Kinds Of Slurries Research Articles

Gradient coating increases the temperature resistance of ceramic fiber fabric

Ceramic fiber fabric embrittlement at 1200 °C, resulting in poor tensile strength. In order to improve the tensile strength of ceramic fiber fabric after high temperature heat treatment. In this study, gradient coating is sprayed on the surface of ceramic fiber fabric by adjusting the composition of two kinds of slurry. The structure and property of ceramic fiber fabric with different coating are thoroughly investigated. The pore size of Al2O3-SiC porous transition layer is less than 1 μm, which limits the infiltration of the high-emission coating into the ceramic fiber fabric. A weak bond is formed between the ceramic fiber fabric and the porous transition layer, which induces the crack deflection. The flexibility of ceramic fiber fabric after heat treatment is significantly improved. After being heated by butane flame at 1200 °C for 20 min, the tensile strength of fiber fabric with gradient coating is double that of raw ceramic fiber fabric. The silicone cross-links to form a network, which improves the bonding strength of the gradient coating. Due to the high emissivity and low thermal conductivity of the gradient coating, the temperature of the ceramic fiber fabric is below 900 °C when heated by the butane flame.

Effects of powder morphology on stereolithography additive manufactured Al2O3 ceramic

The digital light processing (DLP) for the preparation of alumina ceramics (Al2O3) is characterized by high molding accuracy and fast rates, making it show great promise for applications in high-end ceramic manufacturing. However, its forming process is greatly influenced by the photosensitive slurry. Although a large number of studies have been conducted to investigate the influence of different variables of the slurry on photo curing, the mechanism of the influence of the powder morphology of the Al2O3 raw material is still unclear. In this study, two kinds of slurry were prepared from spherical and laminated Al2O3 powders and DLP was carried out. The results showed that some of the spherical Al2O3 powder would break down after ball milling, resulting in a reduced flow-ability of the slurry. The relative density of the ceramic was 91.1 % and strength was 92.1 MPa. In contrast, the laminated Al2O3 could be oriented in the flow direction during flow, showing a lower viscosity. At the same time, the orientation allowed the lamellar powder to build up more tightly. The relative density of the ceramic was 93.2 % and strength was 165.5 MPa.

Effects of Electrostatic Force and Network Structure on the Stability of Proton-Exchange Membrane Fuel Cell Catalyst Ink

The stability of the catalyst slurry of a proton-exchange membrane fuel cell (PEMFC) is of great significance to its large-scale production and commercialization. In this study, three kinds of slurries with different stabilities were prepared using different probe ultrasonic powers. The influence of electrostatic force and network structure on slurry stability was also studied. In addition, the catalyst layer (CL) and membrane electrode assembly (MEA) were further tested to determine the relationship between slurry stability, CL, and MEA performance. The results showed that the slurry prepared with 600 W dispersion power had the least agglomeration on day 12, which is due to the clusters in the slurry having the smallest average particle size and the largest surface area, thereby allowing them to absorb the most Nafion and have the largest electrostatic force to inhibit agglomeration. However, the slurry with 1200 W dispersion power had the least sedimentation after 9.4 days because the strength of the network structure in the slurry strengthened the most, resulting in a significant increase in viscosity and inhibition of sedimentation. Electrochemical tests showed that the MEA gradually exhibited worse electrical performance and higher impedance due to the agglomeration of catalyst particles caused by the standing process. Altogether, this study provides insights to better understand and regulate the stability of catalyst slurries.

Experimental Study on Waterproofing of Pipe Jacking Shaft and Pipe Joint in Metro Station

Through the indoor waterproof test, the water pressure resistance performance of the waterproof system formed by setting embedded grouting pipe in the middle of double water swelling sealants was studied to ensure that the station pipe joint could meet the operation requirements. The results show that there must be enough distance between the outside sealant and the edge of the pouring concrete, otherwise the new and old concretes cannot be poured tightly; after swelling, the water pressure resistance of sealants is improved in the range of 0-0.55 MPa, with individual differences; the two kinds of slurries have obvious influence on the improvement of water pressure resistance, but the improvement effect of waterborne epoxy slurry is better than that of polyurethane slurry.

Infiltration behaviour into sand of bentonite slurry with guar gum

Bentonite slurry is widely used in various projects due to its excellent engineering properties. The behaviour of slurry infiltration, especially filter cake formation, is directly related to the effect of slurry. This paper proposes an improved apparatus to investigate the infiltration of a novel bentonite slurry, especially in the dynamic infiltration process of the slurry-driven shield, which provides significant references for tunnel excavation. According to monitoring indicators of water discharge volume, pore-water pressure and electrical conductivity, the hydraulic conductivity of filter cake and the major zone of infiltration were analysed. Besides, the results of scanning electron microscopy reveal the micro-interaction between slurry and the soil. The results illustrate that the bentonite slurry with guar gum could immediately form an external filter cake with an infiltrated zone. The external filter cake formed again with a denser bentonite clay platelet network after excavation in the condition of relatively short excavation distance. Therefore, this kind of slurry could rapidly stabilise the excavation surface in slurry-driven shield tunnelling.

Numerical Simulation of the Diffusion of Fissure Slurry at High Temperature

Deep-buried tunnel at high-ground temperature is prone to the sudden surge of water when crossing the water-rich formation, resulting in casualties and economic losses. Slurry injection is a common and effective method of governance for addressing this issue. However, there has been little research into pulping at high-ground temperature, with most of the existing research focusing on room temperature conditions. We studied two kinds of slurry commonly used in grouting, cement slurry and cement-sodium silicate slurry. Indoor testing was used in this paper to clarify the effect of temperature on slurry viscosity, and numerical simulation was used to study slurry diffusion in flat cracks at different temperatures. The results showed that in a hydrostatic environment, the spread rate of slurry was independent of temperature and type of slurry. For the same kind of slurry, the higher the temperature, the greater the maximum slurry pressure. The higher the temperature in a flow environment, the faster the slurry diffusion. As the temperature rised, the grouting pressure required for crack sealing decreased at first then rises. In a flow environment, the sealing effect of cement-sodium silicate slurry was superior to that of cement slurry.

Preparation and infrared properties of Ni3Al–Cr3C2 composite films deposited by electrohydrodynamic atomization technology

The purpose of this work is to provide a clean and efficient preparation process for Ni3Al–Cr3C2 composite films. In this work, two kinds of slurries were prepared to deposit Ni3Al–Cr3C2 composite films on a 316L stainless steel substrate by electrohydrodynamic atomization (EHDA) technology. The slurry used for deposition was prepared with magnetic stirring and ball milling, respectively. The influence of the atomization parameters (atomization distance, operating voltage, and flow rates) on the characteristics of deposited films was investigated. Homogenous and compact films, with a structure of ∼10 layers, were fabricated under the optimized deposition parameters. The composition and micro-morphology of the composite films were examined. The spectral reflectivity of the Ni3Al–Cr3C2 composite films was characterized by the Fourier transforms infrared spectroscopy (FTIR) to study the infrared properties of the composite films. The results showed that because the slurries used to deposit the composite films were prepared by various methods, the infrared reflectivity and emissivity of the two composite films were different in the middle and far-infrared region. However, in the whole middle and far-infrared spectrum, the emissivity of the two films was significantly low. Therefore, the Ni3Al–Cr3C2 composite films deposited by EHDA are expected to be used in mid-high temperature solar films.

The Cycle Characteristics of Slurries in Chemical Mechanical Polishing (CMP) of Fused Silica

AbstractThe role of the polishing slurry is crucial in chemical mechanical polishing (CMP) of fused silica (FS). Researching on cycle characteristics of slurry contributes to exploring the deterioration mechanism and prolonging the service time. In this paper, cycle characteristics of colloidal silica slurry and ceria slurry applied in CMP of FS were investigated when the two slurries were recycled for 53 and 42 hours, respectively. The changes of the material removal rate (MRR) and surface roughness (Rq) of FS were analyzed, and the material removal mechanism of both slurries had been discussed. Scanning electron microscopy (SEM) and X‐ray photoelectron spectroscopy (XPS) were employed to interpret the changes of the slurry characteristics. The results indicate that with the increase of recycling time, decrease of pH value and increase of solid content are two common factors which affected MRR improvement for both two kinds of slurries. For colloidal silica slurry, the Rq value fluctuates probably due to unchanged sizes and deformed shapes of SiO2. For ceria slurry, the Rq value increases probably due to the size reduction of ceria particles.

Experimental Research on Viscosity Characteristics of Grouting Slurry in a High Ground Temperature Environment.

The grouting method is a technical means to prevent and control the thermal damage of the tunnel with high ground temperature in the underground hot water area, and the viscosity characteristic of the slurry is the key factor of grouting treatment. When grouting in high ground temperature geological conditions, the slurry inevitably has both time-varying and temperature-varying characteristics of viscosity in the process of filling high-temperature fissures and plugging geothermal water. At present, the research on the viscosity characteristics of slurry at high temperature is rarely reported in the literature. In this paper, laboratory tests were carried out to measure the time-varying viscosity of ordinary cement slurry; cement-sodium silicate slurry, widely used in engineering; and high ground temperature grouting slurry (HGTGS), independently developed by our research group, at different preheating temperatures (20, 40, 60, 80 °C). The viscosity function curves of the three kinds of slurry were obtained by function fitting method, and the viscosity variation law of slurry was analyzed. The study found that the time-varying process of viscosity of the cement-sodium silicate slurry and the HGTGS in specific temperature conditions can be divided into two stages: The slow rising period of viscosity and the rapid rising period of viscosity. Whereas, the time-varying process of viscosity of ordinary cement slurry in specific temperature conditions includes only one stage of the slow rising period of viscosity. The viscosity of ordinary cement slurry and cement-sodium silicate slurry increases with the increase of temperature, while the viscosity of the HGTGS decreases with the increase of temperature. There are corresponding viscosity time-varying equations for the three kinds of slurry in different temperature conditions. The viscosity time-varying equation of the ordinary cement slurry accords with the linear function form, and the viscosity time-varying equation of the cement-sodium silicate slurry accords with the power-law function form. The viscosity time-varying equation of the HGTGS conforms to the exponential function form. On this basis, the unified description equation of the viscosity characteristics of grouting slurry in high ground temperature and the applicability of different types of grouting materials are obtained. This study has a certain reference value and guidance for theoretical analysis, numerical simulation and engineering application of grouting in high ground temperature environment.

Preparation and tribological properties of MoS2-based multiple-layer structured films fabricated by electrohydrodynamic jet deposition

As a kind of solid lubricant, molybdenum disulfide (MoS2) plays a pivotal role in reducing wear and friction. How to prepare MoS2 films with excellent tribological properties has become a research hotspot. In this paper, four kinds of slurries were prepared to deposit pure MoS2 films, MoS2/Ti composite films and Ti-MoS2/Ti multiple-layer structured films on cemented carbide surfaces by electrohydrodynamic jet deposition. The composition and microstructure of the deposited films were investigated. The adhesive strength between the film and the substrate was evaluated by scratch tests. Furthermore, the friction and wear properties were investigated by reciprocating sliding friction tests. The results show that the Ti layer can improve the film-substrate adhesive strength, and the construction of multiple-layer structure can significantly reduce the friction coefficient and prolong the friction life of the MoS2 films.

Preparation of novel microencapsulated phase change material with Cu-Cu2O/CNTs as the shell and their dispersed slurry for direct absorption solar collectors

In this study, a novel microencapsulated phase change material paraffin@Cu-Cu2O/CNTs was successfully prepared by hydrothermal reduction and in situ deposition method, in which paraffin as the core, Cu, Cu2O and carbon nanotubes (CNTs) as the shell. SEM and TEM results proved that the microcapsules have a core-shell structure, the CNTs were irregularly wrapped on the shell, and the diameter of the microcapsules was about 600-800 nm. The melting temperature and latent heat of the paraffin@Cu-Cu2O/CNTs microcapsules were 61.17 °C and 81.31Jg-1, respectively, and the encapsulation rate of the microcapsules was calculated to be 41.53% from the results of the DSC measurement. Due to the shell material, the paraffin@Cu-Cu2O/CNTs microcapsules displayed excellent thermal stability, its thermal decomposition temperature is increased by 97 °C compared to paraffin. Moreover, the paraffin@Cu-Cu2O/CNTs microcapsules were dispersed in water to form a new kind of slurry, such fluid exhibited great improvement in terms of thermal conductivity, specific heat capacity, light absorption performance and photo-thermal conversion efficiency than that of paraffin@Cu-Cu2O microcapsules slurry. Therefore, the high heat storage capability and excellent photo-thermal conversion performance of the paraffin@Cu-Cu2O/CNTs microcapsule slurry make it to be the most potential heat transfer fluid for direct absorption solar collector.

Ultraviolet-excitation Polishing using Photocatalyst and Cathilon

The availability of ultraviolet-excitation polishing for 4H-SiC wafer and the chemical state of the 4H-SiC surface polished using photocatalyst and cathilon were investigated in absence and presence of an ultraviolet (UV). X-ray absorption fine structure (XAFS) spectroscopy conducted the qualitative analysis of the polished 4H-SiC surface. This analysis was used to clarify the oxides that are formed/removed by decomposition of cathilon dye and water during the polishing of 4H-SiC using TiO2 slurry, cathilon slurry and TiO2-cathilon slurry (mixed slurry), all of which included diamond particles. In polishing the previously sandblasted and handlapped 4H-SiC, TiO2 slurry provides large polishing efficiency and large polished surface roughness, and cathilon slurry provides small polishing efficiency and small polished surface roughness under UV irradiation. The large polishing efficiency, small polished surface roughness and large roughness decrease rate were attained using mixed slurry that is suitable to polish 4H-SiC under UV irradiation. The differences of XAFS spectrum are observed in UV absence/presence among three kinds of slurries. The XAFS analysis mainly investigates and indicates that some oxides form on the surface polished using cathilon and mixed slurries in UV absence/presence. Polishing using mixed slurry provides less volumes of oxides inside SiC on the polished surface, particularly.

Multilayer LTCC structures based on glass-cordierite layers with different porosity

PurposeThe paper aims to report on fabrication procedure and present microstructure and dielectric behavior of multilayer porous low-temperature cofired ceramic (LTCC) structures based on glass-cordierite and glass-alumina.Design/methodology/approachThe LTCC structures were created as multi-layered composites with dense external layers and inner layers with intentionally introduced porosity. Two preparation methods were applied – subsequent casting of both kinds of slurries and conventional isostatic lamination of dried green tapes arranged in the designed order. Optical microscope observations were carried out to analyze the microstructure of green and fired multilayer structures and pore concentration. To evaluate the adhesion strength of the composite layers, pull test was performed. Dielectric behavior of the composites was studied in the frequency range 50 kHz-2 MHz.FindingsThe fabricated porous LTCC structures showed dielectric constant of 3-5.6. The lowest dielectric constant was attained for glass-cordierite composite made by the conventional tape casting/lamination/firing method from slurry with 50 per cent graphite content. The samples prepared using multiple casting were of worse quality than those fabricated in conventional process, contained irregular porosity, showed tendency for deformation and delamination and exhibited a higher dielectric constant.Originality/valueSearch for new low dielectric constant materials applicable in LTCC technology and new methods of their fabrication is an important task for development of modern microwave circuits.

Study on the antiseepage mechanism of the PBFC slurry for landfill site

In order to develop a kind of slurry with low permeability which has some adsorption and retardation to the pollutants in leachate to be used in antiseepage engineering of leachate for landfill site, experiments based on orthogonal method were performed. The optimal PBFC slurry was selected: bentonite 18–26%, cement 16–24%, fly ash 18–20%, TOJ800-10 water reducing agent 0.01–0.03%, polyvinyl alcohol 0.2–0.8%, sodium carbonate 0.8–1.5% and water 680–780/1000 mL seriflus. The material has good groutability and a concretion stone ratio which is greater than 99.6%. The coefficient of permeability of 28-day concretion body is 0.53 × 10[Formula: see text]–1.86 × 10[Formula: see text] cm/s and the compressive strength is 0.64–1.04 MPa. The slurry has good adsorption and retardation properties. The block rate of NH4-N and phosphorus reached 98.28%, and the block rate of CODCr and BOD5 reached 85.67%. The block rate of Hg, Pb and other heavy metal ions reached 99.8%. The PBFC slurry improved the retardation capability of the pollutants of the leachate at the landfill site by its infiltration sedimentation and adsorption fixation.

A new kind of chelating agent with low pH value applied in the TSV CMP slurry**Project supported by the Major National Science and Technology Special Projects (No. 2009ZX02308), the Fund Project of Hebei Provincial Department of Education, China (No. QN2014208), the Natural Science Foundation of Hebei Province, China (No. E2013202247), and the Colleges and Universities Scientific Research Project of Hebei

TSV (through silicon via) is an emerging technology, which can realize micromation compared with the conventional packaging and extend Moore's law. Chemical mechanical polishing (CMP) is one of the most important steps in the process of TSV manufacture, and it is an enabling technology to extend Moore's law in the past two decades. Low pressure, low abrasive and low pH value are the main requirements for copper interconnection. In this paper, the effect of different kinds of TSV slurry with FA/O II or FA/O IV type chelating agent on CMP are studied. All kinds of slurry used in this study are alkaline with no added inhibitors. From the experiment results, it can be seen that the copper removal rate and surface roughness achieved by using the FA/O IV type chelating agent with a low pH value is superior to using the FA/O II type chelating agent.

Preparation of Silicon Nitride Hollow Quasi‐Spheres by RF Thermal Plasma

Silicon nitride hollow quasi‐spheres (SNHQSs) are prepared via a two‐step method: producing micrometer‐sized agglomerated granules with β‐Si3N4, and sintering additives of nano‐alumina and nano‐yttria by spray‐drying and then hollowing the spray‐dried granules (SDGs) by radio frequency thermal plasma sintering. Five kinds of slurry with different content of sintering additives are prepared for spray‐drying, and the attained five kinds of SDGs have similar morphology and properties. However, different SDGs generate diverse hollow structures via plasma sintering. The cavity formation mechanism of the SNHQSs is deeply investigated. In addition, the obtained SNHQSs possess low apparent density (0.371–0.481 g/mL), high compressive strength (up to 50 MPa), and good thermal stability (up to 1600°C), which will enable their promising applications in porous ceramics.

Preparation of Porous Carbon Preform by Casting Camphene Based Charcoal Slurry

This paper describes the process of fabricating porous carbon preform by casting the camphene based charcoal slurry. Five kinds of slurry with different solid content varied from 20vol% to 40vol% has been prepared, we have studied the rheological behavior of slurries and the sublimation behavior of casted bodies. Porous carbon preform with negligible linear shrinkage (<0.6%), high porosity (>67vol%) and interconnected pore structure has prepared.

Wpływ temperatury składowania oraz typu gnojowicy na przeżywalność pałeczek z rodzaju Salmonella

The aim of this study was determination of the inactivation rate of Salmonella Senftenberg W775 and Salmonella Typhimurium in cattle and swine slurry stored under laboratory conditions at 4 and 20˚C. Salmonella bacilli underwent constant, gradual elimination from the slurry during its storage. This process occurred more efficiently in samples stored at 20˚C than at 4˚C. At both studied temperatures elimination of bacteria was faster in swine slurry than in cattle. Shorter survivability in research material, in both temperature variants and kinds of slurry, showed Salmonella Typhimurium.

Investigation on the plastic shrinkage of cementitious materials under drying conditions: mechanism and theoretical model

The plastic shrinkage behaviours of fresh paste under drying conditions were investigated for several typical cementitious materials, including cement, silica fume, fly ash and calcium carbonate powder. For all four kinds of slurries, pore water under pressure (PWP) at different depths, shrinkage both in the vertical and horizontal directions, and water evaporation were measured simultaneously. Preliminary experimental investigations show an obvious anisotropic character of the plastic shrinkage behaviour in the vertical and horizontal directions and strong dependence on the PWP development. At the beginning of exposure, no PWP is generated, the total shrinkage is fully displayed by vertical displacement, and the responsible mechanism for plastic shrinkage is water evaporation. Once PWP arises, the investigated pastes exhibit vertical expansion and horizontal shrinkage; the responsible mechanism is the capillary tension in pore fluid. Based on the experimental observations, a two-phase theoretical model is proposed, which builds a quantitative relationship between water evaporation and vertical shrinkage before PWP is generated, as well as between PWP and horizontal shrinkage after PWP arises.

An Alkaline SiO<sub>2</sub> Slurry for Fine Atomizing CMP

A kind of slurry which is applicable for fine atomizing CMP was made and the optimal results were obtained through orthogonal experiments by comparing fine atomizing CMP and traditional CMP. The research results show that the material removal rate of fine atomizing CMP is 52.23% of traditional CMP, and the dosage of the slurry used in fine atomizing CMP only accounts for 10 vol% compared to traditional CMP. The surface roughness after the fine atomizing CMP is 2.5nm which is better than that of the traditional CMP (3.0nm).