Aluminosilicate Research Articles

Experimental investigation and optimization of loop heat pipe performance with nanofluids

High heat generation from electronic devices needs to cool down properly to prevent overheating. Loop heat pipe (LHP) is one of the excellent cooling devices for high heat generation of electronic devices. Nanofluid is a working fluid which has nanoparticle dispersed in based fluid. Nanofluid is proven to have better thermal performance compared with conventional fluids. In this paper, we investigate on the thermal performance of loop heat pipes using different types of nanofluids. The desired nanofluids used in this study are diamond nanofluid, aluminium oxide (Al2O3) nanofluid and silica oxide nanofluid (SiO2) with 0–3% of mass concentrations. The results showed that as the mass concentration of nanofluids increased, the thermal resistance for diamond nanofluid and Al2O3 nanofluid decreased, but SiO2 nanofluid results show the opposite trend of thermal resistance with increasing mass concentration. The lowest thermal resistance is 3.0872 °C W−1, 3.1465 °C W−1 and 3.2816 °C W−1 for diamond, Al2O3 and SiO2, respectively. Moreover, all types of nanofluids show better heat transfer performance compared with water. Diamond nanofluid also had higher heat capacity than Al2O3 nanofluid as it had a lower vapour line temperature reading. Optimization result also shows that diamond nanofluid has better thermal enhancement than Al2O3 with 1.19% of mass concentration.

Optimization and Prediction of Reaction Parameters of Plastic Pyrolysis oil Production Using Taguchi Method

Design of Experiments (DoE) is a powerful guiding tool that can help researchers to identify the main variables that affect the performance characteristics. The present paper elaborates on the optimization and prediction of reaction parameters like type of plastic, catalyst, and temperature using Taguchi’s L9 orthogonal array method with three levels and three parameters to obtain the highest yield of plastic oil. To determine the effect of each parameter, the Signal to Noise (S/N) ratio was calculated based on the experiments conducted. In this investigation, contributions of reaction parameters were analyzed by Analysis of Variance (ANOVA) using statistical software Minitab-16. Based on the investigation, the reaction parameters like type of plastic: Low-Density Polyethylene (LDPE), catalyst: Silica alumina (SA), and temperature: 500°C are optimized to get the better yield of oil. Based on the confirmatory trial, the oil yield of about 95.4%, the gas yield of about 3.4%, and solid residue as 1.2% were obtained, which is better than the normal trails.

Flexural behaviour of reinforced concrete beams with partial replacements of metakaolin and marble powder

Concrete is the most widely used and versatile building material which is generally used to resist compressive force. By addition of some pozzolanic materials as admixtures, the various properties of concrete can be improved. Many modern concrete mixes are modified with the addition of admixtures, which improve the micro structural properties as well as decrease the calcium hydroxide concentration by consuming it through a pozzolanic reaction. Metakaolin is a cementitious pozzolanic material highly efficient and can react rapidly with the excess calcium hydroxide resulting from OPC hydration by a pozzolanic reaction, to produce calcium silicate hydrate and calcium alumino silicate hydrates. Due to rapid growth of construction activity, the available sources of natural sand are getting exhausted. Therefore, it is necessary to replace natural sand in concrete by an alternate material either partially or completely without compromising the quality of concrete. Waste marble dust is one such material which can be used to replace sand as fine aggregate in concrete. The present study describes an experimental program conducted to investigate the flexural behaviour of Reinforced Concrete beams with metakaolin as partial replacement for cement and marble powder as partial replacement for river sand in preparation of concrete. The percentage replacement of cement by metakaolin considered in this experimental study are 0, 2, 4, 6 and 8% by weight of cement and sand by marble powder are 20, 15, 10, 5 and 0%. The mechanical properties such as compressive and split tensile strength are analysed for conventional and modified concretes, at the age of 7, 14 and 28 days. A total of five RC beams, with dimensions 150 × 200 × 1500 mm was cast and tested under four point loading. The observations made were initial crack load, ultimate failure load and deflection of the beams. The results show that metakaolin and marble powder can be used as alternate construction materials at lower percentage replacement levels.

Effect of GGBS Addition on Reactivity and Microstructure Properties of Ambient Cured Fly Ash Based Geopolymer Concrete

Geopolymer concrete is an eco-friendly alternate to conventional concrete that considerably lower green house gases emitting into the atmosphere. Fly ash based geopolymer concrete is reported to become hardened during heat curing process which comes as a major constraint for cast in in-situ applications. In this study, the aluminosilicate materials such as Ground Granulated Blast Furnace Slag (GGBS) with varying percentages such as 0%, 10%, 20%, and 30% replaces the fly ash (FA) in geopolymer concrete was used. Manufactured sand (M-sand) is used as full replacement material for natural sand as fine aggregate owing to its increasing demand. This work aims at investigating the effect of alumino silicate materials on strength properties, characterization and micro structural analysis using Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray spectroscopy (EDX), Fourier Transform Infrared spectroscopy (FTIR) and X-ray diffraction (XRD) in geopolymer concrete under ambient curing condition. The SEM and EDX results reveals that, the micro structural properties of fly ash, GGBS materials, CaO, Si/Al ratio, and gel formation have a significant effect on compressive strength and setting time of geopolymer concrete. The FTIR analysis reveals that the stretching vibration of fly ash shifts to low wave number values due to changes in geopolymerization. The X-ray diffraction (XRD) reports show that the C-S-H gel formed around 27–30° 2theta value due to increase of GGBS in geopolymer concrete.

Self-Organization of Large Alumina Platelets and Silica Nanoparticles by Heteroaggregation and Sedimentation: Toward an Alternative Shaping of Nacre-Like Ceramic Composites.

Nacre-like ceramic composites are of importance in a wide range of applications, because of their mechanical properties, combining high mechanical strength and high fracture toughness. Those mechanical properties are the result of strongly aligned platelets glued in a matrix. Different methods exist to shape such a "brick-and-mortar" hierarchical structure. In this paper, we propose to use the phenomenon of heteroaggregation between silica nanoparticles and large alumina platelets. Experimental and numerical results show that silica nanoparticles can adsorb on alumina platelets with good distribution. This adsorption promotes the deagglomeration of alumina that can self-organize in layers by sedimentation. This phenomenon can be exploited to shape alumina-silica nacre-like composites.

CO2 mineralisation of Portland cement: Towards understanding the mechanisms of enforced carbonation

Reductions of CO2 emissions associated with Portland cement production represent currently the main challenge for the cement industry. A promising approach is to substitute the traditional hydration of cement by carbonation of cement clinker for the hardening of the material in concrete production. This work is a tailor-made experimental approach to explore the mechanisms of Portland clinker carbonation under wet conditions. The carbonation is found to be fast at the beginning of the reaction, provided enough CO2 is present in the system. Particularly, the calcium silicate phases react rapidly, where the kinetics is explained by the high undersaturation of these phases. Furthermore, the carbonation reaction can be divided into three stages when the reaction is limited by the different mechanisms: precipitation of products or dissolution of clinker or CO2. The main carbonation products are calcium carbonate and amorphous alumina silica gel. These phases precipitate in a different locations forming a special microstructural pattern.

Influence of Dealumination by Acetylacetone on Acidity and Activity of Amorphous Silica‐Aluminas

AbstractThe influence of dealumination of two commercial amorphous silica‐aluminas (ASAs) with acetylacetone on their textural properties, acidity and catalytic activity was studied by N2‐sorption, NH3‐TPD, FTIR of adsorbed pyridine as well as 1H and 27Al MAS NMR. Acetylacetone treatment increases the pore volume and surface area (+20→+30%) of commercial ASA without changing the pore size. More than half of the Al species are extracted from ASA but the total acidity is preserved or even slightly increased (for the ASA with higher Al content). The percentage of acidic Al is increased by a factor 2. Dealumination results in a better access to acid sites and an increase of medium Brønsted acid sites (BAS), leading to a 1.5 higher catalytic activity for 3,3‐Dimethyl‐1‐butene (33DMB1) isomerization.

Durability of mortars modified with the addition of amorphous aluminum silicate and silica fume

In modern concrete technology, the use of various types of additives and admixtures is standard. They not only affect the mechanical properties of cement composites but also significantly facilitate the formation of a concrete mix. The paper presents the effect of the content of silica fume (SF) and an amorphous aluminum silicate (AAS) on selected properties of cement mortars, such as flexural and compressive strength, water absorption, freeze–thaw resistance, and shrinkage. The dynamics of strength development, determined after 7, 28, and 90 days of maturing of test samples, are also presented in the paper. Mortars modified with the addition of amorphous aluminum silicate in amounts of 5% and 10% of the cement mass exhibited increased flexural strength within the range of 25–30% in comparison with standard mortar and mortar modified with the addition of SF of the same amount. In the case of compressive strength, both additives resulted in similar increases in the strength within the whole maturation period. The freeze–thaw resistance tests showed that the mortars with the addition of AAS were the most resistant to variable freezing and thawing cycles, in relation both to the control mortar and to the mortar modified by SF. The application of AAS resulted in a significant reduction of shrinkage strain (by more than twice) in comparison with mortars prepared with the analogous amount of silica fume.

Characterization of Marine Clay Under Microstructure Examination as a Potential Pozzolana

Globally, marine clay is found in coastal areas. It is often regarded as a profitless material because it affects building foundations, dredging and replacing it with a more suitable material before construction is therefore inevitable. However, the dumping of this marine clay after excavation has become a major problem in most countries like Singapore where dumping of clay is prohibited. Thus, the quest towards determining its potential use for sustainability. In that regards, this paper seek to investigate the characterization of two marine clay samples under microstructure examination through particle size analysis (PSA), X-ray fluorescence (XRF), thermo gravimetric and differential thermal analysis (TGA/DTA) and X-ray diffraction (XRD) to study the microstructural features of the marine clay under magnification in an attempt to examine its potential use as a pozzolana. Characterization is a very important stage in order to know the characteristics of a material before the initiation of any necessary modification. From the microstructure analysis, the PSA revealed that the particles are in micro size with less than 35% of the materials retained when wet sieved on 45 μm sieve. The XRF showed the chemical compositions of the marine clay with dominance of aluminum oxide (Al2O3), silica oxide (SiO2) and ferric oxide (Fe2O3). These three oxides made up over 70% of the chemical constituents in both samples. From TGA/DTA, maximum weight loss occurred at the temperature range 400–650 °C and the percentage of kaolinite was determine to be 42.7% and 45.1% for S1 and S2 respectively. From the XRD, the structural pattern and crystal orientation of marine clay gave rise to a diffraction pattern showing a high intensity of quartz and kaolinite indicating yet again that the marine clay belongs to the kaolinite group with basic composition of aluminosilicate, hence can be used as a potential pozzolana.

Adsorption kinetics in removal of basic nitrogen-containing compounds from practical heavy oils by amorphous silica-alumina

The adsorption behavior of basic compounds in practical vacuum gas oil is quantitatively analyzed on amorphous silica-alumina with acid sites, mesopores and thermal stability. Time course of adsorption capacity was found to be controlled by kinetics but not by equilibrium. The rate of adsorption was found to have pseudo second-order but not pseudo first-order kinetics, indicating that the adsorption rate was mainly controlled by the diffusion of large molecules. The particle size did not influence the adsorption quantity at equilibrium, whereas the smaller particle size increased the adsorption rate. The adsorption quantity at equilibrium was influenced by the molecular structure of basic compound due to steric hinderance around the basic site, whereas the adsorption rate strongly depended on the molecular size, supporting that the adsorption rate was mainly controlled by the diffusion of compounds in the pores of amorphous silica-alumina. Comparison of solvents showed that the adsorption quantity at equilibrium was influenced by the polarity but not by the molecular size, while the adsorption rate strongly depended on both the polarity and molecular size. The reusability of adsorbent silica-alumina was demonstrated by the stable adsorption capacity and rate after calcination for the regeneration.

A facile method to fabricate monolithic alumina–silica aerogels with high surface areas and good mechanical properties

In this study, monolithic alumina–silica aerogels with high surface areas and good mechanical properties were synthesized via a facile sol–gel method without solvent exchange. Furthermore, surface areas, microstructures (up to 1300 °C), and mechanical properties of the prepared alumina–silica aerogels were investigated. The sintering and phase transformations of metastable alumina nanoparticles are suppressed owing to the uniformly distributed Si in the alumina–silica aerogels; therefore, the alumina–silica aerogels can maintain much higher specific surface areas after being calcined at 800 °C (575.5 m2/g), 1000 °C (443.2 m2/g), and 1200 °C (120.6 m2/g) compared to pristine alumina aerogels. In addition, the prepared high surface area alumina–silica aerogels show considerably higher strengths than those obtained in previous works. The compressive stress (3 % strain) and elastic modulus of the alumina–silica aerogels reached 1.78 and 65.6 MPa, respectively. The reported alumina–silica aerogels in this study can be good candidates as high-temperature thermal insulators and catalysts.

Acidity enhancement through synergy of penta- and tetra-coordinated aluminum species in amorphous silica networks

Amorphous silica-aluminas (ASAs) are widely used in acid-catalyzed C-H activation reactions and biomass conversions in large scale, which can be promoted by increasing the strength of surface Brønsted acid sites (BAS). Here, we demonstrate the first observation on a synergistic effect caused by two neighboring Al centers interacting with the same silanol group in flame-made ASAs with high Al content. The two close Al centers decrease the electron density on the silanol oxygen and thereby enhance its acidity, which is comparable to that of dealuminated zeolites, while ASAs with small or moderate Al contents provide mainly moderate acidity, much lower than that of zeolites. The ASAs with enhanced acidity exhibit outstanding performances in C–H bond activation of benzene and glucose dehydration to 5-hydroxymethylfurfural, simultaneously with an excellent calcination stability and resistance to leaching, and they offer an interesting potential for a wide range of acid and multifunctional catalysis.

Flash Catalytic Pyrolysis of Polyethylene over (Alumino)silicate Materials

AbstractA series of amorphous and crystalline (alumino)silicate catalysts, with variable acidity, are evaluated for the flash pyrolysis of polyethylene (PE). Catalysts morphology, acidity as well as textural properties are influencing the process of decomposition of PE. Incomplete PE conversion and significant wax formation are obtained under the reaction condition with pure amorphous and MFI‐type silica. Complete conversion, and limited formation of wax, are observed with amorphous and MFI‐type Si−Al containing catalyst. Acidity has a significant influence on the molecule size and nature. Then, the increase of the catalyst acidity leads to the decrease of the molecular weight of pyrolysis products and the increase of the gas and the light liquid fractions. In addition, the acidity increase promotes cyclization reaction, resulting in the increase of the cycled hydrocarbon/aromatic proportion in the liquid fraction. Then, from PE catalytic pyrolysis, up to 25 wt.% of aromatics can be obtained in the liquid fraction with Si/Al ZSM‐5 zeolite, while olefins remain the major fraction with the less acidic amorphous aluminosilicate catalyst.

Pb 10 Al 10 Si 8 O 41 : Lead aluminosilicate with the narsarsukite-related structure

Pb ₁₀ Al ₁₀ Si ₈ O ₄₁ : Lead aluminosilicate with the narsarsukite-related structure

Кристаллографический анализ боро- и алюмосиликатов со структурами, близкими к структурам анальцима и поллуцита

Для кубических структур анальцима Na1.71(Al1.8,Si4.2)O12.2H2O, поллуцита CsAlSi2O6 и тетрагональных (но псевдокубических) кирчхоффита (kirchhoffite) CsBSi2O6 и лейцита KAlSi2O6 установлен общий шаблон (трафатет) распределения катионов по ключевым позициям пространственных групп симметрии, родственный с конфигурациями в структурных типах шпинели, алмаза, граната и др. Для совместного упорядочения позиций крупных катионов с анионами показано присутствие двух подрешеток, связанных псевдоосью шестого порядка в дифракционном (обратном) пространстве.

Study on the effect of reaction and calcination temperature towards glucose hydrolysis using solid acid catalyst

Levulinic acid (LA) comes from the family of ketone and carboxyl, which contributes to a very versatile building block for the synthesis of high value-added chemicals. Glucose can be converted into LA at certain conditions preferably at temperature of 80 °C–200 °C. Hence, a study on the effect of reaction and calcination temperature towards the conversion of glucose to LA was conducted. The effect was studied by varying the reaction and calcination temperature from 80 °C to 100 °C and 200 °C to 400 °C respectively. The solid acid catalyst was prepared using a wet impregnation method to incorporate 30 wt% SO42- on silica alumina. FTIR analysis was conducted to characterize the solid acid catalyst where the catalytic conversion took place in a batch reactor. It was found that the highest temperature used for the reaction (100 °C) contributes to a higher conversion of glucose to LA which is 56.8%. The reaction took place for 6 h. Meanwhile, as for the effect of calcinations temperature, it was revealed that lower temperature of calcinations favors the reaction where it tends to retain the SO42- content on the silica alumina support as shown in the FTIR analysis. This is because up to 48% of glucose was converted into LA. From this study, it is proven that parameters such as reaction and calcinations temperature highly influence the conversion of glucose to LA.

Effect of cure kinetics and nanomaterials on glass fiber/vinyl ester composites: An assessment on mechanical, thermal and fracture morphology

In this article, optimization of post-cure temperature for glass fiber/vinyl ester (GVE) composite at 80 °C, 110 °C and 140 °C for 6 hr, laminate fabricated by hand layup method was studied. Also, mechanical strength and glass transition temperature (Tg) of GVE composites reinforced with 0.1 wt% of various nanofillers such as carboxyl functionalized multi-walled carbon nanotube (CNT-COOH), nanoclay (surface-modified), nano alumina (Al2O3) and nano silica (SiO2) by solution processing method were investigated. Optimum properties for GVE composite were obtained at 140 °C post-cure temperature. With the addition of nanomaterials, flexural properties were improved for all the materials at specified parameters, whereas significant improvement acquired in the case of nanoclay GVE composite with a optimum flexural strength of 381.16 MPa and Tg of 102 °C was obtained. Post failure analysis of the tested samples was studied using a scanning electron microscope (SEM) at room temperature.

Analysis and Evaluation of 7 Indictor Polychlorinated Biphenyls (PCBs) Residues in Dried Kelp by Gas Chromatography (GC)

In this study, a special method was developed for the determination of 7 kinds of polychlorinated biphenyls (PCBs) residues in dried kelp by gas chromatography (GC) with electron capture detector (ECD). The PCBs were extracted with hexane/dichloromethane (1/1, v/v) by ultrasonic extraction. Clean-up methods were used by concentrated sulphuric acid, neutral alumina oxide solid phase extraction cartridge and silica solid phase extraction cartridge. The analytical compounds were quantified by an internal standard method. Under optimal experimental conditions, good linearity was observed in the range of 5~200ng/mL, and the correlation coefficients were 0.9993~0.9998. The limit of quantification (LOQ) for target analytical compounds ranged from 6.0 to 7.5μg/kg. At the spiked levels of 10，20，50 μg/kg，the average recoveries ranged from 81.8% to 105% with the relative standard deviations 3.05%～11.2%. The result showed that the proposed method was accurate and could be used for the determination of the PCBs in dried kelp.

Performance evaluation of fly ash/slag based geopolymer concrete beams with addition of lime

This paper evaluates the structural properties of geopolymer concrete beams with the addition of hydrated lime. The fly ash and GGBS are added in powder form with the ratio of 60% and 40%. A total number of six beam specimens are tested under two point static loading condition. The beams are cured under room temperature in ambient condition. Out of six beams three beams are geopolymer concrete beams with molarity concentration of 8 M, 10 M and 12 M respectively and another three beams the hydrated lime is replaced by 5% by weight of alumino silicate materials. The load deflection behaviour and flexural parameters like stiffness, ductility and energy absorption capacity are studied and compared with conventional geopolymer concrete specimen.

Experimental investigation on physical and mechanical properties of alkali activated concrete using industrial and agro waste

Increasing infrastructure demands the need for using huge quantities of concrete. Concrete manufacture requires large amounts of cement whose production of one-ton results nearly one ton of CO2 emission into the atmosphere attributing to global warming. As a step towards sustainability, the use of supplementary cementitious materials (SCMs) for cement has been adopted globally. Alkali Activated Concrete (AAC) and Geo polymer Concrete (GPC) are great alternatives for regular conventional concrete because they make use of industrial and agro wastes as binders without cement. AAC is composed of two components-paste and aggregates. The paste is essentially a mixture of rich Calcium silicate or Alumino silicate materials as solid precursor and alkaline activator. Activators like alkali silicates, alkali hydroxides, alkali sulphates, alkali carbonates can be used to increase the value of pH of the mixture and quicken the splitting of the solid precursor. The present study proposed the novel mix proportioning of alkali activated concrete with possible industrial and agro wastes as precursors and homogeneous mixture of sodium silicate (Na2SiO3) and sodium hydroxide (NaOH) as alkaline solution activator followed by experimental investigations. Series of experimental investigations are conducted to evaluate the fresh and hardened properties of AAC with constant NaOH molarity of 10 M and alkaline solution to binder ratio of 0.5. Several combinations involving fly ash, fly ash and slag, slag, fly ash and rice husk ash, slag and rice husk ash, etc will be adopted for the experimental investigations. Fresh concrete properties like workability and mechanical properties like compressive strength will be evaluated based on the work carried out using different combinations. Curing of AAC specimens is carried out in ambient temperature and the expected outcome will be a benchmark in making small scale concrete products like balusters, concrete benches at parks, paver blocks, and any other non-load bearing components using AAC mixes.