Eco-fabrication of hierarchical porous silica monoliths by ice-templating of rice husk ash

Bahrami, Amin; Simon, Ulla; Soltani, N.; Zavareh, Sara; Schmidt, Johannes; Pech-Canul, M.I.; Gurlo, Aleksander

doi:10.1039/c6gc02153k

Cited by 67 publications

(29 citation statements)

References 32 publications

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“…In freeze‐casting processes, the solidification (freezing) stage can be altered in terms of its velocity, [ 11 ] temperature and direction [ 12 ] as well the application of additional external force fields. [ 13 ] Manipulating the freezing‐front velocity and temperature gradient of the solutions changes the spacing and thickness of resulting scaffold walls.…”

Section: Principles Of Freeze Castingmentioning

confidence: 99%

Freeze Casting: From Low‐Dimensional Building Blocks to Aligned Porous Structures—A Review of Novel Materials, Methods, and Applications

2020

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Freeze casting, also known as ice templating, is a particularly versatile technique that has been applied extensively for the fabrication of well‐controlled biomimetic porous materials based on ceramics, metals, polymers, biomacromolecules, and carbon nanomaterials, endowing them with novel properties and broadening their applicability. The principles of different directional freeze‐casting processes are described and the relationships between processing and structure are examined. Recent progress in freeze‐casting assisted assembly of low dimensional building blocks, including graphene and carbon nanotubes, into tailored micro‐ and macrostructures is then summarized. Emerging trends relating to novel materials as building blocks and novel freeze‐cast geometries—beads, fibers, films, complex macrostructures, and nacre‐mimetic composites—are presented. Thereafter, the means by which aligned porous structures and nacre mimetic materials obtainable through recently developed freeze‐casting techniques and low‐dimensional building blocks can facilitate material functionality across multiple fields of application, including energy storage and conversion, environmental remediation, thermal management, and smart materials, are discussed.

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Section: Principles Of Freeze Castingmentioning

confidence: 99%

Freeze Casting: From Low‐Dimensional Building Blocks to Aligned Porous Structures—A Review of Novel Materials, Methods, and Applications

2020

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“…[ 65 ] However, the use of low cost, abundant, and intrinsically nanostructured starting materials can potentially decrease the high fabrication cost of nanomaterial synthesis. [ 66–68 ]…”

Section: Use Of Wastes In the Synthesis Of Te Materialsmentioning

confidence: 99%

Waste Recycling in Thermoelectric Materials

Bahrami

Schierning

Nielsch

2020

Advanced Energy Materials

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power plants, factories, motor vehicles, computers, or even human bodies into electricity. TEGs are suitable for small applications because of their compatibility, simplicity, and scalability. For example, electricity can be generated from small heat sources and by taking advantage of small temperature differences for powering wristwatches or wearable devices such as miniaturized accelerometers or electroencephalography (EEG) devices. [3,4] However, low efficiency and high fabrication cost are the main disadvantages of TEGs which hinder their vast application in the market. Although many studies have explored the ways to increase the efficiency of TEGs in converting the thermal to electric energy, cost of TE materials synthesis and miniaturized TEGs fabrication has not been addressed widely.TEGs require materials with high electrical conductivities and low thermal conductivities, as well as high thermopower (Seebeck coefficient, S) which in turn constrains the types of materials that can be used as a TE material. The direct conversion of thermal to electrical energy in response to a temperature gradient across a material can be calculated by using the following equationwhere ΔV is the generated voltage, S is the Seebeck coefficient or thermopower, and ΔT is the temperature difference. The performance of a TE material is defined by the dimensionless figure of merit (zT), which relates the material properties to its conversion efficiency, in the following way 2 l e ZT S T σ κ κ ) ( = +where σ is the electrical conductivity, κ l and κ e are the lattice and electronic contributions to the thermal conductivity of TE material, respectively, and T is the absolute temperature. High S 2 σ (power factor, PF) and low thermal conductivity, κ = κ l + κ e , lead to better performance. In practice, however, the mutual dependence between these material properties makes an optimization of zT difficult. For many decades since the 1950s, when research and development of bulk homogenous materials for TE applications started to increase, research and development efforts focused on elements derived from raw materials for synthesizing TE materials. The compounds synthesized from raw elements such as Thermoelectric (TE) technology enables the efficient conversion of waste heat generated in homes, transport, and industry into promptly accessible electrical energy. Such technology is thus finding increasing applications given the focus on alternative sources of energy. However, the synthesis of TE materials relies on costly and scarce elements, which are also environmentally damaging to extract. Moreover, spent TE modules lead to a waste of resources and cause severe pollution. To address these issues, many laboratory studies have explored the synthesis of TE materials using wastes and the recovery of scarce elements from spent modules, e.g., utilization of Si slurry as starting materials, development of biodegradable TE papers, and bacterial recovery and recycling of tellurium from spent TE modules. Yet, the outcomes of such work have no...

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“…Porosity in ceramics offers many potential advantages, making them lightweight, ideal for filtration and insulation [1,2], useful in tissue engineering [3,4], high-performance structural applications [5], catalysis [6], gas distributors, fuel cells and batteries [7,8]. Common processing methods to fabricate porous synthetic materials include template replication [9,10], direct foaming [11,12], 3D-printing [13,14], sol-gel methods [15,16] or electrospinning [17].…”

Section: Introductionmentioning

confidence: 99%

External Field Assisted Freeze Casting

Niksiar

Frank

et al. 2019

Ceramics

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Freeze casting under external fields (magnetic, electric, or acoustic) produces porous materials having local, regional, and global microstructural order in specific directions. In freeze casting, porosity is typically formed by the directional solidification of a liquid colloidal suspension. Adding external fields to the process allows for structured nucleation of ice and manipulation of particles during solidification. External control over the distribution of particles is governed by a competition of forces between constitutional supercooling and electromagnetism or acoustic radiation. Here, we review studies that apply external fields to create porous ceramics with different microstructural patterns, gradients, and anisotropic alignments. The resulting materials possess distinct gradient, core–shell, ring, helical, or long-range alignment and enhanced anisotropic mechanical properties.

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Eco-fabrication of hierarchical porous silica monoliths by ice-templating of rice husk ash

Abstract: In this study, within a sustainable chemistry approach, a clean and eco-friendly synthesis process of silica monoliths compatible with environmental limitations is developed.

Cited by 67 publications

References 32 publications

Freeze Casting: From Low‐Dimensional Building Blocks to Aligned Porous Structures—A Review of Novel Materials, Methods, and Applications

Freeze Casting: From Low‐Dimensional Building Blocks to Aligned Porous Structures—A Review of Novel Materials, Methods, and Applications

Waste Recycling in Thermoelectric Materials

External Field Assisted Freeze Casting

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