Valorization of Byproducts of Hemp Multipurpose Crop: Short Non-Aligned Bast Fibers as a Source of Nanocellulose

Nanocellulose was extracted from short bast fibers, from hemp (Cannabis sativa L.) plants harvested at seed maturity, non-retted, and mechanically decorticated in a defibering apparatus, giving non-aligned fibers. A chemical pretreatment with NaOH and HCl allowed the removal of most of the non-cellulosic components of the fibers. No bleaching was performed. The chemically pretreated fibers were then refined in a beater and treated with a cellulase enzyme, followed by mechanical defibrillation in an ultrafine friction grinder. The fibers were characterized by microscopy, infrared spectroscopy, thermogravimetric analysis and X-ray diffraction after each step of the process to understand the evolution of their morphology and composition. The obtained nanocellulose suspension was composed of short nanofibrils with widths of 5–12 nm, stacks of nanofibrils with widths of 20–200 nm, and some larger fibers. The crystallinity index was found to increase from 74% for the raw fibers to 80% for the nanocellulose. The nanocellulose retained a yellowish color, indicating the presence of some residual lignin. The properties of the nanopaper prepared with the hemp nanocellulose were similar to those of nanopapers prepared with wood pulp-derived rod-like nanofibrils.     

Influence of drying method on the material properties of nanocellulose I: thermostability and crystallinity

The effect of drying method on selected material properties of nanocellulose was investigated. Samples of nanofibrillated cellulose (NFC) and cellulose nanocrystals (CNC) were each subjected to four separate drying methods: air-drying, freeze-drying, spray-drying, and supercritical-drying. The thermal stability and crystallinity of the dried nanocellulose were evaluated using thermogravimetric analysis (TGA) and X-ray diffraction. Supercritical-drying produced NFCs with the least thermal stability and the lowest crystallinity index. Air-drying or spray-drying produced NFCs which were more thermally stable compared with freeze-dried NFCs. The CNCs dried by the three methods (air-drying, freeze-drying, and spray-drying) have similar onset temperature of thermal degradation. The different drying methods resulted in various char weight percentages at 600 °C for the dried NFCs or CNCs from TGA measurements. The dried NFCs are pure cellulose I while the dried CNCs consist of cellulose I and II. The calculated crystallinity indices differ with each drying method. The cellulose II content in CNCs changes as a function of drying method. For the application of nanocellulose in non polar thermoplastics, spray-dried products are recommended according to their higher thermal stability and higher crystallinity index.     

Facile preparation and properties of superhydrophobic nanocellulose membrane

Superhydrophobic nanocellulose membrane was prepared by synergistically modifying biodegradable nanocellulose with low-carbon perfluoroorganosiloxane and ethyl orthosilicate. The effects of four kinds of low-carbon perfluoroorganosiloxanes with different structures and their ratio to ethyl orthosilicate on the hydrophobic properties of nanocellulose membrane were investigated, and then FT-IR, XPS, XRD, SEM, TEM, AFM, TG and contact angle goniometer were used to characterize the structure and hydrophobic properties of nanocellulose membrane before and after modification. It is found that when the molar ratio of 1H,1H,2H,2H-perfluorooctyltrimethoxysilane (PFOTMS) to ethyl orthosilicate (TEOS) is 1, the modified nanocellulose membrane PFOTMS-TEOS-CNF is loaded with silica nanoparticles both inside and on its surface, and a micro-nano hierarchical rough morphology with low surface energy is constructed. At this point, the root-mean-square roughness (Rq) of nanocellulose membrane is 112 nm, and the static contact angle of water droplet is 153.5°, successfully realizing superhydrophobicity. In addition, compared to unmodified nanocellulose membrane, PFOTMS-TEOS-CNF with better thermal stability includes an additional maximum weight loss rate temperature (491.2 °C). The above advantages markedly improve the shortcomings of pristine nanocellulose, such as superhydrophilicity and insufficient thermal stability, and also broadens its high-value application in many fields.     

Ultrasonic assisted synthesis of nanocrystalline cellulose as support and reducing agent for Ag nanoparticles: green synthesis and novel effective nanocatalyst for degradation of organic dyes

In this study, nanocrystalline cellulose (NCC) prepared from microcrystalline cellulose using high‐intensity ultrasonication as mechanical method without any chemical treatment. The obtained NCC with around 30–50 nm diameters, utilized as support, reducing and stabilizing agent for in‐situ green and eco‐friendly synthesis of silver nanoparticles (Ag NPs). The catalytic activity of composite was examined for degradation of environmental pollutants. The structure of as‐synthesized composite (Ag@NCC) was characterized by ultraviolet–visible spectroscopy (UV–vis), field emission scanning electron microscopy (FE‐SEM); Transmission electron microscopy (TEM); Energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FT‐IR), X‐ray diffraction (XRD) and thermogravimetric analysis (TGA). The results of the catalytic reaction experiments showed that spherically shaped silver nanoparticles of around 20 nm distributed on the surface of nanocellulose demonstrated high catalytic efficiency towards the removal of methyl orange (MO) and 4‐nitrophenol (4‐NP).     

Nanocrystalline hydroxyapatite powders by a chitosan–polymer complex solution route: Synthesis and characterization

Nanocrystalline hydroxyapatite (HAp) powders were successfully synthesized by a simple method using chitosan–polymer complex solution. To obtain HAp nanopowders, the prepared precursor was calcined in air at 400–800 °C for 2 h. The phase composition of the calcined samples was studied by X-ray diffraction (XRD) technique. The XRD results confirmed the formation of HAp phase with a small trace of monotite phase. With increasing calcination temperature, the crystallinity of the HAp increased, showing the hexagonal structure of HAp with the lattice parameter a in a range of 0.94030–0.94308 nm and c of 0.68817–0.68948 nm. The particle sizes of the powder were found to be 55.02–73.36 nm as evaluated by the XRD line broadening method. The chemical composition of the calcined powders was characterized by FTIR spectroscopy. The peaks of the phosphate carbonate and hydroxyl vibration modes were observed in the FTIR spectra for all the calcined powders. TEM investigation revealed that the prepared HAP samples consisted of rod-like nanoparticles having the particle size in the range of 100–300 nm. The corresponding selected-area electron diffraction (SAED) analysis further confirmed the formation of hexagonal structure of HAp.     

Preparation of Nanosized Perovskite‐type Oxides via Polyol Method

Several perovskite‐type nanosized oxides were prepared via polyol‐mediated synthesis. The crystallinity of the materials was analysed by X‐ray diffraction (XRD). While the “as synthesized” materials are amorphous or show very poor crystallinity, highly ordered materials could be obtained by annealing at 700 °C. Morphology of the materials was analysed by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Particle size of the materials lay between 20 and 200 nm.     

Nanocellulose characteristics from the inner and outer layer of banana pseudo-stem prepared by TEMPO-mediated oxidation

Many tonnes of agricultural wastes are generated annually, which contains a relatively high amount of cellulose; banana pseudo-stem is one waste type that is a promising material for nanocellulose production. This research characterised nanocellulose from inner and outer layers of banana pseudo-stem as a preliminary research strategy for designing biodegradable packaging material from banana pseudo-stem nanocellulose. Nanocellulose was successfully prepared through TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl)-mediated oxidation. The extracted nanocellulose from both the inner and outer layers had observed widths of approximately 7–35 nm and long fibrillated fibre. They had high negative zeta potential (lower than ?33.6) that provided good colloidal stability. The purity of the nanocellulose was high as demonstrated by ¹³C solid-state NMR and Fourier transform infrared spectroscopy. Nanocellulose from both layers was significantly more crystalline than the raw materials. Thermal stability of nanocellulose sourced from inner and outer layers was relatively similar, with degradation temperature of approximately 220 °C, which was slightly lower than the degradation temperature of its native form (232 °C for inner layer and 261 °C for outer layer).     

The effect of different substrate temperatures on the structure and luminescence properties of Y2O3:Bi3+ thin films

Y₂O₃:Bi³⁺ phosphor thin films were prepared by pulsed laser deposition in the presence of oxygen (O₂) gas. The microstructure and photoluminescence (PL) of these films were found to be highly dependent on the substrate temperature. X-ray diffraction analysis showed that the Y₂O₃:Bi³⁺ films transformed from amorphous to cubic and monoclinic phases when the substrate temperature was increased up to 600 °C. At the higher substrate temperature of 600 °C, the cubic phase became dominant. The crystallinity of the thin films, therefore, increased with increasing substrate temperatures. Surface morphology results obtained by atomic force microscopy showed a decrease in the surface roughness with an increase in substrate temperature. The increase in the PL intensities was attributed to the crystallinity improvement and surface roughness decrease. The main PL emission peak position of the thin films prepared at substrate temperatures of 450 °C and 600 °C showed a shift to shorter wavelengths of 460 and 480 nm respectively, if compared to the main PL peak position of the powder at 495 nm. The shift was attributed to a different Bi³⁺ ion environment in the monoclinic and cubic phases.     

Characterization of iron(III) oxide and oxide-hydroxide as Sr-sorbent

Iron(III) hydroxide and oxide-hydroxide samples prepared by precipitation of 0.2M iron(III) nitrate solution by 5M NaOH and subsequently aged at pH 12 for times of up to 50 h have been characterized. The sorption properties towards Sr²⁺ were characterized by radiotracer method using⁸⁵Sr, morphology of the samples was characterized by Transmission Electron Microscopy and Emanation Thermal Analysis. X-ray diffraction patterns characterized the crystallinity of the samples aged for various times. The maximum (100%) sorption capacity for⁸⁵Sr corresponding to amorphous iron(III) hydroxide decreased to 75% with the time of precipitate ageing (up to 40 h). This finding corresponds to the development in crystallinity and morphology of the sorbent.     

A facile one-step way for extraction of nanocellulose with high yield by ball milling with ionic liquid

93.1% yield of nanocellulose was successfully extracted from cellulose powder (CP) by planetary ball milling in the presence of ionic liquid (IL) of 1-butyl-3-methylimidazolium chloride (BMIMCl). The morphology of nanofibrillated cellulose present in fibrous network with 10–25 nm in diameter and micrometer scale in length and the chemical composition and crystal structure were maintained as cellulose type I. At 600 °C degradation temperature, the residue amount of the obtained nanocellulose was about 55% more that of CP, implying it had higher thermal stability. The used BMIMCl was recovered and reused at least 4 times. The nanocellulose obtained by using the recovered IL also demonstrated the same properties as those from the fresh one. For comparison, another kind of IL of 1-ethyl-3-methylimidazolium acetate (EMIMOAc) was also used in this study. It is found that the ball milling of cellulose in the presence of IL is an effective and environmental friendly way for the production of nanocellulose with high yield.     

Preparation of nanostructure hydroxyapatite scaffold for tissue engineering applications

Hydroxyapatite due to its good biocompatibility and similar chemical composition to the mineral part of bone has found various applications in tissue engineering. Porous hydroxyapatite has high surface area, which leads to excellent osteoconductivity and resorbability, providing fast bone ingrowth. In this study, highly porous body of nanostructure hydroxyapatite was successfully fabricated via gelcasting method. The pure phase of hydroxyapatite was confirmed by X-ray diffraction. The result of scanning electron microscopy analysis showed that the prepared scaffold has highly interconnected spherical pores with a size in the range 100–400 μm. The crystallite size of the hydroxyapatite scaffold was measured in the range 30–42 nm. The mean values of true (total) and apparent (interconnected) porosity were calculated in the range 84–91 and 70–78%, respectively. The maximum values of compressive strength and elastic modulus of the prepared scaffold were found to be about 1.5 MPa and 167 MPa, respectively, which were achieved after sintering at 1,000 °C for 4 h. Transmission electron microscopy analysis showed that the particle sizes are smaller than 80 nm. In vitro test showed good bioactivity of the prepared scaffold. The mentioned properties could make the hydroxyapatite scaffold a good candidate for tissue engineering applications, especially applications that did not need to stand any loading.     

Effect of annealing temperatures and of high content of the iron ion (Fe<Superscript>3+</Superscript>)-doping on transition anatase–rutile phase of nanocrystalline TiO<Subscript>2</Subscript> thin films prepared by sol–gel spin coating

Titanium dioxide doped with iron (III) was prepared by sol–gel Spin Coating method. The phase structures, morphologies, particle size of the doped TiO₂ have been characterized by X-ray diffraction (XRD), Raman spectroscopy, atomic force microscopy (AFM) and ultraviolet–visible (UV–Vis) spectrophotometer. The XRD and Raman results show that the 10% Fe³⁺-doped TiO₂ thin films crystallize in anatase phase between 600 and 800 °C, and into the anatase–rutile phase at 1,000 °C, and further into the rutile phase when the content of Fe³⁺ increases (20%). The grain size calculated from XRD patterns shows that the crystallinity of the obtained anatase particles increased from 39.4 to 43.4 nm as the temperature of annealing increase, whereas the size of rutile crystallites increases, with increasing Fe³⁺ concentrations from 36.9 to 38.1 nm. The AFM surface morphology results confirmed that the particle size increases by increasing the annealing temperature and also with an increasing of Fe³⁺ content. The optical band gap (E _g) of the films was determined by the UV–Vis spectrophotometer. We have found that the optical band gap decreased with an increasing of annealing temperatures and also with an increasing of Fe³⁺ content.     

The nanocellulose biorefinery: woody versus herbaceous agricultural wastes for NCC production

In the present work two agricultural residues (apple tree pruning and pea stalks) were studied as sources of nanocellulose. Different pretreatments that might be used in a biorefinery were applied to these lignocellulosic materials: autohydrolysis, organosolv (acetosolv) and alkaline pretreatments. After conventional bleaching, the resulting cellulosic fractions were submitted to a classical acid hydrolysis for nanocellulose crystal (NCC) production. The results showed that after applying different pretreatments, the resulting NCCs had different lengths (from 300 to 676 nm), surface charges (from 17 to 98 μmol acid groups/g NCC), purity (from 0.3 to 11.6% w/w of inorganics), crystallinity indexes and even allomorphism. These results highlighted the importance that cellulose source and particularly the applied pretreatments have on nanocrystal properties and suggest how biorefining pathways for lignocellulosic materials could customize such NCC features as surface reactivity or suitability for chemical modification.     

Synthesis and photocatalytic activity of TiO2 nanoparticles prepared by chemical vapor condensation method with different precursor concentration and residence time

Nanosized TiO(2) photocatalysts were synthesized using a chemical vapor condensation method under a range of synthesis conditions (precursor vapor concentration and residence time in a tubular electric furnace). X-ray diffraction showed that the prepared TiO(2) powders consisted mainly of anatase (>94%) with a small amount of rutile. The mean particle diameter from the Brunauer-Emmett-Teller surface area and transmission electron microscopy measurements ranged from 9.4 to 16.6 nm. The specific surface area (92.5-163.5 m(2) g(-1)) of the prepared TiO(2) powders was found to be dependent on the synthesis conditions. The content of hydroxyl groups on the surface of the prepared TiO(2) sample was higher than those on commercial TiO(2), resulting in increased photocatalytic oxidation. The photocatalytic activity of the TiO(2) samples prepared in a methylene blue solution was strongly dependent on the crystallinity and specific surface area, which were affected by the TTIP vapor concentration and residence time.     

A facile synthesis of NaNbO<Subscript>3</Subscript> powders by decomposition of ammonium niobium oxalate with sodium salt at low temperature

A facile synthesis of NaNbO₃ powders was performed by solid-state reaction at low temperature. Stoichiometric ammonium niobium oxalate and Na₂CO₃ were mixed in water and then calcined at different temperatures for various times after drying. A combination of X-ray diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared (FTIR) spectroscopy and thermogravimetric (TG) analysis was used to characterize the product and precursor compound. The XRD patterns show that single-phase NaNbO₃ powders with high crystallinity can be synthesized at 425 °C for 15 min. The particle size from XRD data is found to be about 40 nm for NaNbO₃ powders calcined at 500 °C for 3 h, which is in good agreement with SEM data. The SEM photograph shows that NaNbO₃ powders are cuboid-like and well crystallized when calcination at 800 °C for 3 h. The product compositions prepared using other sodium reactants, such as HCOONa and NaNO₃, are also discussed.     

An improved method for chemical bath deposition of ZnS thin films

ZnS thin films were prepared by an improved chemical bath deposition method, which the substrates were preheated before being mounted in the reaction solution. X-ray diffraction (XRD) and energy dispersive spectrometer (EDS) reveals that thin film ZnS has a cubic structure and the typical composition ratio of Zn/S is 52:48. Scanning electron microscopy (SEM) characterization shows that the surface of the sample is compact and uniform. The transmission spectrum indicates a good transmission characteristic with an average transmittance of 82.2% in the spectra range from 350 nm to 800 nm and the optical band gap is about 3.76 eV.     

Ultra porous nanocellulose aerogels as separation medium for mixtures of oil/water liquids

A novel type of sponge-like material for the separation of mixed oil and water liquids has been prepared by the vapour deposition of hydrophobic silanes on ultra-porous nanocellulose aerogels. To achieve this, a highly porous (>99%) nanocellulose aerogel with high structural flexibility and robustness is first formed by freeze-drying an aqueous dispersion of the nanocellulose. The density, pore size distribution and wetting properties of the aerogel can be tuned by selecting the concentration of the nanocellulose dispersion before freeze-drying. The hydrophobic light- weight aerogels are almost instantly filled with the oil phase when selectively absorbing oil from water, with a capacity to absorb up to 45 times their own weight in oil. The oil can also be drained from the aerogel and the aerogel can then be reused for a second absorption cycle.     

Extraction and characterization of highly pure alumina (α, γ, and θ) polymorphs from waste beverage cans: A viable waste management approach

The recycling and recovery of important materials from inexpensive feedstock has now become an intriguing area and vital from commercial and environmental viewpoints. In the present work, extraction of different single phases of alumina (α, γ, θ-Al₂O₃) having high purity (>99.5 %) from locally available waste beverage cans (～95 % Al) through facile precipitation route calcined at distinct temperatures has been reported. The optimization of process technology was done by a variety of different synthesis parameters, and the production cost was estimated between 84.47-87.45 USD per kg of alumina powder. The as prepared alumina fine particles have been characterized using different sophisticated techniques viz. TG-DTA, WD-XRF, XRD, FT-IR, SEM, DLS-based particle size analysis (PSA) with zeta (ζ) potential measurement and UV–Visible Spectroscopy. X-ray diffractogram confirms the formation of γ-, θ-, and α-alumina at 500–700 °C, 900–1000 °C, and 1200 °C respectively and crystallite size, crystallinity, strain, dislocation density, and specific surface area were measured using major X-ray diffraction peaks which varies with temperature. The SEM studies showed that the as prepared alumina particles were agglomerated, irregular-shaped with particle size (0.23–0.38 µm), pore size, and porosity were calculated from SEM image. ζ-potentials at different pH values as well as isoelectric point (IEP) of α, γ, and θ alumina were calculated in an aqueous medium which changes with temperature. The direct band gap (E_g) energies were found between 4.09 and 5.19 eV of alumina obtained from different calcination temperatures. The synthesized materials can be used in sensors, ceramics, catalysis, and insulation applications.     

Liquid crystal of nanocellulose whiskers’ grafted with acrylamide

12%acrylamide(AM) was grafted onto the surface of nanocellulose whiskers(NCW),which was self-assembled to be the chiral nematic suspension at 3%content.The acrylamide grafted NCW(AM-g-NCW) was characterized with Fourier Transform Infrared Spectroscopy(FTIR).The grafting ratio was measured by elemental analysis.The degrees of crystallinity of the AM-g-NCW were measured by X-ray diffraction(XRD).The liquid crystalline properties of the AM-g-NCW were investigated by the polarizing optical microscopy(POM).The AM-g-NCW was found to self-assembly to be a lyotropic state.     

Statistical Experimental Design for Obtaining Nanocellulose from Curaua Fiber

Summary: This study focuses on the methodology to obtain nanocellulose from vegetal fibers. An experimental planning was carried out for the treatment of curaua fibers and parameters were estimated, having the concentration of H₂SO₄, hydrolysis time, reaction temperature and time of applied sonication as independent variables for further statistical analysis. According to the estimated parameters, the statistically significant effects were determined for the process of obtaining nanocellulose. With the results obtained from the thermogravimetric analysis (TGA) it was observed that certain conditions led to cellulose with degradation temperatures near or even above that of the untreated cellulose fibers. The crystallinity index (I_C) obtained after fiber treatment (by X-ray diffraction technique) was higher than that of the pure fiber. Treatments with high acid concentrations led to higher IC. After the statistical experimental design, mixtures of polypropylene with fibers prepared after different treatments were performed in a mini-extruder. It was possible to observe a sharp increase in the mechanical properties through the dynamic mechanical thermal analysis (DMTA).