Mechanical Grinding Processes Research Articles

Preparation and Characterization of Nano-waste glass powder

This experimental study investigates top-down grinding to turn used waste glass into nano-glass powder. The study explores a new instrument locally manufactured to synthesize nano-glass powder. The high-energy ball mill was manufactured based on design, material, assembly, testing, optimization, and quality control. Two milling environments were examined: wet with water as a surfactant liquid and dry with varying grinding times. In addition, this study compared the output of nano glass created from mechanical and chemical grinding processes. Blaine's method for surface area measurement results of nanoscale powder samples produced by the wet grinding method showed a steady increase commensurate with the grinding duration, as the 12-h grinding specimen was the highest in surface area. In contrast, dry grinding samples showed anomalies in some instances due to the agglomerate phenomenon, such as 8- and 10-h grinding samples. Moreover, FE-SEM showed that the 12-h grinding specimen has the smallest particle size. But the AFM illustrated accurately with the 2D measurement that these particles have cortical shapes, which may describe the secret beyond the high surface area. X-ray diffraction (XRD) and AFM tests showed that in the case of nanoscale glass particles, regardless of their morphology status, the shape of the particle itself is the deciding factor in giving the Nano powder the highest particle surface area. The specimen milled with 4 h of dry grinding is best suited for civil engineering research applications, while other applications that need a small amount of nano glass are recommended to use chemical methods despite their dangerous processes.

Facile formulation of graphene oxide modified commercial polyurea grease and its enhanced tribological capability under extremely high contact stress

Grease lubricants have been widely applied to the rubbing components to increase the operation stability and reliability. In this study, graphene oxide modified polyurea grease was prepared by formulating different amounts of exfoliated expandable graphite (EG) into commercial polyurea grease with combined mechanical agitation and grinding processes, tribological characteristics of graphene oxide modified polyurea grease were subsequently evaluated under extremely higher contacting stress. Among all the formulated polyurea grease specimens, polyurea grease with 2.0 wt.% graphene oxide displays better capabilities of minimizing friction and wear. In particular, the wear loss reduces considerably by 80% meanwhile the averaged friction coefficient decreases to 0.10, as referenced with existing polyurea grease. The improved tribological behavior is proposed to be associated with the in‐situ produced graphene oxide solids that enhances extremely lower shearing ability and promotes the fatigue resistance of grease, as well as its desired chemical compatibility with resulting iron sulfide tribofilm. Particularly, graphene oxide works as the dispersed precipitate within the dense iron sulfide/oxide layer induced from ZDDP that covers on the steel substrate.

Laser-fabricated axicons challenging the conventional optics in glass processing applications.

Laser-based fabrication can be an alternative technology to mechanical grinding and polishing processes. However, the performance of these elements in real applications still needs to be validated. In this paper, we demonstrate that the subtractive fabrication technology is able to produce high-quality axicons from fused silica, which can be efficiently used for glass processing. We comprehensively investigate axicons, fabricated by ultrashort pulsed laser ablation with subsequent CO2 laser polishing, and compare their performance with commercially available axicons. We show that laser-fabricated axicons are comparable in quality with a precision commercial axicon. Furthermore, we demonstrate the intra-volume glass modification and dicing, utilising mJ-level laser pulses. We show that the tilting operation of the laser-fabricated axicons results in the formation of directional transverse cracks, which significantly enhance the 1 mm-thick glass dicing process.

Direct bonding of high dielectric oxides for high-performance transistor applications

We developed a plasma activation process using a gas mixture of O2/NH3/H2O for direct bonding, which realized the combination of bulk aluminum oxide (Al2O3) and yttria-stabilized cubic zirconia (YSZ) without interlayers for the first time. The bonding could withstand multiple mechanical grinding and polishing processes and exhibited sufficient bonding strength for device micro/nanofabication. A nanoscale, sharp, and layered crystalline bonding interface with fewer grain boundaries was confirmed by transmission electron microscopy. The interfacial structure is well-suited for superior performance in high dielectric constant metal–oxide–semiconductor field-effect transistors. Moreover, this bonding method is universal for the fabrication of Al2O3/SiO2 and YSZ/SiO2 heterostructures.

Research needs for nanocellulose commercialization and applications

This short review deals with some applications and research needs for nanocellulosic (NC) materials; primarily cellulose nanocrystals (CNC), cellulose nanofibers (CNF), and bacterial cellulose (BC). Whereas CNC and BC materials are fairly homogenous, CNF materials represent a wide sector of different materials, often with a high heterogeneity. This is due to different pretreatment methods (mechanical, chemical, enzymatic), woodbased or agricultural-based materials, delignification and bleaching procedures, etc. The purpose of this comprehensive review is not to discuss the various production methods, for which the reader may consult with a selected number of reviews [1-6]; thus, the focus is on practical applications. Practical applications and potential markets were also discussed some years ago by other investigators [7-8]. Upscaling and choice of pretreatment methods, as well as economic considerations and different business models, have also been discussed, along with: • Toxicity and environmental issues [9-10] • The complex characterization of cellulose nanomaterials [4] The reader should also be aware of new contenders to the three classic groups of cellulosic nanomaterials, which are already in a commercial phase. These include cellulose filaments [11-12] and materials from mechanical grinding processes [13], and these materials may be nanostructures or not, depending on our classification. Finally, as indicated by the editorial on p. 275, scientists are currently taking a deep dive into the fundamental features of nanocellulosic materials [14-15].

Correlation between Local Strain Distribution and Microstructure of Grinding-Induced Damage Layers in 4H-SiC(0001)

Evaluation of surface damage layers formed by mechanical grinding processes is indispensable in epi-ready SiC wafer preparation. As well as microstructure, the analysis of local strain distribution in the damage layers gives a clue on control of the wafer quality. Advanced electron backscatter diffraction (EBSD) technique is applied to evaluate the strain distribution of the damage layers. It is revealed that the elastic strain distribution can be classified into a hierarchy of three regions with respect to depth from the surface. Combining EBSD analysis with TEM observation, large compressive elastic strain and misorientation are introduced in the highly-defective region underneath the ground wafer surface. In addition, the gradient distribution of the strain is observed clearly below the highly-defective region. The knowledge of correlating between strain distribution and microstructure is promising to control the damage layer for the wafer preparation.

Investigation of Thermal Treatment Processes for Dissimilar Wafer Bonding

Wafer bonding, also termed as “direct bonding” or “wafer direct bonding”, has one of the main advantages for its ability to integrate dissimilar materials in various areas of microelelctronics, optoelectronics, micro/nanoelectromechanical systems (M/NEMS). Silicon is the most extensively used material for semiconductor industry. To meet demands on superior electrical, optical and acoustic applications, it is important to combine silicon with appropriate materials, such as GaAs, quartz glass, and LiTaO3. In general, two wafers are brought into contact at room temperature (~25ºC) and followed by thermal treatment processes (>100ºC) enabling reliable bonding strength to withstand subsequent mechanical grinding or polishing processes. During thermal treatments, the major concern in dissimilar bonded wafer pairs is the thermal stress originating from a mismatch in thermal expansion coefficients. Higher thermal stresses above a critical temperature may cause sliding, debonding, cracking or misfit dislocation between two bonded wafers. It is therefore highly desirable to predict the critical temperatures and optimize the thermal steps for dissimilar bonded wafer pairs with various materials and thicknesses. In this paper, a thermal stress model is developed based on analytical as well as finite element methods. To ensure a good bonding, the thermal stress should be smaller than the critical yield stress of the bonded materials. Meanwhile, the deformation energy should be lower than the bonding energy so that no sliding or debonding occurs during the thermal treatments. Under these two conditions, the critical temperatures for various dissimilar bonded wafer pairs (Si/GaAs, Si/Quartz and Si/LiTaO3) are calculated and predicted. The effects of wafer thickness are also demonstrated. To verify our calculation results, 100-mm silicon wafers are combined to LiTaO3 wafers by plasma activated bonding process. The bonded wafer pairs are heated at different temperatures to strengthen bonding. Experimental results show the critical temperature value is in agreement with our calculation. We believe our model provides a tool to optimize the thermal treatment processes during the dissimilar wafer bonding. It has great potentials to improve the bonding processes for wafer-level hybrid integration.

Thermoelectric Properties of n-Type Half-Heusler Compounds Synthesized by the Induction Melting Method

The n -type Hf_0.25Zr_0.25Ti_0.5NiSn_0.998Sb_0.002 Half-Heusler (HH) alloy composition was prepared by using the induction melting method in addition to the mechanical grinding, annealing, and spark plasma sintering processes. Analysis of X-ray diffraction (XRD) results indicated the formation of a pure phase HH structured compound. The electrical and thermal properties at temperatures ranging from room temperature to 718 K were investigated. The electrical conductivity increased with increasing temperatures and demonstrated nondegenerate semiconducting behavior, and a large reduction in the thermal conductivity to the value of 2.5 W/mK at room temperature was observed. With the power factor and thermal conductivity, the dimensionless figure of merit was increased with temperature and measured at 0.94 at 718 K for the compound synthesized by the induction melting process.

Design of a Machine by Low Cost and the High Performance for Produced Powder Materials

Mechanical alloying and mechanical fine grinding processes are mostly based on the high energy milling technique. Equipment of a horizontal high-energy ball mill that has been developed in the Cefet-BA is a low cost machine with high performance. These milling machines are equipped with a cylindrical stainless steel horizontal container. Inside the container, a chamber of water circulation is used to maintain, powdered materials, the room temperature. The grinding container inside to chamber horizontal container is a container, cylindrical stainless steel, opened of the two sides. The container with the powder particles is a sealed of two sides and vacuum out-gassed is realized. A motor driven rotor is used to accelerate the grinding media and the milling process is realized due to the ball to ball/rotor/wall impacts as their kinetic energy is transferred into the powder which is randomly located between the colliding balls. The rotor milling machine equipment permits two rpm e.g. 500 and 1500 rpm. Machines based on this design from lab scale (3.0 liter volume), mainly to develop new powders and materials.

Toners for Xerographic Textile Printing Produced by Means of Thermally Induced Phase Separation

The xerographic process is one of the digital printing technologies with a potential for textile printing. One barrier to the use of xerography for printing textiles is the lack of textile-specific toners that produce the required textile properties. Attempts have been made to produce textile-specific toners through mechanical grinding processes such as jet milling, but mechanical grinding requires that the toner resins be sufficiently brittle. In our previous work, toner compounds containing resins that are sufficiently flexible for the required textile properties could not be ground to the required particle size for xerography. In this paper, thermally induced phase separation (TIPS) is used to overcome this difficulty. Isotactic polypropylene (IPP) and poly(ethylene-co-vinyl acetate) (EVA) are converted into toners by means of TIPS. The EVA polymers meet the flexibility and colorfastness require ments of textile printing.

Xerographic Toners for Textile Printing

Fabric printing is a bottleneck in the textile-apparel supply pipeline. It is commonly believed that digital printing systems will replace the current methods of printing textiles. Xerography is one of the digital printing technologies being investigated for textile printing at the Georgia Institute of Technology. The research reported in this paper has focused on developing polymerbased xerographic toners giving required printed fabric properties. The suitability of toners produced through mechanical grinding processes for xerographic textile printing is discussed. Three classes of polymeric binders (amorphous polyester, three thermosets, and five polyamides) were studied. The potential of these binders was evaluated using crockfastness (rub fastness) and fabric flexural rigidity tests. Materials that could be ground to the required particle size were too rigid. Thus the printed fabrics had high flexural rigidities and, in many cases, unacceptable wet crockfastness ratings. The potential of a more flexible resin, which could not be ground to the required particle size, was assessed by applying toners via a solvent medium. The flexible resin gave the required textile properties.

Temperature dependence of mechanical alloying and grinding in NiZr, CuTa and FeB alloy systems

The ambient temperature effect on the mechanical alloying and mechanical grinding processes was studied, using a mixture of nickel and zirconium powders ( ΔH mix<0), that of copper and tantalum powders ( ΔH mix>0) and the Fe 2B compound. We confirmed in the NiZr system that the higher the ambient temperature, the faster the amorphization proceeds. This temperature effect is observed as soon as mechanical alloying starts. The temperature effect exists also in the Cu 30Ta 70 powders but becomes noticeable after the average grain size is reduced below 100 Å. Hence, we believe that the retarded temperature effect is unique to a system with a positive heat mixing. Neither the formation of an amorphous phase nor a sizable temperature effect is observed in the mechanical grinding process of the Fe 2B compound.

Mechanochemical Transformation and Synthesis of Polymers

Abstract The mechanical grinding, milling, mixing, homogenization, freezing and other processes of the physico-mechanical processing of high polymers are widely used in the industries of plastics, rubbers, synthetic fibers, food products, silicates and many other branches of technology. Some of these processes have a great significance in biochemistry, medicine and biology. An analysis of the available experimental data permits one to reach the conclusion that in the intensive grinding of natural polymers (cellulose, starch, proteins or synthetics (polystyrene, rubber, polyisobutylene, etc.) a mechanical scission (cracking) of the macromolecules is observed. The possibility of macromoleeular scission under the grinding of high molecular weight substances is due to the high probability of a localization of mechanical energy at different sections of the polymer chain, which under certain conditions causes internal stresses exceeding the strength of covalent or ionic bonds. Mechanical breakdown of macromolecules is possible not only with dry or wet grinding, but also by mechanical action on polymer solutions. Thus, for instance, Staudinger has shown that the high speeds and forces of friction developed in forcing a 0.005 molar tetralin solution of polystyrene, average molecular weight = Mave=6⋅106, through a platinum capillary bring about a scission of the macromolecules which is revealed in a decrease of about 30% in the specific viscosity of the solution. Forcing a solution of polyisobutylene (Mave=3.9×104–23×104) in dichlorobenzene through a capillary with a diameter of 0.2 mm causes a decrease in the intrinsic viscosity and an increase in the constant of the Huggins equation. An increase in the Mave of the polymer structure formation (cross-linking) and a repeated forcing through is conducive to the mechanical breakdown of the macromolecules. It has been established that in mixing together solutions of polymeric substances (starch, gelatine, polyvinyl alcohol, etc.) with high-speed mixers having a rotation speed of over 4000 rpm, a sharp decrease in the intrinsic viscosity [ν] is observed, while the degree of scission increases, with an increase in the rotation speed of the mixer, and also with a decrease in the concentration of the solution.