Microporous Morphology Research Articles

Using Micro-Arc Oxidation and Alkali Etching to Produce a Nanoporous TiO2 Layer on Titanium Foil for Flexible Dye-Sensitized Solar Cell Application

To increase the specific surface area of a TiO2 layer synthesized by micro-arc oxidation (MAO), an alkali etching process was developed to form a nanoflaky structure in place of the existing microporous morphology of the MAO-TiO2 layer for dye-sensitized solar cell (DSSC) electrode application. An annealing treatment was also carried out to enhance the crystallinity of the nanofeatured TiO2 layer for a higher photovoltaic efficiency. Experimental results show that a 6-µm-thick crystalline porous TiO2 layer was fabricated on a Ti foil by MAO treatment, which consists of major amorphous and anatase phases with a minor rutile phase. As expected, the pores in the MAO-TiO2 layer exhibited micrometer-scale dimensions. The maximum photovoltaic efficiency realized in a device assembled with the MAO-TiO2 layer was only 0.061%. After alkali etching, a nanofeatured layer was developed over the MAO-TiO2 layer surface with numerous pores and nanoflakes of 50 nm size. These nanoflakes were uniformly distributed over the entire surface of the treated layer. The device assembled with the alkali-etched TiO2 layer exhibited an improved photovoltaic efficiency of 0.329%. This fivefold increase of the photovoltaic efficiency for the MAO-TiO2 layer indicates the effectiveness of enlarging the specific surface area by alkali etching. Furthermore, after postannealing, the crystallinity and fraction of the anatase phase in the overall TiO2 layer were enhanced. As a result, the photovoltaic efficiency ultimately reached 2.194%.

Synthesis and structural characterization of dendritic-linear PMA-APM-r-PS copolymers for a self-assembled microporous matrix

A set of dendritic-linear copolymers, poly(maleic anhydride-grafted-3,3′-dimethyl-(4-aminophenylazanediyl)bis(2-methylpropanoate))-random-polystyrene (PMA-APM-r-PS), was successfully prepared by copolymerization of the novel dendritic macromonomer, 4-(4-(bis(3-(4-(bis(3-methoxy-2-methyl-3-oxopropyl)amino)phenylamino)-2-methyl-3-oxopropyl)amino)phenylamino)-4-oxobut-2-enoic acid (MA-APM), with styrene monomer. The dendritic MA-APM macromonomer dendron 3,3′-dimethyl-(4-aminophenylazanediyl)bis(2-methylpropanoate) (APM) was then grafted by using the divergent growth method. FTIR, 1H NMR, and 13C NMR spectra were used to identify the structures of the dendron, the dendritic macromonomer, and the dendritic-linear PMA-APM-r-PS copolymer. Furthermore, microporous dendritic-linear PMA-APM-r-PS copolymer films were prepared by using solvent-induced phase separation at room temperature. We investigated the phase separation behavior and morphological structures of the dendritic-linear copolymer film as functions of dendritic GMA-HPAM segments in the content using SEM. Self-assembly of the dendritic-linear PMA-APM-r-PS copolymer in the MG2-X system, which represented the second generation dendron containing X wt % of the dendritic MA-APM segment, resulted in submicron phase segregation. Interestingly, the submicron phase segregation morphology of the MG2–43 sample presented a uniform size distribution of ordered-array structures. The results of this study demonstrate that controlling the appropriate macromonomer content via the grafting of a three-dimensional structure results in a self-assembly process that is capable of providing an ordered-array microporous morphology in a polymer film. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3290–3301, 2010

Effect of Solvent–Nonsolvent Miscibility on Morphology and Electrochemical Performance of SiO2/PVdF‐HFP‐Based Composite Separator Membranes for Safer Lithium‐Ion Batteries

AbstractAs a new approach to improve the thermal stability of separator membranes crucially affecting the internal short‐circuit failures of lithium‐ion batteries, we develop a new composite separator membrane. The composite separator membrane is prepared by introducing microporous composite coating layers onto both sides of a polyethylene (PE) separator membrane. The composite coating layers consist of silica (SiO2) nanoparticles and gel‐type polymer electrolytes (PVdF‐HFP, polyvinylidene fluoride‐hexafluoropropylene). The microporous morphology of composite coating layers is determined by controlling the phase inversion, more specifically the solvent–nonsolvent miscibility in the coating solutions. To induce the phase inversion, three different nonsolvents are chosen in the decreasing order of solubility parameter (δ) difference against the solvent (acetone, δ = 20 MPa1/2); the non‐solvents are water (δ = 48 MPa1/2), ethanol (δ = 26 MPa1/2), and isopropyl alcohol (δ = 24 MPa1/2). The microporous structure of composite coating layers becomes more developed with the increase of not only the nonsolvent content, but also the solubility parameter difference between acetone and the nonsolvent. Based on this understanding of the phase inversion, the influence of the morphological variation on the thermal shrinkage and electrochemical performance of the composite separator membranes is quantitatively identified.magnified image

In vitro cellular response and in vivo primary osteointegration of electrochemically modified titanium

Anodic spark deposition (ASD) is an attractive technique for improving the implant-bone interface that can be applied to titanium and titanium alloys. This technique produces a surface with microporous morphology and an oxide layer enriched with calcium and phosphorus. The aim of the present study was to investigate the biological response in vitro using primary human osteoblasts as a cellular model and the osteogenic primary response in vivo within a short experimental time frame (2 and 4 weeks) in an animal model (rabbit). Responses were assessed by comparing the new electrochemical biomimetic treatments to an acid-etching treatment as control. The in vitro biological response was characterized by cell morphology, adhesion, proliferation activity and cell metabolic activity. A complete assessment of osteogenic activity in vivo was achieved by estimating static and dynamic histomorphometric parameters at several time points within the considered time frame. The in vitro study showed enhanced osteoblast adhesion and higher metabolic activity for the ASD-treated surfaces during the first days after seeding compared to the control titanium. For the ASD surfaces, the histomorphometry indicated a higher mineral apposition rate within 2 weeks and a more extended bone activation within the first week after surgery, leading to more extensive bone-implant contact after 2 weeks. In conclusion, the ASD surface treatments enhanced the biological response in vitro, promoting an early osteoblast adhesion, and the osteointegrative properties in vivo, accelerating the primary osteogenic response.

Preparation and electrical characterization of poly(vinyl amine) hydrogels, crosslinked with Cu(II) ions, and evaluation of their potentiality as water sensor material

AbstractA method to prepare water sensitive composites employing crosslinked poly(vinyl amine) (PVAm) and Cu(II) ions as reticulation agent is disclosed in this work. This article presents in detail, the reticulation reaction and its pH dependence, as well as its electrical, rheological, and thermal properties of the PVAm‐Cu(II) composites obtained. The complex bonds formed between the Cu(II) ions and the amine groups of PVAm produce an interesting network of crosslinked structures that generate a microporous morphology when the material is extruded. This characteristic favors fast absorption of water when it is wetted, and a concomitant decrease in its apparent resistivity in a very short period of time. Furthermore, they present an excellent thermal stability and suitable processability. These characteristics make them interesting candidates to design ultra fast water sensors. © 2009 Wiley Periodicals, Inc. J Appl Polym Sci, 2010

Highly porous titanium (Ti) scaffolds with bioactive microporous hydroxyapatite/TiO 2 hybrid coating layer

Highly porous Ti scaffolds with a bioactive microporous hydroxyapatite (HA)/TiO 2 hybrid coating layer were fabricated using the sponge replication process and micro-arc oxidation (MAO) treatment to produce the porous Ti scaffold and hybrid coating layer, respectively. In particular, the morphology and chemical composition of the hybrid coating layer were controlled by carrying out the MAO treatment in electrolyte solutions containing various concentrations of HA, ranging from 0 to 30 wt.%. The fabricated sample showed high porosity of approximately 70 vol.% with interconnected pores and reasonably high compressive strength of 18 ± 0.3 MPa. Furthermore, the surfaces could be coated successfully with a bioactive microporous HA/TiO 2 hybrid layer. The amount of HA particles in the hybrid coating layer increased with increasing HA content in the electrolyte solution, while preserving the microporous morphology. This hybrid coating improved the osteoblastic activity of the porous Ti scaffolds significantly.

Electrochemical surface modification of titanium for implant abutments can affect oral bacteria contamination.

This research concerns the characterization of an electrochemical surface treatment applied to titanium, focused especially on the treatment of the transmucosal area of dental implants and abutments. The treatment is applied to improve soft tissue adhesion, to control and limit bacteria adhesion and proliferation, and to improve the aesthetic performance through a proper colorization of the metal surface. The electrochemical treatment considered, obtained on titanium by Anodic Spark Deposition technique (ASD), was performed in a calcium phosphate enriched solution. The bacteria behaviour was assessed by in vitro and in vivo tests. The investigated ASD treatment showed some antibacterial effect. No negative cytocompatibility effects were found on MG63 - human osteosarcoma cell lines and L929 - murine fibroblasts. The ASD modified treatment was found capable of modifying the titanium oxide layer providing a prevalent anatase crystalline structure and a microporous morphology, which can play an important role in the tissue integration process. The treatment was found capable of enriching the surface with calcium, providing improved biocompatibility and a light gray colorization. This last point is important for the aesthetic improvement of dental implant systems in the transgingival area.

Effects of local strain rate and micro-porous morphology on tensile mechanical properties in PP/EPR blend syntactic foams

This study characterizes the effects of local strain rate and micro-porous shape on the tensile mechanical properties at the intermediate and high strain rates in the thermoplastic polymer syntactic foams. Four types of syntactic polypropylene (PP)/ethylene propylene rubber (EPR) blend foams are developed with respect to the micro-porous morphologies. Tensile tests are conducted at the nominal strain rates from 0.3 to 100 s −1. Finite element (FE) models are constructed based on the morphological pictures. The corresponding tensile test simulation is conducted on the microstructural FE models to estimate the local strain rate and investigate the relation between the micro-porous morphology and the local strain rate. It is found that the local strain-rate distribution gets broader in the spherical-shape porous foams than the elliptical-shape porous foams. The strain-rate dependencies of the apparent elastic modulus and the yield stress of the syntactic foams are mainly caused by the matrix material's properties. The magnitude of the yield stress is dependent on the micro-porous shape although that of the apparent elastic modulus is not influenced by the porous morphology. When the local strain rate is taken into account, the yield stress can be predicted by the simple rule of mixture in the spherical shape of the syntactic foams.

Preparation and properties of alginate/polyaspartate composite hydrogels

This study examined the swelling behavior andin vitro release of a model drug, tetracycline-HCl, from alginate and alginate-polyaspartate (Alg-PASP) composite gel beads. The alginate and Alg-PASP composite beads were prepared using an ionic crosslinking method with aqueous Ca2+. Their microporous morphology was observed by scanning electron microscopy. The swelling ratio of the beads in different media varied according to their composition, cross-linking density (Ca2+ concentration), and pH of the aqueous medium. Thein vitro release experiment of the tetracycline-HCl encapsulated beads in different media suggests that the release of the drug is governed mainly by the swelling properties of the polymer network. The presence of PASP was found to significantly influence the swelling properties and drug release profile.

Formation of microporous membrane of isotactic polypropylene in dibutyl phthalate‐soybean oil via thermally induced phase separation

AbstractIsotactic polypropylene (iPP) microporous membranes were prepared via the thermally induced phase separation (TIPS) process with the diluents being dibutyl phthalate (DBP) and soybean oil mixture. By changing the weight ratio of DBP to soybean oil systematically, it was determined experimentally that the cloud‐point curves were influenced to a great extent, while the crystallization curves showed much less dependence on the diluents composition. Scanning electron microscopy (SEM) showed that the resulting membrane morphologies changed significantly by varying the composition of the diluents, i.e., by changing the interaction parameter and other characteristics of diluents, the interwoven or celluar structure can be fabricated successfully at a fixed polymer concentration under the same cooling conditions. Different growth rates of iPP spherulite were obtained in the diluents with different composition. It is shown that the spherulites growth rates may be also attributed to the great variations of the final microporous morphology to a certain extent. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007

A novel ordered nano hydroxyapatite coating electrochemically deposited on titanium substrate

A novel porous nano hydroxyapatite (HA) coating has been prepared on commercially pure titanium substrate by a modified electrochemical deposition method. The physico-chemical and biological properties of the coating were characterized by SEM, XRD, FTIR, Raman, and in vitro cell culture test respectively. The SEM patterns show a uniform microporous morphology consisting of wirelike crystals at nanometer scale. It is suggested that under controlled deposition conditions, the primary HA nanowires grow and self-assemble to construct an ordered microporous nest-like morphology, thus to form a nano-micro two-level structure. The XRD results demonstrate that the HA nanowires are orderly arranged with their c-axis preferentially perpendicular to the substrate surface. The Raman and IR spectra affirm that the main component of the coating is well crystallized HA. An interdigitation phenomenon of the MG63 human osteosarcoma cells with the HA nanowires is observed in the in vitro test, indicating excellent biocompatibility and bioactivity for the prepared coating.

Influence of the acid concentration on the morphology of micropores and mesopores in porous glasses

The polymodal microporosity and mesoporosity of porous glasses prepared by through leaching of phase-separated alkali borosilicate glasses in hydrochloric acid solutions of different concentrations are investigated by two new methods based on an analysis of the kinetic and equilibrium isotherms of gas desorption at a temperature of 77.5 K under low partial pressures, as well as by a modified classical adsorption method under medium and high pressures. It is established that an increase in the concentration of hydrochloric acid in the leaching solution brings about transformations in the microporous and mesoporous structures of the porous glasses. The structural transformations can be summarized as follows: (i) a considerable decrease in the specific surface of mesopores and the corresponding increase in the diameter of secondary silica globules, (ii) a decrease in the mesopore volume and the corresponding increase in the coordination number of the packing of secondary silica globules in channels formed upon phase separation, (iii) an increase in the diameter of mesopores arising from gaps between secondary silica globules in channels formed upon phase separation, (iv) an increase in the diameter of regions in these channels that are partially or completely free from secondary silica globules, and (v) the formation of ultramicropores with a molecular size of 0.4–0.5 nm.

Imaging the structure and porosity of active carbons by scanning tunneling microscopy

Scanning tunneling microscopy (STM) has been employed for a comparative structural characterization, down to the atomic scale, of a representative set of porous carbons with different adsorption characteristics and prepared either by activation (physical or chemical) or templating techniques. The studied materials included a chemically activated, supermicroporous high surface area carbon, two activated carbons containing both micro- and mesopores synthesized by physical activation, an ultramicroporous carbon molecular sieve, and an ordered microporous carbon templated in the nanochannels of zeolite Y. In general, good agreement was found between the porous structures as imaged by STM and the porous texture derived from gas adsorption data for all the carbons investigated. The activated carbon samples were dominated by networks of slit type micropores and, in some cases, by mesopores of varied morphologies. By contrast, the zeolite-templated carbon exhibited rounded micropore morphology, and the carbon molecular sieve displayed a rather featureless conformation dominated by voids only below 1 nm wide. The structural differences observed by STM were interpreted in terms of the different preparation procedures of the studied carbons. In particular, the templated carbon consisted of minute clusters about 1 nm in diameter that were interpreted to be formed within the extremely confined, microporous spaces of the zeolite Y template.

Hydroxyapatite coating on stainless steel pre-coated with bovine serum albumin at ambient conditions

A biomimetic process for coating of nanosized hydroxyapatite on stainless steel, which capitalises the dual nature of the protein bovine serum albumin in both metal binding and a strong affinity for calcium ions, has been developed. The novelty of the process lies in pre-conditioning the metallic surface using the above protein prior to its mineralization with hydroxyapatite at ambient conditions. The microporous morphology of these coatings may provide favourable solubility and resorbability as desired by many orthopaedic and orthodontic applications.

Hydrogen-bonding-directed layer-by-layer polymer films: Substrate effect on the microporous morphology variation

The layer-by-layer (LbL) films composed of poly(4-vinylpyridine) and poly(acrylic acid) were assembled on four kinds of different substrates and their morphology variation in basic solution was comparatively studied. It was discovered that the morphology variation of the films on hydroxyl-tailored substrates was much faster than on amino-tailored substrates. Similarly, the films on carboxyl-tailored substrates could more easily yield microporous morphology than on amino-tailored substrates. The experiment results indicated that substrates played a critical role in the formation and variation process of the microporous morphology. The attractive interaction between substrates and PVP influenced the reconformation/aggregation of poly(4-vinylpyridine) chains, which led to gradually variational microporous morphology. The stronger attraction between substrates and PVP would result in slower microporous morphology variation. The investigation results in this article not only have provided some helpful experience for controlling microporous films but also have deepened the understanding of the formation mechanism of microporous morphology.

Microporosity Affects Bioactivity of Macroporous Hydroxyapatite Bone Graft Substitutes

This paper describes an investigation into the influence of microporosity on early osseointegration within porous hydroxyapatite scaffolds. Two batches of phase pure porous hydroxyapatite were produced with total porosities of approximately 80%, but with varied levels of microporosity such that the strut porosity of the two batches were 10 and 20%. Cylindrical specimens 4.5mm in diameter were implanted in the distal femur of 6 month New Zealand White rabbits and retrieved for histological and histomorphometric analysis at 1 and 3 weeks. Optical microscopy demonstrated variation in the degree of capillary penetration and bone morphology within scaffolds at 1 and 3 weeks, respectively. Moreover, histomorphometry demonstrated that there was significantly more bone ingrowth within HA80-2 scaffolds and that the rate of bone formation within these scaffolds was significantly faster. These results indicate that the bioactivity of porous hydroxyapatite scaffolds may be improved by increasing the level of microporosity within the ceramic struts. Introduction The combined affects of an ageing population and greater expectations in quality of life have resulted in an increasing global demand for orthopaedic implants for the replacement or augmentation of damaged bones and joints. In bone grafting current ‘gold standards’ include the use of autograft (living bone from the patient) or allograft (dead, sterilised bone from bone banks) but these methods are increasingly recognised as non-ideal due to limitations in supply and consistency [1]. Porous ceramics have been considered for use as bone graft substitutes in the treatment of bone defects for over 30 years [2]. In particular, calcium phosphates such as hydroxyapatite (HA) have been promoted as a result of their osteoconductive properties. However, while it is well recognised that both the rate of integration and the final volume of regenerated bone may be primarily dependent on various features of the macro-porosity, such as volume fraction, pore size and pore connectivity [3], recent in vitro studies have demonstrated bone cell sensitivity to the level of microporosity within the ceramic struts [4]. The aim of this study was to investigate the influence of microporosity on early osseointegration within porous HA (PHA) scaffolds. Materials and Methods Two batches of phase pure PHA were produced using a novel slip foaming technique [5], both had total porosities of approximately 80%, but varied in the volume fraction of porosity distributed 2 Title of Publication (to be inserted by the publisher) Figure 1 – (a) Porosity distribution within batches HA80-1 and HA80-2. Micropore morphology within the struts of batches (b) HA80-1 and (c) HA80-2. Bar = 50 μm between their macropore (>50μm) and micropore (<20μm) populations (Fig. 1). This variation was such that the strut porosity of batches HA80-1 and HA80-2 were 10 and 20%, respectively. Morphological characterisation of both the macroand microporosity was performed through a combination of immersion densitometry and image analysis of serial sections using a Zeiss Axioskop optical microscope linked to a KS300 image analyser. Macropore size, interconnection size and connectivity index, a measure of inter-pore connectivity, were all measured. Both the open and closed % of microporosity within the struts was quantified. Cylindrical specimens 4.5mm in diameter were implanted in the distal femur of 6 month New Zealand White rabbits and retrieved for histological and histomorphometric analysis at 1 and 3 weeks. The volume of new bone ingrowth was calculated using a Weibel grid and the mineral apposition rate (MAR) was determined through the administration of fluorochrome labels at 1 and 2 weeks and measurement of the inter-label distance using a Zeiss Axioskop optical microscope with a UV light source, linked to KS300 image analyser. Figure 2 – (a) Macropore interconnection data and (b) porosity distribution of open and closed microporosity within batches HA80-1 and HA80-2. 0 1 2 3 4 5 6 7 8 HA80-1 HA80-2 M ic ro po ro si ty (% ) Open Closed (b) (a) 0 10 20 30 40 50 60 70 80 90 HA80-1 HA80-2 P or os ity (% ) Microporosity Macroporosity (a) (b) (c) 0 100 200 300 400 500 600 Interconnection Size Connectivity Index HA80-1 HA80-2 Figure 3 – Variation in ingrowth morphology within batches (a) HA80-1 (Goldner’s trichrome) and (b) HA80-2 (Toluidine blue). Bar = 100 μm

Porous poly(D,L-lactide) and poly(D,L-lactide-co-glycolide) produced by thermal salt elimination from halogenocarboxylatesElectronic supplementary information (ESI) available: detailed results of the combustion calorimetric experiments. See http://www.rsc.org/suppdata/dt/b1/b104979h/

Poly(D,L-lactide) has been obtained by thermal elimination of alkali chloride from alkali 2-chloropropionates. Preparative studies and differential scanning calorimetry (DSC) have shown that while the sodium and potassium compounds undergo a clean polymerisation, the lithium analogues decompose on heating without polymerisation. The energetics of the polymerisation reaction have also been investigated by determining the enthalpies of formation of sodium and lithium (S)-2-chloropropionates (from reaction-solution calorimetry), and the enthalpies of formation of poly(L-lactide) and poly(D,L-lactide) (from micro combustion calorimetry). The results suggest that the polymerisation process is thermodynamically favourable for the sodium compounds but not for the lithium compounds, in good agreement with the experimental observations. Copolyesters of glycolic acid (polyglycolide) and lactic acid (polylactide) have been prepared by thermal reaction of crystal mixtures of sodium or potassium chloroacetates and sodium or potassium 2-chloropropionates, which were obtained by co-precipitation of the precursor compounds from methanol solutions. The crystal mixtures and reaction products have been characterised by a number of techniques, including solid state NMR spectroscopy and X-ray powder diffraction. For high contents of glycolide, the reaction occurred entirely in the solid state, whereas for cases with more than 10 mol% lactide, a melt is formed which solidifies on cooling to room temperature. The products are lactide-terminated block copolymers with typical chain lengths of 40 monomer units. Due to the solvent-free nature of the synthesis, all polymers can be obtained with microporous morphology.

Resorbable bioceramics based on stabilized calcium phosphates. Part II: evaluation of biological response

Synthetic materials capable of being remodelled in vivo by the same processes responsible for natural bone turnover have long been sought for use as an artificial bone substitute. These materials must ideally combine osteoinductive capacity with the ability to withstand random dissolution at normal physiological pH, while being resorbed by natural cell-mediated processes. Resorbable calcium phosphate based coatings and bulk ceramics have been developed which promote the uniform deposition of new mineralized bone matrix thus enabling rapid integration with the surrounding host bone tissue in vivo. Furthermore, a critical result of this study is the determination that the silicon-stabilized calcium phosphate ceramics are essentially insoluble in biological media but are resorbed when acted upon by osteoclasts. In vitro biological testing and preliminary in vivo testing show that the important features of this new biomaterial are a characteristic calcium phosphate phase composition and a unique microporous morphology.

Novel Microporous Poly(vinylidene fluoride) Blend Electrolytes for Lithium‐Ion Batteries

In the present paper, novel microporous poly(vinylidene fluoride)‐hexafluoropropylene copolymer (PVDF-HFP) blend electrolyte/electrode films were obtained as the result of phase separation between PVDF-HFP and polyethylene oxide (PEO) oligomer additives, which were cast from a common solvent. Upon solvent evaporation and removal of the additives, an interconnected microporous morphology was formed. The additives can either be removed from the films by vacuum evaporation or methanol extraction. The conductivities of the methanol extracted microporous (pore sizes range from 1 to 5 μm) films formed from PVDF-HFP/PEO oligomer blends after electrolyte activation are more than 70% higher than those of the methanol extracted nanoporous (pore size in range from 10 to 100 nm) films prepared from PVDF-HFP/dibutyl phthalate blends. Microporous films formed by vacuum evaporation had conductivities similar to solvent extracted nanoporous separators. Battery performance tests were carried out using lithium cobalt dioxide as the cathode and mesocarbon microbeads as the anode. The cells prepared using extracted microporous PVDF-HFP/PEO oligomer blend films as separators show more than 40% higher specific discharge capacity at the C/2 rate, and 70% higher rate capability than those using extracted nanoporous separators. © 2000 The Electrochemical Society. All rights reserved.

Resorbable bioceramics based on stabilized calcium phosphates. Part I: rational design, sample preparation and material characterization.

It has long been the goal of biomaterials research in the field of orthopedics to develop synthetic structures exhibiting comprehensive bioactivity. In particular, an ideal bone-biomaterial would support the activity of osteoblasts in the development of new bone, while simultaneously being resorbed by osteoclasts as part of the lifelong orderly process of bone remodelling. Such resorbable calcium phosphate-based thin films and bulk ceramics have now been created by the high-temperature processing of a fine precipitate, formed from a colloidal sol and stabilized using an additive such as silicon. The materials have two characteristic features: a phase composition which is a mixture of calcium hydroxyapatite and a silicon stabilized tricalcium phosphate, and a microporous morphology based on inter-connected particles (0.2-1 microm in diameter). X-ray diffraction, infrared spectroscopy, nuclear magnetic resonance spectroscopy, and light scattering experiments indicate that the characteristic phase composition arises during sintering through substitution reactions where silicon enters the calcium phosphate lattice under conditions of high chemical reactivity. The crystallographic features are linked through the glaserite form of the apatite structure.