Increasing Pretreatment Temperature Research Articles

Effect of heat treatment on charge states, thermophysical and mechanical properties of polypropylene doped with ZrO2 nanoparticles

Charge states, thermophysical and mechanical properties of polypropylene doped with zirconium oxide nanoparticles, and their changes during heat treatment at temperatures 60 °C, 100 °C, and 140 °C are studied. The methods used are thermal stimulated depolarization (TSD), scanning differential calorimetry (SDC), and mechanical life assessment. It is shown that with an increase in the concentration of the filler, the intensity of the TSD peaks increases up to 3 vol.%. A further increase in concentration leads to a decrease in the intensity of the peaks. The activation energy of charge release from traps, temperature of maximum of the peaks, and the magnitude of the accumulated charge in the traps have also maximal value at nanoparticle concentration of 3 vol.%. The study of charge characteristics of the nanocomposite with concentration of 3 vol.% after heat treatment shows that the intensity of TSD peaks, the temperature of peak maxima, and the activation energy of charge release increase with increasing pretreatment temperature. The magnitude of the charge accumulated in traps has a maximal value at treatment temperature of 140 °C owing to the increase in the number of traps. The melting point of the composite is 149.38 °C and shifts to 146.88 °C after heat treatment at 140 °C. It indicates that the high temperature of heat treatment leads to partial destruction of polymer chains, leading to a decrease in the critical melting temperature. The mechanical durability of PP + 3%ZrO2 nanocomposite decreases with increase in pretreatment temperature.

Simultaneous production of furfural, lignin and cellulose-rich residue from Eucalyptus urophylla × E. grandis by ChCl/1,2-propanediol/MIBK biphasic system pretreatment

A facile biphasic system composed of choline chloride (ChCl)-based deep eutectic solvent (DES) and methyl isobutyl ketone (MIBK) was developed to realize the furfural production, lignin separation and preparation of fermentable glucose from Eucalyptus in one-pot. Results showed that the ChCl/1,2-propanediol/MIBK system owned the best property to convert hemicelluloses into furfural. Under the optimal conditions (MRChCl:1,2-propanediol = 1:2, raw materials:DES:MIBK ratio = 1:4:8 g/g/mL, 0.075 mol/L AlCl3·6H2O, 140 °C, and 90 min), the furfural yield and glucose yield reached 65.0 and 92.2 %, respectively. Meanwhile, the lignin with low molecular weight (1250–1930 g/mol), low polydispersity (DM = 1.25–1.53) and high purity (only 0.08–2.59 % carbohydrate content) was regenerated from the biphasic system. With the increase of pretreatment temperature, the β-O-4, β-β and β-5 linkages in the regenerated lignin were gradually broken, and the content of phenolic hydroxyl groups increased, but the content of aliphatic hydroxyl groups decreased. This research provides a new strategy for the comprehensive utilization of lignocellulose in biorefinery process.

Soy protein isolate-catechin complexes conjugated by pre-heating treatment for enhancing emulsifying properties: Molecular structures and binding mechanisms

This study aimed to investigate the impact of different pre-heating temperatures (ranging from 40 °C to 80 °C) on the interactions between soy protein isolate (SPI) and catechin to effectively control catechin encapsulation efficiency and optimize the emulsifying properties of soy protein isolate. Results showed that optimal heat treatment at 70 °C improved catechin encapsulation efficiency up to 93.71 ± 0.14 %, along with the highest solubility, enhanced emulsification activity index and improved thermal stability of the protein. Multiple spectroscopic techniques revealed that increasing pretreatment temperature (from 40 °C to 70 °C) altered the secondary structures of SPI, resulting in a more stable unfolded structure for the composite system with a significant increase in α-helical structures and a decrease in random coil and β-sheet structures. Moreover, optimal heat treatment also leads to an augmentation of free sulfhydryl groups within complex as well as exposure of more internal chromophore amino acids on molecular surface. Size-exclusion high-performance liquid chromatography and SDS-PAGE analysis indicated that the band intensity of newly formed high-molecular-weight soluble macromolecules (>180 kDa) increased as the pre-heating temperature rose. Furthermore, fluorescence spectroscopy and molecular docking analysis suggest that hydrophobic and covalent interactions were involved in complex formation, which intensified with increasing temperature.

Bifunctional metal–acid sites on nickel boride catalysts: Phenol hydrodeoxygenation and water-promoted C = C hydrogenation

Modification of earth-abundant metal catalysts with optimized catalytic performance can be potential alternatives to precious metal catalysts for more sustainable processes. Using a chemical reduction method, nickel boride (Ni3B) alloy catalysts were prepared with a Ni/B ratio of 3. Ex-situ and in-situ characterization indicates that the structure of Ni3B changes from amorphous to crystalline with increasing pretreatment temperatures. The presence of B does not seem to alter the electronic properties of Ni. However, after pretreatment, oxidized B species (i.e., BOx and H3BO3) ex-solve from the bulk, leading to the formation of a B-enriched surface. In-situ titration and dehydration reaction experiments demonstrate the presence of acid sites, which play an important promoting role in the hydrogenation of C = C bonds. Moreover, Ni3B catalysts show a remarkable activity towards phenolic ring hydrogenation with the added ability to deoxygenate the secondary products via dehydration on the acid sites. Under water-free reaction conditions, the Ni3B catalysts exhibit similar hydrogenation activity to that of a pure Ni catalyst. Remarkably, the addition of small amounts of water leads to a > 100-fold increase on Ni3B catalysts, while it inhibits the reaction on bare Ni catalyst by blocking active sites. These observations highlight the cooperative role of bifunctional sites in Ni3B catalysts and solvent composition for C = C hydrogenation reactions.

Evaluating performance of CrCl3-catalyzed ethanol pretreatment of poplar on cellulose conversion

As green and effective depolymerization processes, CrCl3 and CrCl3-catalyzed ethanol pretreatment were comprehensively investigated to improve cellulose conversion from pretreated residues in poplar in the present study. The influence of pretreatment temperature on delignification, structural characteristics of lignin, and the yield of glucose and ethanol was comparatively analyzed to emphasize the synergy effect of CrCl3 and ethanol solvent. Particularly, CrCl3-catalyzed ethanol pretreatment at 200 °C resulted in the pretreated substrates with >94% removal of hemicellulose and lignin, consequently reaching 88.88% and 56.11% yields of glucose and ethanol, respectively. Lignin's structural change was observed by Gel permeation chromatography and 2D nuclear magnetic resonance spectroscopy and its relationship with the efficiency of enzymatic hydrolysis and fermentation was determined. Results indicated that the increased pretreatment temperature enhanced the lignin depolymerization with smaller molecular weight, fewer β-O-4 linkages, and higher S/G ratio, especially in CrCl3-catalyzed ethanol pretreatment, which was positively associated with poplar cellulose conversion. In addition to offering a comprehensive illustration of the sugar/ethanol generation during CrCl3-catalyzed organosolv pretreatment, this work also provided theoretical support for biofuel and biochemical production from poplar.

Metal Salt-Based Deep Eutectic Solvent Pretreatment of Moso Bamboo to Improve Enzymatic Hydrolysis

Research on metal salt-based deep eutectic solvent (DES) pretreatment is still in its infancy, and the effect of hydroxyl groups on Cl− in choline chloride (ChCl) is not resolved. In this study, a type IV DES composed of metal salt and glycerol (Gly) was prepared for pretreatment of moso bamboo to improve its enzymatic hydrolysis. The correlation between enzymatic hydrolysis and the contents of hemicelluloses and lignin was evaluated using the Box–Behnken design. The results showed that FeCl3-based DES was optimal among various DES. The solid recovery was reduced to 55.54% following FeCl3/Gly pretreatment, which was effective in the removal of hemicelluloses and lignin compared with ternary DES pretreatment (with ChCl) under mild conditions (100 °C, 3 h). With the increase of pretreatment temperature (120 °C, 2 h), a significant proportion of hemicelluloses (76.07%) and lignin (62.77%) was removed. The structure of FeCl3/Gly pretreatment residue was seriously damaged, and the glucose yield increased to 91.13% following enzymatic hydrolysis. This correlation indicated that the hemicelluloses’ content had a significant influence on enzymatic hydrolysis of the residue following FeCl3/Gly pretreatment. This study elucidates the pretreatment effect of metal salt-based DES, which will be helpful in the value-added conversion of moso bamboo under mild conditions.

Study on mechanism of cellulose hydrolysis during alkali thermal pretreatment of lignocellulose by density functional theory

Alkali thermal pretreatment can effectively destroy the compact three-dimensional aggregated structure of lignocellulose, and further promote the production of high value-added chemicals. Cellulose is an important component of lignocellulose, and in this study the mechanism of cellulose hydrolysis in alkali thermal pretreatment was studied by density functional theory. The hydrolysis was divided into two steps, firstly the hydroxide ion captured a proton from the hydroxyl of which had most positive potential value of 1.23 eV. Subsequently, the glycosidic bond was cleaved to form a new C–O bond, and the hydroxide ion attacked the intermediate forming a glucose residue by a new covalent. The amount of electron transfer of the two steps were natural orbitals for chemical valence eigenvalue 0.31 and 0.34, and the corresponding energy barriers were 147.11 and 101.17 kJ/mol at 298.15 K, respectively. With the increase of pretreatment temperature from 298.15 to 413.15 K, the enthalpy and Gibbs free energy change of cellobiose hydrolysis decreased by 2.97 and 2.34 kJ/mol and the thermodynamic feasibility and reaction rate increased. This study will providing an important guidance for the process control, reactor design and performance enhancement of lignocellulose pretreatment.

Effect of pretreatment process on microstructure and mechanical properties in Inconel 718 alloy

The residual stress reduction, the precipitation behavior of γ" phase and the evolution of mechanical properties of Inconel 718 alloy in solid solution annealed with different pretreatment were investigated. The results show that the pretreatment process can effectively reduce the quenching residual stresses. With the increase of pretreatment temperature from 680 °C to 720 °C, the residual stress reduction rate increased from 52% to 65%, and the corresponding stress relaxation mechanism changed from dislocation slip dominated to both dislocation slip and grain boundary migration. Meanwhile, the pretreatment process promotes the nucleation and precipitation of the γ" phase, which is uniformly nucleated and always consistent with the matrix. The yield strength of the pretreated samples was slightly increased compared to the purely aged state, with an extreme value of 5.1%. The increase in strength is mainly attributed to the coherent hardening effect associated with the morphology and distribution of the γ" phase.

Prediction of compressive strength of alkali-activated construction demolition waste geopolymers using ensemble machine learning

This paper mainly employed the random forest (RF), gradient boosting (GB) and extreme gradient boosting (XGB) to predict the compressive strength of alkali-activated construction demolition waste geopolymers (CDWG). The performances of three ensemble machine learning (ML) models were evaluated and the effects of eight different input features on the compressive strength of CDWG were deeply analyzed. The results confirm the applicability of RF, GB and XGB algorithms in aspect of strength prediction for the CDWG with the high predictive accuracy (R2 > 0.9). Among them, the performances of GB and XGB models are better than RF model. The liquid to solid ratio (L/S) has a negative correlation with the compressive strength of CDWG, while the pretreatment temperature, heat treatment time and curing age have a positive correlation with the compressive strength of CDWG. The obvious enhancement of compressive strength of CDWG mainly occurs in the early age. Decreasing L/S and raising pretreatment temperature have a significant positive gain on the compressive strength of CDWG. In the preparation process of CDWG, it is suggested that the L/S and %Na2O of Na2SiO3-based alkaline activators are controlled at about 0.3 and 7 % respectively, and appropriately increasing pretreatment temperature and prolonging heat treatment time.

Shape Effect of Atomically Precise Au25 Nanoclusters on Catalytic CO Oxidation

Understanding the catalytic behavior of metal nanoclusters at the atomic level remains a major dream in nanocatalysis research. Here, we study the catalytic behavior of two different Au25 nanoclusters (sphere vs rod) supported on TiO2 nanorods and obtain insights into the structure–property relationship for CO oxidation. The spherical [Au25(SCH2CH2Ph)18]− nanocluster exhibits a catalytic activity trend of volcano-shape with the increase of pretreatment temperature in oxygen from 150 to 300 °C. It is found that low-temperature pretreatment could make the cluster expose more active sites; hence, an increase in activity, while high-temperature pretreatment leads to a decrease in activity due to the thermally induced aggregation of clusters into larger particles. For the rod-shaped [Au25(PPh3)10(SCH2CH2Ph)5X2]2+ cluster, its activity decreases with the increase of pretreatment temperature from 150 to 300 °C. The different trends of spherical and rod-like Au25 catalysts are ascribed to their distinctly different atomic packing structures. This work demonstrates a control of the atomic structure of catalysts and the effects on the catalytic performance.

Effect of hydrothermal and hydrothermal oxidation pretreatment on the physicochemical properties of biofuel pellet

The effects of hydrothermal pretreatment with and without H2O2 addition on the properties of the resulted biofuel pellets prepared from cotton stalk (CS) and Chinese fir wood sawdust (WS) were mainly studied in the paper. Based on the changes of three main components (hemicellulose, cellulose and lignin) of biomass during the pretreatment process, the relaxation density, compressive strength, heating values (HVs), and combustion characteristics of the resulted pellets were analyzed to evaluate the feasibility of the utilization as biofuel pellets. The results indicate that the hydrothermal pretreatments with and without H2O2 addition are beneficial to the quality of the resulted biofuel pellets. Particularly, the hydrothermal pretreatment with H2O2 addition, namely the hydrothermal oxidation pretreatment can significantly alleviate the pretreatment severity of the high-strength biofuel pellet preparation. H2O2 addition promotes the decomposition of hemicellulose and cellulose during the pretreatment. Compared with CS, WS is more sensitive to the pretreatment, especially hydrothermal oxidation pretreatment. The crystallinity index and the cellulose content of the biomass sample both increase firstly and then decrease with the increasing pretreatment temperature. In the study, the pretreatment temperature for the biofuel pellets with the best mechanical properties is 230 °C for the hydrothermal process and 200 °C for the hydrothermal oxidation process, respectively. The HVs of the resulted biofuel pellet increases with the increasing pretreatment intensity and the suitable pretreatment can improve the combustion characteristics of the resulted biomass. The mechanical properties of the pretreated biofuel pellets were positively correlated with the crystallinity and the content of the cellulose. HVs of WS pellets is higher than CS pellets, with the better mechanical properties. The cellulose is more favorable for the improvement of the combustion properties of the biomass sample than the hemicellulose and lignin. In addition, HVs and the compressive strength of all the biofuel pellets prepared from the pretreated biomasses meet the Sweden Standard (SS18 7120) and the Ministry of Agriculture of China standard (NY/T1878–2010), respectively.

Preparation and Characterization of Glass-Ceramic Foam from Clay-Rich Waste Diatomaceous Earth.

In this study, the potential use of waste diatomaceous earth from the production of diatomaceous earth for filtration purposes, as an alternative raw material for foam glass production, was explored. The chemical and mineralogical composition and the high temperature behavior of waste diatomite were studied to assess its suitability for foam glass production. Glass-ceramic foams were prepared using NaOH solution as a foaming agent, via a hydrate mechanism. The influence of different pretreatments and firing temperatures on the foam’s structure, bulk density and compressive strength was investigated. High temperature behavior was studied using TG/DTA analysis and high temperature microscopy. Phase composition was studied using X-ray diffraction analysis. Glass-ceramic foam samples of a high porosity comparable to conventional foam glass products were fabricated. The pretreatment temperature, foaming temperature and sintering holding time were found to have a significant influence on foam properties. With increased pretreatment temperature, pyrogenic carbon from the thermal decomposition of organic matter contained in the raw material acted as an additional foaming agent and remained partially unoxidized in prepared foams. The bulk densities of prepared samples ranged from 150 kg/m3 to 510 kg/m3 and their compressive strengths were between 140 and 1270 kPa.

Chemical composition and porcine in vitro digestibility of corn whole stillage pretreated with heat at various temperatures and times

A study was conducted to identify optimal conditions (time and temperature) for heat pre-treatment of corn whole stillage (WS). Six samples of WS from different sources were divided into 13 sub-samples to give a total of 78 sub-samples. Thirteen treatments were applied to 13 sub-samples from each source (1 sub-sample/treatment). The treatments were untreated WS, and WS that was pre-treated (70 psi) for 10, 20, or 30 min and at 100, 120, 140, or 160 °C in a 3 × 4 factorial treatment arrangement. Sub-samples were subjected to in vitro digestion with porcine pepsin and pancreatin, followed by in vitro fermentation for 72 h. Accumulated gas production was recorded and modeled to estimate kinetics of gas production. Heat pretreatment of WS at ≥ 120 °C decreased (P < 0.05) its total dietary fiber (TDF) and chemically available lysine content by approximately 10 and 19 %, respectively; and increased (P < 0.05) total furans (TF) content from 0.50 to approximately 154 mg/kg. Pretreatment time and temperature interacted on TDF and TF content in WS, such that an increase in pretreatment time had no effect on TDF and TF content in WS when pretreated at 100, 120, or 140°C, but reduced (P < 0.05) TDF content and increased (P < 0.05) TF content in WS when pretreated at 160°C. Pretreatment time and temperature interacted (P < 0.05) on chemically available lysine content of WS, such that an increase in pretreatment time unaffected chemically available lysine content when the WS was pretreated at 100 or 120 °C, but reduced (P < 0.05) chemically available lysine content when the WS was pretreated at 140 or 160 °C. Pre-treatment time and temperature did not interact on in vitro disappearance of dry matter (IVD-DM), and total gas production. The coefficient of IVD-DM for untreated WS was 0.734. An increase in pre-treatment temperature from 0 to 160 °C resulted in linear increase (P < 0.05) in coefficient of IVD-DM by 13 %, and of total gas production by 16 %. Response surface analysis indicated that maximum coefficient of IVD-DM and total gas production resulted from longer pretreatment times (20–30 min) and highest pretreatment temperature, whereas maximum chemically available lysine content resulted from pretreatment at 100 °C for 20 min. In conclusion, the optimal conditions for pretreatment of WS for production of distillers dried grains with solubles of improved digestibility and fermentability by pigs were temperature of 140–160 °C, and duration of approximately 20 min.

Modeling and statistical analysis of heat-shocked sulfate-reducers and methanogens rich consortiums for hydrogen and methane production in a bio-electrochemical cell

This study was carried to investigate the effect of thermal pre-treatment at 55 °C, 65 °C, 75 °C, and 85 °C on sulfate-reducing bacteria (SRB) and methanogens to check their potential in a Bio-electrochemical system (BES) for hydrogen and methane production. The experimental results indicate that SRB culture pre-treated at 55 °C could be used efficiently in hydrogen production up to 2.814 ± 0.091 M/M of glucose. A significant drop in methane production from Phase-I to Phase-III with an increase in pre-treatment temperature was observed. Volatile fatty acids production was found highest in Phase-III, with butyric acid in major concentration at the pre-treatment temperature range of 55 °C–65 °C in SRB-based BES. The higher hydrogen production conditions were tested with various models i.e. the Gompertz model, Richard model, and Logistic model to confirm its validity and hydrogen production prediction. Richard's model was found best fitted for cumulative hydrogen production.

Variation of the Prokaryotic and Eukaryotic Communities After Distinct Methods of Thermal Pretreatment of the Inoculum in Hydrogen-Production Reactors from Sugarcane Vinasse.

The aim of this study is to evaluate the effect of different thermal pretreatments of the inoculum on the diversity of the microbial community producing hydrogen from sugarcane vinasse. High-throughput sequencing of the 16S and 18S rRNA genes was performed. The reactor samples were also selected for the isolation of strict anaerobes. Decreased microbial diversity was observed with increasing pretreatment temperatures, with Firmicutes predominating: 90% to 97%. The highest abundance of Staphylococcus (7.9%) was found in pretreatment at 120 °C / 20 min at pH 6. The fungal analysis revealed a high prevalence of Candida (47%), Agaricomycetes, Pezizomycotina and Aspergillus in assays with higher H2 production (90° C / 10 min at pH 6). Three species of Clostridium were isolated: C. bifermentans, C. saccharoperbutylacetonicum and C. saccharobutylicum. The isolates were tested separately and in co-cultures for the production of hydrogen. Hydrogen-producing capacity by co-culture of Clostridium species was increased by 18%. Knowing microorganisms and understanding the interaction between eukaryotes and prokaryotes is essential to obtain strategies for biotransformation of vinasse for the production of bioenergy.

Kinetics of hydrolysis of microalgae biomass during hydrothermal pretreatment

Hydrothermal pretreatment is an efficient method for increasing the biogas yield and the amount of energy generated via the anaerobic digestion of microalgae biomass. Few studies have investigated the effects of pretreatment conditions on the rate of the hydrolysis of microalgae biomass into carbohydrates and proteins and the changes in hydrolysis residues, which significantly limit further performance enhancement. In this study, we analyzed the effects of pretreatment conditions on the hydrolysis characteristics and rate of microalgae biomass hydrolysis into carbohydrates and proteins. The results revealed that the yields of soluble carbohydrates and proteins increased with increasing pretreatment temperature and retention time. Conversely, the yields remained unchanged as the mass fraction of microalgae biomass in the microalgae slurry increased from 1% to 10%. The activation energies for the hydrolysis of microalgae biomass into carbohydrates and proteins were 35.07 and 39.66 kJ/mol, respectively. During hydrothermal pretreatment, organic matter within microalgae biomass was converted into relatively small molecules with poor stability, and hydrolysis exposed the major functional groups of microalgae biomass. This study provides guidance for controlling the hydrolysis reaction, designing hydrolysis reactors, and predicting the yields of carbohydrates and proteins.

Experimental Study on the Characteristics of the Spontaneous Combustion of Coal at High Ground Temperatures

ABSTRACT Understanding the influence of high ground temperatures on the characteristics of the spontaneous combustion of coal is important for increasing safety in deep mines, where high temperatures are encountered. In this experimental study, long flame coal samples were treated at a constant temperature of 30, 40, and 50°C to simulate the high ground temperatures found in deep mines. By Fourier transform infrared spectroscopy, thermogravimetry, and gas chromatography, changes to the functional groups, gas generation, and characteristic temperatures resulting from the exposure to elevated temperatures were reported. The results demonstrate that as the ground temperature rises, the abundance of hydroxyl groups and oxygen-containing functional groups increases, and the coal becomes more reactive. Results from gas chromatography show that the quantity and rate of production of CO, C2H4, and C2H2 during oxidation all increased with increasing pretreatment temperature. Additionally, results from the thermal analysis indicate that the critical temperature, dry cracking temperature, and ignition temperature all decreased with increasing pretreatment temperature. These results all suggest that high ground temperatures can regularly increase the risk of spontaneous combustion of coal by enhancing the activity of functional groups.

Pretreatment of spent coffee grounds with alkaline soju bottle-washing wastewater for enhanced biomethanation

The production of spent coffee grounds (SCG) is steadily increasing, and its proper treatment has become an increasingly challenging task. This study explored the potential use of alkaline bottle-washing wastewater (BWW) from a soju (a Korean hard liquor) manufacturer as an alternative pretreatment agent to enhance the biodegradability and thus the biomethanation of SCG through anaerobic digestion. Thermo-alkaline pretreatment with BWW was effective in increasing the soluble organic fraction of SCG (i.e., improved bioavailability) at all temperatures tested (23–70 °C). The disintegration degree of the particulate organic matter in SCG ranged from 8.6 to 13.1% and increased with increasing pretreatment temperature. The 30-day methane yield (per g chemical oxygen demand (COD) of SCG fed) was significantly higher for the BWW-pretreated SCG (342.4–361.2 mL/g COD) than for the raw SCG (284.7 mL/g COD) and even for the NaOH-pretreated SCG (at the same pH as BWW, pH 12.3) tested for comparison (299.7–320.9 mL/g COD). This significant increase in methane production can be attributed to the presence of readily biodegradable ethanol derived from waste soju in BWW and the alkaline solubilization of SCG. Our results suggest a straightforward way to manage SCG and BWW together in a sustainable and economical manner.

Poly(ε-Caprolactone)/Brewers’ Spent Grain Composites—The Impact of Filler Treatment on the Mechanical Performance

Waste lignocellulose materials, such as brewers’ spent grain, can be considered very promising sources of fillers for the manufacturing of natural fiber composites. Nevertheless, due to the chemical structure differences between polymer matrices and brewers’ spent grain, filler treatment should be included. The presented work aimed to investigate the impact of fillers’ reactive extrusion on the chemical structure and the poly(ε-caprolactone)/brewers’ spent grain composites’ mechanical performance. The chemical structure was analyzed by Fourier-transform infrared spectroscopy, while the mechanical performance of composites was assessed by static tensile tests and dynamic mechanical analysis. Depending on the filler pretreatment, composites with different mechanical properties were obtained. Nevertheless, the increase in pretreatment temperature resulted in the increased interface surface area of filler, which enhanced composites’ toughness. As a result, composites were able to withstand a higher amount of stress before failure. The mechanical tests also indicated a drop in the adhesion factor, pointing to enhanced interfacial interactions for higher pretreatment temperatures. The presented work showed that reactive extrusion could be considered an auspicious method for lignocellulose filler modification, which could be tailored to obtain composites with desired properties.

Effective calcination pretreatment of Lu2O3 powders for LuAG transparent ceramics

Lutetium aluminium garnet (LuAG) ceramics as host materials has been widely used in lighting, laser, displaying and scintillators after doping different rare earth ions. Right selection of raw powder and controlling its characteristics during the preparation can greatly improve the optical quality of transparent ceramics. In this paper, the influence of different pretreatment temperatures of commercial Lu2O3 powders in oxygen atmosphere on solid state sintering of LuAG ceramics was systematically investigated. The pretreatment gradually decreased the specific surface area of Lu2O3 powders and greatly removed the absorbed impurities, which seriously deteriorated the optical quality before. The mean particle size increased from 4.53 to 5.66 μm, and the in-line transmittance of samples (Thickness = 2 mm) at 1064 nm was 68.4% for the pretreated Lu2O3 powder at 1000 °C without any sintering additives. Further increase of pretreatment temperature would lead to the coarsening of Lu2O3 powders and the decrease of sintering activity, which finally resulted in a large number of micro pores in LuAG ceramics. These results revealed that the pretreatment of Lu2O3 powders has prodigious impact on the optical quality of LuAG transparent ceramics, and the adsorbed materials should be removed as much as possible for their applications in lasers or lighting.