Ceramic Materials Research Articles

PROCESSO DE APLICAÇÃO NO ASSENTAMENTO DAS PEÇAS EM CERÂMICAS

This study aims to explore the process of applying ceramic tiles, with a special focus on ceramic coatings used in high humidity environments, such as bathrooms and kitchens. The main objective is to deepen knowledge in the area of ​​ceramic coatings, understanding their properties, performance and implications for the durability of residential buildings. To answer this question, a detailed bibliographic review will be carried out on the ceramic materials available on the market, their technical characteristics and behavior in the face of humidity. In addition, case studies and experiments will be analyzed to assess the efficiency of ceramic coatings in preventing problems such as infiltration, mold and premature wear. The research will also include an analysis of the thermal properties of ceramic materials to understand their contribution to the energy efficiency of buildings. The expected results of this study aim to provide practical guidelines for civil engineers in the correct selection and application of ceramic coatings in humid environments. The findings are expected to help increase the lifespan of residential buildings and promote more efficient use of energy resources.

An Ultra-Broadband Electromagnetic Wave Absorbing ZrB2-Based Ceramic Composite Inspired by Barbule of Peacock.

Broadband electromagnetic wave (EMW) absorbing ceramic materials are highly required for the thermal parts of aerocraft. As members of ultrahigh temperature ceramics, ZrB2-based ceramics have great potential for applications in more extreme environments relative to the currently used silicon-based and oxide-based ceramics. However, ZrB2 is not among the traditional EMW absorbing material candidates due to its high conductivity, which induces the strong reflection of EMW due to the impedance mismatch with free space. Herein, ZrB2-based ceramic with a bionic microstructure inspired by peacock barbules is proposed. Boron nitride nanotubes acting as polarization centers inside the ZrB2-based material cause massive EMW dissipation. The ceramic shows an ultra-broadband absorption of 9.6GHz (<-10dB from 8.4 to 18GHz), almost covering the entire X and Ku bands, superior to the reported ceramics. The polarization centers successfully turn the ZrB2-based ceramic from EMW reflecting material to an excellent EMW absorbing material by the bionic barbule interspersed microstructure. The simulated metamaterial of the ceramic achieves an ultra-broad absorption (lower than -15dB) in the range of 2-40GHz. This work provides valuable insights for the development of broadband absorption material for high-temperature environments.

Self-Etching Ceramic Primer Affects Surface Topography and Roughness of Two Zirconia-Reinforced Lithium Silicate Ceramics.

This article evaluates the etching efficacy of a self-etching ceramic primer (SECP) on zirconia-reinforced lithium silicate (ZLS) ceramics. Celtra Duo (DeguDent GmbH, Hanau-Wolfgang, Germany) and Vita Suprinity (Vita Zahnfabrik, Bad Säckingen, Germany) were used in this study. A total of 36 ceramic slices were prepared from each ceramic material and randomly distributed into three groups according to the surface treatment applied (n = 12 per group). Group 1 (polished) was polished with silicon carbide paper discs and did not undergo any surface treatment; group 2 (SECP) was surface treated with SECP (Monobond Etch and Prime, Ivoclar Vivadent, Schaan, Liechtenstein); group 3 (hydrofluoric acid [HF]) was surface treated with 4.7% HF etching. Half of the specimens (n = 6) from each group were gold-sputtered, and the surface topographic alterations were evaluated by scanning electron microscopy at magnifications of 5,000× and 10,000 × . The surface roughness of the other half (n = 6) from each group was tested using a three-dimensional optical profiler. Data were statistically analyzed using two-way analysis of variance and Tukey's multiple comparisons test. Both SECP and HF etching surface treatments resulted in a statistically significant increase (p < 0.05) in the surface roughness of both ceramic materials, compared to that of their respective control group specimens (polished). HF etching resulted in a significant dissolution of the glassy phase of each ceramic. SECP can effectively etch ZLS ceramics. The etching patterns created after the application of SECP were mild compared to those produced by HF etching. The topographic surface features of ceramics are affected by both, surface treatment and material composition.

Cytotoxicity and Microbiological Properties of Ceramic CAD/CAM Materials Subjected to Surface Treatment with Nanometric Copper Layer

The aim of this study is to present the characteristics and a comparison of four different commercial materials dedicated to the CAD/CAM technique in dentistry, all of which can be classified as ceramic materials. Its purpose is also to evaluate the impact of surface treatment on the cytotoxicity and microbiological properties of the materials. The CAD/CAM technique has a perpetually growing role in modern reconstructive dentistry. It requires a material’s possession of peculiar characteristics, such as mechanical resistance, durability, functionality (similar to natural tissues), good aesthetics and biocompatibility. To critically evaluate a biomaterial, both manufacturer claims and in vitro tests should be considered. Further steps of evaluation may include animal tests and clinical trials. There are certain attributes of biomaterials that may be modified by surface treatment that can be crucial to the clinical success of the material. The evaluated materials were Vita Suprinity (VITA-Zahnfabrik, Germany), Vita Mark II (VITA-Zahnfabrik, Germany), Celtra Duo (Dentsply Sirona, USA) and Empress Cad (Ivoclar Vivadent, Liechtenstein). They are available in the form of prefabricated blocks of various diameters and are popular among operators performing clinical procedures using CAD/CAM. Standardized blocks of each material were prepared. Half of them had their surface polished. Further, half of all the samples were covered by a nano-copper layer. The samples were evaluated for cytotoxicity, presented on a 0–4 scale, adhesion susceptibility and potential of forming a biofilm on their surface. Physicochemical properties such as the water contact angle (WCA) were evaluated for the tested materials. The influence of copper coating on cytotoxicity cannot be unequivocally stated or denied. Surface polishing did not affect the materials’ cytotoxicity, but it increased the WCA of all materials and, therefore, their hydrophobicity. Different degrees of adhesion ability and biofilm formation were dependent on the species of microorganisms and properties of the dental materials.

Impact of ceramic packaging on the quality and safety of Armenian fermented dairy product Matsoun

Background: Packaging is essential for food safety, as it acts as a barrier against contaminants that can cause spoilage and affect human health. The Armenian fermented dairy product, matsoun, is packaged not only in plastic and glass but also in clay pots. However, the impact of traditional packaging on the quality and safety of matsoun, especially heavy metal migration, remains under-researched. Objective: This study aimed to investigate the impact of ceramic packaging material on the quality and safety of matsoun during storage. Specifically, it compared the physicochemical properties (pH, titratable acidity), lactic acid bacteria (LAB) populations, and metal migration during storage. Methods: Six samples of matsoun were prepared and packaged in sterilized glass and ceramic containers. The samples were stored at 4 °C and analyzed on days 1, 7, and 15 of storage. The parameters measured included pH, titratable acidity, and LAB counts (coccus and bacillus). Heavy metal migration (Cd, Pb, Hg, As) was analyzed using atomic absorption spectroscopy. Results: The pH of samples packaged in ceramic and glass containers decreased over 15 days of storage, from 4.61 to 4.24 and 4.6 to 4.27, respectively. Titratable acidity increased in both groups, reaching 1.2 % lactic acid. A decrease in bacilli was observed in ceramic-packaged matsoun. The lead concentration remained constant at 0.0045 ppm across all samples. In ceramic containers, cadmium concentration increased from 0.0015 ppm to 0.0029 ppm by day 15. Conclusion: This study observed a decrease in pH, an increase in titratable acidity, and a relatively constant number of lactic acid bacteria indicating ongoing fermentation. The results showed nondetectable concentrations of arsenic (As) and mercury (Hg). The lead (Pb) concentration in all samples remained within the World Health Organization’s (WHO) allowed limit of 0.02 ppm. However, the concentration of cadmium (Cd) concentration in ceramic-packed increased, exceeding the WHO limit of 0.002 ppm. Further research is necessary to identify the sources of cadmium contamination. Keywords: food packaging, ceramic, matsou​​n​, heavy metal migration, food safety

Sintering polycrystalline silicon carbide composite ceramics with ultra-high hardness under high pressure

Silicon carbide (SiC) is an important structural ceramic material, exhibiting exceptional comprehensive properties that are unmatched by metals and other structural materials. In this study, a combination of α-SiC micron powder and β-SiC nanopowder was utilized as precursor materials for high pressure and high temperature (HPHT) sintering. Under a pressure of 5.0 GPa, polycrystalline SiC samples with mixed grain size were sintered within a temperature range from 1000 to 1700 °C, and compared with SiC samples sintered from single micron powder under identical temperature and pressure conditions. The microstructures of the two sets of SiC samples were observed using scanning electron microscopy. Additionally, the stress states and strengthening mechanisms among SiC grains with mixed grain size under HPHT were further analyzed in conjunction with X-ray diffraction results. The polycrystalline SiC composite ceramics sintered at 1700 °C exhibited superior mechanical and thermal properties, achieving a Vickers hardness of 35.2 GPa that is 23.5 % higher than that obtained by conventional spark plasma sintering and even surpassing the hardness of single crystal SiC, demonstrating thermal stability up to 1405 °C in air environment. Transmission electron microscopy was employed to analyze defects and plastic deformation in these samples. The study suggests that the primary strengthening mechanisms of the sintered polycrystalline SiC composite ceramics under HPHT include the increase in micro defects induced by in-situ plastic deformation at elevated temperatures and the effects of high-temperature creep. This study provides new insights into the HPHT sintering of hard materials.

High‐temperature thermal conductivity measurement of porous ceramic coatings with a high heat flux CO2 laser rig

AbstractYttrium‐stabilized zirconia (YSZ) plays a crucial role in thermal barrier coatings widely used to protect metallic components in gas turbine engines against high‐temperature combustion product gases and harsh environments. The thermal conductivity of these coatings is a critical parameter influencing the gas turbine design, performance, and service life. In this study, a laser temperature gradient method is utilized to measure the thermal conductivity of porous YSZ coatings. The method employs specialized laser energy delivery to create a one‐dimensional temperature gradient through the sample thickness, closely simulating the operational condition. This approach provides an effective, direct means to determine the thermal conductivity of high‐temperature heat‐resistant porous ceramic materials.

Investigating radiation shielding parameters for X-ray attenuation at various energies in locally produced ceramic materials used in Saudi Arabia

To assess shielding effectiveness against X-rays, a number of locally collected ceramic samples were obtained from the Kingdom of Saudi Arabia. Based on elemental analysis, all of the ceramic samples have a density in the range of 1.68–1.85 g/cm3, with the highest proportions of O, Si, C, and Al atoms and the lowest amounts of Na, Mg, K, Ca, Ti, and Fe. The 320 kV X-ray source (Gulmay Limited, Byfleet, UK) was used to assess the attenuation properties of the ceramic samples. An Exradin A4 ionization chamber (Standard Imaging, Middleton, USA) connected to a UNIDOS electrometer (PTW, Freiburg, Germany) in the control room was used to detect the attenuation properties. Several X-ray attenuation coefficients are evaluated at different X-ray energies in the range of 40–150 kV in this study. These include the mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), half-value layer (HVL), tenth-value layer (TVL), and mean free path (MFP). The ability of any ceramic sample under investigation to shield radiation at low X-ray energy is indicated by the theoretical and experimental values of LAC. The potential applications of these easily accessible, reasonably priced ceramic materials for radiation protection in X-ray labs and low-energy X-ray shielding in a variety of fields have been shown by this investigation.

Use of Computerised X-ray Tomography in the Study of the Fabrication Methods and Conservation of Ceramics, Glass and Stone Building Materials

This work will review and discuss the use of computerised X-ray tomography (CXT) for analysing ancient, manufactured items, like stone building materials, glass and ceramics. It will consider particular techniques required, and/or of benefit, for CXT of heritage materials, such as special precautions during the experimentation to ensure there is no damage to the materials, special imaging methods such as elemental-specific imaging, and sample-specific image analysis requirements. This study shows how the knowledge of internal features, particularly pores, discerned from CXT can be used to reverse engineer the artefact fabrication process. CXT can be used to obtain information on both the raw materials (such as types and impurities) and fabrication techniques used. These abilities can then be used to establish technological evolution and the incidence of ancient behaviours like recycling and allow the linking of particular items to specific production sites. It will also be seen how CXT can aid the development of effective conservation techniques. This work will also consider how conclusions drawn from CXT data can be amended or augmented by the use of complementary non-destructive characterisation methods, such as gas overcondensation.

The Effect of Silane Treatment of a Resin-Based Composite on Its Microtensile Bond Strength to a Ceramic Restorative Material

The Effect of Silane Treatment of a Resin-Based Composite on Its Microtensile Bond Strength to a Ceramic Restorative Material

Technological choices and practices of Early Bronze Age pottery production in the Central Plains: Focusing on the sites of Xinzhai and Huadizui

Aspects of the Early Bronze Age (ca. 2050–1640 BCE) pottery production technology and knowledge transfer in the Central Plains of China (i.e., the Zhengzhou-Luoyang area) were studied. To this aim, 120 domestic pottery samples and ten geological samples from two central sites at Xinzhai and Huadizui were studied macroscopically and analysed with X-ray fluorescence spectrometry. Based on a discussion of macroscopical evidence and chemical composition, the results tentatively indicate the technological knowledge transfer between the potters in Xinzhai and Huadizui sites despite being located about 80 km apart. Pottery of the same category was manufactured with similar selection and preparation strategies of ceramic raw materials, decorated with similar patterns, and adopted similar forming techniques. More specifically, the cookware from the Xinzhai and Huadizui sites was hand-made and Ca-poor, while the storage- and drinking wares were wheel-made and Ca-rich. These results likely indicate the existence of one overarching community of practice, potters located at Xinzhai and Huadizui, who shared strategies for raw materials selection, paste preparation, and finishing.

Effects of Samarium Doping on the Dielectric Properties of BaBi2Nb2O9 Aurivillius Ceramics.

This study investigates the influence of samarium (Sm3+) doping on the structural, microstructural, mechanical, and dielectric properties of BaBi2Nb2O9 (BBN) ceramics. Using the solid-state reaction method, samples of BaBi2-xSmxNb2O9 with varying concentrations of Sm (x = 0.01; 0.02; 0.04; 0.06; 0.08; 0.1) were prepared. Thermal analysis, microstructure characterization via SEM and EDS, X-ray diffraction, mechanical testing, and dielectric measurements were conducted. The results revealed that increasing Sm3+ concentration led to the formation of single-phase materials with a tetragonal structure at room temperature. Mechanical properties, such as Young's modulus and stiffness, improved with Sm doping, indicating stronger atomic bonding. Dielectric properties showed that low concentrations of Sm3+ slightly increased electrical permittivity, while higher concentrations reduced it. The presence of Sm3⁺ also affected the relaxor properties, evidenced by changes in the freezing temperature and activation energy. Overall, the study concludes that samarium doping enhances the structural and functional properties of BBN ceramics, making them promising candidates for high-temperature piezoelectric and dielectric applications. The findings provide valuable insights into tailoring ceramic materials for advanced technological applications.

THE MODERN AND PROSPECTIVE STRUCTURAL MATERIALS` FOR WHEELED ARMORED VEHICLES STRENGTH CHARACTERISTICS ANALYSIS

The article presents the results of research in those the modern structural materials` strength characteristics for wheeled armored vehicles (WAV) production, as well as the technical requirements for them, were analyzed. It has been established that ordinary structural steels are used for armored car frames, and special armored steels with high strength and hardness characteristics are used for armored plating. It is expedient to use new promising materials - martensitic steels, which are characterized by extremely high strength, new ceramic materials and glass, and the latest nanomaterials - for the WAV armoring. A military vehicles protection promising direction is modern modular armor protection with the use of various materials.

Advancing greener LNG-fueled vessels: Compact simultaneous reduction system for CH4, NOX and CO2 emissions

Stringent ship regulations necessitate simultaneous emission reductions, challenged by cargo loss and energy constraints. This study proposes a compact reduction system that simultaneously mitigate CH4, NOX, and CO2 emissions onboard LNG-fueled vessels. The proposed system integrates two pivotal technologies: a metal support-based compact methane oxidation catalyst (MOC)-selective catalytic reduction (SCR) system to capture CH4 and NOX, and a cryogenic CO2 capture (CCC) system to capture and store CO2 in its solid phase utilizing LNG's cold energy. This innovative approach addresses two challenges. First, the compact MOC-SCR system employs metal support with an enhanced surface area-to-volume ratio surpassing the capabilities of ceramic support materials, achieving a volume reduction of 80.02% and 79.82% respectively. Secondly, the CCC system significantly lowers specific energy consumption by 61.54% by harnessing LNG's cold energy compared to the absorption-based CO2 capture system. As a result, the proposed system not only reduces CH4, NOX, and CO2 emissions simultaneously with a high capture rate but also reduces volume and weight. Furthermore, it achieves a high CO2 capture rate of 92.12%, while diminishing cargo losses by 25.30%. These findings provide valuable guidance for developing environmentally sustainable vessels, aligning with the continuously increasing stringency of regulations.

Optical properties of crystals and two-phase ceramics of the AgCl0.25Br0.75 – AgI system

Research of materials’ optical properties is critical for further development and manufacturing of optical products. While recently, single crystals and two-phase ceramics of the AgCl0.25Br0.75 – AgI system have been developed by the authors. This work is focused on studying the transmission ranges, refractive index dispersion, optical losses, and photoresistance of materials in the AgCl0.25Br0.75 – AgI system, as well as comparing the properties of single-crystals and ceramics. The materials are transparent in the visible and IR regions from 0.49 to 54 um, as well as in the terahertz (far IR and millimeter regions) of 300–1500 um (0.3–1.0 THz). For all compositions, the refractive index in the IR varied from 2.107 to 2.436. The materials’ absorption coefficients were (0.06–6.67) ∙ 10-4 in the middle IR, which is lower compared to other halide materials known and indicates low optical loss. Finally, both single-crystals and two-phase ceramics showed a trend towards an increase in photoresistance with a rise of the AgI content in the AgCl0.25Br0.75 solid solution. After UV irradiation, the materials showed a decrease in transmission in the visible and middle IR (to 10 µm) with negligible loss at a wavelength of 10 µm or more. For a single crystal and two samples of ceramics with a composition of 20 mol. % AgI in AgCl0.25Br0.75, a comparison of properties was conducted in this study. Based on the comparison results, close but not identical values of the refractive indices, an increase in the absorption coefficient for ceramic materials, and a low photoresistance of the sample obtained from the mechanical mixture were revealed. The last two characteristics are associated with the high heterogeneity of two-phase ceramics based on a mechanical mixture, which leads to a deterioration in functional properties. These results prove high prospects for the use of these materials in fiber optics and photonics for medical technologies, thermography, and optoelectronics.

Ceramics for Microelectromechanical Systems Applications: A Review

A comprehensive review of the application of different ceramics for MEMS devices is presented. Main ceramics materials used for MEMS systems and devices including alumina, zirconia, aluminum Nitride, Silicon Nitride, and LTCC are introduced. Conventional and new methods of fabricating each material are explained based on the literature, along with the advantages of the new approaches, mainly additive manufacturing, i.e., 3D-printing technologies. Various manufacturing processes with relevant sub-techniques are detailed and the ones that are more suitable to have an application for MEMS devices are highlighted with their properties. In the main body of this paper, each material with its application for MEMS is categorized and explained. The majority of works are within three main classifications, including the following: (i) using ceramics as a substrate for MEMS devices to be mounted or fabricated on top of it; (ii) ceramics are a part of the materials used for an MEMS device or a monolithic fabrication of MEMS and ceramics; and finally, (iii) using ceramics as packaging solution for MEMS devices. We elaborate on how ceramics may be superior substitutes over other materials when delicate MEMS-based systems need to be assembled or packaged by a simpler fabrication process as well as their advantages when they need to operate in harsh environments.

Enhancing craniofacial bone tissue engineering strategy: integrating rapid wet chemically synthesised bioactive glass with photopolymerized resins

BackgroundCraniofacial bone regeneration represents a dynamic area within tissue engineering and regenerative medicine. Central to this field, is the continual exploration of new methodologies for template fabrication, leveraging established bio ceramic materials, with the objective of restoring bone integrity and facilitating successful implant placements.MethodsPhotopolymerized templates were prepared using three distinct bio ceramic materials, specifically a wet chemically synthesized bioactive glass and two commercially sourced hydroxyapatite variants. These templates underwent comprehensive characterization to assess their physicochemical and mechanical attributes, employing techniques including Fourier transform infrared spectroscopy, scanning electron microscopy, and nano-computed tomography. Evaluation of their biocompatibility was conducted through interaction with primary human osteoblasts (hOB) and subsequent examination using scanning electron microscopy.ResultsThe results demonstrated that composite showed intramolecular hydrogen bonding interactions with the photopolymer, while computerized tomography unveiled the porous morphology and distribution within the templates. A relatively higher porosity percentage (31.55 ± 8.70%) and compressive strength (1.53 ± 0.11 MPa) was noted for bioactive glass templates. Human osteoblast cultured on bioactive glass showed higher viability compared to other specimens. Scanning micrographs of human osteoblast on templated showed cellular adhesion and the presence of filopodia and lamellipodia.ConclusionIn summary these templates have the potential to be used for alveolar bone regeneration in critical size defect. Photopolymerization of bioceramics may be an interesting technique for scaffolds fabrication for bone tissue engineering application but needs more optimization to overcome existing issues like the ideal ratio of the photopolymer to bioceramics.

Synthesis of α-LiAlO&lt;sub&gt;2&lt;/sub&gt; powders of controlled particle size composition for a matrix electrolyte based on carbonate melts

Three methods of synthesis α-LiAlO2 powders for the preparation of a matrix electrolyte for a molten carbonate fuel cell have been considered. The submicron fraction with a specific surface area of 79 m2/g was obtained from an aqueous solution by spray pyrolysis and the large rod-shaped fractions with particles up to 19 μm in length were obtained by synthesis in halide melt and in aqueous solution. Tape casted ceramic matrices were tested in the single fuel cell with 53Li2CO3–47Na2CO3 melt as an electrolyte. The matrices have demonstrated good gas tightness; nitrogen inleakage in anode space did not exceed 0.6 % during 1100 h lifetime test, which included 15 thermal cycles with cooling the cell below melting point of the electrolyte.

Automatic tiling method for mosaic ceramic art images based on subpixel edge fitting localization and collaborative operation of multiple manipulators

Mosaic ceramics are not limited to use solely as building materials, they also possess artistic value. Artists can create images by arranging and combining mosaic ceramics, resulting in a perfect fusion of large-scale public art for external walls and ceramic materials. However, the current approach for artists to create mosaic ceramic exterior wall art images involves manual laying and assembling of individual mosaic ceramics. This manual process suffers from issues such as low efficiency, eye fatigue, selection errors, and the risk of high-altitude operations. These challenges significantly impact the quality and efficiency of creating mosaic ceramic exterior wall art image images. To address these problems, this paper proposes an automatic mosaic ceramic art image stitching method based on subpixel edge fitting positioning and collaborative operation of multiple robotic arms. Additionally, a new U + I type conveying method is designed for efficient and space-saving transportation of mosaic ceramics. Experimental results demonstrate a high success rate of recognition, absorption, and placement of multi-color mosaic ceramics using this method reaching 95.45%, with a positioning error within 0.5 mm. The method can also adapt to varying levels of light intensity or noise interference. This approach effectively enhances the quality and efficiency of creating mosaic ceramic exterior wall art images and promotes the development of mosaic ceramic exterior wall public art creation.

Advancements of biomaterial in hip replacement technology incorporating ceramic materials

The increasing prevalence of hip joint diseases is closely linked to improved living standards and an aging population, leading to a rise in conditions like degenerative arthritis and severe hip injuries. These conditions cause significant pain and functional impairments, greatly reducing the quality of life for affected individuals. Total hip arthroplasty (THA) has become a well-established surgical intervention to address these debilitating conditions. Within the realm of hip replacement materials, ceramics have garnered attention for their exceptional wear resistance and ability to minimize complications, such as bone dissolution caused by wear particles. Ceramics, such as alumina and zirconia, offer biocompatibility and low wear rates, making them favourable choices for hip prostheses. However, despite these advantages, the use of ceramics in hip replacements is not without challenges. Issues such as ceramic fragmentation and abnormal joint noise have been noted, posing significant obstacles to their widespread adoption. This review explores the advancements in hip replacement technology with a particular focus on ceramic materials. It delves into the properties that make ceramics suitable for this application, such as their biocompatibility and mechanical strength, enhanced through advanced manufacturing techniques. Additionally, the review addresses the ongoing challenges, including strategies to mitigate the risk of fragmentation through material toughening and improved prosthesis design. Furthermore, it examines the phenomenon of abnormal joint noise, proposing solutions that involve refinements in implant design, surgical techniques, and post-operative patient management. The aim of this review is to provide a comprehensive overview of current advancements and future directions in the use of ceramic materials in hip replacement technology, highlighting the potential for improved patient outcomes and the need for continued research and innovation in this field.