Table 3.

Use of halloysite in “ceramic composites”.

Origin of Halloysite	Synthesis	Processing	Product	Application	Ref.
New Zealand	Electroless deposition/heat tretment	Activated tubular halloysite ceramic substrate by Pd particles and electroless deposition of Ni nanoparticles on halloysite and heat treatment at 400 °C	Metallized-ceramic material	Used as magnetic material	Fu et al. (2004)
New Zealand	Electroless deposition/heat treatment	Activated tubular halloysite ceramic by Pd particles and electroless deposition of Ni nanoparticles and wires on s halloysite template and heat treatment at 400 °C	Metallized-ceramic material	Used as magnetic material	Fu and Zhang (2005)
China, New Zealand	Pelletization	Halloysite with ethylcellulose, ethanol and sucrose were mixed for 12 h at room temperature and pelletized by extrusion (under extruder rotation 30 rpm) and spheronization (under sheronizer speed and time 1500 rpm and 10 min, respectively)	Porous aluminosilicate ceramic pellets	Used as a drug delivery vehicle	Byrne and Deasy (2005)
New Zealand	Pelletization	Halloysite, microcrystalline cellulose and a fentanyl base were mixed for 10 min. Powder was mixed with water(forming paste). Paste extruded as spaghetti-like threads which were spheronized to pellets with 1.5 mm diameter and, consequently, they were dried for 24 h.	Ceramic drug delivery vehicle	Used as a drug delivery vehicle for release of potent opioids	Forsgren et al. (2010)
USA	Mixing and centrifugation/filtering	Loading of halloysite in a solution of inhibitors by consequent vacuation in 3 cycles. Separation of loaded tubes from the solution by centrifugation or filtering, drying at 60–70 °C and grinding. Mixing of loaded halloysite with a solution of polymers.	Ceramic–polymer composite	Used as anticorrosion coating of alloys	Fakhrullin et al. (2014)
New York	Deposition and vacuum evaporation	Halloysite nanotubes were deposited on aluminum foil. A thin metal film of 15 nm was coated on an aluminum-halloysite substrate in a vacuum evaporator	Al-ceramic HNTS substrate	Substrate for surface enhanced raman spectroscopy	Vinokurov et al. (2015)
New Zealand	Electrospinning and sintering	Preparation of halloysite–polyvinyl pyrrolidone nanofiber mats by electrospinning (at 120–240 mm distance of the spinning and collecting electrode, 0–80 kV voltages, ~40% humidity). Sintering of the mats at 1100 °C in N2 and 1200–1400 °C in air	Ceramic nanofiber mat	Support for zeolite membranes	Chen et al. (2016).
USA	Sintering	Mixing of halloysite with carbon fibers and lubricating agent for 15 min. Pressing samples with 30 mm diameter under 100 MPa at 20 °C. Sintering at 1500 °C and air atmosphere.	Porous ceramic preform	Used in metal matrix synthesis for novel applications	Kujawa et al. (2016)
Commercial	Sintering, gas pressure infiltration	(I) Synthesis of porous mullite performed: mixture prepared of halloysite powder and 30 wt% carbon fibers. Pressing at 100 MPa. Sintering at 1300 °C. (II) Infiltration of aluminium alloy into the porous perform matrix under nitrogen pressure of 3 MPa in 3 s.	Metalized-porous ceramic composite	Used for advanced applications, especially under high temperatures	Pawlyta et al. (2016)
Commercial	Modification, dispersion, electrospinning	Modification of halloysite nanotubes (HNT-NH2, HNT-COOH) after reactions of HNT with APTES and maleic anhydrite. Preparation of drug-loaded halloysite in appropriate solutions and stirring at 37° for 24 h. Dispersion of neat HNT, HNT-NH2, HNT-COOH into an electrospun substrate of PCL (polycaprolactone) under 25 °C and 13–14 kV. In vitro release of drug load.	Polymer–ceramic nanocomposites	Used as a drug release carrier	Ghaderi-Ghahfarrokhi et al.(2017)
New York	Schiff base binding	Production of halloysite nanotubes by rolling aluminosilicate sheets. Mixing of halloysite tubes with furfuraldehyde and ultrasonic dispersion for 30 min. Mixing of furfuraldehyde loaded halloysite with hydrazine hydrate and stirring for 30 min at 70 °C forming a Schiff base.	Metal–ceramic core–shell composite	Industrial applications of metal nanocatalyst or as metal adsorbent from solutions	Vinokurov et al. (2017)
China	Sintering	Preparation of three different mixtures of MVQ/HNT with different borates as additives: mixing time 20 min, pressing under 15 MPa at 170 °C for 15 min. Heating at 1000 °C for 30 min.	Ceramizable silicone rubber (MVQ)/halloysite (HNT) composite	Special application as fire-resistant wires and cables	Guo et al. (2018)
China	Microwave sintering	Mix of low-grade pyrite cinder (LPC) with coal powder (in ratio 10/1) and 5% calcium fluoride. Preparation of discs after pressing and sintering in ab electric furnace up to 1450 °C (5 °C/min and slow cooling in a room)	Microwave heating ceramics (MHCs)	Used as magnetic ceramic and aggregate for asphaltic mixtures	Zhang et al. (2018)
Commercial	Plasma electrolytic oxidation (PEO)	PEO coating of AM50 alloy was prepared in an alkaline electrolyte (at 20 °C and frequencies ranging from 100 to 5000 Hz) and consisting of HNTS, Na2SiO3, KOH, NaF	Incorporated halloysite into forsterite ceramic coating	Used as coating	Mingo et al. (2019)
Commercial	Electrophoretic deposition (EPD)	Mixture of chitosan (CS), bioglass (BG), hydroxyapatite (HA) and halloysite nanotubes (HNT) powders added to ethanol–water solvent and stirred for 24 h at room temperature. Deposition on the titanium substrate at voltages of 10–50 kV and times of 5–25 min	Chitosan-based nanocomposite	Used as coating of metallic substrate	Molaei et al. (2019)
USA	Metal deposition/casting method	2 wt% metal of Pd, Pt derived from chemical solutions with H2PtCl6 and salt PdCl2, laid down in the halloysite tubes. 4 wt% of the hybrid Pd, Pt /HNT mixed with sulfopolymer solution in isopropanol or dimethylformamide with a magnetic stirrer for 30 min.	Metal–ceramic shell halloysite syntheses in hybrid membranes	Used as a separating membrane in fuell cells or in an electromembrane	Petrova et al. (2019)
Commercial	Sulphuric acid treatment, sol–gel method and heating	Etching of Al2O3 in HNTS by sulphuric acid at 70 °C for 20 h producing SiO2 (SiNP). Sol–gel synthesis of clay-based Na2ZnSiO4 (Clay NZS) using a mixture of SiNP, sodium acetate, zinc acetate dehydrate. Drying for 24 h, calcining at 350 °C for 6 h, pressing at 2 tons and sintering at 700, 750 and 800 °C	Ceramic clay-based Na2ZnSiO4 compound	Used as ceramic electrolyte	Johari et al. (2020)
Commercial	Plasma electrolytic oxidation (PEO)	HNTS loaded with corrosion inhibitors (vanadate, molybdate, 8-hydroxyquinoline) after mixing with a aqueous solution under a vacuum. PEO coating of AZ31 magnesium alloy was prepared in an alkaline electrolyte (at 20 °C and frequencies up to 5000 Hz) and consisting of HNTS, Na2SiO3, KOH, NaF. PEO-coated and immersed in an aqueous solution with 20 gr/L loaded HNTS for 10 min, at 22 °C, pH values under 6.5–7.5.	Smart ceramic coating	Used as coating	Mingo et al. (2020)