Alloying has been very common practice in materials engineering to fabricate metals of desirable ... more Alloying has been very common practice in materials engineering to fabricate metals of desirable properties for specific applications. Traditionally, a small amount of the desired material is added to the principal metal. However, a new alloying technique emerged in 2004 with the concept of adding several principal elements in or near equi-atomic concentrations. These are popularly known as high entropy alloys (HEAs) which can have a wide composition range. A vast area of this composition range is still unexplored. The HEAs research community is still trying to identify and characterize the behaviors of these alloys under different scenarios to develop high-performance materials with desired properties and make the next class of advanced materials. Over the years, understanding of the thermodynamics theories, phase stability and manufacturing methods of HEAs has improved. Moreover, HEAs have also shown retention of strength and relevant properties under extreme tribological conditions and radiation. Recent progresses in these fields are surveyed and discussed in this review with a focus on HEAs for use under extreme environments (i.e., wear and irradiation) and their fabrication using additive manufacturing.
In this study, a novel polymer filler polytetrafluoroethylene was used in the fabrication and tes... more In this study, a novel polymer filler polytetrafluoroethylene was used in the fabrication and testing of dental composite. The effect of low content of polytetrafluoroethylene (0 wt%-9 wt%) on mechanical and wear behavior of dental composite was investigated. The mechanical behavior was studied using Micro-Hardness, Compressive strength, Dynamic mechanical analysis and Thermo-gravimetric analysis. The in vitro wear tests were performed on dental wear simulator by varying number of cycles, sliding speed, normal load and filler content. The finding of results indicated that composites with increased in polytetrafluoroethylene fillers exhibited better mechanical and wear properties and showed smoother worn surface in artificial saliva medium. The hardness and compressive strength of dental composite were increased by 54.32% and 13.36% respectively with the addition of 9 wt% polytetrafluoroethylene. The storage modulus and damping ratio were increased with the increase in polytetrafluoroethylene. In two-body abrasive wear, the wear rate of dental composite was increased with increase in the number of cycles, normal load and sliding speed. Apart from excellent aesthetic properties, PTFE slightly improved the mechanical and wear properties of dental material.
Advances in Micro and Nano Manufacturing and Surface Engineering , 2019
Single crystal diamond (SCD) is the ideal tool material in ultra-precision
machining because of i... more Single crystal diamond (SCD) is the ideal tool material in ultra-precision machining because of its high hardness, wear resistance, chemical stability, and the ability to sharpen the cutting edge in nanometers. The sub-micron level in the cutting edge profile could affect the accuracy of the fabricated surfaces, since cutting edge radii strongly influence the specific cutting energy, cutting forces, cutting temperature, residual stress in the workpiece. Therefore, cutting edge profile of an SCD tool should be checked periodically. The measurements of cutting edge radii of SCD tools are very difficult because of their geometric features (angles, radius... etc) and their dimensions in the nanometric level. This paper deals with various methods of cutting edge characterization of SCD tool by Atomic ForceMicroscopy (AFM). The change to measurement of the cutting edge radii has been done based on the methodology of the least square circle fit over cutting edge radius with error minimization in the calculation and determined iteratively.
Advances in Mechanical Processing and Design, 2020
The effects of gas nitriding have been studied for Ti-6Al-4V alloy at different time and temperat... more The effects of gas nitriding have been studied for Ti-6Al-4V alloy at different time and temperatures. Gas nitriding was performed from 600°C to 1200°C for the duration of 4 to 8 hours using Dilatometer. The surface roughness values were compared to get insight into the surface morphology. Sample appearance after nitriding was different from the base metal, and color demonstrated variation with time and temperature. After nitriding the basic metallic silver color was converted into blue, golden and gray. At lower temperatures, blue and golden color was common and as temperature increased the color changed to grayish. Initially at lower temperatures (i.e. 600°C and 700°C), titanium alloy's silver metallic color turned into blue/golden, and the intensity of this color was increased with the increase in temperature and time of nitriding. Moreover, above beta transus temperature (i.e. 1000°C, 1100°C and 1200°C), the material appeared to be gray. The hardness after nitriding was increased with increase in nitriding layer thickness. The maximum hardness value HV 0.5 was reported to be 1735. Surface images were taken by Scanning Electron Microscopy (SEM), and these images revealed that the formation of nitrides was started from the grain boundaries.
Single crystal diamond (SCD) is the preferred tool material for ultra-precision machining for cut... more Single crystal diamond (SCD) is the preferred tool material for ultra-precision machining for cutting operation at nanometric level. Due to the well-known and exceptional difficulty in shaping, the fabrication of diamond-cutting tool requires special processing methods. If there is any damage (wear, chipping) on the tool, it is directly reflected on workpiece surfaces. Patterning and sharpening have been done on diamond tools with a nano level, which can be used for some special applications like micro-lens arrays, sinusoidal grid, Fresnel lenses and pyramids array. The limitation of conventional techniques like polishing and lapping can produce up to the scale of tens of microns. Focused ion beam (FIB) technique is a well-established technique for machining materials at micro and nanoscale. Our point of focus is on the fabrication of texture on the diamond tool using focused ion beam (FIB) milling technology. Effect of parameters as beam current, milling time, surface conductivity is studied and optimized.
In this study, a novel polymer filler polytetrafluoroethylene was used in the fabrication and tes... more In this study, a novel polymer filler polytetrafluoroethylene was used in the fabrication and testing of dental composite. The effect of low content of polytetrafluoroethylene (0 wt%-9 wt%) on mechanical and wear behavior of dental composite was investigated. The mechanical behavior was studied using Micro-Hardness, Compressive strength, Dynamic mechanical analysis and Thermo-gravimetric analysis. The in vitro wear tests were performed on dental wear simulator by varying number of cycles, sliding speed, normal load and filler content. The finding of results indicated that composites with increased in polytetrafluoroethylene fillers exhibited better mechanical and wear properties and showed smoother worn surface in artificial saliva medium. The hardness and compressive strength of dental composite were increased by 54.32% and 13.36% respectively with the addition of 9 wt% polytetrafluoroethylene. The storage modulus and damping ratio were increased with the increase in polytetrafluoroethylene. In two-body abrasive wear, the wear rate of dental composite was increased with increase in the number of cycles, normal load and sliding speed. Apart from excellent aesthetic properties, PTFE slightly improved the mechanical and wear properties of dental material.
The aim of this study was to fabricate BisGMA based nanosilica filled dental composites and to st... more The aim of this study was to fabricate BisGMA based nanosilica filled dental composites and to study the effect of varying nanosilica filler content on their wear characteristics. The composites were developed by varying filler content of silane treated nanosilica from 0 to 9 wt%, into the resin matrix consisting of 51 wt% Bisphenol-A glycidyl methacrylate, 46.5 wt% Tri-ethylene glycol dimethacrylate, 0.24 wt% Camphorquinone, 1.5 wt% Butyl hydroxyl toluene and 0.76 wt% Dimethylamino ethyl methacrylate. The hardness was determined using Vickers's micro hardness tester. The two body abrasive wear experiments were performed in the artificial saliva medium as per Taguchi Orthogonal Array and steady state condition by varying parameters such as filler content, normal load, and chewing speed. The finding of results indicated that the wear resistance and hardness were improved with increase in filler fraction. The dental composite filled with 9 wt% of nanosilica filler exhibited maximum hardness (31.4 HV), maximum compression strength (360.5 MPa) and flexural strength (120.5 MPa) and minimum volumetric wear rate. Also, the wear volume increased with the increase in normal load, chewing speed and number of cycles but decreased with the increase in filler content. Statistical significance of each factor as per generalized linear model of Analysis of Variance showed that filler content was the most influencing factor followed by applied normal load, numbers of cycle and chewing speed. Worn surfaces were studied using a scanning electron microscope (SEM) to give an insight into the wear mechanisms.
Alloying has been very common practice in materials engineering to fabricate metals of desirable ... more Alloying has been very common practice in materials engineering to fabricate metals of desirable properties for specific applications. Traditionally, a small amount of the desired material is added to the principal metal. However, a new alloying technique emerged in 2004 with the concept of adding several principal elements in or near equi-atomic concentrations. These are popularly known as high entropy alloys (HEAs) which can have a wide composition range. A vast area of this composition range is still unexplored. The HEAs research community is still trying to identify and characterize the behaviors of these alloys under different scenarios to develop high-performance materials with desired properties and make the next class of advanced materials. Over the years, understanding of the thermodynamics theories, phase stability and manufacturing methods of HEAs has improved. Moreover, HEAs have also shown retention of strength and relevant properties under extreme tribological conditions and radiation. Recent progresses in these fields are surveyed and discussed in this review with a focus on HEAs for use under extreme environments (i.e., wear and irradiation) and their fabrication using additive manufacturing.
In this study, a novel polymer filler polytetrafluoroethylene was used in the fabrication and tes... more In this study, a novel polymer filler polytetrafluoroethylene was used in the fabrication and testing of dental composite. The effect of low content of polytetrafluoroethylene (0 wt%-9 wt%) on mechanical and wear behavior of dental composite was investigated. The mechanical behavior was studied using Micro-Hardness, Compressive strength, Dynamic mechanical analysis and Thermo-gravimetric analysis. The in vitro wear tests were performed on dental wear simulator by varying number of cycles, sliding speed, normal load and filler content. The finding of results indicated that composites with increased in polytetrafluoroethylene fillers exhibited better mechanical and wear properties and showed smoother worn surface in artificial saliva medium. The hardness and compressive strength of dental composite were increased by 54.32% and 13.36% respectively with the addition of 9 wt% polytetrafluoroethylene. The storage modulus and damping ratio were increased with the increase in polytetrafluoroethylene. In two-body abrasive wear, the wear rate of dental composite was increased with increase in the number of cycles, normal load and sliding speed. Apart from excellent aesthetic properties, PTFE slightly improved the mechanical and wear properties of dental material.
Advances in Micro and Nano Manufacturing and Surface Engineering , 2019
Single crystal diamond (SCD) is the ideal tool material in ultra-precision
machining because of i... more Single crystal diamond (SCD) is the ideal tool material in ultra-precision machining because of its high hardness, wear resistance, chemical stability, and the ability to sharpen the cutting edge in nanometers. The sub-micron level in the cutting edge profile could affect the accuracy of the fabricated surfaces, since cutting edge radii strongly influence the specific cutting energy, cutting forces, cutting temperature, residual stress in the workpiece. Therefore, cutting edge profile of an SCD tool should be checked periodically. The measurements of cutting edge radii of SCD tools are very difficult because of their geometric features (angles, radius... etc) and their dimensions in the nanometric level. This paper deals with various methods of cutting edge characterization of SCD tool by Atomic ForceMicroscopy (AFM). The change to measurement of the cutting edge radii has been done based on the methodology of the least square circle fit over cutting edge radius with error minimization in the calculation and determined iteratively.
Advances in Mechanical Processing and Design, 2020
The effects of gas nitriding have been studied for Ti-6Al-4V alloy at different time and temperat... more The effects of gas nitriding have been studied for Ti-6Al-4V alloy at different time and temperatures. Gas nitriding was performed from 600°C to 1200°C for the duration of 4 to 8 hours using Dilatometer. The surface roughness values were compared to get insight into the surface morphology. Sample appearance after nitriding was different from the base metal, and color demonstrated variation with time and temperature. After nitriding the basic metallic silver color was converted into blue, golden and gray. At lower temperatures, blue and golden color was common and as temperature increased the color changed to grayish. Initially at lower temperatures (i.e. 600°C and 700°C), titanium alloy's silver metallic color turned into blue/golden, and the intensity of this color was increased with the increase in temperature and time of nitriding. Moreover, above beta transus temperature (i.e. 1000°C, 1100°C and 1200°C), the material appeared to be gray. The hardness after nitriding was increased with increase in nitriding layer thickness. The maximum hardness value HV 0.5 was reported to be 1735. Surface images were taken by Scanning Electron Microscopy (SEM), and these images revealed that the formation of nitrides was started from the grain boundaries.
Single crystal diamond (SCD) is the preferred tool material for ultra-precision machining for cut... more Single crystal diamond (SCD) is the preferred tool material for ultra-precision machining for cutting operation at nanometric level. Due to the well-known and exceptional difficulty in shaping, the fabrication of diamond-cutting tool requires special processing methods. If there is any damage (wear, chipping) on the tool, it is directly reflected on workpiece surfaces. Patterning and sharpening have been done on diamond tools with a nano level, which can be used for some special applications like micro-lens arrays, sinusoidal grid, Fresnel lenses and pyramids array. The limitation of conventional techniques like polishing and lapping can produce up to the scale of tens of microns. Focused ion beam (FIB) technique is a well-established technique for machining materials at micro and nanoscale. Our point of focus is on the fabrication of texture on the diamond tool using focused ion beam (FIB) milling technology. Effect of parameters as beam current, milling time, surface conductivity is studied and optimized.
In this study, a novel polymer filler polytetrafluoroethylene was used in the fabrication and tes... more In this study, a novel polymer filler polytetrafluoroethylene was used in the fabrication and testing of dental composite. The effect of low content of polytetrafluoroethylene (0 wt%-9 wt%) on mechanical and wear behavior of dental composite was investigated. The mechanical behavior was studied using Micro-Hardness, Compressive strength, Dynamic mechanical analysis and Thermo-gravimetric analysis. The in vitro wear tests were performed on dental wear simulator by varying number of cycles, sliding speed, normal load and filler content. The finding of results indicated that composites with increased in polytetrafluoroethylene fillers exhibited better mechanical and wear properties and showed smoother worn surface in artificial saliva medium. The hardness and compressive strength of dental composite were increased by 54.32% and 13.36% respectively with the addition of 9 wt% polytetrafluoroethylene. The storage modulus and damping ratio were increased with the increase in polytetrafluoroethylene. In two-body abrasive wear, the wear rate of dental composite was increased with increase in the number of cycles, normal load and sliding speed. Apart from excellent aesthetic properties, PTFE slightly improved the mechanical and wear properties of dental material.
The aim of this study was to fabricate BisGMA based nanosilica filled dental composites and to st... more The aim of this study was to fabricate BisGMA based nanosilica filled dental composites and to study the effect of varying nanosilica filler content on their wear characteristics. The composites were developed by varying filler content of silane treated nanosilica from 0 to 9 wt%, into the resin matrix consisting of 51 wt% Bisphenol-A glycidyl methacrylate, 46.5 wt% Tri-ethylene glycol dimethacrylate, 0.24 wt% Camphorquinone, 1.5 wt% Butyl hydroxyl toluene and 0.76 wt% Dimethylamino ethyl methacrylate. The hardness was determined using Vickers's micro hardness tester. The two body abrasive wear experiments were performed in the artificial saliva medium as per Taguchi Orthogonal Array and steady state condition by varying parameters such as filler content, normal load, and chewing speed. The finding of results indicated that the wear resistance and hardness were improved with increase in filler fraction. The dental composite filled with 9 wt% of nanosilica filler exhibited maximum hardness (31.4 HV), maximum compression strength (360.5 MPa) and flexural strength (120.5 MPa) and minimum volumetric wear rate. Also, the wear volume increased with the increase in normal load, chewing speed and number of cycles but decreased with the increase in filler content. Statistical significance of each factor as per generalized linear model of Analysis of Variance showed that filler content was the most influencing factor followed by applied normal load, numbers of cycle and chewing speed. Worn surfaces were studied using a scanning electron microscope (SEM) to give an insight into the wear mechanisms.
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machining because of its high hardness, wear resistance, chemical stability, and the
ability to sharpen the cutting edge in nanometers. The sub-micron level in the cutting
edge profile could affect the accuracy of the fabricated surfaces, since cutting edge
radii strongly influence the specific cutting energy, cutting forces, cutting temperature,
residual stress in the workpiece. Therefore, cutting edge profile of an SCD tool
should be checked periodically. The measurements of cutting edge radii of SCD tools
are very difficult because of their geometric features (angles, radius... etc) and their
dimensions in the nanometric level. This paper deals with various methods of cutting
edge characterization of SCD tool by Atomic ForceMicroscopy (AFM). The change
to measurement of the cutting edge radii has been done based on the methodology
of the least square circle fit over cutting edge radius with error minimization in the
calculation and determined iteratively.
machining because of its high hardness, wear resistance, chemical stability, and the
ability to sharpen the cutting edge in nanometers. The sub-micron level in the cutting
edge profile could affect the accuracy of the fabricated surfaces, since cutting edge
radii strongly influence the specific cutting energy, cutting forces, cutting temperature,
residual stress in the workpiece. Therefore, cutting edge profile of an SCD tool
should be checked periodically. The measurements of cutting edge radii of SCD tools
are very difficult because of their geometric features (angles, radius... etc) and their
dimensions in the nanometric level. This paper deals with various methods of cutting
edge characterization of SCD tool by Atomic ForceMicroscopy (AFM). The change
to measurement of the cutting edge radii has been done based on the methodology
of the least square circle fit over cutting edge radius with error minimization in the
calculation and determined iteratively.