The structure of the phases obtained upon dehydration and decomposition of Friedel's salt [Ca 2 Al(OH) 6 ]Cl‚2H 2 O, also known as hydrocalumite, was investigated by several experimental techniques, in particular, high-temperature in situ XRD measurements, which allowed the detection of a metastable intermediate phase. Thermogravimetric analyses show that Friedel's salt, like most of the layered double hydroxides, undergoes a three-step decomposition on heating (dehydration, dehydroxylation, and anion expulsion) over the following temperature ranges: 25-280, 280-400, and >400 °C. Sharp phase transitions are observed as a result of the ordered distribution of Ca and Al atoms in the hydroxide layer and the well-ordered interlayer structure. Upon cooling to room temperature and exposure to the atmosphere, the dehydrated phase obtained by calcination between 80 and 280 °C was found to recover the basal spacing characteristic of hydrated galleries (7.81 Å) within a few minutes. The structural determination of this thermally metastable phase based on X-ray powder diffraction data recorded at 116 °C reveals a quasi-pillared layer structure with chloride anions situated midway in the interlamellar space at only 2.904(3) Å from Ca atoms of adjacent hydroxide layers. Friedel's salt becomes amorphous at ca. 400 °C, and above 750 °C, it crystallizes into a mixture of CaO and mayenite Ca 12 Al 14 O 33 . Exposure of the amorphous residue obtained at 400 °C to aqueous solutions of KCl led to reconstructionintercalation phenomena.

Nanodiamond (ND) seeding is a well-established route toward the CVD (chemical vapor deposition) synthesis of diamond ultrathin films. This method is based on the deposition onto a substrate of diamond nanoparticles which act as pre-existing sp(3) seeds. Here, we report on a straightforward method to disperse diamond nanoparticles on a substrate by taking advantage of the electrostatic interactions between the nanodiamonds and the substrate surface coated with a cationic polymer. This layer-by-layer deposition technique leads to reproducible and homogeneous large-scale nanoparticle deposits independent of the substrate's nature and shape. No specific functionalization of the nanoparticles is required, and low concentrated solutions can be used. The density of NDs on the substrate can be controlled, as shown by in situ ATR-FTIR (attenuated total reflection Fourier transform infrared) analysis and QCM (quartz crystal microbalance) measurements. Highly dense and compact ND deposits can be obtained, allowing CVD growth of nanocrystalline diamond ultrathin films (70 nm) on various substrates. The synthesis of 3D structured and patterned diamond thin films has also been demonstrated with this method.