Biomorphous ceramics from lignocellulosics

doi:10.1016/S0955-2219(00)00179-5

Journal of the European Ceramic Society

Volume 21, Issue 2, February 2001, Pages 105-118

https://doi.org/10.1016/S0955-2219(00)00179-5 Get rights and content

Abstract

Lignocellulosics represent the organic matter produced by trees. Biopolymers such as cellulose, hemicellulose and lignin are the major macromolecular constituents of ligneous cell walls which are distinguished by a hierarchical fibrilar composite micro structure. Fundamental aspects of anatomy of wood and molecular structure of wood cell wall affecting the bioorganic–inorganic conversion process are reviewed. Basic approaches to convert the native biopolymeric materials into non-oxide as well as oxide ceramic products include: (i) pyrolytic decomposition resulting in a porous carbon replica (template) which may subsequently be reacted to form carbide phases or may be infiltrated with non-reacting sols or salts which can further be processed to yield oxide reaction products; (ii) infiltration of chemically preprocessed native lignocellulosic products with gaseous or liquid organometallic and metalorganic precursors and subsequent oxidation to remove the free carbon phase. Conversion of native (wood tissue) lignocellulosics into ceramics with a microstructure pseudomorphous to the bioorganic template anatomy offers a great potential for designing novel ceramics with anisotropic cellular morphologies. These might be of interest for applications as high temperature resistant exhaust gas filters and catalyst carriers in energy, environmental and automotive industries, bioinert and corrosion resistant immobilization supports for living cells, microbes, or enzymes in biotechnology and medicine.

Introduction

Lignocellulosics from the class of organic matter produced by land-growing plants in the form of trees, shrubs, and agricultural crops. It is the essential carbon sink on the planet which is formed by catalytic conversion of carbon dioxide to an organic mass mainly consisting of the elements C–O(–N)–H. Lignocellulosic biocomposites are intricate materials with great biodiversity, but with chemical compositions that make use of only minor variations of principally two different monomeric repeat units: mono-saccharides (pentoses and hexoses) forming celluloses and hemicelluloses, and p-OH phenylpropanes present in lignin. Cellulose-rich fibers are separated, isolated, and purified by aqueous delignification and mild hydrolysis in an acidic or alkaline medium which is the only large scale chemical technology dealing with lignocellulosics.¹ Major products are paper and pulp and only a minor part of isolated cellulose is dedicated for fiber and cellulose derivatives (carboxymethylcellulose, cellulose acetate) production. Future activities are expected to make use of lignocellulosics as an alternative source of biobased polymers for use in structural materials. Biopolymers are abundant, renewable, biodegradable, and recycleable.

Design of novel ceramic structures by mimicking the cellular tissue anatomy of native lignocellulosic structures such as wood, fibers, surfaces of leafs, etc. has recently attained increasing interest.2, 3, 4, 5 For example, anti-adhesive plant surfaces caused by different cuticular microstructures (trichomes, cuticular folds, wax crystals) were analyzed⁶ in order to generate self-cleaning, water-repellent surfaces (Lotus effect). Another example is the formation of Al₂O₃,⁷ TiO₂,⁸ SiC and Si₃N₄ fibers⁹ from natural fibers such as sisal, jute, hemp, or cotton, and SiC whiskers from rice husks and coconut shells.10, 11, 12 The highly anisotropic cellular structure of wood may serve as a hierarchical template to generate novel cellular ceramics with a micro-, meso- and macro-structure pseudomorphous to the initial porous tissue skeleton ranging from nanometers (cell wall fibrils) to milimeters (growth ring patterns).3, 4, 5, 13 Wood typically contains 10–20 wt.% of hemicellulose, 10–30 wt.% of lignin, and 30–55 wt.% of cellulose (and less than 2 wt.% of ash including minerals).¹⁴ Previous work on converting wood into ceramic focused on liquid infiltration of the pyrolysed carbon template with sols of tetraethylorthosilicate (TEOS) at low temperature³ or silicon melt at high temperatures.14, 15 Subsequently, the infiltrant was converted into SiC by pyrolysis in inert atmosphere (TEOS) or reaction with carbon (silicon). A variety of different kinds of wood such as oak (Quercus robur), maple (Acer pseudoplatanus), beech (Fagus sylvatica), ebony (Diospyros celebica), balsa (Ochroma pyramidale), and pine (Pinus sylvestris) were converted to isomorphous cellular silicon carbide ceramics.4, 13 Due to the uniaxial pore channel orientation pronounced anisotropic differences of mechanical properties e.g. strength, elastic modulus, failure strain, fracture patterns were found. Generally, the mechanical properties scale by a power law of 2nd or 3rd order with fractional density.¹⁵ Properties in axial direction (parallel to the trunk axis) of SiC ceramics pseudomorphous to wood were found to attain significantly higher values compared to the tangential and radial loading directions.¹³

Biomophous ceramics with the cellular structure of the native or preprocessed lignocellulosics precursor but consisting of high temperature and corrosion resistant ceramic compounds such as carbides, nitrides, oxides, etc. are of particular interest because:

•
native tissue is supposed to be in a mechanical state of equilibrium optimally adopted to the external loading situation during growth;
•
native tissue exhibits unique structural features such as hierarchy, selectivity and anisotropy combined in the cellular anatomy;
•
native tissue is available in an almost infinite diversity and variety of structures;
•
growth of natural plants can be manipulated by chemical and physical methods in order to tailor tissue structures with optimized functionality e.g. pore size distribution, strut thickness, etc.;
•
preprocessing of lignocellulosics by delignification and surface treatment of cellulose fibers offers a versatile pool of cellulose fiber macrostructures to be used for manufacturing of light weight ceramic structures.

Cellular ceramics with homogeneous (monomodal) or heterogenous (multimodal or fractal) anisotropic pore structures might be of interest for high temperature resistant exhaust gas filters and catalyst carriers in energy and environmental technology, bioinert and corrosion resistant immobilization supports for living cells, microbes, or enzymes in medicine and biotechnology, etc.

While previous work on “ceramic wood” was focused on converting native wood or a pyrolyzed carbon template primarily into SiC3, 4, 5 fundamental questions remain to be addressed for future development of products. For example, conversion processes have to be developed which allow manufacturing of oxide ceramics of variable composition. An adequate chemical pretreatment of lignocellulosics is necessary to reduce shrinkage and to achieve net shape conversion of complex structures. Structural limitations with respect to size and shape of pores and cell wall structures have to be identified and the effects of non-uniformity of native cellular structures on property variations have to be examined.

In the following, basic principles of conversion of lignocellulosics into ceramic structures mimicking the initial precursor structure at various hierarchical micro- and macro structural levels, will be discussed. Fundamental aspects of the anatomy of wood and the molecular structure of wood cell wall affecting the bioorganic–inorganic conversion process are reviewed.

Basic approaches to convert the native biopolymeric materials into non-oxide as well as oxide ceramic products include:

(i) pyrolytic decomposition resulting in a porous carbon replica (template) which may subsequently be reacted to form carbide phases or may be infiltrated with non- reacting sols or salts which can further be processed to yield oxide reaction products;
(ii) infiltration of chemically preprocessed native or technical lignocellulosic products with gaseous or liquid organometallic and metalorganic precursors and subsequent oxidation to remove free carbon phase.

Conversion of native (wood tissue) lignocellulosics into ceramics with a microstructure pseudomorphous to the bioorganic template anatomy offers a great potential for designing novel ceramics with anisotropic cellular morphologies.

Section snippets

Anatomy of wood

Wood is a naturally grown composite material of complex hierarchical cellular structure.¹⁶ Both hardwoods (deciduous wood which is botanically classified as dicotlyedonous angiosperms) and softwoods (coniferous wood or gymnosperms) are comprised of elongated tubular cells (sclerenchyma cells) aligned with the axis of the tree trunk. Fig. 1 shows some examples of native wood tissue with different pore structures in the axial direction (axial cross section). Vessel elements (tracheas), also

Molecular structure of wood cell wall

While the anatomical differences in gross cellular structure between different kinds of wood (both hard- and softwoods) can be very large, the general structure of the cell wall is relatively consistent. A single longitudinal tracheid exhibits a layered wall structure, a thin primary (first-formed) wall and a thicker secondary wall composed of three sublayers known as S1, S2, and S3 layers, Fig. 4. The basic framework of each secondary wall layer (S1–S3) consists of cellulose with varying

Conversion of lignocellulosics into ceramics

Conversion of lignocellulosics into ceramic products may start from native plant tissue or from preprocessed technical structures, e.g. delignified cellulose precursor materials. Direct tissue reproduction generally deals with the problem of heterogeneity on the macro-, meso- and microscale levels of the naturally grown biostructure. Using preprocessed technical products such as paper, cardboards, matchwood, etc. may provide precursors which are homogeneous on the macroscale level, though the

Applications of biomorphous ceramics

Fig. 12 shows principal cellular structures which may be derived from native plants. Ceramics with a homogenous porosity structure are possible candidates for filter, catalyst carrier, aerator structures, etc. Filter structures require a well defined monomodal pore size to provide a cut off dimensional limit necessary for filter selectivity. Due to the specific cell microstructure of naturally grown traeidal tissue, small pores in the cell walls offer the possibility to provide gas flow between

Conclusions

Native or preprocessed lignocellulosics may be successfully used as a template for generating ceramic materials pseudomorphous to the initial cellular structure. Depending on the wide variety of native wood structures ceramics with a uniform as well as non-uniform (hierarchical) pore structure can be processed. The resulting cellular ceramics, which might be called “lignocers”, are generally characterized by a highly anisotropic microstructure giving rise to anisotropic material properties.

Acknowledgements

Financial support from Volkswagen-Foundation is gratefully acknowledged.

References (38)

C.E. Byrne et al.
Carbonization of wood for advanced materials applications
Carbon
(1997)
A. Oberlin
Carbonization and graphitization
Carbon
(1984)
F. Shafizadeh et al.
Development of aromaticity in celluosic chars
Carbon
(1983)
W.A. Glasser
Chemical products from lignocellulosics
Mat. Res. Soc. Bull.
(1994)
H. Li et al.
Biomimicry of bamboo bast fiber with engineering composite materials
Mat. Sci. Eng.
(1995)
T. Ota et al.
Biomimetic process for producing SiC wood
J. Am. Ceram. Soc.
(1995)
P. Greil et al.
Biomorphic cellular silicon carbide ceramics from woodI. Processing and Microstructure; II. Mechanical Properties
J. Eur. Ceram. Soc.
(1998)
D.W. Shin et al.
Silicon/silicon carbide composites fabricated by infiltration of a silicon melt into charcoal
J. Am. Ceram. Soc.
(1999)
C. Nienhuis et al.
Characterization and distribution of water-repellent, self-cleaning plant surfaces
Annals of Botany
(1997)
M. Patel et al.
Production of alumina fibre through jute fibre substrate
J. Mat. Sci.
(1990)

M. Patel et al.

Titania fibres through jute substrates

J. Mat. Sci. Lett.

(1993)

R.V. Krishnaro et al.

Preparation of silicon carbide and silicon nitride fibres from cotton fibre

J. Mat. Sci. Lett.

(1996)

N.K. Sharma et al.

Formation and structure of silicon carbide whiskers from rice hulls

J. Am. Ceram. Soc.

(1984)

M. Patel et al.

SiC Whiskers from rice huskrole of catalysts

J. Mat. Sci. Lett.

(1989)

S.K. Singh et al.

Thermal plasma synthesis of sic from rice hull

J. Mat. Sci. Lett.

(1993)

Kaindl, A., Cellular SiC Ceramics from Wood, PhD thesis, University of Erlangen-Nuernberg (2000) (in...

Wagenführ, R., HOLZatlas, Fachbuchverlag Leipzig (1996) (in...

L.J. Gibson et al.

Cellular Solids, Structure and Properties

(1988)

L.J. Gibson

Wooda natural fibre reinforced composite

Metals and Materials

(1992)

Cited by (308)

Cork derived TiO<inf>2</inf> biomorphic ecoceramics
2022, Open Ceramics
Environmentally conscious biomorphic ceramics (Ecoceramics) are a new class of material manufactured from renewable resources and wastes. Sustainable cork wastes were pyrolysed, and this activated carbon template infiltrated with a sol-gel precursor (from aqueous green-chemistry) to form TiO₂ on heating in air, with the honeycomb microstructure of cork. Physical and optical band gap properties were characterised by XRD, SEM and Raman and UV–vis spectroscopy, and differences between alkaline and acidic activation of the carbon template also studied. With activation by HCl, HNO₃ or H₂SO₄, a mixture of anatase and rutile formed. NaOH activation resulted in pure anatase, but a large amount of Na was retained. At 1000 °C acid activated ecoceramics formed pure rutile, but the NaOH activated one formed Na₂Ti₆O₁₃ (sodium hexatitanate) as the major phase, coexisting with anatase, brookite and rutile. This material is worth further investigation, as Na₂Ti₆O₁₃ is reported as a photocatalyst in its own right.
Insights into the phase evolution-composition-structural aspect of silicon carbide powders preparing from nature silica sands of south Libya
2021, Materials Chemistry and Physics
The silicon carbide (SiC) powders were prepared from four types of silica sands taken as a silica source. These sand samples were collected from Alhasawneh Mountain, Murzuq city, Sebha city and Zalaf region located in the southern of Libya. Here, the carbon source was citrus sinensis tree branches and the sol-gel method was used for preparing the samples. The calcination process was performed by immersing SiC samples in a bath containing silica/carbon mixture (∼600 °C) for 6 h. The X-ray diffraction (XRD) results confirmed the formation of three polytypes of 6H, 3C and 21R–SiC. The cell parameter values of SiC samples were very close to the actual value. Excluding in the 21R phase, a slight increasing in the cell parameter c value of 53.08, 53.49, 53.82, 53.30 Å was observed for SiC_{Alhasawneh Mountain}, SiC_{Murzuq sand}, SiC_{Sebha Sand} and SiC_{Zalaf sand} samples, respectively. The particle morphology was measured using a field emission scanning electron microscopy (FE- SEM). The SiC_{Alhasawneh Mountain} sample showed larger particles sizes with irregular shapes. The irregular particle with large holes (from 0.5 to few microns) was observed in the SiC_{Murzuq sand} sample. The SiC_{Sebha Sand} sample contains a few hexagonal flakes ∼179 nm in diameter. The SiC_{Zalaf sand} sample showed irregular particles with an average size of 138 nm. Raman spectra of all samples showed D and G bands at 1360 cm⁻¹ and 1600 cm⁻¹, respectively. The weak peak at 798 cm⁻¹ corresponded to the transverse optical (TO) mode that appeared in SiC_{Zalaf sand} sample. The results showed that it is possible to use natural silica sands and silica/carbon bath method for synthesis of SiC product with low cost and inexpensive materials to be used in many applications of industrials.
Characterization of silicon carbide ceramics obtained from porous carbon structure achieved by plant carbonization
2020, Materials Chemistry and Physics
Citation Excerpt :
After the break down of the ―C―C― chains in the bio-polymer structures, an aromatic poly-nuclear carbon structure starts to form at temperatures above 600 °C [18]. The major mechanism [19] can be presented by the following steps: a) desorption of adsorbed water up to 150 °C; b) splitting of wood structural water between 150 °C and 260 °C; c) chain scissions, or depolymerization, and breaking of C–O and C–C bonds within ring units evolving water, CO and CO2 between 260 °C and 400 °C; d) aromatization forming graphitic layers above 400 °C and e) above 800 °C, thermally induced decomposition and rearrangement reactions. Three major pseudo-components of wood, hemicelluloses, cellulose, and lignin, break down in a stepwise manner at 200–280 °C, 260–350 °C and 280–500 °C, respectively [20,21].
The aim of this research was to obtain a carbon solid residue by the carbonization process of biomass in an inert atmosphere which, through physical activation and chemical treatment (using TEOS - tetraethyl orthosilicate) would allow creation of highly porous and spatially distinct ordered bio-SiC ceramics. The results of carbonization experiments at several operating temperatures and activation of carbons with multiple-cycle treatments TEOS clearly showed the possibility of obtaining SiC nano-structures, after performing the carbothermal reduction at 1400 °C. The increase in the activation temperature and the duration time starts the development of the SiC particles inside the porous structure. The XRPD analysis showed that the major SiC polytype has cubic SiC (β-SiC) structure and remainder is hexagonal SiC polytypic (α-SiC) structure. It was established that the carbons obtained from carbonization of the Platanus orientalis L. plane tree fruit (PTF) precursor and activated at 850 °C with longer holding times (1 and 2 h) exhibit β-SiC (cubic) nano-wires. A possible nano-wires increment mechanism was suggested. The obtained results represent significant contribution in understanding the process as well as the main characteristics of SiC nano-materials and their possible applications.
Wood-derived ultra-high temperature carbides and their composites: A review
2020, Ceramics International
Wood gains much attention owing to its unique characters such as cellular pore structures, low density etc. Wood-derived carbides have great potential applications as the high-temperature filters for gas or liquid, catalyst carrier, fluid/gas reservoir devices, biocatalyst supports, etc. In this paper, we review recent progress in comprehensively understanding the processing techniques, properties and applications of wood-derived carbides. The key techniques for producing wood-derived carbides involves the infiltration techniques which are categorized into six parts (slurry infiltration, polymer precursor infiltration, melting infiltration, molten salt infiltration, sol-gel infiltration, and chemical or physical vapor infiltration). The advantages and disadvantages of these techniques are discussed in details, and the according solutions for solving the problems of each technique are further proposed. The infiltration kinetics of processing carbides are also discussed in details. The investigated properties of wood-derived carbides are summarized, which includes the mechanical properties and thermal properties. The potential applications of wood-derived carbides are explored, along with an overview of the existing challenges and practical limitations. In the end, we provide future perspectives to highlight the future directions of research in this growing area.
Ceramics with the signature of wood: a mechanical insight
2020, Materials Today Bio
In an attempt to mimic the outstanding mechanical properties of wood and bone, a 3D heterogeneous chemistry approach has been used in a biomorphic transformation process (in which sintering is avoided) to fabricate ceramics from rattan wood, preserving its hierarchical fibrous microstructure. The resulting material (called biomorphic apatite [BA] henceforth) possesses a highly bioactive composition and is characterised by a multiscale hierarchical pore structure, based on nanotwinned hydroxyapatite lamellae, which is shown to display a lacunar fractal nature. The mechanical properties of BA are found to be exceptional (when compared with usual porous hydroxyapatite and other ceramics obtained from wood through sintering) and unique as they occupy a zone in the Ashby map previously free from ceramics, but not far from wood and bone. Mechanical tests show the following: (i) the strength in tension may exceed that in compression, (ii) failure in compression involves complex exfoliation patterns, thus resulting in high toughness, (iii) unlike in sintered porous hydroxyapatite, fracture does not occur ‘instantaneously,’ but its growth may be observed, and it exhibits tortuous patterns that follow the original fibrillar structure of wood, thus yielding outstanding toughness, (iv) the anisotropy of the elastic stiffness and strength show unprecedented values when situations of stresses parallel and orthogonal to the main channels are compared. Despite being a ceramic material, BA displays a mechanical behavior similar on the one hand to the ligneous material from which it was produced (therefore behaving as a ‘ceramic with the signature of wood’) and on the other hand to the cortical/spongy osseous complex constituting the structure of compact bone.
Microstructure, mechanical and ablation behaviour of C/SiC–Si with different preforms
2019, Ceramics International
In this paper, carbon fibre reinforced SiC–Si dual matrix composites (C/SiC–Si) with two-dimensional (2D) and three-dimensional needled (3DN) preforms were prepared. Compared with the 3DN preform, there was a higher effective volume fraction of carbon fibre (20 vol%) in the loading direction for the 2D preform, leading to higher flexural strength (348 ± 29 MPa) and fracture toughness (15.0 ± 1.7 MPa·m^1/2) of the 2D C/SiC–Si. The silicon agglomerated in the inter-bundle area to form a silicon pool in the 2D preform, and thus the silicon melt can easily be scoured by the heat flux. The silicon uniformly dispersed in the SiC matrix of the 3DN preform, which can allow them to protect each other in the ablation process, and thus the 3DN C/SiC–Si had a lower mass ablation rate (6.2 mg∙s^-1) than the 2D C/SiC–Si (12.3 mg∙s^-1).

View all citing articles on Scopus

View full text

Biomorphous ceramics from lignocellulosics

Abstract

Introduction

Section snippets

Anatomy of wood

Molecular structure of wood cell wall

Conversion of lignocellulosics into ceramics

Applications of biomorphous ceramics

Conclusions

Acknowledgements

Carbon

Carbon

Carbon

Chemical products from lignocellulosics

Mat. Res. Soc. Bull.

Biomimicry of bamboo bast fiber with engineering composite materials

Mat. Sci. Eng.

Biomimetic process for producing SiC wood

J. Am. Ceram. Soc.

Biomorphic cellular silicon carbide ceramics from woodI. Processing and Microstructure; II. Mechanical Properties

J. Eur. Ceram. Soc.

Silicon/silicon carbide composites fabricated by infiltration of a silicon melt into charcoal

J. Am. Ceram. Soc.

Characterization and distribution of water-repellent, self-cleaning plant surfaces

Annals of Botany

Production of alumina fibre through jute fibre substrate

J. Mat. Sci.

Titania fibres through jute substrates

J. Mat. Sci. Lett.

Preparation of silicon carbide and silicon nitride fibres from cotton fibre

J. Mat. Sci. Lett.

Formation and structure of silicon carbide whiskers from rice hulls

J. Am. Ceram. Soc.

SiC Whiskers from rice huskrole of catalysts

J. Mat. Sci. Lett.

Thermal plasma synthesis of sic from rice hull

J. Mat. Sci. Lett.

Cellular Solids, Structure and Properties

Wooda natural fibre reinforced composite

Metals and Materials