White Light Interferometer Microscope Research Articles

Organic-inorganic core-shell materials as reinforced fillers of UHMWPE to improve its tribological and mechanical properties

Generally, modification of materials by adding multiple types of nano particles could cause dispersion problems, generally limited the performance improvement effect. Herein, we report the modification of UHMWPE materials by organic-inorganic core-shell particles with PTFE as the core and Al(OH)3 as the shell, which prepared by in-situ polymerization of sodium bicarbonate and aluminum sulfate solution. Core-shell particles were filled in UHMWPE matrix and sintered into composite by spark plasma sintering (SPS). The mechanical and tribological properties of the composites were characterized by tensile compression testing machine, universal micro tribometer (UMT-5), three-dimensional white light interferometer and scanning electron microscope (SEM). The results showed that the addition of core-shell structural materials effectively improved the tribological properties (friction coefficient decreased by 40%, wear rate decreased by 30%) and mechanical properties (compression strength increased by 2.4 times) of the composites. It was demonstrated that the inorganic framework provided strength to improve the mechanical properties and wear resistance of materials, and the organic phase was used as a lubricating phase to reduce the friction coefficient of materials. Surface treatment of core-shell particles both improved the binding between particles and matrix and decreased the formation of agglomerations, thus significantly reducing ploughing phenomena’s effect produced by abrasive wear of agglomeration

Experimental investigation on mode I fracture characteristics of Longmaxi formation shale after cyclic thermal shock and high-temperature acid etching treatments

Fracture toughness is a key parameter for shale hydraulic fracturing design, which directly affects the fracture initiation pressure. In this paper, the influence of cyclic thermal shock and high-temperature acid etching on the Mode I fracture of Longmaxi Formation shale was investigated. The crack propagation was obtained by using acoustic emission (AE) and digital image correlation (DIC) techniques. Meanwhile, the fracture surface morphology and microstructure of the specimens were analyzed using white light interferometer and scanning electron microscope (SEM). The experimental results demonstrate that cyclic thermal shock severely degrades the nominal strength and fracture toughness of shale. The average fracture toughness is found to be only 0.67 MPa·m0.5, which accounts for a reduction of 25.9 %. AE analysis reveals that microfracture is the dominant mechanism, with the highest amplitude of AE source only 78 dB. The critical strain value of the fracture propagation zone (FPZ) is determined to be 1.35 ‰, and SEM images indicate that along-crystal fracture is the primary fracture mechanism. On the other hand, the shale specimen subjected to high-temperature acid-etching treatment exhibits an average fracture toughness of 0.86 MPa·m0.5, with the AE source amplitude reaching 86 dB. The critical strain value of the FPZ was measured to be 2.38 ‰. The fracture surface appears smooth and is mainly characterized by perforated-crystal rupture. The findings of this study not only enhance our understanding of shale mode I fracture toughness but also provide valuable insights for optimizing process parameters to reduce initiation pressure in deep shale formations.

Osseointegration of Sandblasted and Acid-Etched Implant Surfaces. A Histological and Histomorphometric Study in the Rabbit.

Titanium surface is an important factor in achieving osseointegration during the early wound healing of dental implants in alveolar bone. The purpose of this study was to evaluate sandblasted-etched surface implants to investigate the osseointegration. In the present study, we used two different types of sandblasted-etched surface implants, an SLA™ surface and a Nanoblast Plus™ surface. Roughness and chemical composition were evaluated by a white light interferometer microscope and X-ray photoelectron spectroscopy, respectively. The SLA™ surface exhibited the higher values (Ra 3.05 μm) of rugosity compared to the Nanoblast Plus™ surface (Ra 1.78 μm). Both types of implants were inserted in the femoral condyles of ten New Zealand white rabbits. After 12 weeks, histological and histomorphometric analysis was performed. All the implants were osseointegrated and no signs of infection were observed. Histomorphometric analysis revealed that the bone–implant contact % (BIC) ratio was similar around the SLA™ implants (63.74 ± 13.61) than around the Nanoblast Plus™ implants (62.83 ± 9.91). Both implant surfaces demonstrated a favorable bone response, confirming the relevance of the sandblasted-etched surface on implant osseointegration.

An Investigation of Effect of Stand-Off Distance on the Material Removal Characteristics and Surface Generation in Fluid Jet Polishing

Fluid jet polishing (FJP) is a versatile polishing process that has many advantages compared to other polishing processes. Stand-off distance (SOD) is one of the key parameters in fluid jet polishing. However, relatively little research work has been carried out to investigate its effect of SOD on material removal characteristics and surface generation in FJP. In this paper, a systematic investigation of the effect of SOD on the tool influence function and surface topography in FJP was conducted. Experiments were designed for FJP two kinds of materials corresponding to ductile and brittle materials. They are nickel copper (NiCu) alloy and BK7 optical glass, respectively. In this study, the SOD was varied from 2 to 35 mm. Analysis and discussions were made on its effect on the shape of TIF, material removal rate, and surface topography. It is interesting to note that the TIF shape becomes a Gaussian-like shape with large SOD both on NiCu and BK7, which provides a novel way to optimize the TIF in FJP. The variation of the material removal rate and surface roughness versus SOD on NiCu and BK7 were also determined from the experimental results. Moreover, the surface topography of NiCu and BK7 were characterized from the results measured from the white light interferometer and scan electron microscope. The outcome of the study provides a better understanding of the material removal characteristics and surface generation mechanism in FJP.

Insight into role and mechanism of Li on the key aspects of biodegradable ZnLi alloys: Microstructure evolution, mechanical properties, corrosion behavior and cytotoxicity.

ZnLi based alloys have been proved as desirable candidates for biodegradable materials accounting for its high mechanical performance and great biocompatibility. However, effects of Li on microstructure and comprehensive properties of Zn alloys are seldom investigated and need to be addressed. Herein, Zn-(0.1-1.4wt%)Li alloys are fabricated and systematically analyzed. Lath-like Zn precipitates are observed in the primary β-LiZn4 (β) phase of Zn-(0.5-1.4wt%)Li alloys, leading to the formation of dense β/Zn lamellar structure with an inter-spacing of 0.8μm. Mechanical tests show that the strengths of the ZnLi alloys have at least tripled due to the formation of dense β/Zn lamellar structure. Early degradation behaviors of the ZnLi alloys in simulated body fluid (SBF) reveal a competitive releasing of Li+ and Zn2+. As the priority of Li+ releasing becomes more obvious with increasing Li content in the alloys, aqueous insoluble Li-rich corrosion products containing LiOH and Li2CO3 form a passivation film on Zn-(0.5-1.4wt%)Li alloys. Consequently, corrosion rate decreases significantly from 45.76μm/y of pure Zn to 14.26μm/y of Zn-1.4Li alloy. Importantly, observations of white light interferometer microscope and transmission electron microscope demonstrate that β phase degrades prior to Zn in the alloys, suggesting that biomedical implants made of ZnLi alloys are likely to degrade completely in human body. Cytotoxicity tests of the alloys exhibit no cytotoxicity in 10% extracts. The most tolerated Zn2+/Li+ concentrations of the alloy extracts to L-929 cells are calculated, which provides guidance for future design of Zn alloys containing Li.

Laser technique in diaphragm cum rupture disc for defence oriented silver oxide zinc reserve batteries

ABSTRACTThis paper deals with a novel method of forming a score mark to develop silver based metal diaphragm cum rupture disc using laser micro machining technique. Defense oriented primary reserve type silver oxide zinc batteries utilize metallic diaphragm cum rupture disc with controlled indentation in the battery activation system. The criticality of the score mark to meet the activation parameters calls for a precise and controlled technique for “scoring” like micro machining using laser. The study of laser machining involves various metals, which act as a safety pressure relief system. The uniqueness of the work relates to devising a process for the making of diaphragm, which bursts at a pre-set pressure to allow flow of electrolyte, to activate a battery and not as a mere safety pressure relief system. Detailed analysis of silver diaphragm is performed through dynamic and destructive tests. Investigations through white light interferometer (WLI) and scanning electron microscope (SEM) have confirmed the repeatability of process. A novel method of making diaphragm catering to the requirements is established in this work and full description of the process including various process parameters is presented.

Fabrication of multi-scale micro-lens arrays on hydrophobic surfaces using a drop-on-demand droplet generator

Abstract A simple method was demonstrated for the fabrication of multi-scale polymer microlenses (µ-lenses) and microlens arrays (MLAs) using a drop-on-demand (DOD) droplet generator. A ultraviolet (UV) curable polymer used as the ink was DOD printed on the hydrophobic surfaces with different wetting conditions and cured by a UV lamp. The high quality µ-lenses and MLAs with good geometrical uniformity were fabricated. The shapes of the µ-lenses and MLAs were controlled by the different surface wetting conditions, and these shape changes affected the optical properties of the µ-lenses and MLAs, such as the numerical aperture (NA), focal distance ( f ) and the f -number ( f # ). The surface roughness of the µ-lens was measured by a white light interferometer (VSI mode) and atomic force microscope (AFM) and proved satisfactory. The influences of the surface wetting conditions on imaging and light gathering characteristics of the MLAs were evaluated by an optical microscope.

Research on full-aperture ductile cutting of KDP crystals using spiral turning technique

Single point diamond face flycutting technique is widely applied to fabricate potassium dihydrogen phosphate (KDP) crystals because of their characteristics of softness, brittleness, deliquescence and anisotropy. This paper studies the feasibility of machining KDP crystals through spiral turning method based on the ductile cutting mechanism of brittle materials. The spiral scratch method is employed to analyze various conditions of achieving brittle–ductile transition in different cutting directions where the critical depth of cut is obtained. The cutting forces and surface formation processes within different cutting parameters are discussed and the parameters ensuring full-aperture ductile turning are acquired. White light interferometer and Atomic Force Microscope (AFM) are used to evaluate the coherence of machined surface qualities in different cutting directions. The results indicate that the critical depth of cut varies from cutting directions significantly and fluctuates from about 200nm to 1000nm under the experimental condition. Cutting forces display periodical variation with the change of cutting direction and the periodical trend blurs, even ultimately disappears, with the decrease of the cutting parameters. Root-Mean-Square (RMS) value of the fabricated surface roughness fluctuates from 1.3nm to 1.7nm on the whole surface with no distinct anisotropic distribution of the surface morphology according to the results observed by AFM. Compared with face flycutting method, spiral turning method has capability to generate complex surface profiles such as aspheric or freeform surfaces and can also be used to compensate the deformation error of KDP crystals caused by vacuum suction during fabrication.

Effects of cavity surface temperature on reinforced plastic part surface appearance in rapid heat cycle moulding

The influences of the cavity surface temperature just before filling on surface appearance and texture of the moulded reinforced plastic parts in rapid heat cycle moulding (RHCM) are investigated. Two typical reinforced plastics including ABS/PMMA/nano-CaCO3 and 20% fibre reinforced polypropylene (FRPP) are tested in experiments. The roughness, gloss and morphology of the part surface are characterized with white light interferometer, gloss meter, and optical microscope, respectively. It is observed that the cavity surface temperature just before filling has a significant influence on part surface appearance. With the increase of the cavity surface temperature just before filling, aesthetic quality of the moulded part can be greatly improved. There is a critical value of the cavity surface temperature just before filling for each plastic. As the cavity surface temperature reaches the critical value, part surface appearance will reach the optimal level with low roughness and high gloss. The weld mark for ABS/PMMA/nano-CaCO3 has a V-shaped structure while that for FRPP has a hump-shaped structure. With the increase of the cavity surface temperature just before filling, the width of the V-shaped weld mark reduces gradually until it disappears completely while the height of the hump-shaped weld mark decreases firstly and then increases. The mechanisms for the improvement of surface appearance by increasing cavity surface temperature just before filling and the generation of the V-shaped and hump-shaped weld mark are disclosed.

Surface observations and material removal mechanisms in rotary ultrasonic machining of brittle material

The numerous unique advantages afforded by rotary ultrasonic machining have led to its extensive utilization in machining hard–brittle materials. However, the material removal mechanisms are still not very clear, leaving many uncertainties of the machined components in practical application. In this research, machining/scratching tests had been undertaken on optical glass K9 with diamond tools under various process parameters. Surface morphologies were characterized using a measuring microscope, white-light interferometer and scanning electron microscope. On the basis of these examinations, the effects of ultrasonic vibration on the material removal mechanisms were investigated. As a result, another material removal mechanism, pulverization, was identified besides brittle fracture and plastic deformation. The pulverizable areas, which resulted from the force of the tortuous cracks propagation, were found to be prominent in the surrounding fracture areas. In addition, the influence of the pulverizable areas on the surface roughness was also investigated. The scratching results presented that the pulverization was induced by the impact effects of the abrasive at the vertex of its sinusoidal trajectory. The vertical inertia force of the abrasive and the inertial effects of the material, which were induced by the immense acceleration of single abrasive at the vertex of its sinusoidal trajectory, should be conducive to the nucleation of the first cracks.

Fabrication and investigation of 1D and 2D structures in LiNbO 3 thin films by pulsed laser ablation

Lithium niobate thin films were deposited on sapphire substrate by radio-frequency magnetron sputtering technique. One and two dimensional structures have been made using a KrF excimer laser at 248 nm and 6 ns pulse width, under various conditions of ablation, in order to assess the applicability of laser direct-writing of photonic waveguides. The optical and waveguiding properties of LiNbO 3 thin films were studied by prism-coupling technique, while micro-Raman spectroscopy was used for structural and composition characterization, as well as laser processing mechanism investigation. The surface morphology of the processed structures was obtained by a Nomarski optical microscope, an atomic force microscope and a White Light Interferometer Microscope.

Tribological Properties of Laser Surface Texturing and Molybdenizing Duplex-Treated Ni-Base Alloy

Laser surface texturing (LST) and surface molybdenizing duplex-treatment was performed on Ni-base alloy in order to improve its wear resistance at high temperature. Surface molybdenizing was performed on the laser surface textured Ni-base alloy by a double glow plasma surface alloying technology. The friction and wear properties of the duplex-treated, the single-treated, and the untreated alloys were tested on a ball-on-disk tribometer by rubbing against an alumina ceramic ball from room temperature to 600°C. The topography of the laser surface textured dimples was measured by a white light interferometer and optical microscope. The dimples are 150-200 μ m in diameter and 45-50 μ m in depth. The distance between the dimples is 500 μ m. The molybdenized layer is approximately 20 μ m in thickness. The elastic modulus of Ni-base alloy is improved by molybdenizing. After texturing and the molybdenizing duplex treatment, the friction coefficient of the Ni-base alloy decreases from 0.38 to 0.26 at room temperature and from 0.42 to 0.34 at 600°C. The wear rate of the duplex-treated alloy is much lower than that of the pristine alloy at 600°C due to the textured dimples storing lubricious oxides.

Calibration of a white light interferometer for the measurement of micro-scale dimensions

Calibration is central to most measurement procedures. This is especially true in those cases where a large number of difficult-to-identify and difficult-to-control factors hinder the experimenters in their efforts to obtain reliable measurement results. Dimensional measurements of features on the micro- and nano-scales is one such case. A white-light interferometer (WLI) microscope can perform measurements of a variety of measurands over a broad dimensional range: from surface texture characterisations on the nano-scale to measurements of step heights of several millimetres. Calibration methods based on the hypothesis of a linear calibration curve can be inadequate to express the relationship between measurement results and traceable reference materials (RMs). A calibration procedure built into a commercially available WLI microscope is critically compared with methods presented in an international standard. This comparison is enabled by a cost-effective procedure for establishing traceable RMs in the micro-range. Advantages of calibration procedures based on more than one RM are then demonstrated within the ranges from 180.5 to 219.5 μm and from 1.5 to 501.5 μm. Calibration methods involving regression modelling of transformed measurement results are considered for these two intervals to overcome the highlighted weaknesses of the calibration procedure built in the examined WLI.

A precision hot embossing mold fabricated by high-resolution powder blasting with polydimethylsiloxane and SU-8 masking technology

In this paper, we applied a three-dimensional micromold by using micropowder and micropattern masking technology. High-resolution powder blasting with polydimethylsiloxane (PDMS) and SU-8 masking is developed for the fabrication of a precision microfluidic mold for hot embossing fabrication. The PDMS is a suitable masking material for powder blasting due to its high erosion resistance. First, a 100 µm SU-8 negative pattern was developed on a stainless steel substrate by standard photolithography. A PDMS solution was then applied to the substrate, mainly filling recessed regions. Excess of PDMS was then physically removed by a blade. The PDMS/SU-8 structure was then cured. Next, silicon carbine (SiC) powder with an average diameter of 50 µm was blasted on a PDMS/SU-8 coated stainless sheet at a constant pressure between 4 and 6 bar and a PDMS mask was removed by ultrasonic cleaning in isopropanol. The three-dimensional structure was examined by an optical microscope, optical white light interferometer and scanning electron microscope. The PDMS pattern is found to be 50 µm wide, and the maximum etched depth at this thickness is around 150 µm at a blasting pressure of 6.2 bar; thus, an aspect ratio of 3 is easily obtained. In principle, the low-cost micromachining hot embossing mold developed can be improved to yield submicrometer- and nanometer-scale resolution.

Variability in measurements of micro lengths with a white light interferometer

AbstractThe effect of the discretionary set‐up parameters scan length and initial scanner position on the measurements of length performed with a white light interferometer microscope was investigated. In both analyses, two reference materials of nominal lengths 40 and 200 µm were considered. Random effects and mixed effects models were fitted to the data from two separate experiments. Punctual and interval estimates of variance components were provided. Copyright © 2008 John Wiley & Sons, Ltd.

Study on the use of white light interferometry for multifiber-end surface profile measurement

An optical microscopic system for measuring multifiber-end surface based on scanning white light interferometer is described. The designed Michelson interferometric configuration in which light reflectivity of a reference flat is selected to match that of a test surface enables a better contrast of the resulting interference fringes to be recorded. A local peak comparison approach is used to determine a fractional phase from the best-focus frame of a correlogram acquired by a vertical scanning achieved with a piezoelectric translator (PZT). The whole field measurement on a 12-fiber array of the plastic ferrule with a low reflective, rough, and discontinuous surface is implemented. Experimental results show that surface geometric profile on a multifiber-end is measurable. Comparison with measurements on standard calibrated objects shows that the accuracy of the proposed system is comparable with that of existing white light interferometer and atomic force microscope.