Excellent Dimensional Stability Research Articles

Polyester-based epoxy vitrimer integrating spent coffee ground as a natural filler

Coffee is a widely consumed beverage, but approximately 80% mass of coffee cherry is discarded as waste. In this study, spent coffee grounds (SCG) were recycled and used as a natural filler in a polyester-based epoxy matrix made from reactions of diglycidyl ethers of Bisphenol A and polyethylene glycol with methyl nadic anhydride. The properties of SCG/epoxy composites with various SCG contents up to 40% w/w were evaluated using various techniques such as FT-IR spectroscopy, tensile testing, optical microscopy, differential scanning calorimetry, and rheology. The SCG filled polyester-based epoxy matrix demonstrated excellent dimensional stability and retained a permanently crosslinked network, but re-shaping was possible at ∼150 °C through transesterification, which occurred due to a dynamic chain exchange reaction between the ester group of the epoxy matrix and the hydroxyl group of the SCG fillers. The transesterification also improved the interfacial adhesion between the matrix and SCG fillers, resulting in tensile strength of over 20 MPa and a modulus of around 2.5 GPa, even with high SCG contents up to 40% w/w. While neat, cured epoxy shows thermoset behavior, filling the matrix with SCG enables reforming and origami-inspired spontaneous change in shape.

Synergetic strategy to fabricate superhydrophobic wood by MTMS for improving dimensional stability, durability and self-cleaning ability

A novel two-step synergetic strategy is proposed, i.e., using an eco-friendly methyltrimethoxysilane (MTMS) to prepare superhydrophobic wood by immersion-spraying method. The wood samples were first immersed in MTMS solution followed by spraying with pre-condensed MTMS-based oligomeric species. The as-prepared superhydrophobic wood was proved to have excellent water resistance, dimensional stability, surface durability and self-cleaning peculiarity. The developed strategy offers a new reference for superhydrophobic modification of 3D-porous materials.

RF Glass Technology Is Going Mainstream: Review and Future Applications

Driven by the increasing demand for high-throughput communication links and high-resolution radar sensors, the development of future wireless systems pushes at ever greater operating frequencies. By analogy, high-performance computing (HPC) systems with high-bandwidth I/Os have become a mainstream solution to address multi Gbit/s data rates. Heterogeneous integration technologies play a vital role here in enhancing the performance and functional density, along with reducing the size and costs of such RF systems. In line with this trend, many passive components, which have once been monolithically integrated, are now implemented on ceramic or polymer-based packages. Besides these long-established material and process technologies, considerable efforts have also recently been devoted to the development of RF components on glass and glass-ceramics. Spurred by their low dielectric losses, extremely smooth surfaces, and excellent dimensional stability, glass technologies are emerging as a promising alternative for high-volume and high-performance RF applications. In this article, relevant glass materials and key enabling technologies are reviewed and put into context with well-established RF substrate technologies. Another focus is set on the latest glass-based packaging and interposer solutions ranging from MHz-to-THz frequencies. To showcase the development activities and practical accomplishments of the RF glass technology, also a large variety of key components is presented. Finally, the paper concludes by discussing future research and development directions of RF glass devices.

Biodegradable implants based on photo-cross-linked aliphatic polycarbonates for long-acting contraception

In this study, a new class of biodegradable contraceptive implants was prepared via the UV irradiation molding method, among which, progestin levonorgestrel (LNG) was used as a model drug. Photo-cross-linked aliphatic polycarbonates (APCs), namely, poly (trimethylene carbonate-co-2,2′-dimethyltrimethylene carbonate) [P(TMC-co-DTC)] elastomers, were used as the drug delivery matrix. The results obtained from the degradation experiments carried out in Sprague-Dawley (SD) rats showed that the cross-linked elastomer had the degradation characteristics of the surface erosion degradation mechanism, with no generation of acid degradation products, and excellent form-stability, which met the performance requirements of the matrix for a long-acting sustained-release delivery system. The in vitro cytotoxicity tests and histological and immunohistochemical evaluations showed good biocompatibility and biosafety of the elastomer matrix material and contraceptive implants. Subsequently, the implant formulations were screened by in vitro release experiments, and their release kinetics were explored. Finally, in the evaluation study of the in vivo anti-fertility effect, the implants exhibited excellent dimensional stability and were degraded by a surface erosion mechanism. LNG achieved a stable and sustained release in female SD rats, maintaining a long-acting contraceptive duration of up to 4 months. The contraceptive implants obtained in this study could be used to address the limitations of currently available formulations, which required secondary surgical removal and a single means of regulating drug release kinetics. Therefore, these implants could provide a new option for birth control needs and may be of significance in reducing the incidence of induced abortion and protecting female fertility.

Influence and mechanism of borax on the physico-mechanical properties of magnesium potassium phosphate cement exposed to high temperatures

This paper studied the effect of borax content on the physic-mechanical properties and microstructure of MKPC at high temperatures. Borax affected the performance of MKPC by changing phase composition and structure at high temperatures. Borax can react with magnesia to form Mg3B2O6 at around 800 °C. The porosity of MKPC reduced at temperatures of higher than 900 °C, mainly due to the melting of Mg3B2O6. As borax content increased from 3% to 15%, MKPC showed a denser structure and higher strength at 1100 °C. Excellent dimensional stability of MKPC at high temperatures can be obtained at low borax content.

An Investigation of Compressive Creep Aging Behavior of Al-Cu-Li Alloy Pre-Treated by Compressive Plastic Deformation and Artificial Aging

In this paper, the effects of compressive pre-deformation and successive pre-artificial aging on the compressive creep aging behavior and microstructure evolution of the Al-Cu-Li alloy have been studied. Severe hot deformation mainly occurs near the grain boundaries during the compressive creep initially, which steadily extends to the grain interior. After that, the T1 phases will obtain a low radius-thickness ratio. The secondary T1 phases in pre-deformed samples usually only nucleate on dislocation loops or Shockley incomplete dislocations induced by movable dislocations during creep, which are especially prevalent in low plastic pre-deformation. For all pre-deformed and pre-aged samples, two precipitation situations exist. When pre-deformation is low (3% and 6%), solute atoms (Cu and Li) can be consumed prematurely during pre-aging at 200 °C, with dispersed coherent Li-rich clusters in the matrix. Then, the pre-aged samples with low pre-deformation no longer have the ability to form secondary T1 phases in large quantities during subsequent creep. When dislocation entangles seriously to some extent, a large quantity of stacking faults, together with a "Suzuki atmosphere" containing Cu and Li, can provide the nucleation sites for the secondary T1 phase, even when pre-aged at 200 °C. The sample, pre-deformed by 9% and pre-aged at 200 °C, displays excellent dimensional stability during compressive creep because of the mutual reinforcement of entangled dislocations and pre-formed secondary T1 phases. In order to decrease the total creep strain, increasing the pre-deformation level is more effective than pre-aging.

A facile strategy to fabricate antibacterial hydrophobic, high-barrier, cellulose papersheets for food packaging

As a traditionally used packaging material, natural cellulose-based paper has poor barrier properties to water and oxygen, which severely limits its wide application in food packaging. In this study, we report a new sustainable approach to producing hydrophobic, high-barrier, and antibacterial packaging materials from cellulose paper. In this process, commercially available microcrystalline cellulose was first modified by long-chain stearic acid to form hydrophobic microcrystalline cellulose ester and then mixed with stearic acid as filler in the subsequent surface coating of bagasse fibre paper. The microcrystalline cellulose ester/stearic acid-coated paper (MSP) exhibited good water repellency and oxygen barrier activity due to a continuous hydrophobic film that formed, which completely covered the pores of the original bagasse fibre paper. The coated MSP sample also showed excellent dimensional stability in water and a good wet tensile strength of 16 MPa. In addition, poly(hexamethylene guanidine) (PHMG) was chemically grafted onto the free carboxyl groups of the MSP surface layer, and the resulting MSP-g-PHMG samples exhibited excellent antibacterial activity against Escherichia coli and Listeria monocytogenes. The biodegradable cellulose-based MSP-g-PHMG sample significantly delayed the decay of raspberry during storage, indicating its potential application in food packaging.

Feasibility of one-time drying for manufacturing bamboo scrimber: fresh bamboo bundle at high initial moisture content impregnated by PF

Optimization of drying process can increase the efficiency of bamboo scrimber manufacture, and remarkably reduce the energy consumption, which contributes to the sustainable development of bamboo in agricultural planting. In this work, fresh bamboo bundles with different initial moisture content (40%, 55%, 70%) were directly impregnated by phenolic resin (PF) followed by a one-time drying method to prepare bamboo scrimber. The distribution of PF, the pore structure of impregnated bamboo bundle, and bonding interface, the properties of bamboo scrimber were studied systematically. The results showed that effective penetration of PF into cells in fresh bamboo bundle was found with high initial moisture content, hence excellent dimensional stability of bamboo scrimber was achieved. MOR and MOE were 140.98–172.09 MPa and 14.58–16.06 GPa, respectively, which all met the outdoor requirements of GB/T 30364–2013. The drying time and energy consumption were decreased by 15–21% and 38–44% respectively compared with traditional two-time drying process. The one-time drying method reported was benefit to prepare bamboo scrimber in an energy-saving and efficient way.

Fabrication and compressive performance of novel lightweight C/SiC honeycomb for ultrahigh stability structures

As for high resolution satellite application field, novel C/SiC honeycomb sandwich structure is the first to propose and develop on account of such many attractive properties as excellent ultrahigh dimensional stability in thermal and moisture coupling environment, lightweight and high load-bearing. Three types of C/SiC honeycomb sandwich structures were fabricated for the first time as opto-mechanical structure in satellite. The innovative interlayer-crosslinking method to weave the continuous carbon fiber fabric of honeycomb core was proposed. The compressive properties of novel C/SiC honeycomb sandwich structures were investigated. Meanwhile, the damage mechanism for sandwich structures were analyzed by non-destructive testing. The results showed that the innovative fabrication processing possessed the capability to prepare high quality C/SiC honeycomb, which was shown from the volume and distribution of pores in the X-ray tomography. The compression modulus and strength of the C/SiC honeycomb reached 927 MPa and 10.76 MPa, and showed better rigidity and higher strength compared with classical honeycombs. Two main types of cracks wall were found in the C/SiC honeycomb, i.e., the horizontal ones in the wall with t thickness and the inclined ones in the wall with 2 t thickness. The outstanding compressive performance was attributed to the high mechanical property of ceramic-matrix composite with fiber pull-out mechanism. The exceptional lightweight capacity was inherited from the low bulk density of honeycomb structure ranged from 0.08 g/cm3 to 0.15 g/cm3. This study can help for the development of lightweight materials for opto-mechanical structure in aerospace optical remote sensing technology.

Proton exchange membrane based on interpenetrating polymer network structure for excellent cell performance and chemical stability

Chemical stability and proton conductivity are the most critical factors for proton exchange membranes (PEMs). Here, we designed and prepared a co-polymer containing radical scavenger groups and imidazole groups. The membrane's acid-base crosslinking and interpenetrating network structure offer the PEM excellent dimensional stability and gas permeation inhibition properties. The continuous acid-base pairs and imidazole groups, which have high water retention, effectively improve the proton conductivity and reduce the PEM's gas permeability. Hence, a membrane electrode assembly based on as-prepared composite membranes exhibits higher single-cell performance and lower impedance than other membranes used for comparison. In addition, the introduction of hindered amine scavenger groups effectively eliminates the free radicals generated in the process of the electrochemical reaction. Both in-situ and ex-situ stability experiments show that the prepared composite membrane has excellent chemical stability. Morphological changes according to degradation level are also systematically analyzed. This paper shows that the introduction of imidazole and HA groups in the PFSA matrix membrane is effective for improving fuel cell performance and lifetime and for constructing continuous proton transport networks and interpenetrating network structures, making this a promising approach for achieving excellent proton conductivity and chemical stability in PEMs.

Sabic introduces LNP™ Konduit™ compound suitable for complex DDR memory IC test sockets and ramps up PCR-offerings

On November 28, SABIC introduced LNP™ KONDUIT™ 8TF36E compound, a new specialty material that should help address the stringent demands of burn-in test sockets (BiTS) used to stress-test double-data-rate (DDR) memory integrated circuits (ICs). As the number of pins and the testing temperature for DDR ICs increase and their dimensions shrink, materials used in BiTS components must deliver enhanced properties. SABIC’s new compound reportedly provides very high flow to help enable complex, miniaturized BiTS designs, excellent dimensional stability and high temperature resistance to enhance BiTS functionality during testing, and high thermal conductivity to rapidly dissipate heat afterwards.

Preparation and characterization of diphenyl silicone rubber/microfiber glass wool composite thermal control films.

Innovative research on the development of thermal control films for spacecraft surfaces is presented. A hydroxy-terminated random copolymer of dimethylsiloxane-diphenylsiloxane (PPDMS) was prepared from hydroxy silicone oil and diphenylsilylene glycol by a condensation reaction, and then liquid diphenyl silicone rubber base material (denoted as PSR) was obtained by adding hydrophobic silica. Microfiber glass wool (MGW) with a fiber diameter of ∼3 μm was added to the liquid PSR base material, which upon solidifying at room temperature, formed a 100 μm thick PSR/MGW composite film. The infrared radiation properties, solar absorption, thermal conductivity, and thermal dimensional stability of the film were evaluated. Moreover, the dispersion of the MGW in the rubber matrix was confirmed by optical microscopy and field-emission scanning electron microscopy. The PSR/MGW films exhibited a glass transition temperature of -106 °C, thermal decomposition temperature exceeding 410 °C, and low α/ε values. The homogeneous distribution of MGW in the PSR thin film resulted in a notable reduction in its linear expansion coefficient, as well as its thermal diffusion coefficient. Consequently, it exhibited a significant capacity for thermal insulation and retention. For the sample with 5 wt% of MGW, the linear expansion coefficient and thermal diffusion coefficient at 200 °C were reduced to 0.53% and 2.703 mm s-2, respectively. Thus, the PSR/MGW composite film has good heat-resistance stability and low-temperature endurance, along with low α/ε values and excellent dimensional stability. Additionally, it facilitates effective thermal insulation and temperature control, and can be an ideal material for thermal control coatings on spacecraft surfaces.

Class of Boehmite/Polyacrylonitrile Membranes with Different Thermal Shutdown Temperatures for High-Performance Lithium-Ion Batteries.

Nowadays, lithium-ion batteries are required to have a higher energy density and safety because of their wide applications. Current commercial separators have poor wettability and thermal stability, which significantly impact the performance and safety of batteries. In this study, a class of boehmite particles with different grain sizes was synthesized by adjusting hydrothermal temperatures and used to fabricate boehmite/polyacrylonitrile (BM/PAN) membranes. All of these BM/PAN membranes can not only maintain excellent thermal dimensional stability above 200 °C but also have good electrolyte wettability and high porosity. More interestingly, the BM/PAN membranes' thermal shutdown temperature can be adjusted by changing the grain size of boehmite particles. The lithium-ion batteries assembled with BM/PAN separators exhibit different thermal stability phenomena at 150 °C and have excellent rate performance and cycle stability at room temperature. After 120 cycles at 1C, the LiFePO4 half-cell assembled by the best BM/PAN separator has almost unchanged discharge capacity, whereas the capacity retention of Celgard 2325 is only about 85%. Meanwhile, the NCM523 half-cell assembled with the best BM/PAN separator shows superb cycle stability after 500 cycles at 8C, with a capacity retention of 79% compared with 56% for Celgard 2325.

An electrolyte-locked thermally stable composite separator for safe lithium ion batteries

The safety issue of lithium ion batteries has always received extensive attention and become the main obstacle restricting their development and applications. Commercial polyolefin separators own poor thermal stability, which cannot ensure the safe operation of lithium ion batteries after heating. Herein, an electrolyte-locked thermally stable composite separator polyimide/poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP@PI) is constructed through coating a layer of PVDF-HFP on the electrospun PI fibers membrane. In this structure, the high electrolyte retention ability and excellent thermal dimensional stability of PVDF-HFP@PI effectively inhibit the continuous reaction between electrolyte and Li anode, and prevent the battery failure after heating. In addition, the prepared PVDF-HFP@PI has good mechanical properties and high ionic conductivity of up to 1.79 mS cm−1, which significantly improves the electrochemical performance of the batteries. Therefore, the pouch cell with PVDF-HFP@PI retains 77.4 % of the original capacity after 300 cycles at 0.1 C. More importantly, the cell with PVDF-HFP@PI can work normally after heated under 140 °C for 1 h, exhibiting high heat tolerance.

Toughening of high-strength scalable laminated nanocomposites with discontinuous Bouligand-type architecture through soft flow-shear-induced alignment

Biological materials such as Arapaima gigas scale, pearls, and armadillos, are known for their outstanding strength and toughness due to the fine Bouligand-type configuration. Inspired by Bouligand-type architectures, some design techniques-including self-assembly-have been used to synthesize high-strength biomimetic laminate nanocomposites. Herein, we propose a bottom-up assembly strategy and prepare nanocomposites with Bouligand-type architectures by controlling the soft-flow-shear-induced directional assembly of cellulose-nanofibril building blocks. The resulting biomimetic laminated nanocomposites (BLNC) exhibited high specific flexural strength (FS) of 243. 6 MPa, flexural modulus (FM) of 9715.8 MPa, and specific fracture toughness (FT) of 8.29 MPa m0.5/(g/cm3), which were 6.06, 4.50, and 1.89 times higher than pure nanolignocellulose bulk (PNLB), respectively. Furthermore, due to the densified twisted Bouligand-type architecture of the micro/nanoscale building blocks, BLNC maintains mechanical liquid resistance stability in several harsh environments, including acid/alkali solutions, boiling water, and liquid nitrogen. It also has excellent dimensional stability and combustion resistance, making it one of the most promising new structural materials in the field of engineering technology.

High-performance aromatic proton exchange membranes bearing multiple flexible pendant sulfonate groups: Exploring side chain length and main chain polarity

Fabrication of aromatic proton exchange membrane (PEM) with excellent conductivity and stability is a long-standing challenge. Here, we propose an aromatic PEM containing multiple sulfonated alkyl side chains (SAFPAEK-x and SAFPAEF-x), and then implement an ideal strategy to address the trade-off between conductivity and stability by optimizing the side chain length and main chain polarity. Specifically, the synthesized PEMs achieve an efficient proton transport (proton conductivity >0.124 S cm−1 at 80 °C) under the synergistic effect of multiple pendant sulfonate groups and a pronounced microphase separation structure. Meanwhile, regulating the polarity of the hydrophobic domain via introducing fluorinated structures can effectively suppress the swelling behavior, so that SAFPAEF-x display excellent dimensional stability (swelling ratio <10% at 80 °C). The theoretical calculations of molecular models and ex-situ experiments demonstrate that appropriate increases in side chain length and main chain polarity lead to noticeably improved radical stability of aromatic PEMs. Finally, the laboratory-assembled direct borohydride fuel cell using our rationally designed PEMs reaches the highest peak power density of 191.17 mW m−2 at room temperature, outperforming the Nafion 115 (95.87 mW m−2) under the same conditions. Therefore, this membrane design strategy stimulates great potential in designing high-performance aromatic PEMs for fuel cells.

Sulfonated graphene oxide doped sulfonated polybenzothiazoles for proton exchange membrane fuel cells

A series of sulfonated polybenzothiazoles (sPBT-E) were synthesized by direct polycondensation of 3,3′-disulfonate-4,4′-dicarboxylbiphenyl (DSBP), 4,4′-dicarboxylic diphenyl ether (DCPE) and 2,5-diamino-1,4-benzenedithiol dihydrochloride (DABDT) in polyphosphoric acid (PPA). The sPBT-E series showed considerable solubility in common organic solvents due to the presence of flexible ether groups in the polymer backbone. Sulfonated graphene oxide (SGO) with different loadings (1, 2, 3, and 4 wt%) was doped into the sPBT-E matrix with the sulfonated monomer ratio of 62.5% to prepare composite PEMs (denoted as sPBT-E62.5/SGO) for the first time. sPBT-E membranes with different sulfonated monomer ratios (55, 57.5, 60, and 62.5) were also prepared for comparison. sPBT-E and sPBT-E62.5/SGO series membranes exhibit excellent dimensional stability, appropriate water uptake, high thermal stabilities, and mechanical properties. Additionally, SGO can provide additional ion-transporting sites (resulting in continuous proton transfer channels) to enhance proton conduction of the sPBT-E62.5/SGO membranes. Therefore, the proton conductivity and power density of sPBT-E62.5/SGO3 were up to 0.139 S cm−1 and 519.9 mW cm−2 at 80 °C and 100% RH, which are superior to sPBT-E series and Nafion 212 (0.133 S cm−1, 413.2 mW cm−2). After 20 h continuous operation, the output voltage of sPBT-E62.5/SGO3 only decreased by 13.2%, which is better than sPBT-E62.5 (22.7%). Hence, the sPBT-E62.5/SGO3 membrane exhibits excellent potential as an alternative PEM for PEMFCs.

The performance characterization of carbon fiber–reinforced plastic for space applications

In this paper, the excellent dimensional stability and vacuum outgassing of high-performance carbon fiber–reinforced plastic (CFRP) were discussed. First, the high-performance resin matrix was obtained by modifying cyanate resin, and the modified cyanate ester was used to make prepreg and laminates. Then, the mechanical property retention rate of laminates reached 90.79% under proton and electron irradiation. The average values of total mass loss and collected volatile condensable material of high-performance CFRP were 0.116% and 0.008%, respectively. Finally, the candidate tube and frame were fabricated based on the ply lay-up design. The candidate tube and frame were subjected to a series of experiments of thermal deformation and hygroscopic deformation to verify the dimensional stability. The thermal deformations of the tube and frame reached 0.468 μm/m and 4.579 μm/m, respectively, with a temperature variation of 4°C. The measured hygroscopic deformation of the tube reached 8.16 μm/m in nearly 3 months. The experimental results show that the high-performance CFRP can be used for precision optical structures of space telescopes.

Alkaline anion exchange membrane containing pyrene-based π-π stacking interactions

Highly conductive and chemically resistant alkaline anion exchange membranes (AAEMs) are highly desirable in various electrochemical devices such as alkaline anion exchange membrane fuel cells (AAEMFCs) and water electrolysis. Here we present the novel AAEMs with pyrene-containing ether-free polymer backbones bearing piperidinium cations. Both morphology analyses and simulations verify that the π-π stacking of pyrene units in polymer backbones can actuate the neighboring piperidinium cations to aggregate and form ion conducting channels, thus enhancing the ion conductivity of AAEMs (153 mS cm−1 at 90 °C). Additionally, the resultant aryl ether-free poly(aryl piperidinium) structure guarantees the chemical durability of the AAEMs, which has 91.5% OH− conductivity retention after treatment in 2 M NaOH at 80 °C for1080 h. Meanwhile, the rigid pyrene units increase the rigidity of polymer backbones, resulting in excellent mechanical strength (46.3 MPa) and dimensional stability (swelling ratio of 11.8% at 90 °C). The molecular design provides an attractive strategy for advancing the development of high-performance AAEMs.

The Effect of Sodium Tetrafluoroborate on the Properties of Conversion Coatings Formed on the AZ91D Magnesium Alloy by Plasma Electrolytic Oxidation

Magnesium and its alloys are widely used in many areas because of their light weight, excellent dimensional stability, and high strength-to-weight ratio. However, the material exhibits poor wear and corrosion resistance, which limits its use. Plasma electrolytic oxidation (PEO) is an effective surface modification method for producing ceramic oxide layers on Mg and their alloys. The influence of the additions of sodium tetrafluoroborate (NaBF4) and sodium fluoride (NaF) into alkaline-silicate electrolyte on the properties of the conversion layers formed in the magnesium AZ91D alloy has been investigated. Surface morphology and chemical composition were determined by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The anticorrosive properties of the layers were evaluated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) methods in simulated body fluid (SBF). The presence of NaBF4 or NaF in the electrolyte increases the corrosion resistance of the protective layer. However, the best anticorrosive properties show the layers obtained in the presence of NaBF4. This is probably caused by the incorporation of boron and fluorine in the form of Mg (BF4)2 mainly in the barrier layer.