was stronger than that of Escherichia coli and Staphylococcus aureus. Surprisingly, the antibacterial activity did not require specific UV activation using artificial lamps, rather activation was achieved under ambient lighting conditions. Overall, the experimental results suggest that ZnO nanorods could be developed as antibacterial agents against a wide range of microorganisms to control and prevent the spreading and persistence of bacterial infections. This research introduces a new concept to synthesize ZnO nanorods by using egg white as a biological template for various applications including food science, animal science, biochemistry, microbiology and medicine.

Current Trends in Electric Discharge Machining Using Micro and Nano Powder Materials- A Review

Powder mixed electric discharge machining (PMEDM) has clearly proven its advantages over EDM without additives. When controlled size and concentration of metal particles are mixed in the dielectric medium of Electrical discharge machining it helps to improve the various machining parameters like increased MRR, reduced surface roughness, reduced tool wear rate and improved topological properties like reduction in microholes, micropores, thin recast layer and improved corrosion resistance of the machined surface. Therefore, PMEDM have attracted the attention of many researchers since last few decade. This paper present a summary of some important research work done on PMEDM by mixing micro and Nano size particle in the dielectric fluid of EDM. Further this review article discuss not only the effect of micro or nano particle size and concentration on the EDM performance but also unfold the other factors like thermal conductivity, electric resistivity and density of micro or nano particles and optimal machine parameters such as peak current, pulse on time andpulse off time which affects the machining performance. From literature review, it has been found that surface finish in PMEDM increases with the decreased particle size and increased powder concentration upto certain limit, but increasing powder concentration beyond the optimal value create short circuit between the tool electrode and workpiece and hence reduces the surface finish. Furthermore micro or nano particles transfer less heat to workpiece by increasing the electrode gap approximately twice as compare to EDM without micro or nano particle, hence improved surface finish and reduced tool wear rate were achieved. Authors have also identified the research gap for further research purpose.

Antibacterial activity of ZnO nanoparticle on Gram-positive and Gram-negative bacteria

The aim of the present study is to determine the antimicrobial activity of ZnO nanoparticles against Gram-negative and Gram-positive bacteria. Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) were used as test microorganisms. The effects of particle size and concentration on the antibacterial activity of ZnO nanoparticles was studied using bacteriological tests such as disc and well diffusion agar methods, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC). These tests were performed in nutrient broth and nutrient agar following standard methods. In addition, the effect of different concentrations of ZnO nanoparticles on the growth of E. coli and S. aureus was measured with respect of time. The minimum inhibitory concentration was determined using seven different concentrations of ZnO nanoparticles including 16, 8, 4, 2, 1 and 0.5 mg/ml. The MIC value for E. coli and S. aureus was 1 and 0.5 mg/ml, respectively. The results showed that ZnO nanoparticles have antibacterial inhibition zone of 29 and 19 mm at the concentration of 10 mg/ml against E. coli and S. aureus, respectively. Gram-negative bacteria seemed to be more resistant to ZnO nanoparticles than Gram-positive bacteria. It was found that the antibacterial activity of ZnO nanoparticles increased with decreasing particle size and increasing powder concentration. The antibacterial effect of ZnO nanoparticles was time dependent and takes effect gradually. ZnO bulk powder showed no significant antibacterial activity. Key word: ZnO nanoparticle, Escherichia coli, Staphylococcus aureus, minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC).

감마선 조사에 따른 미역귀(Undaria pinnatifida Sporophyll) 열수추출물 첨가 파운드케이크의 품질 특성

This study investigated the quality changes and characteristics (0, 3, 6, 9%) of pound cake made with flour that included gamma irradiated (50 kGy) hot water extracts of Undaria pinnatifida sporophyll (WEUS). The pH of pound cakes decreased with increasing powder concentration, and gamma-irradiated pound cakes had lower pH than non-irradiated pound cakes at the same powder concentrations. The height, volume, specific loaf volume, and baking loss showed no significant differences between control and experimental groups. With increasing powder concentration, the L value of the crust and crumbs decreased, but the a value increased. The b value showed different tendencies between crust and crumb. The crust value was reduced with higher content of WEUS, but the crumb value increased. Gamma-irradiated pound cakes were also less hard than non-irradiated pound cakes. On the other hand, adhesiveness and springiness decreased with increasing powder concentration, but were not significantly different from the control. Also, gumminess and chewiness decreased but not significantly so. The hardness after several days of storage (5, 10, and 15 days) was higher than the control, and the springiness and cohesiveness were significantly reduced with increasing concentration compared to the control. The retrogradation increased in the control group, but it did not in the experimental groups. Results of radical scavenging activity using DPPH indicated that the gamma-irradiated group was higher than the non-irradiated group and it was also higher with higher concentrations of powder. In a sensory evaluation, when compared to the control, pound cake with 3% WEUS was superior in taste, flavor, and overall preference. Therefore, it was found that pound cake with 3% WEUS powder with gamma irradiation of 50 kGy added could improve the yield, taste, and antioxidant activity of pound cake.

들깻잎 분말을 첨가한 파운드케이크의 품질 특성

기능성 소재로서의 들깻잎 분말의 이용가능성을 알아보기 위해 들깻잎 분말 0, 5, 10 및 15% 첨가한 파운드케이크를 제조하여 품질 특성을 조사하였다. 반죽 및 파운드케이크의 pH는 들깻잎 분말 첨가에 의해 감소하였고, 굽기손실률은 첨가량에 따른 유의차가 나타나지 않았다. 높이는 들깻잎분말의 첨가량이 증가할수록 감소하는 경향을 보였으며, 무게는 대조군의 값이 가장 높았지만 시료간의 유의차이는 나타나지 않았다. 파운드케이크의 색도 측정 결과는 L(lightness) 값과 b(yellowness)값에서 crust와 crumb 모두 들깻잎 분말첨가량이 증가할수록 유의적으로 감소하였고, a(redness)값은 crust가 들깻잎 분말 첨가량이 증가할수록 유의적으로 감소하였지만, crumb은 대조군의 값이 가장 높았고 첨가군에서는 첨가량이 증가할수록 증가하는 것으로 나타났다. 파운드케이크의 관능검사 결과 들깻잎 분말 첨가는 색, 향미, 맛, 촉촉함, 전반적인 기호도를 향상시키는 긍정적인 영향을 미치나 10% 이상의 너무 많은 들깻잎 분말 첨가는 관능적인 기호도를 오히려 떨어뜨리는 것으로 나타났으며, 들깻잎 분말 5% 첨가군의 선호도가 가장 좋아 파운드케이크의 품질 및 관능적 특성을 고려한 들깻잎 분말 첨가량은 5% 첨가군이 최적 조건일 것으로 판단된다. 물성 측정 결과는 들깻잎분말 첨가량이 증가함에 따라 경도는 증가한 반면, 탄력성, 응집성은 감소하였고, 검성과 씹힘성은 시료 간 유의적 차이를 보이지 않았으며, 저장 7일에는 들깻잎 분말 첨가에 따라 일정한 경향을 나타내지 않았다. 저장함에 따라 노화도는 증가하였는데, 들깻잎 분말 무첨가군의 노화도가 296.36%로 가장 낮았으며, 들깻잎 분말 첨가에 따라 5% 첨가군 306.44%, 10% 첨가군 334.47%로 증가하는 경향을 보이다가 15% 첨가군에서는 320.83%로 다소 감소하였다. 항산화 활성은 들깻잎 분말 첨가량이 증가할수록 유의적으로 증가하였으며, 저장에 따라 감소하는 경향을 보였다.

Antibacterial characteristics of CaCO3–MgO composites

Dentifrices, such as tooth-paste, are pastes containing insoluble abrasives that aid in the removal of plaque from the teeth and help to polish them. Composite powders contributing to oral hygiene application, i.e., nano-scale MgO crystallite dispersed in CaCO 3 grain, were fabricated by the thermal decomposition of dolomite. The composite obtained by heating at 800 °C consisted of CaCO 3 grains including 20 nm MgO fine crystallite, being the purpose powder in this study. The antibacterial activity of these powders related to gram-positive and gram-negative bacteria was evaluated in vitro . The thermal decomposition above 800 °C resulted in the mixture of CaO and MgO. Antibacterial activity of the composite enhanced with increasing powder concentration. Though antibacterial action toward Staphylococcus aureus was greater than towards Escherichia coli , the death rate constant was identical in both bacteria. It can be concluded that the obtained composite possesses two functions able to improve the oral hygiene: as a tooth abrasive and as an antibacterial agent.

Antibacterial activity of ZnO powder with crystallographic orientation

ZnO powder with crystallographic orientation was prepared from the mixed aqueous solution of zinc chloride, tri-ethanol amine and thio-urea. From X-ray diffraction measurement, as-prepared powder was found to have the orientation along a-b axes of hexagonal structure, and a needle-like shape with the aspect ratio of 5 was observed by scanning electron microscope, indicating that as-prepared powder had crystallographic orientation. In the tests of antibacterial activity by colony count method, ZnO powders with and without crystallographic orientation were used in present work. Survival ratio of bacteria decreased with increasing powder concentration, i.e., increase in antibacterial activity. The antibacterial activity in ZnO powder with crystallographic orientation was weaker than that in commercial ZnO powder without orientation at same powder concentration. Regarding specific surface area of the powders used in antibacterial tests, however, antibacterial activity in powder with orientation was found to be similar to that without orientation; that is, the crystallographic orientation of ZnO did not affect antibacterial activity. The activity toward Staphylococcus aureus was stronger than that toward Escherichia coli, irrespective of the kind of powders.

Influence of particle size on the antibacterial activity of zinc oxide

The influence of particle size on the antibacterial activity of ZnO powders was investigated using powders with different particle sizes ranging from 0.1 to 0.8 μm. By measuring the change in electrical conductivity with bacterial growth, it was found that the antibacterial activity of ZnO increased with decreasing particle size and increasing powder concentration. The changes of antibacterial action for Staphylococcus aureus were similar to those for Escherichia coli. However, the influence of particle size for Staphylococcus aureus was less than that for Escherichia coli.

Kinetic analysis of death of bacteria in CaO powder slurry

The process of Escherichia coli and Staphylococcus aureus death in calcium oxide (CaO) powder slurry was assumed to follow first-order reaction kinetics. The apparent death rate constant ( k) was found to increase with increasing powder concentration and was higher than that for a NaOH solution having the same pH as the CaO powder slurry. The slurry temperature was found to significantly affect the bactericidal action of the CaO powder slurry against both E. coli and S. aureus. The slope of the Arrhenius plot of k for both bacteria changed at a slurry temperature of approximately 22°C, suggested to correspond to a change in the activation energy required to induce the death of bacteria in CaO powder slurry as a result of a phase transition of the cell membrane.

Mechanism of particle shape modification by dry impact blending

It was confirmed that it is possible to prepare particles of different shape by a dry impact blending method in our previous study. Here, the particle shape modification process is analyzed on the basis of a mechanical model. The particle shape is assumed to be spheroidal and is represented by an inverse of the elongation index. Then the shape becomes more spherical with treatment time and peripheral velocity of the rotor irrespective of particle size, but the shape index decreases with increasing powder concentration. It is, therefore, proposed that particle shape is to be deformed by impact force and to attain the limiting condition. The experimental results with stainless steel powder were well fitted with the present model.