Slurry Layer Research Articles

Slurry-based additive manufacturing of ceramic parts by selective laser burn-out

Abstract This study proposes a novel process of slurry-based additive manufacturing of ceramic parts by selective laser burn-out (SLB). The process employs the slurry layer to replace the sheet material used in the process of laminated object manufacturing (LOM) and computer-aided manufacturing of laminated engineering materials (CAM-LEM). A part of binder and solution in the fresh slurry layer permeated into the dried green layers to achieve a good binding strength; then the green part was build with laser irradiation to burn out binder. Two scanning modes were used; the outline scanning traced out the outline of the predefined part slice geometry, and cutting scanning facilitated removal of excess material. Consequently, the new process benefits the fabrication of the large parts as LOM and CAM-LEM possessing. Many accessory facilities used in LOM and CAM-LEM are not required. The feasibility of the new process is verified through the fabrication of the alumina parts.

Improved electrochemical performance of the Silicon/Graphite-Tin composite anode material by modifying the surface morphology of the Cu current collector

Electrochemical performance of the as-prepared silicon based composite electrode for lithium ion battery can be enhanced by modifying the surface morphology of the Cu foil used as the anode current collector. Increasing the roughness of the Cu foil, contributes to the strong interface adhesion between the anode current collector and the silicon based active composite material slurry layer. The electrode with surface morphology modified Cu current collector delivers higher specific capacity and exhibits better rate capability than that with unmodified Cu current collector. It is also found that the cycle-life of the silicon based composite electrode has been significantly improved by using a surface morphology modified anode current collector. The enhanced cyclability is attributed to the good electrical contact integrality between the active materials and the anode current collector. The improved electrochemical performance indicates that optimizing the anode current collector system can be a valuable alternative for improving electrochemical properties of lithium ion rechargeable batteries.

Taguchi approach for modelling of surface hardness in investment casting

This paper deals with modelling of surface hardness in investment casting as a case study of ball valve spherical disc. Three controllable factors of the investment casting process (namely, volume/surface area ratio of components, slurry layer combination and type of metal/metal pouring temperature) were studied by Taguchi’s parametric approach, and single-response optimisation was conducted to identify the main factors controlling surface hardness. Investment casting was prepared with aluminium, mild steel and stainless steel at recommended parameters. The microstructure analysis supported with cooling curves has been presented. The result of the study suggests that the surface hardness of investment casting can be improved significantly by controlling the type of metal. Confirmation experiments were conducted for final validation of model.

Solidification of a Binary Solution (NH<sub>4</sub>Cl+H<sub>2</sub>O) under Shear Flow: A Numerical Study

In the present work, the solidification behaviour of a metal analogues transparent binary solution (8 wt% of NH4Cl in H2O) under shear flow is investigated numerically. The shear flow in the mush is developed due to flow over an inclined cooling plate. The dendrites formed during solidification are fragmented under the shear flow and transported into the bulk solution. The suspended dendrites form a slurry layer in the domain. Consequently, a suitable mathematical model is considered to study the transport phenomena. In the mathematical model, the free surface of the solution is represented by the volume-of-fluid (VOF) method. The solidification process is modelled by a set of volume-averaged-single-phase mass, momentum, energy and species conservation equations. A separate equation is considered for the solid velocity based on Stokes model. The governing equations are solved based on the pressure-based semi-implicit finite volume method according to the SIMPLER algorithm using TDMA solver along with the enthalpy update scheme. Finally, the simulation predicts temperature, velocity, solid fraction and the species distributions in the computational domain. Normal 0 false false false EN-US X-NONE X-NONE /* Style Definitions */ table.MsoNormalTable {mso-style-name:"Table Normal"; mso-tstyle-rowband-size:0; mso-tstyle-colband-size:0; mso-style-noshow:yes; mso-style-priority:99; mso-style-qformat:yes; mso-style-parent:""; mso-padding-alt:0in 5.4pt 0in 5.4pt; mso-para-margin:0in; mso-para-margin-bottom:.0001pt; mso-pagination:widow-orphan; font-size:11.0pt; font-family:"Calibri","sans-serif"; mso-ascii-font-family:Calibri; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Calibri; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi;}

Slime thickness evaluation of bored piles by electrical resistivity probe

The bottoms of bored piles are generally stacked with soil particles, both while boreholes are being drilled, and afterward. The stacked soils are called slime, and when loads are applied on the pile, increase the pile settlement. Thus to guarantee the end bearing capacity of bored piles, the slime thickness should be precisely detected. The objective of this study is to suggest a new method for evaluating the slime thickness, using temperature compensated electrical resistivity. Laboratory studies are performed in advance, to estimate and compare the resolution of the electrical resistivity probe (ERP) and time domain reflectometry (TDR). The electrical properties of the ERP and TDR are measured using coaxial type electrodes and parallel type two-wire electrodes, respectively. Penetration tests , conducted in the fully saturated sand–clay mixtures, demonstrate that the ERP produces a better resolution of layer detection than TDR. Thus, field application tests using the ERP with a diameter of 35.7 mm are conducted for the investigation of slime thickness in large diameter bored piles. Field tests show that the slime layers are clearly identified by the ERP: the electrical resistivity dramatically increases at the interface between the slurry and slime layer. The electrical resistivity in the slurry layer inversely correlates with the amount of circulated water. This study suggests that the new electrical resistivity method may be a useful method for the investigation of the slime thickness in bored piles. • The slime thickness in bored piles is evaluated by electrical resistivity. • The ERP produces a better resolution of layer detection than TDR. • Electrical resistivity increases at the interface of slurry and slime layers.

Laser Compensation for Ceramics Accuracy Improvement of Selective Laser Sintering

This research developed a feedback control system of laser compensation for the rapid prototyping (RP) machine using layer-wise slurry deposition and selective laser sintering (SLS). The slurry was prepared by silica power and silica sol with 60 and 40 wt.% with suitable rheological properties for 0.1 mm layer deposition. Four ceramics for comparison of the formability of fabricated ceramic green parts with/without the feedback control system of laser energy density for models were designed With this laser feedback control, batter quality ceramic green parts can be manufactured and the rapid prototyping machine with steady laser energy radiated on slurry layer was achieved. Experimental results validate the well performance of the measuring laser power and feedback control system.

Solidification of a Binary Solution (NH4Cl+H2O) on an Inclined Cooling Plate: A Parametric Study

A parametric study on the solidification behaviour of a binary solution (NH4Cl + H2O) on inclined cooling plate is presented numerically. During solidification of the solution, a shear layer is developed in the mush where a part of the dendrites is fragmented under shear flow and transported into the bulk solution. Accordingly, a slurry layer is found over the mush. The present solidification behaviour primarily depends on inclination angle of the plate and composition of the solution. In the present work, a mathematical model is developed where the free surface of solution is represented by the volume-of-fluid (VOF) method and the solidification behaviour is represented by a set of volume averaged single phase mass, momentum, energy, species conservation equations. The Stokes model is used to represent the solid velocity. The governing equations are solved based on the pressure-based finite volume method according to the SIMPLER algorithm using TDMA solver along with the enthalpy update scheme. The final simulation predicts the effect of process parameters on temperature, velocity, solid fraction and the species distributions.

Dimensional Accuracy Comparison of Investment Castings Prepared with Wax and ABS Patterns for Bio-medical Application

In this research work comparison has been made for dimensional accuracy of hip joint prepared by investment castings process using conventional wax and acrylonitrile butadiene styrene (ABS) as pattern material. Two controllable process variables namely: numbers of slurry layers and type of pattern material have been considered for comparison. An approach to model dimensional accuracy of hip joint has been proposed and applied. International tolerance (IT) grade of cast components was tested and found acceptable as per ISO standard UNI EN 20286-I (1995) and further at proposed parametric settings, process has been found to be statistically controlled.

Fundamental performance of Magnetic Compound Fluid (MCF) wheel in ultra-fine surface finishing of optical glass

This study investigates a new semi-fixed-abrasive, ultra-fine finishing method for optical glass using a magneticcompound fluid (MCF) wheel. This MCF wheel generates a thin, uniform MCF slurry layer on the entire circumferentialsurface of a ring-shaped permanent magnet placed between two non-magnetic plates. The MCF slurry is composed ofnano-sized magnetite particles, micron-sized iron particles, several 10 μm-sized α-cellulose fibres and sub-micron-sizedabrasive particles that react to the magnetic field. Following modifications to the design of the MCF, experiments wereconducted to evaluate the performance of the modified wheel in spot-polishing fused silica glass. This paper describes themodifications to the MCF wheel and the experimental setup used to measure its performance. The improvement of themodified wheel over the unmodified wheel in terms of material removal and surfaces roughness is experimentallyconfirmed. The effects of the wheel rotational speed and the clearance between the wheel and the workpiece on materialremoval and the workpiece surface roughness are investigated. The polishing forces are measured, the structure of the MCFslurry is examined and the magnetic field distribution is analysed. A model of material removal in polishing with themodified MCF wheel is developed. The results indicate the following: (1) more material was removed, i.e., greater spotdepths, and better surfaces were obtained in the regions that were near the edges of the magnet; (2) the modified MCF wheelperformed much better than the unmodified wheel in terms of material removal and surface roughness, e.g., 3.1 μm vs. 1.7μm for the maximum spot depth, 0.04 mm3 vs. 0.0088 mm3 for the volume of material removed and Ra = 5.624 nm vs.14.67 nm for the surface roughness; (3) a better work surface and greater material removal were obtained with smallerworking clearances and higher wheel rotational speeds.

Development of Performance Optimization of Recycled Aggregate

Recycled aggregate concrete (RAC) differ from natural aggregate concrete in mechanical and durability properties. The poorer qualities of recycled aggregate (RA) limit utilization of RAC in engineering. Cement mortar attached on the surface of recycled aggregate result in higher water absorption rate. Also, interfacial zone between recycled aggregate and new mortar consist of loose and porous hydrates. Investigation is devoted to effects of different approaches on improving performance of RA to compensate the lower quality of RA. The pre-soaking treatment approach reduces the old cement mortar and removes the weaker link in interfacial zone. Moreover, The two-stage mixing approach (TSMA) is adopted, leads to the formation of a thin layer of cement slurry on the surface of RA which permeates into the porous old cement mortar, filling up the old cracks and voids for increasing compressive strength. Correlations in methods have been obtained and discussed.

Investigating the Effect of Shape Factor, Slurry Layers and Pouring Temperature in Precision Investment Casting

This paper aimed to investigate the effect of shape factor, slurry layers and pouring temperature in precision investment casting. Three controllable factors of the precision investment casting process (namely: shape factor, slurry layers (mold thickness) and pouring temperature) were studied at three levels each by Taguchis parametric approach and single-response optimization was conducted to identify the main factors controlling surface hardness, dimensional accuracy (Δd) and surface roughness (Ra). Castings were produced using aluminum (Al), mild steel (M.S.) and stainless steel (S.S) at recommended parameters through ceramic shell precision investment casting process. The micro structure analysis has been used to study the surface morphology. Analysis shows that for surface hardness, contribution of shape factor, slurry layers and pouring temperature is 0.07%, 0.70% and 99% respectively. As regards to surface roughness, contribution of shape factor, slurry layers and pouring temperature is 1.14%, 16.80% and 81.90% respectively. Further for Δd contribution of shape factor, slurry layers and pouring temperature is 1.53%, 22.47% and 72.88% respectively. Confirmation experiments were conducted at an optimal condition showed that the surface hardness, Δd and Ra of the precision investment casting were improved significantly.

Investigating the effect of moulding sand properties on investment castings: a process capability study

The purpose of the present investigation is to study the effect of molding sand properties on investment casting (IC) for process capability analysis. Starting from the identification of component/benchmark, ICs were produced with different grades of silica slurry layers (coarse, medium and fine) over the patterns (in the form of a tree). Measurements on a coordinate measuring machine (CMM) helped in calculating the dimensional tolerances of the castings produced. Some important mechanical properties were also compared to verify the suitability of the castings. The study suggested the long-term performance level of the IC process after it has been brought under statistical control as casting solution for plain carbon steel. The provided data from the experimentation highlights the ability of the IC process to produce a product that will consistently meet the design requirements and the customer expectation.

Effect of process parameters on surface hardness, dimensional accuracy and surface roughness of investment cast components

This paper deals with investment casting (IC) application for development of spherical disc of ball valve as a case study. Three controllable factors of the IC process, namely: volume/surface-area (V/A) ratio of components, slurry layer’;s combination (LC) and type of metal (MT), were studied at three levels by Taguchi’s parametric approach and single-response optimization was conducted to identify the main factors controlling surface hardness (SH), surface roughness (Ra) and dimensional accuracy (=d). Ceramic shell moulds were made on wax plate using primary slurry and fused-silica sand as stucco. Castings were produced using Al, M.S and S.S at recommended arameters by following Taguchi L9 orthogonal array through ceramic shell IC process. The microstructure analysis has been used to study the surface morphology.

A Study into Digital Dermatitis Transmission and Bacterial Associated Pathological Changes Involved in the Disease

Digital dermatitis is a highly prevalent painful lesion affecting the feet in dairy cattle. Even though the pathogenesis has been subject of investigation since 1974, there is still a lack of knowledge about the spread of the disease among cows within a herd as well as between herds. The purpose of this study was to monitor transmission of digital dermatitis under experimental conditions between naive heifers and affected animals, to monitor the changes in clinical appearance, microbial colonisation of the skin as lesions progressed and to apply a q-PCR for the detection of Treponema spp. in faecal samples. Eight heifers with clinical normal digital skin were housed with 5 heifers with severe digital dermatitis lesion for 8 weeks on a solid concrete floor with an accumulating layer of slurry. Digital skin was examined daily and lesions were clinically scored. Skin biopsies were taken from the healthy heifers at introduction and weekly from all lesions for histopathological evaluation and fluorescence in situ hybridization. None of the healthy heifers developed digital dermatitis and in 4 out of 5 infected heifers the lesions healed during the study. All samples from healthy skin were negative for Treponema spp. and one sample were positive for Dichelobacter nodosus. Colonization of healthy skin could not be identified in this study. There was no significant relation between clinical scoring of the lesions and histopathological score and the presence of Treponema spp. There were however a significant relation between the prevalence of Treponema spp. in the skin and severity of changes in epidermis and dermis. By qPCR all the healthy heifers were found to excrete Treponema spp. in their faeces.

Mathematical modeling for surface hardness in investment casting applications

Investment casting (IC) has many potential engineering applications. Not much work hitherto has been reported for modeling the surface hardness (SH) in IC of industrial components. In the present study, outcome of Taguchi based macro-model has been used for developing a mathematical model for SH; using Buckingham’s π-theorem. Three input parameters namely volume/surface-area (V/A) ratio of cast components, slurry layer’s combination (LC) and molten metal pouring temperature were selected to give output in form of SH. This study will provide main effects of these variables on SH and will shed light on the SH mechanism in IC. The comparison with experimental results will also serve as further validation of model.

Methods for improvement of clay slurry or sewage sludge

Clay slurry or sewage sludge may be used as fill materials for land reclamation. However, the treatment of very soft materials of high water content is difficult. One major difficulty is how to create a working platform on top of the slurry layer for required soil improvement works such as vacuum preloading to be carried out. Several methods that can be used to create a working platform on top of a slurry layer are reviewed in this paper. These include (1) sun drying; (2) capping with sand or other good soil; (3) use of geotextile; (4) cement mixing; and (5) dewatering using drainage. The advantages and disadvantages of each method are elaborated. Practical examples are given to illustrate the application of some of those methods. Sewage sludge is more difficult to treat because of its organic content and a combined chemical and mechanical method needs to be used. Two conceptual methods for using sewage sludge and other waste materials for land reclamation are also proposed.

Accounting for Surface Cattle Slurry in Ammonia Volatilization Models: The Case of Volt'Air

Process based models have been developed to simulate ammonia (NH3) volatilization after surface slurry spreading, but none of them have managed to realistically represent slurry infiltration into the soil and the development of a specific slurry interface that modifies surface temperature and humidity conditions. To account for these physical effects, it is proposed to add to the model a layer of slurry on the surface of the soil. It is hypothesized that the slurry layer can be regarded as a soil layer from the hydrological point of view, characterized by its specific hydraulic parameters, and whose thickness depends on the quantity and bulk density of the slurry dry matter. An assessment was performed by comparisons with measurements of NH3 volatilization fluxes from two specific datasets. The addition of the slurry layer clearly improved the simulations of both the NH3 volatilization flux and ammoniacal nitrogen (NHX–N) distribution in the soil. This concept together with its parameterization proved to be relevant for accounting for effect of the slurry application rates on volatilization, and subsequent abatement obtained with band spreading. The efficiency factor was improved from –0.35 to 0.71. This concept also succeeded in describing the slurry layer state over the whole range from slurry ponding at the surface to the dried‐out state, via a slurry in an intermediate drying state. This was actually a prerequisite for the good simulation of NH3 volatilization over the whole volatilization event. This approach is promising for extension to various organic materials present at the soil surface.

Fundamental Study on Setting of Diamond Abrasive Grains Using Electrostatic Force for Single-Layered Metal Bond Wheel

Single-layered metal bond diamond wheels are useful to high efficient grinding of difficult-to-grind materials because of the high gripping force of abrasive grains and the controllable grain density. In this paper, fundamental information are obtained for an application of electrostatic force to setting of diamond grains into pasted metal bond slurry layer on wheel surface, investigating experimentally jumping phenomenon of diamond grains in an electrostatic field between a electrode plate and metal bond slurry layer. The SD grains and the SDC grains coated with Ti are selected. SDC grains jump into a metal bond layer as quick as making an electrostatic field, however SD grains jump with short time lags. The setting rate of SDC grains is larger than that of SD grains, and setting position accuracy of SDC grain array is better than SD grain array. The possibility of setting abrasive grains into single-layered metal bond diamond wheel surface using electrostatic force is obtained and SDC grains are suitable to the proposed abrasive setting method.

P-PEDOT:PSS as a heterojunction partner with n-ZnO for detection of LPG at room temperature

Investigation towards the performance of room temperature (27 °C) liquefied petroleum gas (LPG) sensor based on the heterojunction between p-PEDOT:PSS and n-type ZnO is reported. The junction was developed by using chemically deposited ZnO film on to fluorine doped tin oxide (FTO) coated glass substrate followed by coating of thin slurry layer of PEDOT:PSS by using spin coating technique. Both these methods are simple, inexpensive and suitable for large area applications. Different characterization techniques were used to characterize structural, surface morphological and compositional of the material deposited. LPG sensing behavior of the heterojunction was studied at room temperature along with the stability studies. At room temperature, the heterojunction showed 58.8% sensitivity upon exposure to 1000 ppm of LPG with good response and recovery time like 225 s and 190 s, respectively. Furthermore, the LPG sensor reported is cost-effective, user friendly, and easy to fabricate using low cost chemical methods at room temperature.

Study on Submerged Jet Problem of Concave Optics Surface in Fluid Jet Polishing

Fluid jet polishing (FJP) is a computer controlled polishing (CCP) process. As the water effect of concave optics surface, the slurry won’t spread immediately until component have a basinful, and jet goes through a layer of slurry firstly before impact in FJP process, the submerged jet will influence material removal rate and bring on inaccurate fabrication results if it is not considered. In this paper, submerged jet characteristics are studied, and researches were taken for submerged jet polishing by simulation with FLUENT software and experiments analysis. Based on that, mathematical material removal correction with submerged depth is established for semi-submerged jet polishing. A BK7 concave surface was polished by semi-submerged jet with removal correction. The results show an affirmative proof for correction in submerged jet polishing.