Copper oxide (CuO), titanium oxide (TiO 2 ), and Cu-doped TiO 2 nanoparticles have been synthesized by pyrolysis of their corresponding precursors initially prepared by precipitation in aqueous solution using A. carambola fruit juice as a natural source of the precipitating agent (oxalate). The precursors were synthesized and characterized by FTIR, TGA, and PXRD. The results revealed that the precursors obtained were CuC 2 O 4 , TiO 2 (OH − ) 2 C 2 O 4 , copper-doped titanium hydroxyl oxalate, and copper titanium hydroxyl oxalate. Complete decomposition for the as-prepared precursors containing titanium ions occurs at 600 ∘ C while impurity free copper oxalate decomposed at 450 ∘ C. The as-prepared precursors were decomposed and calcined at 600 ∘ C for 4 hours and the calcination products were characterized by XRD, SEM, and EDX. The results revealed the decomposition products to correspond to CuO, TiO 2 , Cu 0.131 Ti 0.869 O 2 , and CuO/TiO 2 .

Autogenous shrinkage is related to the chemistry and changes in the internal structure of the cement concrete paste on drying. This problem of drying shrinkage in early stages that occur without any moisture transfer to the surrounding environment has triggered the incorporation of fibres in the cement concrete matrix to fill the micropores and control cracking (autogenous shrinkage). This study aimed at investigating the potential use of Urena lobata (UL) fibre as microreinforcement in enhancing mechanical properties of hybrid UL-fibre/gypsum cement composites used for plasters. The fibre was harvested from the coastal region of Cameroon and treated with 0.06 M NaOH over different periods. Dispersion of treated fibre bundles in the composite (at Wt. % UL-fibre dosages of 0, 1.5, 2.5, and 3.5) was facilitated by blending with the cement paste which also helped to improve interfacial bonding between the fibre and the cement matrix. The moisture/water absorption and flexural properties within the hardened cement matrix were quantitatively assessed, and it was observed that the incorporation of treated fibre accelerated the hydration process. The test results showed an increment in compressive strength and reduction in autogenous shrinkage for the hybrid UL fibre/gypsum cement composites, while lower percentage additions (less than 2.5%) of untreated fibre appeared to have adverse effects on specimens. It was observed that properly dispersed (blended) treated UL fibres filled the fine pores in the cement matrix by providing an additional nucleation site that resulted in a denser microstructure, which in turn enhanced the strengths and limited the autogenous shrinkage.

Ti-doped zinc oxide and pure zinc oxide nanoparticles were synthesized by a modified oxalate route using Averrhoa carambola fruit juice as a natural source of oxalate. The characteristics of the precursors have been investigated by FTIR, TGA, and XRD. The results from the investigation revealed that the precursors are zinc oxalate and Ti-doped zinc oxalate which readily decompose at 450 ∘ C. The as-prepared precursors were calcined at 450 ∘ C for 4 hours, and the decomposition products have been characterized by XRD, SEM, EDX, and VSM. XRD results revealed crystallinity with hexagonal wurtzite structure, while the average grain size was found to be 26 nm for Ti-doped ZnO and 29 nm for ZnO, using calculations based on Debye-Scherrer equation. Furthermore, the morphological studies by SEM showed particle agglomeration, while the presence of Ti 3+ in the zinc oxide lattice is indicated by EDS analysis. Finally the hysteresis loop from VSM results shows that Ti-doped ZnO exhibits ferromagnetism.

The oil and raffia palm species are indigenous to West and Central Africa, and their exploitation both at industrial and artisanal scale generate important quantities of renewable fibrous biomass that can be converted to high and low value bio-based products. Fibre samples were prepared from three raffia palm species drawn from three locations and Oil Palm Empty Fruit Bunch (OPEFB) from an industrial palm oil mill, all in the South West Region of Cameroon. The samples were tested for chemical composition using wet chemical methods and an elemental analyzer. The functional groups were determined by Fourier Transform Infrared Spectrometer (FT-IR) spectroscopy while morphological analysis and crystallinity were evaluated by scanning electron microscopy and powder X-ray diffraction respectively. The results obtained show that extractives-free raffia palm fibres are similar to OPEFB with respect to lignin, hemicellulose and cellulose contents, morphology, occurrence of silica bodies on the surface of fibres and internal porosity. Scanning Electron Microscopy (SEM) indicated that the diameter of raffia fibre were larger than those of OPEFB stalk and spikelet fibres. The content of extractives determined by gravimetric method showed significantly lower values for raffia biomass compared to EFB fibres. The response of the fibres to hypochlorite treatment as revealed by FT-IR and morphological studies was very similar. The raffia fibres reflected significantly lower ash content and the powder X-ray studies showed slight differences in crystallinity index between raffia and OPEFB. The variability in key characteristics of biomass from the different species of palm are within the limits of the variability shown by biomass from the same species of plants. This leads to the conclusion that, the two types of palm which are both indigenous to the West and Central Africa can serve as source of blended renewable biomass. Promotion of cultivation and conservation of existing raffia plantations presents as a strategy for a more sustainable supply of biomass feedstock for bio-based products.

Improving on the very high temperatures used in solid-state synthesis routes to prepare CCTO ignited the idea of using oxalate routes which make use of organic solvents in the synthesis of CCTOX as oxalate intermediates to the decomposition product, CCTO. The use of commercial oxalic acids and oxalate has not only recorded a solubility problem which reflects on the size, shape, homogeneity, and morphology of the final product but also has an environmental impact originating from the solvents used. Both the composition and morphology of these inhomogeneities play a role in the behaviour of the final product, pointing out the need to assess the dependence of size, shape, homogeneity, and morphology and the material performance on the sample synthesis history. In this study, nanosized particles of calcium copper titanium oxide, CaCu3Ti4O12 (CCTO), were successfully synthesized by pyrolysis of the corresponding heterometal oxalate precursors obtained via coprecipitation using the edible carambola fruit juice as a precipitating agent and investigated in detail. The precursors were characterized, and the results revealed the formation of a single molecular precursor represented by the formula CaCu3(TiO)4(C2O4)8·9H2O (CCTOX). The decomposition products, obtained via calcination in air, were subsequently subjected to thermal treatments at different temperatures for 4 hours. The morphology and microstructure were characterized, and analysis showed the formation of a single phase, CaCu3Ti4O12 (CCTO) with CuO and CaTiO3 as impurity. It was observed from microscopy that the samples obtained from sintering at 600°C for four hours had discrete particles with regular morphology, limited size distribution, high degree of homogeneity, and multiple dimensions ranging between 10 and 35 nm and showed some degree of ellipticity in shape. Increasing the sintering temperature from 600°C to 700°C and 800°C increased the grain growth in the ceramic as well as the densification. The method makes advantage of the fact that oxalate precursors decomposed at relatively lower temperatures and the fact that the oxalate in the juice is in the solution which downplays both the solubility and environmental pollution problems since no additional solvents are used.