Laser Processing of Silica Aerogels Using Ultrashort Pulses

2000 ◽  
Author(s):  
J. Sun ◽  
J. P. Longtin ◽  
P. M. Norris
Keyword(s):  
Laser Processing ◽  
Material Removal ◽  
Removal Rate ◽  
High Surface ◽  
Laser System ◽  
High Surface Area ◽  
Ultrashort Pulses ◽  
Silica Aerogels ◽  
Ultrafast Laser ◽  
Breakdown Threshold

Abstract Silica aerogels are unique nanostructured materials that possess many distinctive qualities, including extremely low densities and thermal conductivities, very high surface-area-to-volume ratios, and large strength-to-weight ratios. Aerogels, however, are very brittle, and are not readily shaped using traditional machining operations. Ultrafast laser processing may provide an alternative for precision shaping and machining of these materials. This paper discusses investigations of ultrafast laser machining of aerogels for material removal and micromachining. The advantages of ultrafast laser processing include a minimal thermal penetration region and low processing temperatures, precision removal of material, and good-quality feature definition. In this work, an amplified femtosecond Ti:sapphire laser system is used to investigate the breakdown threshold, material removal rate, and specific issues associated with laser processing of aerogels, as well as recommendations for further investigations for these unique materials.

Investigation to Semi-Fixed Abrasives Plate Lapping SUS440 Stainless Steel

2009 ◽  
Vol 69-70 ◽  
pp. 113-117
Author(s):  
Qian Fa Deng ◽  
Dong Hui Wen ◽  
Feng Chen ◽  
Li Tao ◽  
Ju Long Yuan
Keyword(s):  
Stainless Steel ◽  
Surface Quality ◽  
Load Distribution ◽  
Material Removal ◽  
Removal Rate ◽  
High Surface ◽  
High Surface Quality ◽  
Rotating Speed ◽  
Size Dispersion ◽  
Fixed Abrasive

To obtain high surface quality and high finishing efficiency in machining SUS440 stainless steel, a novel machining technology employing a semi-fixed abrasive plate (SFAP) is adopted. The SFAP is developed for preventing lapped surface from damage caused by larger particles (from grain size dispersion or from outside of processing area, larger particles could bring uneven load distribution on processing region). The effects of different parameters on the surface quality and the material removal rate (MRR) of SUS440 stainless steel which is lapped by SFAP are investigated in this paper. The control parameters of the lapping process include the lapping time, the load, the rotating speed of the lapping plate, and etc. SFAP of 800# SiC abrasive used, Experimental results indicate that SFAP can avoid the large scratch effectively and the surface roughness (Ra) of the workpiece could be improved from 250 nm to 50 nm in 12 Min. A nearly mirror-like surface can be obtained.

Nitrogen and Water Sorption Properties of Ethyl-Substituted Silica Aerogels and Xerogels

1994 ◽  
Vol 371 ◽  
Author(s):  
Chunling Liu ◽  
Sridhar Komarneni
Keyword(s):  
Pore Structure ◽  
Surface Area ◽  
Water Sorption ◽  
Ph Value ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels ◽  
Modified Silica ◽  
Surface Areas ◽  
Water Sorption Properties

AbstractHigh surface area ethyltrimethoxysilane (ETMS) modified silica aerogels and xerogels were synthesized by cohydrolyzing the mixtures of ETMS and tetramethylorthosilicate (TMOS). The effects of ETMS content, pH value and solvent addition were investigated. The surface area, pore structure and hydrophobicity were studied using nitrogen and water sorption measurements. By ETMS modification of TMOS gels, high surface area, density and hydrophobicity were achieved. The 25 mole% ETMS-75 mole% TMOS was found to be the best composition for both aerogel and xerogel, which are hydrophobic and have surface areas of 1221 and 832 m2/g, respectively.

scholarly journals Effect of the Lapping Platen Groove Density on the Characteristics of Microabrasive-Based Lapping

Micromachines ◽  
2020 ◽  
Vol 11 (8) ◽  
pp. 775
Author(s):  
Taekyung Lee ◽  
Haedo Jeong ◽  
Sangjik Lee ◽  
Doyeon Kim ◽  
Hyoungjae Kim
Keyword(s):  
Surface Roughness ◽  
Film Thickness ◽  
Material Removal ◽  
Removal Rate ◽  
High Surface ◽  
Abrasive Particle ◽  
Process Conditions ◽  
Abrasive Particles ◽  
Oil Film ◽  
Process Characteristics

Microabrasive-based lapping is widely used in the manufacturing of single-crystal substrates such as sapphire, SiC, and GaN. Although many studies have been conducted to improve the lapping process characteristics, most of them focused on process conditions or consumables. In this study, the effect of the lapping platen groove density on the lapping characteristics was studied using a sapphire substrate. Groove density was defined as the ratio of groove width to groove pitch, and the displacement of the lapping head was measured to calculate the oil film thickness. It was confirmed that, for groove densities below 0.30, hydroplaning occurs when the oil film thickness increases. When the oil film thickness is larger than the abrasive particle size, the material removal rate is low because the abrasive does not participate in the lapping process. When the oil film was developed, the experimental results showed a high surface roughness and poor flatness of the substrate, as only large abrasive particles participated in the lapping process. Therefore, to improve the lapping characteristics, it is important to reduce the groove density by reducing the groove pitch, which prevents the development of the oil film.

Investigation of Thermo-Chemical Polishing of CVD Diamond Film

2007 ◽  
Vol 329 ◽  
pp. 195-200 ◽  
Author(s):  
Wen Chen Chou ◽  
Choung Lii Chao ◽  
Hsi Hsin Chien ◽  
Kung Jeng Ma ◽  
Hung Yi Lin
Keyword(s):  
Diamond Film ◽  
Material Removal ◽  
Removal Rate ◽  
High Surface ◽  
Diamond Films ◽  
Chemical Vapor ◽  
Chemical Polishing ◽  
Machined Surface ◽  
Cvd Diamond Film ◽  
Very High

ZnO/Diamond structure has attracted a lot of attentions and heavy investment recently just because diamond has the capability of producing very high surface acoustic wave (around 10,000m/s). In this present study, the microwave chemical vapor deposition (CVD) method was employed to produce diamond films on silicon single crystal. Thermo-chemical polishing experiments were then conducted on the obtained diamond films. The underlying material removal mechanisms, microstructure of the machined surface and related machining conditions were also investigated. Thermo-chemical polishing was proved to be able to remove the diamond film very effectively (4.8μm deep of diamond film was removed in 30 minutes when polishing at 550oC and 5.7m/s). The material removal rate was increased with polishing speed and pressure. Higher polishing temperature would improve the chemical reaction and result in better surface finish.

scholarly journals Fractal Structure in Silica and Composites Aerogels

Gels ◽  
2020 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Thierry Woignier ◽  
Juan Primera ◽  
Adil Alaoui ◽  
Philippe Dieudonne ◽  
Laurent Duffours ◽  
...  
Keyword(s):  
Fractal Structure ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels ◽  
High Porosity ◽  
Material Density ◽  
X Ray ◽  
Synthesis Conditions ◽  
Fractal Characteristics ◽  
Synthesis Procedure

Silica aerogels are known to be materials with exceptional characteristics, such as ultra-low density, high surface area, high porosity, high adsorption, and low-thermal conductivity. In addition, these unique properties are mainly related to their specific processing. Depending on the aerogel synthesis procedure, the aerogels texture can be tailored with meso and/or macroporosity. Fractal geometry has been observed and used to describe silica aerogels at nanoscales in certain conditions. In this review paper, we describe the fractal structure of silica aerogels that can develop depending on the synthesis conditions. X-ray and neutron scattering measurements allow to show that silica aerogels can exhibit a fractal structure over one or even more than two orders of magnitude in length. The fractal dimension does not depend directly on the material density but can vary with the synthesis conditions. It ranges typically between 1.6 and 2.4. The effect of the introduction of silica particles or of further thermal treatment or compression of the silica aerogels on their microstructure and their fractal characteristics is also resumed.

scholarly journals The Methodologies Adopted To Improve the Machinability in Die-Sinking EDM

2019 ◽  
Vol 9 (1S4) ◽  
pp. 645-647
Keyword(s):  
Tool Wear ◽  
Material Removal Rate ◽  
Material Removal ◽  
Electrical Discharge Machining ◽  
Removal Rate ◽  
High Surface ◽  
High Hardness ◽  
Machining Process ◽  
Work Piece ◽  
Machining Processes

Electrical discharge machining (EDM) is one of the oldest nontraditional machining processes, commonly used in automotive, aerospace and ship building industries for machining metals that have high hardness, strength and to make complicated shapes that cannot be produced by traditional machining techniques. The process is based on the thermoelectric energy between the work piece and an electrode. EDM is slow compared to conventional machining, low material removal rate, high surface roughness, high tool wear and formation of recast layer are the main disadvantages of the process. Tool wear rate, material removal rate and surface quality are important performance measures in electric discharge machining process. Numbers of ways are explored by researchers for improving and optimizing the output responses of EDM process. The paper summarizes the research on die-sinking EDM relating to the improvements in the output response.

scholarly journals Graphene oxide reinforced high surface area silica aerogels

2017 ◽  
Vol 465 ◽  
pp. 31-38 ◽  
Author(s):  
Saoirse Dervin ◽  
Yvonne Lang ◽  
Tatiana Perova ◽  
Steven H. Hinder ◽  
Suresh C. Pillai
Keyword(s):  
Graphene Oxide ◽  
Surface Area ◽  
High Surface ◽  
High Surface Area ◽  
Silica Aerogels

The Experiment Research of Precision Grinding of Li-Ti Ferrite with Graphite Grinding Wheel

2010 ◽  
Vol 431-432 ◽  
pp. 322-325
Author(s):  
Bei Zhang ◽  
Hong Hua Su ◽  
Hong Jun Xu ◽  
Yu Can Fu
Keyword(s):  
Surface Quality ◽  
Material Removal ◽  
Removal Rate ◽  
High Surface ◽  
Ground Surface ◽  
Grinding Wheel ◽  
Precision Grinding ◽  
High Surface Quality ◽  
Good Surface ◽  
Good Surface Quality

Li-Ti ferrite used in aviation occasions needs good surface quality. In conventional grinding it is difficult to meet the surface demand. Accordingly, this paper proposed a new grinding process to change the situation. The process employed graphite grinding wheel which is always used in ultra-precision grinding of steel piece. The process can obtain good surface quality and ensure certain material removal rate. The ground surface appearance is nearly mirror-like. The lowest surface roughness of Ra value of the ground surface is 0.05μm in the experiment. The ground surface morphology is made up of spread glazed area and dispersed minute pits. The ductile regime dominates the material removal mechanism and no surface damage is induced in the process. In consideration of the results in the experiment it can be seen that grinding with graphite grinding wheel is a good finishing procedure in ferrite machining because of its obtained high surface quality.

Preparation and Properties of Hydrophobic Silica Aerogels by Ambient Pressure Drying Method

2011 ◽  
Vol 71-78 ◽  
pp. 1040-1043
Author(s):  
Hui Wang ◽  
Shi Ming Liu ◽  
Ling Ke Zeng
Keyword(s):  
Surface Area ◽  
Ambient Pressure ◽  
High Surface ◽  
High Surface Area ◽  
Volume Ratio ◽  
Silica Aerogels ◽  
Ambient Pressure Drying ◽  
Drying Method ◽  
Hydrophobic Properties ◽  
Large Pore Volume

Silica alcogels were prepared by hydrolysis with hydrochloric acid and condensation with NH4OH of ethanol diluted tetraethylorthosilicate (TEOS) precursor and trimethylchlorosilane and hexane as surface modifying agent. The physical properties such as density, appearance, hydrophobicity, surface area, pore size distribution and thermal stability were measured. It was found that the physical and hydrophobic properties of the silica aerogels depend on the TMCS/hexane (V) volume ratio. The density decreased with increase ofV, and the aerogels are more hydrophobic asV=3%. The aerogels were thermally stable up to a temperature of 350 °C, and the aerogel prepared has a high surface area and large pore volume.

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