Low density rigid polyurethane foam incorporated with renewable polyol as sustainable thermal insulation material

Palm olein-based polyol (PP) was used as a partial replacement for commercial sucrose/glycerine initiated polyether polyol (GP) for the production of low density rigid polyurethane foams (RPUFs). The hydroxyl value (OHV) of the GP was 380 mg KOH/g, whereas the OHV for PP was 360 mg KOH/g. The RPUFs were prepared by replacing the GP with PP up to 50 parts per hundred parts of polyols (pph). Characterisation of the RPUFs, including density, compressive strength and strain, cell morphology and thermal conductivity ( k-value), were conducted. The dimensional stability of the foams was also evaluated. The study showed improvement in the compressive strength and strain for palm-based RPUFs with the incorporation of up to 30 pph PP as compared to GP foams. The lowest k-value (0.0232 W/m.K) of RPUF with density below 30 kg/m3 was obtained with the incorporation of 10 pph PP. This was due to the smallest and uniform pore size distribution observed using SEM images. The dimensional stability of the RPUF prepared from PP was within the acceptable range. Thus, the RPUFs made from PP are potential candidates to be used as insulation for refrigerators, freezers and piping.

A Short Review on Synthesis, Characterization, and Applications of Zeolites

The review emphasizes on synthesis, characterization, and application of zeolite. Zeolite is a hydrated aluminosilicate having a tetrahedral structural framework; it contains channels and cages which are occupied by exchangeable active metal ions and water molecules. Zeolite was synthesized through different synthesis methods, particularly, hydrothermal and green synthesis methods. The review also has tried to address the structure of zeolite such as morphology, functional group, and particle size using different characterization methods as reported via different authors. The characterization results verify that zeolite shows many unique properties such as uniform pore size, acidic properties, thermal stability, mobile extra cation, hydrophilicity, and hydrophobicity. These lead to a number of applications in catalysis, water purification, adsorption, and agriculture.

Polyvinyl Alcohol/Chitosan and Polyvinyl Alcohol/Ag@MOF Bilayer Hydrogel for Tissue Engineering Applications

In this paper, polyvinyl alcohol/Ag-Metal-organic framework (PVA/Ag@MOF) and polyvinyl alcohol/chitosan (PVA/CS) were used as the inner and outer layers to successfully prepare a bilayer composite hydrogel for tissue engineering scaffold. The performance of bilayer hydrogels was evaluated. The outer layer (PVA/CS) has a uniform pore size distribution, good water retention, biocompatibility and cell adhesion ability. The inner layer (PVA/Ag@MOF) has good antibacterial activity and poor biocompatibility. PVA, PVA/0.1%Ag@MOF, PVA/0.5%Ag@MOF, and PVA/1.0%Ag@MOF show anti-microbial activity in ascending order. However, its use as an inner layer avoids direct contact with cells and prevents infection. The cell viability of all samples was above 90%, indicating that the bilayer hydrogel was non-toxic to A549 cells. The bilayer hydrogel scaffold combines the advantages of the inner and outer layers. In summary, this new bilayer composite is an ideal lung scaffold for tissue engineering.

Thiosemicarbazide-Linked Covalent Organic Framework: Preparation, Properties and Applications

With the unique advantages in structure and property, covalent organic frameworks have been widely employed for separation and enrichment. In this work, the thiosemicarbazide-linked covalent organic framework (TpTc) was prepared by using 1,3,5-triformylphloroglucinol and non-rigid thiosemicarbazide as building blocks for the first time. The as-prepared TpTc COF was fully characterized, presenting an agaric-like structure, large specific surface area (63.5 m2 g-1), uniform pore size distribution (1.36 nm), inherent porosity and ordered crystallinity. The potential of TpTc as adsorbent for metal ions capture was investigated by static batch adsorption experiment using the one-factor procedure. The maximum adsorption capacities of 73.50, 56.53 and 94.13 mg g-1 were obtained for Cu (II), Pb (II) and Cd (II) at natural pH, respectively. The anchoring of three metal ions onto TpTc is a multi-layer sorption involving chemical adsorption, and obeys the Freundlich and pseudo-second-order model. According to XPS analysis, the adsorption mechanism may be attributed to the coordination and electrostatic interaction between metal ions and N, O and S atoms on TpTc COF. This work not only provides a candidate for the application of COFs in metal ions capture, but also a reference for exploring functional design of COFs .

Highly Mesoporous g-C3N4 with Uniform Pore Size Distribution via the Template-Free Method to Enhanced Solar-Driven Tetracycline Degradation

A highly mesoporous graphitic carbon nitride g-C3N4 (GCN) has been produced by a template-free method and effectively photodegrade tetracycline (TC) antibiotic under solar light irradiation. The mesoporous GCN (GCN-500) greatly improves the photoactivity (0.0247 min−1) by 2.13 times, as compared to that of bulk GCN (0.0116 min−1). The efficiently strengthened photoactivity is ascribed to the high porosity (117.05 m2/g), and improves the optical absorption under visible light (Eg = 2.65 eV) and good charge carrier separation efficiency. The synthesized mesoporous GCN shows a uniform pore size (~3 nm) distribution. GCN-500 shows large pore volume (0.210 cm3/g) compared to GCN-B (0.083 cm3/g). Besides, the GCN-500 also exhibits good recyclability and photostability for TC photodegradation. In conclusion, GCN-500 is a recyclable photocatalyst for the removal of TC under visible light irradiation.

Real-time imaging of Na+ reversible intercalation in “Janus” graphene stacks for battery applications

Sodium, in contrast to other metals, cannot intercalate in graphite, hindering the use of this cheap, abundant element in rechargeable batteries. Here, we report a nanometric graphite-like anode for Na+ storage, formed by stacked graphene sheets functionalized only on one side, termed Janus graphene. The asymmetric functionalization allows reversible intercalation of Na+, as monitored by operando Raman spectroelectrochemistry and visualized by imaging ellipsometry. Our Janus graphene has uniform pore size, controllable functionalization density, and few edges; it can store Na+ differently from graphite and stacked graphene. Density functional theory calculations demonstrate that Na+ preferably rests close to -NH2 group forming synergic ionic bonds to graphene, making the interaction process energetically favorable. The estimated sodium storage up to C6.9Na is comparable to graphite for standard lithium ion batteries. Given such encouraging Na+ reversible intercalation behavior, our approach provides a way to design carbon-based materials for sodium ion batteries.

High Nanopore Volume Tetrethoxysilane Based Aerogels Prepared with Addition of N, N-Dimethylformamide at Different Stage of the Sol-Gel Process

Using tetraethoxysilane (TEOS) as a precursor, silica aerogels were synthesized via the sol-gel polymerization followed by supercritical drying process. During the polymerization period, N, N-dimethylformamide (DMF), acting as a chemical additive for the structure control, was introduced in the hydrolysis step and condensation step, respectively. As a result, the nanopore volumes for the pores smaller than 100 nm were up to 6.0 cm3/g and 5.7 cm3/g for the samples that produced with DMF addition in the hydrolysis step and condensation step, while the value for the sample without DMF was only 4.6 cm3/g. Besides, the sample with DMF addition in the condensation step possessed more uniform pore size distribution while compared with that with DMF addition in the hydrolysis step. DMF can provide a shielding layer around the colloid particles through hydrogen bonds, inhibiting the aggregation of colloid particles and the enlarging of pore sizes.

Pyromellitic diamide-diacid bridged mesoporous organosilica nanospheres with controllable morphologies: A novel PMO for the facile and expeditious synthesis of imidazole derivatives

In this work, novel pyromellitic diamide-diacid bridged mesoporous organosilica (PMAMOS) nanospheres with controllable morphologies and active catalytic centers were designed and prepared with high surface area and uniform pore size...

Investigation of gas-phase processes for the preparation of fiber-reinforced organomorphic ceramic composites with a SiC-matrix

The isothermal process of gas-phase chemical deposition for the compaction of organomorphic carbon-fiber preforms with a SiC-matrix obtained by carbonization of compressed fibers of oxidized polyacrylonitrile has been investigated. Their feature is high (up to 70 %) and uniform pore size (reduced pore diameter from several micrometers to several tens of micrometers) porosity. The problem of optimizing the technological parameters of the process of obtaining ceramic-matrix composites (CMC) was solved by a combination of experimental research and numerical modeling. Experimental samples of CMC were obtained using a non-halogen precursor of methylsilane CH3SiH3, and their residual porosity was determined. For the numerical study of the gas-phase process of compaction of preforms, a 1D model was used. The simulation results were compared with experimental observations.

Electropolymerization of robust conjugated microporous polymer membranes for rapid solvent transport and narrow molecular sieving

Pore size uniformity is one of the most critical parameters in determining membrane separation performance. Recently, a novel type of conjugated microporous polymers (CMPs) has shown uniform pore size and high porosity. However, their brittle nature has prevented them from preparing robust membranes. Inspired by the skin-core architecture of spider silk that offers both high strength and high ductility, herein we report an electropolymerization process to prepare a CMP membrane from a rigid carbazole monomer, 2,2’,7,7’-tetra(carbazol-9-yl)-9,9’-spirobifluorene, inside a robust carbon nanotube scaffold. The obtained membranes showed superior mechanical strength and ductility, high surface area, and uniform pore size of approximately 1 nm. The superfast solvent transport and excellent molecular sieving well surpass the performance of most reported polymer membranes. Our method makes it possible to use rigid CMPs membranes in pressure-driven membrane processes, providing potential applications for this important category of polymer materials.